QAQC MANUAL - Onshore Hydraulic Fracturing Manual_V1_Jul04

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Version 1.0

July 2004

George A. Turk, EPTG Cecil Parker, EPTG Mark Glover, EPTG Harmon Heidt, OUSBU Ian Lambeth, EPTG

BP Onshore Hydraulic Fracturing QA/QC Manual July 2004 - ii -

BP Onshore Hydraulic Fracturing QA/QC Manual July 2004 - iii -

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Review Date Reviewers

August 2003

Mark Glover, EPTG Harmon Heidt, OUSBU

Cecil Parker, EPTG George Turk, EPTG

September 2003 Melissa Beck, Frontline Group June 2004 OUSBU Wells Team

BP Onshore Hydraulic Fracturing QA/QC Manual July 2004 - iv -

BP Onshore Hydraulic Fracturing QA/QC Manual July 2004 - v -

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Taking Execution out of the Equation ..................................................................... 2

Leave a Trail ............................................................................................................... 5

The Rest of the Story................................................................................................. 5

The BP Fracturing QA/QC Principles....................................................................... 6

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1–1 Introduction ..................................................................................................... 8

1–2 Fluids ............................................................................................................... 8 1–2.1 Fann 50 Recipe Validation ______________________________________ 8 1–2.2 Fluid Formulation Sensitivity Tests_______________________________ 11 1–2.3 Chemical Batch/Lot Tests______________________________________ 13 1–2.4 Water Analysis ______________________________________________ 13 1–2.5 Pad Lab Pilot Test ___________________________________________ 14 1–2.6 Pilot Test Acceptable Variance Ranges ___________________________ 17

1–3 Proppant ........................................................................................................ 19 1–3.1 Pre-Job Proppant Quality Assurance _____________________________ 21

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2–1 Introduction ................................................................................................... 24 2–1.1 Personnel Requirements ______________________________________ 24

2–2 Fluid Testing.................................................................................................. 24 2–2.1 Equipment _________________________________________________ 24 2–2.2 Materials___________________________________________________ 25 2–2.3 Water Analyses _____________________________________________ 25 2–2.4 Pad Pre-Job Pilot Test ________________________________________ 26

2–3 Proppant Testing .......................................................................................... 33

2–4 Pumping and Metering Validation ............................................................... 34 2–4.1 Equipment Layout ___________________________________________ 35 2–4.2 Metering ___________________________________________________ 36 2–4.3 Gelling the Hydration Unit______________________________________ 41 2–4.4 Materials___________________________________________________ 42 2–4.5 Frac Van Preparation _________________________________________ 42 2–4.6 Densometers _______________________________________________ 45

BP Onshore Hydraulic Fracturing QA/QC Manual July 2004 - vi -

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3–1 Introduction ................................................................................................... 46

3–2 Densometers ................................................................................................. 46

3–3 Gel Quality Monitoring.................................................................................. 47 3–3.1 “Bad Gel” Decision Process ____________________________________ 47 3–3.2 Mass Balance Process________________________________________ 48 3–3.3 Contingency Plans ___________________________________________ 50

Unplanned Shutdowns ....................................................................................... 51 Planned Pump Rate Unachievable..................................................................... 52 Proppant Concentration...................................................................................... 53 Loss of Automatic Control for Additive Pumps.................................................... 53 Loss of Blender and/or Wellhead Densometer ................................................... 54 “Bad” Gel Samples ............................................................................................. 54 Unachieved Designed Liquid Gel Concentration ................................................ 55 Unacceptable Crosslinker Additive Rate ............................................................ 56 Unacceptable Buffer Additive Rate..................................................................... 56 Unacceptable Surfactant Additive Rate .............................................................. 56 Unacceptable Unencapsulated (Granular or Liquid) Breaker (SP) Additive Rate57 Unacceptable Encapsulated Breaker Additive Rate ........................................... 57

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4–1 BP QA/QC Form and Mass Balance Spreadsheet...................................... 58

4–2 Post-Frac Job Review................................................................................... 58

4–3 Additional Stages.......................................................................................... 58

AAAAAAAAppppppppppppppppeeeeeeeennnnnnnnddddddddiiiiiiiixxxxxxxx........................................................................................................................................................................................................................................................................................................................................................................................................................................................................6666666600000000 Glossary ............................................................................................................. 60 Generic Frac QA/QC Guidelines ........................................................................ 65

BP Onshore Hydraulic Fracturing QA/QC Manual July 2004 - 1 -

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This manual defines and documents the quality assurance/quality control (QA/QC) process for hydraulic fracture stimulations performed in the Onshore U.S. Business Unit. Numerous case studies and examples are included to demonstrate and explain the process in real-world terms. It is hoped that this manual clearly explains each step to the novice and serves as a valuable reference for the more experienced practitioner.


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In late 2000, BP’s Exploration and Production Technology Group (EPTG)—Completions Team became involved in a fracturing fluid R&D project in one of BP’s Lower 48 Business Unit assets. Initial project results were excellent—the wells with the new fluid were outperforming the offset wells fractured with the standard borate-guar fluid systems. However, as the number of wells in the frac-fluid project increased over time, the average initial production significantly declined. Investigation into the details revealed that the screen-out frequency had increased dramatically. Various solutions were discussed and evaluated, and some were attempted but with no improvement. The frac-fluid project was scrapped, and subsequent wells were stimulated with conventional borate-guar fluids. Despite this, the screen-out rate did not return to “acceptable” levels.

What could be the problem? Geology? Probably not. This was not a new development. Some of the screen-outs were in wells with numerous 160-acre offsets. Was the completion technique the problem? Possibly. Engineers are always changing some phase of the program, looking for ways to reduce completion costs. Still, even this could not explain the high screen-out frequency. Was the problem the frac treatment design goals, e.g., length, height, or conductivity? Possibly. But with the majority of frac jobs screening out, it was difficult to say the problem was a design that did not get executed to completion. After a significant amount of evaluation, it was determined that nothing could be resolved until we’d first answered the simple question, “Are we pumping what we think we’re pumping?”

BP then began an intense examination of the job execution phase of fracturing in this field. The process included tests to answer such questions as

Fluids Is the water quality OK? Is it clean? Is the temperature OK? Is the base gel OK? Is it mixed correctly? Are the right additives being added? Is the quality of each OK? Is the gel crosslinking like it should? Is the gel crosslinking when it should? Does the crosslinked fluid look right? Proppants

Is the proppant “right-sized?” Is the proppant quality OK? Is the proppant metered correctly?


Equipment Are the right amounts of water, gel, and additives being added? How much variance in the additive rates is acceptable? Are the additives being added at a rate the equipment can adequately handle? Are the meters properly calibrated? Do the post-job straps confirm the meters? If not, what is being done to correct the error? Is the equipment being used to its full capability? Is the equipment right for the job? Is the equipment maintenance program adequate? Are the frac tanks clean? Personnel

Are the service company personnel sufficiently capable? Are sufficient numbers of personnel on location? Are personnel adequately experienced? Are the key positions staffed appropriately?

And so on.

BP’s QA/QC process philosophy is simple: Pump the job as designed and prove it. To “pump the job as designed” means that only a 5% deviation from job design specifications is permitted. This might seem unreasonably precise. Nonetheless, in areas where the QA/QC process is fully implemented and now second nature, it is not uncommon to see margins of error below 2%. If the fluids, proppant, meters, or pumps are incapable of performing within 5% of design, the job is postponed and the problem fixed. Jobs are not started until the margin of error is 5% or less. No exceptions.

Here’s a hypothetical situation to put it into perspective:

Let’s say you’re the BP representative on a job and it’s 2 p.m. The service company has been trying to get the delay crosslinker additive pump calibrated for over two hours. If the job doesn’t start within the hour, time will run out to pump today. And of course, if the job is delayed until tomorrow, tomorrow’s frac job will be pushed back a day. And so on, leading to a growing backlog of wells to fracture. Delayed production costs money.

The crosslinker additive pump meter is showing a fairly steady rate of between 0.8 and 1.2 gpt (gallons of chemical per 1,000 gallons of fluid). The target is 1.0 gpt. We have a Fann 50 test (viscosity profile) for the design recipe, but no additive


sensitivities have been run. The service company electronics expert is confident he knows what the problem is, but it cannot be repaired in the field—only in the yard, 100 miles away. The service company treater assures everyone the problem will be repaired after they get back to the yard tonight. Besides, if the additive is 20% too low one moment but then 20% too high the next, the average is right on target. The design pump rate is 60 bpm. The blender has a 1-barrel tub.

Do you pump today? For several reasons, the answer is no. Here’s why:

The +/- 20% rate variance doesn’t average out to no error. At 60 bpm, the fluid is in the tub for only one second. That’s not much time for mixing. Are you sure + or – 20%

does not affect fluid quality? Figure I-1 shows a Fann 50 plot of a 30 ppt borate fluid. Look at the effect of increasing the delay crosslinker additive on viscosity. An additional 10% or 15% has little impact. However, when an additional 20% is added, the viscosity drops from about 230 to 125 cp. That’s a 45% loss of viscosity! Are you willing to pump this fluid? Perhaps the most important reason not to pump is to send a message that job

quality is important to BP. Suppose you go ahead and pump and get the job away as planned? Then for whatever reason, the meter isn’t repaired. The same equipment will show up on your location the next day, and guess what? It’s still +/- 20%. Don’t you think you’ll hear, “Hey, we got away with it yesterday! If it was all right yesterday, why not today?” Will you be able to tell the service company that it is not all right to pump today when it was all right yesterday? If anything, you will be lucky if the meter isn’t reading +/- 40%. Problems don’t improve with time.

Our choice is simple. We can have either:

• a frac job pumped as designed with a resulting high-quality fracture but with a 24-hour delay in production, or

• a lower-quality, lower-conductivity fracture, and a possible screen-out, resulting in lower well productivity, but with gas-to-sales one day sooner.

YF130LGD System at 195F - Varying Delay Agent

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Figure I-1. Fann 50 plot of viscosity at different delay agent concentrations vs. time.


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The second half of the BP Fracturing QA/QC philosophy, after the charge to “pump the job as designed,” is to “prove it.” Documentation is a critical component of the learning process. Job performance must be documented properly so we can learn from our mistakes. For example, without proper documentation, an engineer new to a field may review last year’s dismal infill drilling program and determine that the poor performance was due to a poor design. In this example, proper documentation may have revealed that the design was fine but the execution was the problem. So, not only must we do everything we can to “pump the job as designed,” but we must also document the results and pass that information on to our successors so we aren’t continually reworking the same problems.

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You might be asking, “What was the result of the QA/QC program on that screen-out-plagued field?” Figure I-2 shows the improvement made from the first to the third quarter of 2001 in both reducing cost and improving rate. The Asset confirms that these improvements could not be explained by better reservoir completion or some other well completion factor. The consensus was that the 35% improvement in mcfd/$M was due to improved job execution.

BP Frac QA/QC Process 2001 BP Frac QA/QC ProcessNot Inconsequential!!!

2001 Per Well Capex, Gross $k

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BP Frac QA/QC Process 2001 BP Frac QA/QC ProcessNot Inconsequential!!!

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Figure I-2. QA/QC program impact.


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Many of the methods in this manual must be tailored for a specific reservoir. The information here is not meant to be taken to the field and used directly as written. The steps may require extensive testing and reviews by all involved before implementation. However, there are fundamentals or key aspects of this process that will apply wherever BP is fracturing wells. Here are the universal principles, which are by no means comprehensive:

All HSE practices required by the BP Drilling & Well Operations Policy, the Golden Rules, Business Unit and/ or Operating Center and the service company must be adhered to. Any deviation from these will require written dispensation from the appropriate authorities. All additive rates and volumes must be pumped to within 5% of design. All equipment, including additive pumps and the proppant delivery system, must

be verified as being capable of delivering the desired rates and concentrations before being dispatched to location. All equipment to be used in the frac job must be fully operational and functional

prior to beginning the treatment. All pre-job test results of the pumps and flow meters must be within 5% of design

before the treatment commences. Except where noted, all additives must be pumped in the “automatic” mode. All additive flow lines and manifolds should be fully primed prior to taking

beginning job straps to ensure an accurate measurement of additive rates and volumes. Alterations to additive concentrations are not to be based solely on samples

obtained during the treatment. Refer to the Contingency Plan (Sec. 3-2.3) for recommended actions for various additives. Every hydraulic fracturing fluid formulation and breaker schedule must be

supported by Fann 50 test data. Any changes in fluid or product formulation must adhere to the BP Management

of Change (MOC) process. Such changes must be supported by relevant QA/QC tests including Fann 50 test data. BP design engineers must approve any design change not validated by a Fann

50 test before pumping. All additive variance guidelines should be based on data provided by the service

company technology center. All QA/QC test results are to be transferred to the BP QA/QC form by the service

company mass balance person and included in the Final Treatment Report.


The purpose of these procedures is to take job execution out of the job design and evaluation process. The frac design engineer must be able to evaluate performance results of a frac design without wondering whether the job was pumped as designed. These guidelines are to be followed so that we:

Pump the job as designed and prove it.


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The key to a successful frac job is preparation. Every facet of the treatment must be thought out in advance. What could go wrong? What tests can be run to preempt a problem? What tests can be run to help with a decision if a problem crops up in the middle of the job? The best place to perform such fluid tests is in the “non-stressed” environment of the service company laboratory, ideally the day or days before the frac job.

Some of these tests (e.g., chemical additive Fann 50 sensitivity tests) need to be run only once for a given fluid system. BP EPTG Completions has collected and stored examples of these on its website to make them accessible around the world. (http://ewpstim.bpweb.bp.com). These tests should be validated by area with each local mix-water. Chemical lot tests need only be run as often as new lots or batches of chemical additives are used. A gel pilot test, a bacteria test, and a breaker test must be run prior to every frac job.

A set of tests run in the lab can be a great resource to the onsite service company fluid technician.

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A frac job should never be pumped without a fluid test being performed to “replicate” downhole pumping conditions. A Fann 50 machine is the state-of-the-art tool for this purpose. Quite expensive (~$50,000), these are generally, though not always, located in the service company lab. The essential difference in the Fann 50 and Fann 35 (Figure 1-1) is that the Fann 50 tests can be run at downhole pumping conditions of temperature, shear rate, and pressure (1000 psi max.). With a heat cup, a Fann 35 can

Fann 50 Fann 35 F 35Figure 1-1. Fann 50 and Fann 35 machines.


Figure 1– 2. Fann 50 plot of apparent viscosity at temperature vs. time.

somewhat duplicate the bottomhole temperature up to perhaps 200°F, but it can only be run at ambient pressure. A Fann 50 is the best routine test we have to infer the key properties of a fluid at downhole fracturing conditions.

Fann 50 tests on the fluid to be used for the pad stage of the frac job should be run at static reservoir temperature. Because the pad stage significantly cools down the fracture face walls, the slurry stages always see cooler temperatures than the pad. Designing the slurry stages at static temperature is unnecessary. Since the slurry stages see cooler temperatures, they can typically be designed with a less robust (less polymer, fewer crosslinkers, and fewer buffers) and less expensive system. Most fracture simulators are capable of generating a fracture temperature profile for use in fluid and breaker design. For a safety margin, run the Fann 50 tests at the simulator-predicted temperature plus 20°F. The minimum Fann 50 temperature setting should be surface temperature plus 20°F. In the absence of this computer-simulator-generated data, tests for the slurry stages should be run at approximately 75% of static reservoir temperature.

Figure 1-2 is an example of a Fann 50 plot of apparent viscosity at temperature versus time. For this particular fluid, note how viscosity rapidly deteriorated after about 45 minutes. Without additional testing, there would be no way of knowing if this degradation were due to poor gel, too high a breaker loading, or too much or too little crosslinker, and so on. Whatever the reason, this fluid should not be pumped on a job lasting over half an hour. On the other hand, if the total pump time were less than 30 minutes, then perhaps this fluid would be fine.

Shear rate in the fracture is estimated to be between 40 and 100 sec-1, depending on the frac width and pump rate. Normally, shear rate ramps are run to generate n’ and k’ (fluid parameters which describe the fluid and generate the above plot). One shear rate (40 or 100 sec-1) should be selected to approximate fracture shear for frac design. Either rate is acceptable to use, but running the Fann 50 tests at 100 sec-1 is recommended. Tests must be run at the same shear rate for comparisons to be meaningful. Ensure that the service company notes on the plot as to how the test was run. Be consistent so “apples-to-apples” comparisons can be made.


Figure 1– 3. Fann 50 bob and sleeve configurations.

Figure 1– 4. Fann 35 machine, bobs and sleeve.

The bob and sleeve configuration can also affect the results. Fann 50 tests are typically run with an R1B1, R1B5, or R1B5 extended bob configuration (R1 is the sleeve, B1, B2, and B5 are bobs), as shown Figure 1-3. The B5 extended bob is being used more and more because its smaller diameter minimizes the crosslinked fluid “climb-up” on the bob and stem (known as the visco-elastic effect), providing greater test consistency. The R1B5 extended bob is the recommended configuration for Fann 50 crosslinked gel testing. The details of the bob/sleeve configuration should be noted on each test. Brookfield PSV viscometers are being used in many locations and are equivalent in performance to the Fann 50. Other available viscometers should be reviewed prior to use to ensure they comply with API specifications.

For linear gel viscosity measurements with the Fann 35, the R1B1 bob and sleeve configuration is recommended. Examples of bob and sleeve configurations for the Fann 35 are shown in Figure 1-4.


Figure 1– 5. Fann 50 plot of viscosity at different delay agent concentrations vs. time.


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Anytime a change is made to a fluid formulation, a Fann 50 test result must be available to validate those changes. Without these data, a fluid change should not be made. For example, suppose the treating pressure during the early pad stage is higher than anticipated. One of several potential solutions is to add chemical to delay the crosslink time until the fluid crosslinks three-fourths of the way down the tubing (rather than at half way) in order to reduce friction pressure. But would it be safe to assume that increasing this additive X% would have no other consequence on the fluid? If you had the Fann 50 data in the graph in Figure 1-5 available, you would see that adding 10% to 15% crosslink-delay chemical has minimal effect on viscosity but that adding 20% reduces the viscosity to ~40% less than designed. The Fann 50 data is essential to determining the safe range of chemical concentration.

Do not assume that a change in one additive is inconsequential to the abilities of the other chemicals to perform their functions. Since an integral part of the QA/QC effort is to reduce the unknowns and provide documentation for as many decisions as possible, do not rely solely on experience or assumptions.

Fann 50 testing for every fracturing fluid formulation and breaker schedule must be performed and validated before pumping that fluid formulation. Sensitivity tests should be run for every critical additive in the formulation. “Critical additives” are those additives that affect the fluid’s ability to perform as designed. For most jobs these are the crosslinker, crosslink-delay, buffer, and breaker additives. Other additives that enhance other characteristics of the fluid, such as surface tension, do not normally affect the ability of the fluid to create and maintain fracture width and to transport proppant and therefore are not deemed to be “critical.” However, even these non-critical additives should pass through an initial screening to determine the effects, if any, on the fluid system.


Figure 1–6. Test matrix used to test critical additive sensitivity.

Test # Buffer Xler Del Xler1 0% 0% 0%2 0% 15% 0%3 0% -15% 0%4 15% 0% 0%5 15% 15% 0%6 15% -15% 0%7 -15% 0% 0%8 -15% 15% 0%9 -15% -15% 0%10 0% 0% 15%11 0% 15% 15%12 0% -15% 15%13 15% 0% 15%14 15% 15% 15%15 15% -15% 15%16 -15% 0% 15%17 -15% 15% 15%18 -15% -15% 15%19 0% 0% -15%20 0% 15% -15%21 0% -15% -15%22 15% 0% -15%23 15% 15% -15%24 15% -15% -15%25 -15% 0% -15%26 -15% 15% -15%27 -15% -15% -15%

Sensitivity Test Combinations for 3 Critical AdditivesA test matrix like the one in Figure 1-6 should be designed and run to ensure all combinations of additives are tested. Sensitivities of +/-15% should be run for each critical additive.

It might be thought that just varying the concentration of one additive at a time would be sufficient. However, it has been found that this is not always the case. Figure 1-7 shows a suite of Fann 50 tests performed on the same fluid system discussed previously. In the plot shown, two additives were changed by various amounts. The “ideal” formulation is the dark blue curve, averaging about 230 cp. Note that when 20% too little crosslinker is added on top of the 20% excess in the delay agent, the viscosity plummets to virtually nil. So, in this hypothetical case, the Fann 50 test shows what could happen if the delay-crosslink additive was increased by 20% to achieve a longer crosslink time to reduce friction pressure and you inadvertently pumped too little crosslinker. The resultant low fluid viscosity would almost certainly result in a failure. The point is that the tests need to be run to check out all combinations.

Figure 1–7. Fann 50 plot of additive sensitivity tests.

Comparison of Viscosity of 30ppt Delayed BorateSystem at 195F Varying both Crosslinker and Delay Agent

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20% More Delay Agent, 20% Less Crosslinker


Figure 1–8. Example of Section 1 of the BP QA/QC Form.

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Not only must every recipe be validated and documented, but every chemical batch or lot should be tested as well. Do not assume that a chemical from a new lot will perform identically with another lot. A single Fann 50 test will validate that Product X performs as required. Every time a new lot arrives at the service company yard, a validating Fann 50 test must be run and compared to the standard for that fluid. These tests need not be run for every set of well conditions. The service company should set up a standard test for a single, uniform set of conditions. The test temperature should be >150°F to minimize the visco-elastic effect of fluids, which can mask the results at low temperatures. Use of distilled water is preferable as it eliminates differences in waters from affecting the results. The viscosity variance from the standard should be less than 15%.

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The following discussion uses examples from generic QA/QC documents. Specific QA/QC forms and related documents for Halliburton and Schlumberger are provided in the appendices.

Collect and transport water tank samples so the analyses can be performed prior to the frac job in the service company lab. Data should be entered into Section I of the BP QA/QC Form. Ensure samples are not taken from the very first water out of the valve. Figure 1-8 shows an example of Section I.

The acceptable ranges for the water analyses should be developed for each fluid system and provided to the fluid technician by the service company technology center. An example table of acceptable ranges built for the Schlumberger fluids in the Arkoma Basin is shown in Figure 1-9.


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A Pad Lab Pilot Test using actual job chemicals and water should be performed in the service company lab ahead of time. This test provides assurance that all materials to be used in the frac job meet specifications and produce a fluid of the required properties. This test also provides a baseline for the Onsite Pilot Test run immediately prior to the frac job. This pilot test should be documented in Section II of the BP QA/QC Form (Figure 1-10) and the form should be on location on frac job day.

The Pad Lab Pilot Test includes:

Oil Viscosity Calibration. The calibration of the Fann 35 should be verified prior to every job. To calibrate, use a standard “calibration oil” with a viscosity of 25-50 cp (close to base gel viscosity) at 300 rpm with an R1B1 configuration. Measure the temperature of the calibration oil and record it in the cell on the BP QA/QC

6 - 7.5

6 - 8 < 25 ppm

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< 600 ppm

< 1200 ppm

< 40,000 ppm

< 25 ppm < 300 ppm

< 25 ppm

< 25 ppm

< 40,000 ppm< 25 ppm < 1400 ppm

< 1100 ppm < 40,000 ppm

< 25 ppm

< 400 ppm

< 8 ppm

NA< 40,000 ppm

< 1100 ppm< 25 ppm < 1200 ppm

< 4%

< 1200 ppm

< 4% < 1200 ppm

NA

6 - 8 < 20 ppm < 500 ppm < 4%

< 20 ppm

< 8 ppm < 450 ppm

< 25 ppm < 400 ppm

< 25 ppm

NA< 50 ppm

YF600

YF500HT

< 4%

< 1100 ppm< 4%

YF100HTD

YF100LG

YF100EC

YF800LpH 6 - 8

6 - 8

6 - 840 - 100 (4.4 - 37.8 o C)

40 - 100 (4.4 - 37.8 o C)

40 - 100 (4.4 - 37.8 o C)

YF100/D < 1200 ppm < 1100 ppm < 40,000 ppm< 25 ppm < 4%

YF200/D

YF100.1HTD < 1100 ppm

(4.4 - 37.8 o C)40 - 100

(4.4 - 37.8 o C)

< 400 ppm < 4% < 1100 ppm5 - 7

WF200 < 40,000 ppm NA

WF100 < 1100 ppm

< 1200 ppm < 1100 ppm

6 - 8 < 25 ppm < 600 ppm

Not Required

5 - 7

YF400LpH

YF300LpH

YF100ST

6 - 8 NA< 600 ppm < 4% < 1200 ppm

< 20 ppm

< 40,000 ppm < 20 ppm< 25 ppm

< 20 ppm(4.4 - 37.8 o C)

< 1200 ppm

< 25 ppm < 400 ppm < 2% < 250 ppm < 20 ppm

< 4%

Table 1: Base water testing requirements for water based fluids.

YF600UT

< 1100 ppm

< 100 ppm < 20,000 ppm6 - 8PrimeFRAC

6 - 8YF800HT

< 40,000 ppm< 1200 ppm

5 - 7 < 400 ppm

< 1200 ppm

< 1200 ppm

6 - 8

< 4%

6 - 8

6 - 8 < 4%

< 1100 ppm< 4%

< 1100 ppm

40 - 100 (4.4 - 37.8 o C)

< 25 ppm

< 1200 ppm

< 500 ppm < 4% < 1200 ppm

< 600 ppm < 40,000 ppm NA

< 40,000 ppm

< 1100 ppm

NA< 40,000 ppm< 1100 ppm

< 1100 ppm

< 20 ppm

< 40,000 ppm

< 50 ppm < 1100 ppm

NA< 40,000 ppm< 1100 ppm

< 40,000 ppm NA

< 4% < 50 ppm

Silica Content:

NA

Total Salts:

< 40,000 ppm

Mg Content: Calcium Content:

< 4%

NA

(4.4 - 37.8 o C)

Chloride Content:

Temperature (o F) at Time of Hydration:

pH:

< 4%

Recommended*

40 - 100 (4.4 - 37.8 o C)

40 - 100

< 1200 ppm

Iron Content:

BiCARB Content:

(4.4 - 37.8 o C)40 - 100

40 - 100 (4.4 - 37.8 o C)

40 - 100

40 - 100 (4.4 - 37.8 o C)

40 - 100 (4.4 - 37.8 o C)

40 - 100

(4.4 - 37.8 o C)40 - 100

(4.4 - 37.8 o C)40 - 100

40 - 100 (4.4 - 37.8 o C)

50 - 90(10 - 32.2 o C)

< 500 ppm

Required

Figure 1– 9. Table of acceptable ranges for water analyses for Schlumberger fluids.


Form labeled “Actual Oil Temp F.” Measure the viscosity of the calibration oil and record it in the “Actual Oil Visc. @ 300 rpm” cell. Then refer to the calibration oil suppliers’ chart of oil viscosity versus temperature. Record the standard viscosity at actual temperature in the “Standard Oil Visc. @ Actual Temp” cell. The “Visc Corr” cell calculates the difference between the actual viscosity and the standard viscosity. All subsequent Fann 35 readings should be corrected by that value.

Gel Concentrate Sp. Gr. Enter the specific gravity measured by weight. All gel concentrates have a known specific gravity at temperature for a given polymer concentration. Figure 1-11 shows an example of a specific gravity chart for the frac fluid gelling agent LGC-8. Every gelling agent pumped should have a similar chart in the fluid van. Gel Concentrate, ppg. Enter the actual pounds of polymer per gallon of gel

concentrate. The chart shown in Figure 1-11 is used to make adjustments, if necessary, in the amount of gel concentrate to be added to the mix water to prepare the desired polymer loading. The process is detailed more completely in Section 2-2.4. Pad Gel Loading, ppt. Enter the designed polymer loading of the pad. This is

the reference point to be used for comparing measured data to known data for that polymer loading. Water pH. Enter the pH of the mix water being used for the pilot test. A pH meter

with an accuracy range of +/- 0.1 units is required. The meter must be calibrated with standard 4.0, 7.0, 10.0 pH solutions prior to each job or as necessary if the pH is in question at any time. The use of broad range pH paper is not recommended. Linear Gel pH. Enter the pH of the linear gel after initial polymer hydration. Cor. Linear Gel Viscosity, 300 RPM. This refers to the Fann 35 reading at 300

rpm with an R1 rotor (sleeve) and B1 bob configuration with the applied correction, if any, from the Calibration Oil Test. Temperature, °F. Enter the temperature, in degrees Fahrenheit, of the linear gel

to be used for referencing the linear gel viscosity reading.

Figure 1-10. Example of Section II of the BP QA/QC Form.Figure 1-10. Example of Section II of the BP QA/QC Form.


LGC-8 / WG-35 (Guar) Specific Gravity vs. Gel Load

2.00

2.50

3.00

3.50

4.00

4.50

5.00

0.95 0.97 0.99 1.01 1.03 1.05 1.07 1.09 1.11

Specific Gravity (g/ml)

LGC-

8 (lb

/gal

)

Desired Polymer ConcentrationAdjusted LGC-8 concentration =Equivalent Lbs. LGC-8

Figure 1– 11. Specific gravity chart for gelling agent LGC-8.

Figure 1– 12. Fann 35 plot of acceptable viscosity ranges for different polymer loadings.


Equivalent Gel Loading, ppt. Enter the equivalent polymer loading of the linear gel based on Fann 35 viscosity and temperature from the data above. Figure 1-12 is a chart of acceptable viscosity ranges for a specific gel type, generated with an R1B1 configuration. Service companies must provide a chart like this for every gel system to be pumped. Be aware that some charts are generated at 100 rpm. Ensure the 300 rpm reference charts are being used. In the field, simply plot the intersection of the linear gel viscosity reading from the Fann 35 with the temperature of the linear gel. As an example, a Fann 35 reading of 32 cp at 300 rpm at 70°F is shown by the yellow dot. Interpolating between 30 and 35 ppt, this fluid is equivalent to a 33 ppt fluid. This is clearly out of the acceptable range for either 30 or 35 ppt. If the gel concentrate has been added at the designed concentration, then we must determine why the viscosity is out of spec. Refer to Section 2-2.4 for a detailed discussion of the procedure to troubleshoot out-of-spec viscosity. Design loading, ppt. Enter the target or design polymer loading of the pad in

ppt. Crosslink time, seconds. Crosslink time from the Pad Lab Pilot Test is a

relative measurement that reflects the actual crosslink time down the wellbore. Crosslink times can vary significantly depending upon the speed and configuration of the blender. The following recommended procedure achieves consistent results. The photographs in Figure 1-13 demonstrate this procedure. 1) Put 200 ml of gel in a 1000 ml blender jar. 2) With a rheostat, adjust rpm until the nut at the bottom of the blender is

exposed. 3) Add crosslinker. 4) Crosslink time is defined as the point at which the fluid vortex closes and the

static fluid surface covers the nut. Crosslink pH. Enter the final pH of the crosslinked fluid. Bacteria Check. Refer to Section 2-2.4. 15-Minute Breaker Test. This test is optional, depending on the type(s) of

breaker used. Refer to Section 2-2.4.

11––22..66 PPiilloott TTeesstt AAcccceeppttaabbllee VVaarriiaannccee RRaannggeess

For each of the items listed above, an acceptable range (as shown in the example) should be provided in Section II of the BP QA/QC Form. These ranges need to be developed by the service company technology center for each field and reservoir and for each fluid system to be pumped. The ranges should be set such that the downhole performance of any fluid outside any of the ranges will be affected. These data give the onsite fluid technician guidance for acceptable ranges for the fluid.


37 sec Nut still exposed.

38 sec Starting to crosslink; vortex

closing.

45 sec Nut not visible, but fluid is still moving at the surface.

47 sec “Crosslinked.”

0 sec Rheostat, crosslinker, buffer water in graduated cylinder, and blender.

28 sec Low rpm. Nut not visible.

30 sec Rpm higher; vortex formed; nut

visible.

34 sec Add dye and crosslinker.

Figure 1-13. (Continued on next page.)


11 –– 33 PP RR OO PP PP AA NN TT

Unlike fluid or equipment, once the proppant is on location, little can be done to improve its quality. API RP-56 and 60 (Recommended Practices for Testing Sand Used in Hydraulic Fracturing Operations) states that 90% of the proppant should fall between the two designated sieves, i.e. 12/20, 20/40, etc. The API specs do not address the mesh-size distribution within a size range, but there is a direct correlation between mesh-size distribution within a size range and the resulting fracture permeability and conductivity. In general, if the proppant distribution is skewed toward the larger or smaller mesh sizes, the fracture conductivity will be similarly skewed. Skewing the proppant distribution toward the smaller sizes will reduce fracture conductivity, while still meeting API specifications. If the well didn’t respond as expected, then fault might be erroneously placed on the design, fluid, or reservoir quality.

Most suppliers submit their proppants to the Stim-Lab Consortium for API testing, which includes a detailed sieve analysis, fracture permeability, and conductivity tests. The results are recorded in their proppant database. The detailed sieve analysis includes all the intermediate sieves within the size designation to characterize the mesh size distribution. For example, a detailed sieve analysis of 20/40 proppant would include 16, 20, 25, 30, 35, 40 and 50 sieves. The sieve analysis defines the weight percent of the proppant retained on each sieve, as well as the cumulative percent to that point. Each proppant size and type has a signature mesh-size distribution associated with the corresponding permeability and conductivity. Most industry frac design computer programs use fracture permeability and conductivity data from the Stim-Lab proppant database.

Man-made proppants generally have smaller variances in mesh-size distribution than naturally occurring sands like Brady or Jordan (Ottawa). Due to the effect of

130 sec “Lip Test.”


Figure 1- 13. A demonstration of the crosslink time test.


mesh-size distribution on fracture conductivity, BP proppant quality guidelines require that actual mesh-size distribution reasonably match the distribution reported in the Stim-Lab database. These requirements are in addition to the standards as outlined in API RP-56 and 60 and are detailed in Section 1-3.1.

For example, the plot in Figure 1-14 shows the result of a recent proppant sieve analysis from a BP frac job. Note that only 6% of the actual proppant was larger than 30 mesh as compared to 38% (1+10+27%) according to Stim-Lab’s database. Essentially, the job sample was 30/40 sand. The actual sample is within API standards, i.e., 90% of all proppant is between (including) the two designated screens, which in this case, were the 20 and 40 mesh screens. However, Stim-Lab data indicate that this 30-40 sample has 14% less conductivity than the standard.

Figure 1- 14. Proppant sieve analysis from a BP frac job.

Figure 1- 15. Example of Sections VI and VII of the BP QA/QC Form.


Figure 1-15 shows the Pre-Job Proppant Sections from the BP Frac QA/QC Guidelines, which explain the required data and refer to the appropriate entries on the BP QA/QC Form.

11––33..11 PPrree--JJoobb PPrrooppppaanntt QQuuaalliittyy AAssssuurraannccee

All proppants used for BP must meet or exceed API RP-56 standards and need to have been tested by Stim-Lab, which should have performed the tests described in API RP-56 as well as standardized industry fracture permeability and conductivity measurements. If this information is not in the Stim-Lab proppant database, Stim-Lab must supply it to BP directly.

Following are the recommended practices for sampling and testing proppant prior to delivery to location. (The mesh-size distribution requirements are detailed later in this section.)

• Take three samples from a moving steam of proppant for every 20,000 pounds of proppant or from each compartment on a truck bulk transport, per API RPs 56 and 60.

• Combine the samples from each 20,000-pound batch or compartment.

• Conduct a sieve analysis on each combined sample and record the results on the designated QA/QC Forms. The results of these analyses must be on location and must be reviewed with the BP foreman prior to pumping.

• Calculate the “sieve average” of all the truckloads and enter it in Section VII of the BP QA/QC Form in the “Ave. Truck Load Composite” column.

In addition to API minimum standards, it is recommended that a particle size distribution standard also be applied. As described earlier, proppant mesh-size distribution significantly impacts fracture conductivity. To assure adherence to reasonable minimum proppant size distributions, a critical sieve size, and a minimum cumulative weight percent coarser than that critical sieve size are specified in the table below for all common proppant sizes (Figure 1-16). The critical sieve size is analogous to median grain size. For each proppant type and size in the Stim-Lab database, a “standard” cumulative weight percent coarser than the critical screen size can be determined. This defines the coarse: fine skewness of the distribution. The minimum required cumulative weight percent coarser than the critical sieve size is defined as the standard minus 10% (to account for sampling and measurement error).


Figure 1- 16. Proppant guidelines for sieve analyses tied to proppant databases.

For proppants not listed in the above table, the following is the recommended procedure for determining the minimum cumulative weight percent for the critical sieve.

1) The Stim-Lab Database PredictK provides a complete sieve analysis for all the proppants. Extract the sieve distribution for the proppant in question from the database.

2) Calculate the cumulative weight percent coarser than and including the critical sieve size. The critical sieve is 25 for 16/30 proppants, 30 for 20/40 proppants, and 40 for 30/50 proppants.

Proppant Type Supplier Proppant

Size Critical Screen

Size

Minimum Cumulative

%

Ottawa Badger 20/40 30 25

Ottawa Santrol (Wedron) 20/40 30 25

Ottawa Santrol (Wedron) 40/70 - -

Brady Unimen 12/20 18 45 Brady Unimen 16/30 25 80 Brady Unimen 20/40 30 40

Ottawa Unimen 16/30 25 75 Ottawa Unimen 20/40 30 25 Brady Oglebay 12/20 16 45

SAND

Brady Oglebay 20/40 30 40 PR-6000 Borden 20/40 30 65 R

ESIN-

CO

ATED

SAND

SB Excel Borden 20/40 30 40

EconoProp Carbo-Ceramics 20/40 30 50

Carbo-Prop Carbo-Ceramics 20/40 30 30

HSP Carbo-Ceramics 20/40 30 85

VersaProp Norton 20/40 30 70 Bauxite Norton 20/40 30 60

InterProp Norton 20/40 30 60 InterProp Norton 30/50 40 75

CER

AMIC

SinterBall Sintex 20/40 30 70


3) To determine the required minimum cumulative weight percent coarser than the critical sieve, subtract 10 percentage points from the value calculated in Step 2 above. That is, if the cumulative weight percent coarser than the 30 sieve is 35% for 20/40 Unimen, then the required minimum cumulative percent coarser than the 30 screen is 25%.

If the proppant tested is outside the guidelines shown in Figure 1-16, the job should not be pumped until BP and service company engineers are consulted to determine the impact on fracture conductivity. Stim-Lab’s proppant database tool PredictK can be used to estimate this impact. A possible solution could be to increase proppant concentration to compensate for lower proppant permeability.

Results from sieve analyses of any samples that did not follow API RPs 56 and 60 sampling guidelines will be considered estimated data. The sieve data from the individual truckloads will determine the proppants’ acceptability. Unless BP grants specific permission, no load of proppant is to be delivered to a BP location that is outside the guidelines listed in Figure 1-16.

Prior to pumping the frac job, review weight tickets and sieve analyses for each truckload of proppant with the BP foreman. Record the weight and type of proppant for each proppant field bin by compartment in Section VI of the QA/QC Form. In the event it is necessary to split loads in order to fill the proppant field bin, use the first column for the entire field bin. If possible, load a known weighed amount (25,000-50,000 pounds) into at least one compartment in order to perform a densometer check during the initial stages of the job as outlined in Sections 2-4.6 and 3-2.2. For continuous tracking of proppant, it is preferable the exact amount of proppant be known for each compartment. If that is not possible, estimate the amount in each compartment before pumping for monitoring during the job.

For reference, detailed proppant sampling and testing regimens are given in the following API publications:

API RP-56: Recommended Practices for Testing Sand Used in Hydraulic Fracturing.

API RP-58: Recommended Practices for Testing Sand Used in Gravel Packing Operations.

API RP-60: Recommended Practices for Testing High Strength Proppant Used in Hydraulic Fracturing Operations.

Additionally, ISO/WD/13503-2 addresses proppant sampling and testing specifications. The ISO proppant guidelines were developed under the auspices of API. ISO/WD/13503-2 combines the proppant testing specifications and guidelines of the above API documents. Currently the ISO guidelines are in the draft stage and are designated as a working document (WD). They are somewhat more comprehensive and current in scope than the API documents and are an acceptable substitute for API proppant guidelines.


FFFFFFFFRRRRRRRRAAAAAAAACCCCCCCC DDDDDDDDAAAAAAAAYYYYYYYY PPPPPPPPRRRRRRRREEEEEEEE--------FFFFFFFFRRRRRRRRAAAAAAAACCCCCCCC PPPPPPPPRRRRRRRREEEEEEEEPPPPPPPPAAAAAAAARRRRRRRRAAAAAAAATTTTTTTTIIIIIIIIOOOOOOOONNNNNNNN


No job should start without a thorough discussion beforehand of the job design, anticipated rates and pressures, wellsite layout, service company equipment layout, frac tank layout and HSE issues. If time permits, this is best performed on site in advance of frac job day. Additionally, the BP company man, service company field supervisor, service company engineer and service company fluid technician should review the status of the corrective actions identified following the prior job. In case of simultaneous operations, all service companies need to be included.

Typically, the fluid van is the first service company equipment to show up on location, and since it requires minimal setup, it can be ready to go long before any other facet of the operation is ready. Therefore, most of the fluids QA/QC forms and testing should be done first to prevent delaying the frac job.

22––11..11 PPeerrssoonnnneell RReeqquuiirreemmeennttss

Though the following list of qualified personnel is not all-inclusive, these staff are critical to a high degree of onsite quality control.

Experienced treater Experienced fluid technician Experienced electronic technician Experienced field engineer for mass balance control Experienced blender, hydration unit, and chemical add unit operators

22 –– 22 FF LL UU II DD TT EE SS TT II NN GG

The fluid van should arrive on location with the Pad Lab Pilot Test data completed on the BP QA/QC Form. Also, gel concentrate specific gravity and base gel viscosity charts, along with past QA/QC forms, should be available.

22––22..11 EEqquuiippmmeenntt

The following equipment is required for each and every fracturing operation: pH meter (accurate to within 0.1 pH units) plus an extra probe. Narrow range pH (5-8 and 8-12) paper as back-ups for the meter and to provide

an additional calibration of the pH meter. Broad (e.g., 0-14) range pH paper is too insensitive to provide minimum accuracy.


Lab scales (accurate to within 0.01 grams). This method is preferred over a hydrometer for measuring the specific gravity of the gel concentrate. A thermometer or temperature probe. Water bath. Microwave oven. Blender with rheostat. Fann 35 viscometer.

1) R1B1 bob/sleeve for linear gel measurements. 2) B5 bob/sleeve for XL gel breaker test. 3) Heat cup. 4) Enclosed sleeve for crosslinked gels. 5) 25 or 50 cp calibration oil with viscosity vs. temperature calibration chart. Water analysis kits (Cl, Fe, bicarbonates, and sulfates). 250 ml beakers. Graduated cylinders (100, 250, 1000 ml). Syringes (1, 5 and 10 ml). Sand sieves (standard kit plus key screens for specific proppants to be pumped). Stopwatch.

22––22..22 MMaatteerriiaallss

The following materials should be collected and/or available prior to each and every frac job:

Water samples from each frac tank. Samples of additives from the frac lots. Samples of fresh, previously proven, validated additives. These should be from

lots previously validated and confirmed, e.g., a prior frac. These may be needed if a fluid chemistry problem arises. Distilled water.

22––22..33 WWaatteerr AAnnaallyysseess

Completing Section I of the BP QA/QC Form (Figure 2-1) should be the first task. Obtain a composite sample and perform water analysis. Compare composite test results with pre-job individual tank analyses. If a water analysis has not been conducted on each frac tank at this point, one must be completed and the data entered in Section I of the BP QA/QC Form before proceeding.


The acceptable ranges for the water analysis for each fluid system are available from the service company and should be provided to the fluid technician by the service company technology center.

22––22..44 PPaadd PPrree--JJoobb PPiilloott TTeesstt

The gel should not be added to the water in the hydration unit or frac tanks until all QA/QC checks have been made. Dumping gel due to poor quality is an expensive delay and an HSE disposal problem. The Pad Pre-Job Pilot Test is exactly the same test as the Pad Lab Pilot Test discussed in Section 1-2.6. All gel and crosslink fluid test data should be recorded in Section II, as shown in Figure 2-2.

Figure 2- 1. Example of Section I of the BP QA/QC Form.

Figure 2- 2. Example of Section II of the BP QA/QC Form.Figure 2- 2. Example of Section II of the BP QA/QC Form.


The Pad Pre-Job Pilot Test includes:

Oil Viscosity Calibration. The calibration of the Fann 35 should be verified prior to every job. To calibrate, use a standard “calibration oil” with a viscosity of 25-50 cp (close to base gel viscosity) at 300 rpm with an R1B1 configuration. Measure the temperature of the calibration oil and record it in the cell on the BP QA/QC form labeled “Actual Oil Temp F.” Measure the viscosity of the calibration oil and record it in the “Actual Oil Visc. @ 300 rpm” cell. Then refer to the calibration oil suppliers’ chart of oil viscosity versus temperature. Record the standard viscosity at actual temperature in the “Standard Oil Visc. @ Actual Temp” cell. The “Visc Corr” cell calculates the difference between the actual viscosity and the standard viscosity. All subsequent Fann 35 readings should be corrected by that value. Gel Concentrate Sp. Gr. Enter the specific gravity measured by weight. All gel

concentrates have a known specific gravity at temperature for a given polymer concentration. Figure 2-3 is an example of a specific gravity chart for the frac fluid gelling agent LGC-8. Every gelling agent pumped should have a similar chart in the fluid van.

Gel Concentrate, ppg. Enter the actual pounds of polymer per gallon of gel concentrate. 1) Ensure that the gel concentrate storage tanks are adequately mixed. 2) Collect samples from the top of the gel storage tanks to be used. 3) Measure the specific gravity by dividing the weight in grams of a tared 10 ml

syringe of gel concentrate by 10.


2.00

2.50

3.00

3.50

4.00

4.50

5.00

0.95 0.97 0.99 1.01 1.03 1.05 1.07 1.09 1.11


LGC

-8 (l

b/ga

l)



2.00

2.50

3.00

3.50

4.00

4.50

5.00

0.95 0.97 0.99 1.01 1.03 1.05 1.07 1.09 1.11


LGC

-8 (l

b/ga

l)




Figure 2- 3. Specific gravity chart for gelling agent LGC-8.


4) Using a chart similar to Figure 2-3, determine the actual polymer loading. If the loading is different than the Pad Lab Pilot Test, a simple correction in gel concentration can be made to obtain desired polymer loading.

Pad Gel Loading, ppt. Enter the designed polymer loading of the pad. This is the reference point to be used for comparing measured data to known data for that polymer loading. Water pH. Enter the pH of the mix water being used for the pilot test. A pH meter

with an accuracy range of +/- 0.1 units is required. The meter must be calibrated with standard 4.0, 7.0, 10.0 pH solutions prior to each job or as necessary if the pH is in question at any time. The use of broad range pH paper is not recommended.

At this point, hydrate ~1000 mls of linear gel at the pad polymer loading for a minimum of 5 minutes, using a composite water sample from all frac tanks to be used. Separate into Samples 1, 2, and 3. These are to be used for measuring linear gel viscosity and pH, crosslink time, crosslink pH, a bacteria check, and a 15-minute break test.

Linear Gel pH. (Sample 1) Enter the pH of the linear gel after initial polymer hydration. Cor. Linear Gel Viscosity, 300 RPM. (Sample 1) This refers to the Fann 35

reading at 300 rpm with an R1 rotor (sleeve) and B1 bob configuration with the applied correction, if any, from the Calibration Oil Test. Temperature, F. (Sample 1) Enter the temperature, in degrees Fahrenheit, of

the linear gel to be used for referencing the linear gel viscosity reading. Equivalent Gel Loading, ppt. (Sample 1) Enter the equivalent polymer loading

of the linear gel based on Fann 35 viscosity and temperature from the data above. Listed below are some troubleshooting procedures to consider when evaluating the linear gel viscosity. 1) Figure 2-4 is a chart of acceptable viscosity ranges for a specific gel type,

generated with a R1B1 configuration. Service companies must provide such a chart for every gel system to be pumped. Ensure that the chart covers the anticipated fluid temperature range. Be aware that some charts are generated at 100 rpm. Ensure that the 300-rpm reference charts are being used. Plot the intersection of the linear gel viscosity from the Fann 35 and the temperature of the linear gel.

2) Is the viscosity where it should be? For example, three different samples are shown by the yellow, green, and pink circles. All samples are at 70ºF. If the gel concentrate has been added at the designed concentration, then it must be determined why the viscosity is out of spec.

3) If the correct amount of gel concentrate was added, for a 30 pptg fluid, then a viscosity between 26 and 28 cp would be expected (i.e., the green circle).


4) If the viscosity is too low (pink circle) or too high (yellow circle), then something is wrong. Possibilities include: Hydration time was too short. Too little or too much gel was used. The temperature was measured incorrectly. Hydration was interfered with by contamination. Hydration equipment was not functioning properly. Bacteria affected the results.

5) Check the water by repeating the tests with distilled water instead of location water. If the viscosity of this test agrees with the polymer loading, then the problem is with the source water, and it is affecting the system chemistry. Attempt to understand and correct the chemistry problem, or run more tests using separate samples from each of the water tanks. Locate and replace the “bad” water or isolate the bad tank(s).

6) If the problem is not the source water, then it may be the additives. Repeat the tests using the “proven additives” instead of the additives from the totes for the frac job. These tests may locate a bad chemical lot.

Figure 2- 4. Fann 35 plot of acceptable viscosity ranges for different polymer loadings.


0 sec Rheostat, crosslinker, buffer water in

graduated cylinder, and blender.

28 sec Low rpm. Nut not visible.

30 sec Rpm higher; vortex formed; nut

visible.

34 sec Add dye and crosslinker.

37 sec Nut still exposed.

38 sec Starting to crosslink; vortex

closing.

45 sec Nut not visible, but fluid is still moving at the surface.

47 sec “Crosslinked.”

Figure 2-5. (Continued on next page.)


7) If these tests still have not isolated the problem, then “call a timeout” and consult with the service company and the BP engineer.

8) If the equivalent gel loading (Section II of the QA/QC Form) is not the correct loading for the 30 pptg fluid (e.g., the specific gravity of the gel concentrate was too low (or too high) then the expected viscosity will be less than 26 cp (or more than 28 cp). If it is correct, then the gel concentrate may be OK. If the specific gravity is too low, then add more gel concentrate to the hydration unit and then repeat the tests. If, however, the specific gravity is too high, then add less gel concentrate.

9) If these tests still have not isolated the problem, then “call a timeout” and consult with the service company and the BP engineer.

Design loading, ppt. Enter the target or design polymer loading of the pad in ppt. Crosslink time, seconds. (Sample 1) Perform a crosslink test using the

chemical additives per the recipe, taken directly from the additive compartments on location. Add crosslinker, measure pH, and run the vortex closure test. If crosslink is OK, gel the hydration unit. 1) For delayed crosslinking systems, fluid must be crosslinked within 75% of the

time at which fluid enters the perforations.

2) Conduct the crosslink test at ambient temperature plus 10°-15°F to account for heat due to friction.

3) Crosslink time from the Pad Lab Pilot Test is a relative measurement which reflects the actual crosslink time down the wellbore. Crosslink times can vary significantly depending upon the speed and configuration of the blender. The following recommended procedure achieves consistent results. The photographs in Figure 2-5 demonstrate this procedure. Put 200 ml of gel in a 1000 ml blender jar.



Figure 2- 5. Photographs showing a demonstration of crosslink time test.


With a rheostat, adjust rpm until the nut at the bottom of the blender is exposed.

Add crosslinker. Crosslink time is defined as the point at which the fluid vortex closes and

the static fluid surface covers the nut. 4) If the fluid does not appear properly crosslinked (e.g., per the vortex closure

test and the common qualitative fluid appearance, lip performance, and dry hand test) or if the pH is not within range, check the calibration of the pH meter and repeat the test. If the same results occur, use the “proven” additives and repeat the test.

Crosslink pH. Enter the final pH of the crosslinked fluid. Bacteria Check. Perform a bacteria test on gel sample 2 that was set aside

earlier. 1) After one hour, measure the viscosity at 300 rpm and measure the

temperature. If the viscosity has dropped more than 1 cp since the initial measurement, bacteria may be present.

2) Check the viscosity again after another 30 minutes. 3) If the viscosity degrades further, notify the BP field foreman/engineer and

service company treater to immediately stop mixing the hydration unit. 4) Take separate samples from each water tank. 5) Gel and hydrate the samples from each tank separately. Measure and record

the viscosity and temperature. 6) Set the samples aside. 7) After one hour, measure the temperature and measure the viscosity for

degradation on each of the samples. 8) Identify the bacteria-contaminated water tanks and dump and refill or isolate

the tanks. 9) Dump the hydration unit if potentially contaminated. Flush all lines as well as

the hydration unit and blender. Under no circumstances is it permissible to add gel to the hydration unit to account for the bacteria degradation.

15-Minute Breaker Test. The Fann 50 test described in 1-2.1 is performed on the complete fluid recipe, which includes breaker. If there were no issues with time, it would be preferable to run a complete breaker test onsite prior to the job. (This entails mixing a crosslinked gel with the breaker, placing the mixture in a water bath, and then waiting for the fluid to break.) But because time is usually an issue, a simpler test can be performed, as follows: On gel sample 3, perform a linear gel breaker test. This test is designed to verify the breaker (unencapsulated) activity level and is not designed to prove the loading amount


is right for the job. That has already been determined from Fann 50 tests. The service company technology center should have run these tests and built a “standard” breaker chart at 140°F. An example is found in Figure 2-6. The field test procedure is as follows: 1) Pull ~50 ml of breaker from

the tote tank. 2) Measure viscosity and

confirm gel loading at ambient temperature.

3) Pre-heat Fann 35 bob and sleeve to 140°F using the heat cup.

4) Microwave gel to approximately 140°F. 5) Pour heated gel into the heat cup. Record the initial temperature. When the

gel stabilizes at 140°F, add breaker at 5 ppt. This is “time zero.” Note: the 5 ppt breaker loading is independent of the loading for the day’s job. This test is strictly run to confirm the breaker activity level by comparing it to a standardized test.

6) Place the heat cup on the Fann 35 with an R1B1 sleeve/bob configuration. 7) Record viscosity and temperature by minute for 20 minutes. 8) Plot viscosity vs. time on a chart similar to the hypothetical one in Figure 2-6.

A breaker will be deemed acceptable if the viscosity drops below 3 cp within +/- 2 minutes of the 15-minute target. If the fluid breaks too quickly or too slowly, re-run the test to verify results. If the results are the same, ensure the breaker is thoroughly mixed, mix up another batch of breaker and re-test, or adjust the breaker concentration accordingly.

22 –– 33 PP RR OO PP PP AA NN TT TT EE SS TT II NN GG

Proppant testing is critical for validating the correct type, size, and amount of proppant on location for the frac job. The testing procedure is as follows:

Collect proppant samples from each compartment of each proppant field bin. Conduct a sieve analysis on a composite sample. Enter the sieve analysis in the BP QA/QC Form Section VII, “Location Pre-Job Composite.” The primary purpose of this step is to ensure that the correct type and size of proppant is on location. The resulting sieve analysis is only for the purpose verifying that

35 ppt Linear Gel Breaker TestR1B1 Bob on Fann 35 @ 511 sec-1

0

3

6

9

12

15

18

21

24

27

0 5 10 15 20

Time (min)

Visc

osity

(cp)

5 ppt4 ppt6 ppt

35 ppt Linear Gel Breaker TestR1B1 Bob on Fann 35 @ 511 sec-1

0

3

6

9

12

15

18

21

24

27

0 5 10 15 20

Time (min)

Visc

osity

(cp)

5 ppt4 ppt6 ppt

Figure 2-6. Example plot of linear gel breaker test.


the mesh size is correct and is not a binding sieve analysis. The mesh-size distribution criterion is established by the sieve analysis of each truckload. Prior to pumping, the following needs to be reviewed by the BP foreman and

service company treater: 1) Examine the proppant samples from the field bin and refer to the stimulation

procedure to ensure the proppant is the correct type and that the mesh size is correct.

2) Examine the weight tickets to ensure the correct amount of proppant is on location. Additionally, verify the proppant type and weight for each field bin compartment on location.

3) Examine the sieve analysis of each truckload of proppant to ensure all the proppant is within specifications as listed in Section 1-3.1.

4) The BP foreman and service company treater must review the proppant type, size, amount, and mesh-size distribution and verify that it is correct before pumping.

5) Prior to pumping, the BP foreman and service company treater must visually inspect the proppant hopper after it is filled to ensure the proppant is correct.

If 100-mesh is used, do not cycle the gates on the proppant bins until all the 100-mesh is in the hopper. This is to avoid contaminating the 100-mesh with larger proppant that may result in a premature screen-out.

22 –– 44 PP UU MM PP II NN GG AA NN DD MM EE TT EE RR II NN GG VV AA LL II DD AA TT II OO NN

At this point in the QA/QC process, we have validated the fluid and proppant quality. It has also been verified that sufficient quantities of both are on location to meet the job specifications. Next, steps must be taken to ensure the pumping equipment can deliver the additives and fluids in the correct concentrations. It is of critical importance not to pump the treatment unless all equipment is fully operational and functional. This includes the hydration unit, blender, all magnetic flow meters, additive flow meters, dry add screws, sand screws, pumps, and the densometer. If any piece of equipment is only marginally within specifications, do not continue the job until the equipment accuracy is improved. The chances are virtually nil that equipment quality or accuracy will improve over time if problems are ignored.

The service company must thoroughly review the frac design and ensure that all equipment, including additive pumps and the proppant delivery system, is capable of delivering the desired rates and concentrations before dispatching equipment to location. As an example, if required additive rates are below the optimum range of the add pumps, then the additive can be diluted to allow pumping within the optimum range.

The goal of all testing is to be within 5% of the target rate. With the advances in oilfield electronics over the past decade, this is easily achievable with properly


maintained equipment. MicroMotion flowmeters are accurate to less than 1% under typical oilfield operating conditions. Turbine flow meters operate easily within 5% accuracy. A 5% goal is very reasonable and routinely achievable.

22––44..11 EEqquuiippmmeenntt LLaayyoouutt

A typical frac layout for a “gel on the fly” job is shown in Figure 2-7. The service companies may have specialized names for their equipment but the functions are essentially the same across the service companies.

The fluid path for the layout in Figure 2-7 is as follows:

Water is sucked from manifolded water tanks into a hydration unit, where the gel is added and allowed to hydrate. (Schlumberger calls their hydration unit a PCM, Halliburton’s is a Gel Pro, and BJ call theirs a hydration unit.) Here the fluid and gel mix until the gel is fully hydrated. If the pump rate is very high and the fluid residence time in the hydration unit is less than four minutes, gel hydration may

Figure 2- 7. Typical frac layout for a “gel-on-the-fly” job.


be compromised. If this is the case, an additional frac tank may be placed between the hydration unit and the blender to increase residence time. The hydrated gel is transferred to the blender via a suction pump on the blender

or a discharge pump on the hydration unit. The blender may have 1 or 2 tubs. Figure 2-8 is a photo of a BJ single-tub blender. As this transfer takes place, flow meters slaved to either of these two pumps

control the rates at which chemicals are added to the frac fluid. Proppant is added to the fluid in the blender tub by either sand screws or gravity-

fed gated mechanisms. High-pressure pumps send this slurry to the well and downhole.

22––44..22 MMeetteerriinngg

All of the pumps are metered. The three basic types of metering are magnetic, Micro Motion, and turbine flowmeters. If properly maintained and calibrated, the magnetic and Micro Motion flowmeters are routinely accurate to within 1% to 2%. Turbine flowmeters are routinely accurate to within 5% and are much more difficult to maintain than the Micro Motion and magnetic flowmeters, further compromising accuracy. The Micro Motion flowmeter can be used for all additives and is the meter of choice. Magnetic flowmeters can be used for electrically conductive additives and frac fluids. Turbine meters must be used for non-conductive, oil-based frac fluids.

Figure 2-8. BJ Services single-tub blender.


Although some service companies have been slow to adopt the more accurate meters, it is strongly recommended that Micro Motion and magnetic flowmeters be used when possible. Sacrificing metering accuracy limits our ability to accomplish our objective: Pump the job as designed and prove it.

Like any other instrument, metering accuracy is only as good as the maintenance and calibration. In some areas miscalibrated or poorly maintained meters have resulted in high error and job delays. At times there is a temptation to bypass “high technology” and revert back to the less accurate but more familiar turbine flowmeters and tachometers. This is not an acceptable practice.

Note: When performing “bucket tests” and “loop tests” as described in the following sections, any necessary changes required to bring the flowmeters into compliance must be done using a “multiplier” or a change in ppu’s (pulses per unit). The calibration factor (cal factor) specific to each flowmeter must not be changed to achieve accuracy compliance.

The Loop Test The accuracy of the blender and hydration unit flowmeters is validated with a “loop test” prior to gelling the hydration unit. As indicated in Figure 2-9, the blender is connected to the hydration unit to form a closed loop and water is pumped at a constant rate for a fixed amount of time. Unless there is a leak, all meters and counters should display the same rates and volumes. This is a very simple and quick test that only requires connecting a hose from the blender discharge pump back to the hydration unit. The blender and hydration unit tubs are to be by-passed. Rather than tie the test to the specifics of the planned frac job, we recommend a standard test (i.e., 5 minutes at 20 bpm). Therefore, the total time for setup and execution takes only 15-20 minutes.

First, validate the accuracy of the hydration unit suction flowmeter. If this flowmeter is accurate to within 5%, it becomes the control flowmeter for the

loop test. If not, the test cannot be performed until this flowmeter is calibrated. Strap all frac tanks and set the hydration unit suction totalizer to zero. If it has not already been done, we recommend an easily visible mark be placed in the tank to define an exact volume. Isolate one frac tank and load the hydration unit from that single tank with a known volume of fluid. Where approved tank access is allowed, validate the volume by strapping the frac tanks after filling the hydration tank. Alternative methods of estimating tank volumes include using internal floats with external level indicators and hydrostatic gauges. Measure and record the volume of all frac tanks to ensure that no valves leaked during the test. Compare the totalizer reading with

MixingCompartment

(Tub)

Gel

Gel

BlenderTub

S

LoopTestLoopTest

DownholeBlender

BlenderTub

Add Add Add

SD

Figure 2-9. Example of loop test configuration.


the hydration unit fill mark and the measured tank volume. Record data in the “Hydration Unit Fill Test” of Section III of the QA/QC form (Figure 2-10).

After calibrating the flowmeter, begin the loop test:

1) Connect the blender discharge to the hydration unit suction and the hydration unit discharge to the blender suction.

2) Set up a monitor in the frac van to chart all flowmeters with a scale small enough to easily see 2%–5% error. At 20 bpm, the error range would be 0.4–1 bpm. For this test, a scale of 15 to 25 bpm is recommended.

3) Chart the flow rates continuously. 4) Achieve a stabilized rate of 20 bpm. 5) Set all flowmeter totalizers to zero. 6) Pump five minutes at this stabilized rate. At 100 bbls, simultaneously read all

flowmeter totalizers and record this information on the BP QA/QC Form. 7) If at any single point in time, there is more than a 5% difference in rate

between the rates of any two flowmeters, troubleshoot the errant flowmeter and repeat the test. Likewise, the totalizer volumes must be within 5%. Repeat troubleshooting/test cycle until all flowmeters are within 5%.

Note that Table III in the BP QA/QC Form has a space to record a rate (bpm) as well as the final counter volume (bbls) for each flowmeter. No flowmeter should have wild fluctuations during the loop test. Fluctuations of that type are induced by electronic or calibration problems and are not actual rate fluctuations. A few errant spikes are acceptable, assuming the general trend is flat and the totalizer is within 5% of the control flowmeter. An erratic, spiking signature is unacceptable, even if the totalizer is within 5%.

The following example demonstrates why flowmeter calibration and apparent fluid rates are important. Since the add pumps are “slaved directly to” (connected to and un by) a designated clean rate flowmeter, they attempt to follow or track any rate change in the clean rate flowmeter. If the clean rate flowmeter bounces up or down 10 bpm, the add pump would speed up or slow down accordingly to deliver the “right” amount of chemical.

%Var

Rate, bpm Total gallons

Hydration Unit Fill Test

4000 gal Blender / Pre Gel Flowmeter Test ( Loop Test ) Blender

Discharge

Variance =(Max - Min) / Min Max Variance +/- 5%

Pre Gel Passenger

Pre Gel Driver

III % Var.

Tank Strap Pre-Gel Flow Meter

Blender Suction

Figure 2- 10. Example of Section III of the BP QA/QC Form.


The plot in Figure 2-11 shows the hydration unit suction and discharge rates and the blender discharge rate from a recent hydraulic fracture treatment. Note that the hydration unit discharge meter was the designated clean flowmeter for additive control. Clearly the two hydration unit flowmeters are not measuring a steady rate as compared to the blender discharge. Remember, the add pumps are trying to track the hydration unit discharge rate. So, in this case, one moment the add pumps are trying to add the right amount of chemical for 25 bpm and then the next moment they are trying to add the right chemical for 35 bpm. Even if the add pumps could keep up—which they probably could not–the fluid quality would be highly questionable.

In Figure 2-12, note the consistent measurement of each flowmeter. The totalizers range from 100-102 bbls and the rates range from 20.4-21.0 bpm, a variance of ~2%. The only recommendation for improvement here is to expand the scale from 20-25 bpm to 17.5-22.5 bpm (~5 bpm bracket of the target rate) to allow better resolution of the pump rate variance.

Blender Discharge RateHydration Unit Suction RateHydration Unit Discharge Rate

Blender Discharge RateHydration Unit Suction RateHydration Unit Discharge Rate

Figure 2- 11. Example plot of hydration unit and blender suction and discharge rates during a loop test.


Bucket Tests After validating the frac fluid flowmeters, the chemical additive “add” pumps, and flowmeters need to be addressed. With the chemical add system in automatic mode, measure the time it takes to pump a known volume from each add pump into a calibrated container. It’s just that simple: Can the pump deliver a known volume in the right amount of time? This should be within +/- 5% of the target time. These tests are standard operating procedures for all service companies and are not new. The only “new” feature of BP’s QA/QC program is the documentation and testing prior to every job as shown in Section IV of the BP QA/QC Form (Figure 2-13).

Hydration Unit Suction RateHydration Unit Discharge RateBlender Suction RateBlender Discharge Rate


TotalHydration Unit Suction 20.4 100Hydration Unit Discharge 20.4 101Blender Suction 21.0 102Blender Discharge 20.6 100





TotalHydration Unit Suction 20.4 100Hydration Unit Discharge 20.4 101Blender Suction 21.0 102Blender Discharge 20.6 100

Figure 2-12. Example loop test plot showing consistent measurement.

Figure 2-13. Example of Section IV of the BP QA/QC Form.

LA 1 LA 2 LA 3 LA 4 LA 5 LA 6 LA 7 CA 1 CA 2 CA3 LGC Test

g) variance, %

a) chemical

e) actual time, sec f) actual gpm

c) flowmeter d) calc time, sec

b) gpm setting

Bucket Tests

% Variance = (d - e) / d Max Variance +/-5%

IV


Some service companies have a dedicated in-line enclosed “bucket-test” system for each pump, as shown in Figure 2-14.. This allows the chemical additive to be pumped straight back into the tote or storage bin, so that no mixing of chemicals occurs. Additionally, the pumps are in-line and contained, and there is no danger of spill or exposure to personnel. Some service companies have developed enclosed and open systems to conduct the test with water, further limiting spill and exposure risk. These tests can be conducted with a simple “calibrated” portable bucket; however, it is strongly recommended that a closed system be used to minimize safety and environmental risk. The fluid tech must confirm that any combination of chemicals on location will not cause a dangerous reaction. Only necessary personnel should be in the vicinity of the equipment during the bucket tests. Appropriate personal protective equipment (PPEs) must be worn to prevent exposure.

These tests can be customized for a specific service company or location. As an example, for Schlumberger POD blenders, the add pump rate is set to run on automatic at 4 gallons per minute. With a stopwatch in hand, record the amount of time it takes to fill a graduated one-gallon container. With a target of 15 seconds and a 5% margin of error, the acceptable range is 14.25 to 15.75 seconds. It is common for this equipment to perform within 2% of target. Repeat the test for every additive flowmeter, including backups, making adjustments in the flowmeter settings as necessary until they are all within the acceptable range. All test results are recorded in Section IV of the BP QA/QC Form.

Typically, 4-7 chemical additives are used on a given job. If all equipment is in good working order, a bucket test is run only once, taking no more than 2-3 minutes per test. A typical set of bucket tests should take no more than 10 to 20 minutes.

22––44..33 GGeelllliinngg tthhee HHyyddrraattiioonn UUnniitt

After the flowmeters have been properly validated, the treating lines have been successfully pressure tested, and the Pad Pre-job Pilot Test completed, the hydration unit can be gelled. The gel tank must be strapped before and after gelling

Figure 2-14. Example of in-line enclosed bucket-test system.


the hydration unit to validate the gel flowmeter. These straps are to be recorded in Section V of the BP QA/AC Form (Figure 2-15).

Note: Schlumberger’s PCM gel storage tank is a dual-compartment tank built with a non-unique baffle placement (i.e., the tank compartment volumes differ from PCM to PCM). Therefore, each tank compartment must have its own unique strap chart. Using a strap chart that came from a different PCM can lead to gross error.

22––44..44 MMaatteerriiaallss

The final pre-frac step is to ensure that all chemicals are on location as required. After the loop and bucket tests have been completed, all water tanks and chemical totes should be strapped and recorded on the mass balance sheets of the BP QA/QC Form (see Section 3-2.2 and Appendix).

22––44..55 FFrraacc VVaann PPrreeppaarraattiioonn

Work with the service company to develop a standard format for the plots and digital readouts you will need to effectively manage the job, as shown in the example in Figure 2-16. We recommend using both tabular and graphical representations of rates and volumes.

V Beginning Ending Gals Gals

LGC Flowmeter Test (Gelling Hydration Unit)

a) Design, gals LGC b) LGC Tank c) Total, strap gals d) Actual, (strap) used gals e) Totalizer, gals f) Variance, %

% Variance = (f - e) / e

Figure 2-15. Example of Section V of the BP QA/QC Form.


Figure 2-16. Sample formats for plots and digital readouts.


It is critical that the plot scales be properly set to reduce confusion and permit the observer to easily identify variance from the 5% target error band. For example, examine the chart in Figure 2-17.

How do the additive rates look? Now look at the second chart in Figure 2-18. The only difference is the scale.

Figure 2-17. Example chart of additive rates with poor scale.

Figure 2-18. Example chart of additive rates with better scale.


The 5% error bars for the chemicals are shown in corresponding color (i.e., the 5% error bars for the crosslinker are in pink). On this particular job, the top plot was on the service company monitor. Based on this plot, the add rates appeared to be within spec. However, when replotted as shown in the second plot it becomes obvious that a significant variance from targets exists. This illustrates the need for properly scaling the charts showing the additive rates or concentrations to identify variances outside the 5% target.

22––44..66 DDeennssoommeetteerrss

Densometers should be checked in the following way: Calibrate the blender and downstream densometers and ensure that the correct

proppant specific gravity is used for the ppa (pounds of proppant added) calculation. Calibrate both the blender and wellhead densometers. Check to ensure correct fluid and proppant densities are entered. Adjust the ppa zero setting after the treating line is primed.


QQQQQQQQAAAAAAAA////////QQQQQQQQCCCCCCCC DDDDDDDDUUUUUUUURRRRRRRRIIIIIIIINNNNNNNNGGGGGGGG TTTTTTTTHHHHHHHHEEEEEEEE FFFFFFFFRRRRRRRRAAAAAAAACCCCCCCC


Eighty percent of the QA/QC work is done prior to the frac job. However, the remaining 20% is not inconsequential—in fact it may be key to the success of the frac. Key components are:

Densometers Gel quality monitoring Mass balance Treatment contingency plans

Under no circumstances should the frac job be pumped unless all equipment is fully operational and functional. This includes the hydration unit, blender, all frac fluid flow meters, additive flow meters, dry add screws, sand screws, pumps, and the densometer. If any piece of equipment is only marginally within specifications, do not continue the job before resolving the problem. The chances are virtually nil that equipment quality or accuracy will improve over time.

33 –– 22 DD EE NN SS OO MM EE TT EE RR SS

It has been our experience that densometers typically underestimate proppant concentration by ~7%, (i.e., more proppant is going downhole than the meter indicates). This inaccuracy could result in running out of proppant early. However, a procedure can be used to adjust the densometer during the job. A “ppa” correction factor can be determined as follows:

During the pad, verify the densometers are reading correctly. Adjust the calibration if necessary. During set up, place one load of proppant in a single compartment to be

designated as Compartment 1. When the frac job begins, load the belt and hopper from another compartment. Empty Compartment 1 during the first part of the job. When Compartment 1 is empty, compare the sand totalizer to the weight ticket to

verify the accuracy of the densometer. Adjust the densometer to compensate for the error. At the end of the job, compare the blender proppant totalizer to the proppant

weight tickets and inspect each compartment to determine the amount of proppant pumped.


33 –– 33 GG EE LL QQ UU AA LL II TT YY MM OO NN II TT OO RR II NN GG

Throughout the frac job, collect linear and crosslinked gel samples downstream of the hydration unit and blender, respectively, to validate the quality. The only measurements made of the uncrosslinked gel during the frac job are viscosity and temperature. The only tests conducted on the crosslinked sample are pH and a visual “lip” test. These data are recorded in the highlighted area of Section II as shown in Figure 3-1.

The sampling frequency should be a function of the job size and available manpower. Clearly the most important sampling period is during the pad and early proppant stages. During these stages, changes can be made or the job stopped temporarily, or permanently, with potentially minimal impact on the final outcome of the frac job. At a minimum, samples should be collected at the following points during the job:

After the initial displacement of the hydration unit. After ~25% of the pad volume. After ~50% of the pad volume. Prior to beginning the proppant. At least every proppant stage or every 200 bbls, whichever is less.

33––33..11 ““BBaadd GGeell”” DDeecciissiioonn PPrroocceessss

Suppose the job has started and the third crosslink gel sample in the pad appears “bad,” i.e., out of spec per pH or with poor visual gel quality. Do we add more buffer to adjust the pH? Do we add more crosslinker to enhance the crosslink and make the “lip test” look better? No! By job time, we will have run two gel quality control checks (a pad lab pilot test and pad pre-job pilot test) under “calm” conditions. All of the additives, frac fluids, and flow meters have been checked out. Everything has been validated on location and in the lab. Now, during the job, a ”bad” sample pops

Figure 3-1. Example of Section II of the BP QA/QC Form.Figure 3-1. Example of Section II of the BP QA/QC Form.


up. Having systematically gotten this far, we don’t want to overreact. The first step is to collect another sample and repeat the test. More often than not, the apparent problem is due to a bad sample. Perhaps the additives were not thoroughly mixed or the sample was contaminated. If the repeat test gives the same result, refer to the frac treatment contingency plans found in Section 3-2.3 of this manual.

If multiple samples are “bad” and all quality control processes described up to now have been rigorously followed, you have a problem. Do not ignore it! Though this rarely occurs when good QA/QC practices are implemented, it can happen. The quality of the water, additives, gel and equipment have been thoroughly validated, and thus sudden changes in gel quality or appearance would not be expected. If the Fann 50 additive sensitivity tests (as outlined in Section 1-2.2) suggest that additive concentrations can be altered to improve gel quality, then make such changes. However, do not change the fluid design on a hunch. Only make changes based on test data.

33––33..22 MMaassss BBaallaannccee PPrroocceessss

All chemical additives should be strapped after all pre-frac testing (bucket tests, loop tests, etc.) has been completed and the lines have been primed. As with the gel sampling frequency, the number of straps during the job is a function of job size and available manpower. Suggested strapping guidelines are as follows:

Schedule the straps after enough additive has been pumped for you to know that the additive is being measured correctly and pumped in the right amount. If treatment time will be less than 45 minutes, perform one to two straps during

the stimulation treatment. At least one strap should be performed during the pad prior to starting the addition of proppant to ensure all additives are in compliance. If treatment time is greater than 45 minutes, stagger the additive straps to allow

time to record the data and take another strap if the reading appears erroneous or outside the guidelines. If the additive volume/rate is outside the design guidelines, take another strap

immediately. If it is still greater than the design guidelines, do another “bucket test” to verify flow rate. If the “bucket test” verifies the error, correct the flow rate by adjusting the additive concentration by the percentage indicated. If any additive rate is outside the design range, refer to the variance guidelines in the Appendices for the appropriate action.

Straps should be scheduled with stage size and chemical tote size in mind. There needs to be at least a half-inch pumped from any chemical tote to determine an accurate rate. For jobs with small pads, the amounts of chemicals may be too small to accurately measure early on. These strap measurements should be taken, but should be used primarily to determine if the additives are being pumped. As an alternative, the smaller liquid additive tanks on the blenders can be used for low-volume critical additives such as buffers and crosslinkers.


Some chemical containers are so large that straps during each stage may measure less than a half-inch difference. Straps are somewhat inaccurate to start with, and a strap in a large container may have a high percentage of error. Be cautious about making any decisions from these straps. The preferred solution is to have the service company size all chemical totes well in advance of the job with accurate strap measurements in mind.

Strap results should be radioed in to the treater at the planned intervals. The service company engineer in the frac van should record these measurements and make the mass balance calculations immediately so that at all times we know where we are in the job. The additive strap is converted to volume pumped and compared to flowmeter totalizers and to the designed volumes. A sample Mass Balance Form is shown in Figure 3-2 (refer to the Appendix for whole sheet). In this example form, the data is input into the cells shaded in gray. The yellow shaded cells are calculations.

In addition to performing the densometer calibration check described in Section 2-4.6, take additional steps to monitor the proppant during the treatment. It is very important that measures similar to those used with liquid additives and fluid volumes be taken during the job to ensure the proppant is added as designed. If the addition of the proppant is not adequately monitored, you could run out of proppant early, compromising final concentrations and frac job length, both of which affect well performance. At predetermined points during the job, compare the proppant totalizer volume with actual or estimated volumes added from the field bins. If necessary, either adjust the densometer or alter the proppant concentration to compensate for

Volume used before adds started 50 bbls

4493 Final Metered Volume 534.03950 Final % off metered to strap -1.7%543 Final % off strap to design 1.8%

Stage

Fluid Volume

bbls

Metered volume gallons

Remaining volume strap

gallonsConc

gal/1000

Clean Volume gallons

Designed strap

volume gallons

Volume used strap

gallons

Volume used

metered gallons

Design volume gallons

Stage % off metered to

strap

Stage % off strap to design

Cum. Stage % off

metered to strap

Cum. Stage % off strap to

design

200 328 4165 5 8400 4461.5 328 328 31.5 0.0% 941.3% 0.0% 941.3%403 74 4419 5 16926 4418.87 -254 -254 42.63 0.0% 0.0% 0.0% -0.2%602 118 4375 5 25284 4377.08 44 44 41.79 0.0% 5.3% 0.0% 1.8%809 162 4331 5 33978 4333.61 44 44 43.47 0.0% 1.2% 0.0% 1.6%1000 203 4290 5 42000 4293.5 41 41 40.11 0.0% 2.2% 0.0% 1.8%1200 246 4257 5 50400 4251.5 33 43 42 30.3% -21.4% 4.2% -2.3%1401 289 4204 5 58842 4209.29 53 43 42.21 -18.9% 25.6% 0.0% 1.9%1601 332 4161 5 67242 4167.29 43 43 42 0.0% 2.4% 0.0% 1.9%1800 374 4119 5 75600 4125.5 42 42 41.79 0.0% 0.5% 0.0% 1.8%2001 417 4076 5 84042 4083.29 43 43 42.21 0.0% 1.9% 0.0% 1.8%2201 450 4333 5 92442 4041.29 -257 33 42 -112.8% 0.0% 181.3% -64.6%2402 502 3991 5 100884 3999.08 342 52 42.21 -84.8% 710.2% 0.0% 1.6%2590 534 3950 5 108780 3959.6 41 32 39.48 -22.0% 3.9% -1.7% 1.8%

0 3959.6 0 0 0 0.0% 0.0% 0.0% 0.0%0 3959.6 0 0 0 0.0% 0.0% 0.0% 0.0%0 3959.6 0 0 0 0.0% 0.0% 0.0% 0.0%0 3959.6 0 0 0 0.0% 0.0% 0.0% 0.0%0 3959.6 0 0 0 0.0% 0.0% 0.0% 0.0%

Totals 18210 764820 543 534.0 533.4

Starting volumeEnding Volume

Crosslinker J920

Quantity Used

Figure 3-2. Example of the BP QA/QC Mass Balance Form.


the observed variance. If possible, add the proppant from one compartment at a time to make tracking easier. This might not be possible at high proppant rates because the volume required may exceed the delivery capacity of a single compartment. Normally, there is a record of the amount of proppant in each compartment of the field bin, i.e. weight tickets. In pre-job planning consider the feasibility of adding full, pre-weighed loads to each compartment. However if the exact volumes for each compartment are not known, estimate the volumes for comparison during the treatment. The data can be entered and tracked in Section VI of the BP QA/QC Form under Compartments 1-5 as shown in Figure 3-3.

33––33..33 CCoonnttiinnggeennccyy PPllaannss

Planning is the key to success and this includes planning what to do if something goes wrong. The best decisions are seldom made in ”the heat of battle.” A key aspect of the BP QA/QC process is gathering key people (service company treater, fluid technician, engineer, field supervisor, BP frac foreman, and stimulation engineer) in a calm, non-distracting environment to develop detailed contingency plans.

Each unplanned event should be examined in the context of how it could affect well performance, i.e., effective frac length and conductivity. Seldom can the urgency of getting the job pumped overcome the impact of production loss due to a poor fracture stimulation.

Note: The Contingency Plan shown below is a generic plan based on guidelines from a U.S. Lower 48 field. All decision point values and specific criteria for job shutdown, alteration, etc are examples only. Specific contingency plans must be developed for each location.

Figure 3-3. Example of Section VI of the BP QA/QC Form.


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During the pad stage: 1) Refer to the hydraulic fracture simulator output for estimated pad leakoff.

Stimplan, as well as all service company frac models, will estimate fluid leakoff rate at any point in the treatment. This information should be included in all frac procedures. The table in Figure 3-4 shows such data for a typical low permeability sand formation. For a pump rate of 20 bpm, the fluid efficiency is approximately 60% during the pad. That is, about 40%, or 8 bpm, is leaking off to the formation. If the job is shut down for 15 minutes during the pad, about 120 bbls will have leaked off during the shutdown. Therefore, if the job can be restarted with only a 15-minute shutdown, simply continue with the frac, adding 120 bbls, or 5,000 gals, to the remaining pad.

2) If the treatment is shutdown at any point during the pad and adequate materials are on location to make up for the fluid lost during the shutdown, the preferred course of action is to continue the treatment as designed.

3) If adequate materials are not available to make up for the fluid lost during shutdown, consult with the BP and service company engineers to redesign the job based on the available materials on location. If adequate materials are not available to accomplish well objectives, restock and perform the original job at a later date.

4) If fluid efficiency is unknown, and consultation with the BP and service company frac design engineer is not possible, assume that everything pumped has leaked off (0% efficiency). If enough material is on location to do so, start the job over. Otherwise, restock and perform the original job at a later date.

5) If a table like the one in Figure 3-4 is not provided on the frac procedure and less than half of the pad has been pumped, assume that everything pumped has leaked off. If enough material is on location to do so, start the job over.

6) If a table like the one in Figure 3-4 is not provided on the frac procedure and greater than half of the pad has been pumped, then consult with BP and service company engineers to redesign the job based on the available

Figure 3-4. Example of frac simulator output showing estimated leak-off rate.


materials on location. If adequate materials are not available to accomplish well objectives, restock and perform the original job at a later date.

During proppant stages with less than 1/3 of the proppant pumped: 1) In order to determine what pumping schedule modifications need to be made,

consult with BP and service company engineers, re-run the frac simulator and make adjustments accordingly. In the absence of such information, proceed to the next two steps.

2) If the problem can be resolved within 5 minutes, continue the job as designed as long as pressures allow.

3) If the problem cannot be resolved within 5 minutes, then over flush by 200% of cumulative slurry volume. Remedy the problem and start the job over.

During proppant stages with more than 1/3 of the proppant pumped: 1) In order to determine what pumping schedule modifications need to be made,

consult with BP and service company engineers, re-run the frac simulator and make adjustments accordingly. In the absence of such information, proceed to the next two steps.

2) If the problem can be resolved within 10 minutes, continue the job as long as pressures allow. Anticipate a (quick!) wellbore screenout. If this occurs do not attempt to reestablish injection.

3) If the problem cannot be resolved within 10 minutes, there is a high risk that the job will not be pumped to completion. There are two options: Proceed with the job, and be aware of the risk of a screenout and the

potential to leave the pipe full of proppant. Or, immediately go to flush.

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During the pad stage: 1) If the planned rate is unachievable because the treating pressure is too high,

shut down and record ISIP. Consult BP and service company engineers to determine if the problem is caused by underestimated frac gradient, excessive fluid friction, or near wellbore pressure effects. Possible solutions include redesigning the job at a lower pump rate, checking fluid friction pressure against known values, or pumping a high-viscosity gel plug or proppant slug.

2) If the pump rate is not reached because of equipment failure, shut down and remedy the problem. After consultation with BP and service company engineers, and based on fluid efficiency estimates, either start the job over or continue the job with adequate pad fluid replacement volume.

During the proppant stages:


1) If enough fluid and additives are available, extend the stages proportionally to actual versus desired rate. For example, if the actual rate that can be achieved is only 50 bpm and the design rate is 60 bpm, then extend each proppant stage 17% [(60-50)/60 = 0.17]. Also be aware that by extending the planned proppant stages, a screen-out is more likely due to additional leak-off exposure. A consideration might be to reduce the proppant concentrations of the early stages accordingly. If possible, rerun the frac simulator to alter proppant schedule as necessary to achieve desired frac geometry.

2) If there are not enough materials to extend the stages, then continue with the job as designed with a heightened awareness of screenout potential.

3) If there are critical design goals that need to be accomplished (e.g., a final proppant concentration, adding special products to the final stage(s), etc.), it is recommended those be started earlier than designed in the event the well should screenout early. Consult BP and service company engineers to determine appropriate job modifications.

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If equipment problems (blender or proppant field bin) limit the ability to achieve designed proppant concentrations, two choices are available. The pump rate can be reduced to a point where the desired proppant concentration can be maintained, or the job can be continued at a reduced proppant concentration. The former sacrifices length for conductivity and the latter sacrifices conductivity for length. BP and service company engineers should rerun the frac simulator to determine the impact of these changes.

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Definitions: 1) Auto Remote—The treatment van computer controls all additive rates based

on a designated fluid flowmeter. This is the preferred method of additive rate control. If the frac equipment is configured for this capability, do not begin the job until it is fully functional.

2) Auto Local—The blender and hydration unit proportion additives based on a designated clean rate from their own independent flowmeters. The chemical add unit can take a clean rate feed from either the blender or hydration unit. Each device has its own computer, which independently proportions its own additives based on its own clean rate input.

3) Manual Local—An operator manually proportions the additives and controls the additive rates on each additive pump. For every clean rate change, intended or otherwise, this requires determining the appropriate rate for up to eight different chemicals, and manually adjusting each pump to deliver that rate. This is the least preferred method. It should be employed as a last resort


only if the point of no return has been passed in the treatment as defined in the following pumping contingency plans. Automated systems were developed because of the extreme difficulty of manually controlling additives with the required accuracy.

Contingency Plans for Loss of Automatic Control:

1) Before the start of the job—Do not begin the treatment until the problem is resolved.

2) During the pad—Shut down and resolve the problem before continuing. Consult with BP and service company engineers to determine volume replacement to account for fluid loss during shut down.

3) During proppant stages with less than 1/3 of the proppant pumped—Overflush by 200% of cumulative slurry volume. Remedy problem and start over.

4) During proppant stages with more than 1/3 of the proppant pumped—Continue to control additive as closely as possible and complete the treatment as scheduled.

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Be sure to check the calibration of the blender and downstream densometers with clean fluid during the pad, and ensure that the correct proppant specific gravity is used for the ppa calculation. If blender or densometer are lost:

Before the start of the job. Do not begin the treatment until the problem is resolved. During the pad stage. Shut down and resolve the problem before continuing.

Consult with BP and service company engineers to determine volume replacement to account for fluid loss during shut down. During proppant stages with less than 1/3 of the proppant pumped. Overflush by

200% of cumulative slurry volume. Remedy problem and start over. During proppant stages with more than 1/3 of the proppant pumped. Complete

the job using the blender mechanical control mechanism (proppant screw rpm or knife/gate setting).

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If repeated gel samples are unsatisfactory and all quality control processes have been rigorously followed:


Verify that the sampling point is in the dynamic fluid stream. Has the sampling point provided valid samples in the past? If the sampling point is valid, proceed to the next step. Identify the problem. What measurement is off? pH? Crosslink quality? What

appears to be wrong, or put another way, what is causing the bad sample? Check the plumbing to ensure that all additives are rigged up correctly and that

there are no leaks. Check the flowmeter reading in the frac van for the potentially “offending”

additive, e.g., if the pH is correct, then perhaps the crosslinker is not being added as designed. Strap the tank of the potential problem additive. Check the strap against the

mass balance calculations and flowmeter totalizer to this point. Does the strap suggest the correct or incorrect concentrations have been added up to now? If there is no discrepancy then proceed to the next step. Perform another bucket test. If the “bucket test” verifies the error, correct the flow

rate by adjusting the additive concentration by the percentage error indicated. Contingency plans if the problem with the gel samples cannot be resolved after

the above procedure. If the “bad” gel samples occur: 1) During the pad stage—Abort the job, remedy the problem, and start over. 2) During the proppant stages with less than 1/3 of the proppant pumped—Abort

the job and overflush by 200% of cumulative slurry volume. Remedy the problem and start over.

3) During the proppant stages with more than 1/3 of the proppant pumped—Continue to investigate and remedy the problem. Continue the treatment.

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Loss of gel pump:

1) During the pad stage—Abort the job. 2) During the proppant stages with less than 1/3 of the proppant pumped—Abort

the job and over flush by 200% of cumulative slurry volume. 3) During the proppant stages with more than 1/3 of the proppant pumped: If an alternative or backup (centrifugal gel pump) is available, attempt to

complete the job. Or, immediately go to flush.

Low linear gel viscosity. If insufficient hydration or low base gel polymer loading occurs for more than 2 minutes:


1) During the pad stage—If equivalent gel loading falls >10% below target, abort the job, remedy the problem, and start from the beginning.

2) During the proppant stages with less than 1/3 of the proppant pumped—If equivalent gel falls >15% below target, abort the job and over flush by 200% of cumulative slurry volume of base liquid or foam. Remedy the problem and start from beginning.

3) During the proppant stages with more than 1/3 of the proppant pumped—Adjust buffer and cross linker loading according to equivalent gel loading and continue job as scheduled.

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During the pad stage: If additive rate variance exceeds +/- 5%, abort the job, remedy the problem, and start over. During the proppant stages with less than 1/3 of the proppant pumped: If additive

rate variance exceeds +/- 10%, overflush by 200% cumulative slurry volume. Remedy the problem and start over. During the proppant stages with more than 1/3 of the proppant pumped: Maintain

additive rate as close to design as possible and continue treatment. Based on additive sensitivity tests, it may also be necessary to adjust the buffer and delay additive rates accordingly.

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rate variance exceeds +/- 10%, overflush by 200% cumulative slurry volume. Remedy the problem and start over. During the proppant stages with more than 1/3 of the proppant pumped: Maintain

additive rate as close to design as possible and continue treatment. Based on additive sensitivity tests, it may also be necessary to adjust the crosslinker and delay additive rates accordingly.

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rate variance exceeds +/- 25%, overflush by 200% cumulative slurry volume. Remedy the problem and start over.


During the proppant stages with more than 1/3 of the proppant pumped: Maintain additive rate as close to design as possible and continue treatment.

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If additive delivery rate is not within agreed tolerances or fails, continue the job as scheduled. Compensate by:

Increasing the encapsulated breaker by an equivalent loading. Adding granular unencapsulated breaker manually to the tub.

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rate variance exceeds +/- 25%, overflush by 200% cumulative slurry volume. Remedy the problem and start over. During the proppant stages with more than 1/3 of the proppant pumped:

1) If additive rate variance exceeds +/- 25%, terminate automated rate control and add encapsulated breaker manually to tub.

2) If additive delivery mechanism fails, add encapsulated breaker manually to tub and continue.


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After the treatment stage, verify that the BP QA/QC Form and Mass Balance Spreadsheet are completed and are attached to the Treatment Report for inclusion in the well record.

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If no other stages are planned, the job should be reviewed in detail before any of the key personnel leave location. Review BP QA/QC Form, mass balance, and additive rate variances. If the actual rates and volumes pumped are not within 5% of the target, verify data with appropriate personnel. Review the mass balance calculations. Were all the additive rate variances within agreed sensitivity ranges? If not, why not? Were the proppant densometer totalizers and weight tickets within 5%? Develop action plans to ensure compliance with QA/QC targets. Agree on the timing for these actions to take place.

Complete Service Company Job Evaluation Form and the BP GWSI scorecard. Constructively review job performance and service quality. Identify opportunities for improvement and develop action plans to close gaps.

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If other stages are planned for the same day, start another BP QA/QC Form. Perform tests and record data on the form as required below.

If additional water has been delivered, conduct appropriate analyses and record in Section I. Conduct the Pad Pre-job Pilot Test on fluid and record in Section II. Gel the hydration unit and record liquid gel concentrate volumes in Section V. Conduct Pad Pre-job Hydration Tank Pilot Test and record in Section II. Obtain beginning straps on all gel and additives and record on a new Mass

Balance Spreadsheet. Repeat the “Bucket Test” only on additive pumps whose mass balance

calculations were outside the design range in the previous stage. If the blender and/or chemical additive units are powered down between stages, the “Bucket Tests” must be repeated prior to beginning the next stage. Record in Section IV.


Conduct another “Loop Test” if the hydration unit or blender is powered down between stages or there is evidence of any fluid flowmeters being out of compliance. Record in Section III.


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API: … American Petroleum Institute. Sets standards for the petroleum industry in the USA. bpm: … Pump rate in Barrels Per Minute. Break: … Reduce viscosity of a fluid. The desire is to reduce the viscosity to <5-10 cp to aid in fracture clean-up and improved production. Additional breaker can be added to attack the broken polymer and reduce it into smaller components and improved clean-up. Breaker Additive: … An additive used to reduce (break) the viscosity of a fluid. For water-based systems, they are usually persulfates (oxidizers) or enzymes. Brookfield PSV: … A brand of rotational viscometer similar and comparable to the Fann 50. Bucket Test: … Used to verify the calibration of a chemical additive flow meter/pump. The flow meter is set to pump at a pre-determined rate. The volume is then verified with a timed test vs. volume. If the flow meter is out of calibration, adjustments are made to bring it into compliance. Buffer Additive: … An additive used to adjust the pH of a fluid system to optimize stability and/or crosslink time. Centipoise (cp): … A standard unit of viscosity measurement, 0.01 of Poise. Water at standard temperature and pressure has a viscosity of 1.0 cp. Crosslinker Additive: … Most fracture fluids contain a base gallant (polymer) that imparts a viscosity usually in the range of a few centipoises, ~20-50 cp. A crosslinker is an additive that binds the polymer chains together creating viscosities from ~100 cp to several thousand cp. The crosslinked viscosity increases as the base polymer loading increases. Crosslink-Delay Additive: … An additive used to delay the crosslink time of the fracturing fluid to reduce the surface treating pressure and/or minimizes viscosity degradation going down tubing or casing. When most fracturing fluids are crosslinked, they typically have increased friction pressure. Also, some crosslinked fluids (other than Borate Crosslinked Systems) are sensitive to shear degradation, especially in pipe, which may cause permanent degradation of the viscosity.


Dry Hand Test: … When performing the “Lip Test” as described below, touch the fluid to the palm of your hand and retract the fluid. If all that remains on your hand is a moist area (no gel), the gel is considered “Dry”. Encapsulated Breaker: … A coating is placed around breakers, usually oxidizers, to prevent/minimize dissolution while pumping. The encapsulated particle size is similar to that of proppant. The breaker is released when the fracture closes, crushing the encapsulation. This reduces the danger of breaking the fluid prematurely and allows more breaker to be run for better fracture clean-up. EPTG: … Acronym for BP Exploration and Production Technology Group providing assistance to BP worldwide. Frac Conductivity: … A measure of flow capacity of the propped fracture, usually in mDft. It is calculated by multiplying the propped frac width and the permeability of the proppant pack. Propped frac width is commonly expressed in inches or feet. The units of permeability are expressed in millidarcies (mD) or Darcies (D). Fann 50: … A rotational viscometer (bob and sleeve) used to measure (estimate) the rheological performance (viscosity) of high viscosity fracturing fluids at simulated (approximated) conditions in the fracture. It is capable of testing the fracturing fluid at up to 500ºF, 1000 psi pressure, and a shear rate of up to ~1000 sec-1. The stress (shear) exerted on the fluid between the rotating sleeve and bob is an attempt to simulate what the frac fluid experiences moving down the fracture. Fann is the name of the company that manufactures the machine, however, Fann 50 has almost become a generic name for all such machines. Fann 35: … A rotational viscometer (bob and sleeve) used to measure the viscosity of fluids at atmospheric pressure. Typically, it is used to measure the base gel viscosity of uncrosslinked frac fluids. However, in the absence of a Fann 50, it can be used to approximate the viscosity performance of crosslinked frac fluids by using a heat cup that can raise the fluid temperature up to ~200ºF. These rheological measurements are not of the same quality as those from a Fann 50 type machine. Fann 35 is a brand and model name and has almost become a generic name for all such viscometer types. Fluid Efficiency: … The volume of the fracture at the end of pumping divided by the total volume of fluid pumped. During the treatment frac fluid leaks off into the reservoir reducing the amount of frac fluid available to generate the designed/desired frac geometry. It is most commonly used to determine Pad size and prepare the proppant schedule. Flush Volume: … The calculated casing/tubing volume to the top perforation, less a safety factor, that is pumped to displace the last proppant stage.


“Gel on the Fly”: … Refers to hydrating and pumping the fluid as it is pulled from the frac tanks. It is also referred to as “Continuous Mixing”. This is opposed to “Batch Mixing” which is pre-gelling all the frac tanks prior to pumping. GWSI Scorecard: … BP system by which well service contractor performance is tracked and managed. HSE: … An acronym for Health-Safety-Environment. These are the primary concerns to be addressed and considered when performing all operations. ISIP: … Instantaneous Shut-in Pressure. This is the observed surface pressure at the cessation of pumping. Leak-off: … The fluid lost to the formation during pumping. Linear Gel: … Hydrated, uncrosslinked base polymer (gel). Lip Test: … A visual observation of a crosslinked fluid. Place a crosslinked sample in a container. Tip the container allowing the fluid to pass over the edge. A “lip” is observed if the fluid remains intact. Loop Test: … Tests to confirm the calibration of all the fluid flow meters on the blender and hydration unit that control additives rates, proppant, and fluid volumes. A closed loop is created which includes all related fluid flow meters. A circulation rate is established. Once the rates are stabilized, a pre-determined volume is circulated. At the end, all flow meter rates and volume totals are compared. To be satisfactory, they must agree within 5%. Overflush: … The amount of fluid over the calculated casing/tubing volume to the top perforation that is pumped to displace the last proppant stage deep into the generated fracture in the event of a fluid or equipment problem early in the job. ISO: … International Standards Organization. Pad Stage: … The initial, non-proppant laden, fluid portion of the frac treatment pumped ahead of the proppant-laden stages. The main purposes of this fluid are to open the frac wide enough to accept proppant and generate the desired frac length. Pad Lab Pilot Test: … Pilot tests (pH, viscosity, crosslink time, etc) conducted in the service company lab facility (district and/or regional) on the Pad fluid formulation using the actual job fluid and additives. This is to serve as a reference for comparison with similar tests to be conducted on location the day of the job. Pad Pre-Job Pilot Test: … Duplicate tests of the “Pad Lab Pilot Test” conducted on location with actual job chemicals and fluid.


Personal Protective Equipment (PPE): … Personal Protective Equipment; safety glasses with side shields, hard toed boots, hard hat, hearing protection, gloves, etc. ppa: … Denotes “Pounds of Proppant Added” to a gallon of fluid. It is commonly used interchangeably with “ppg” (pounds of proppant per gallon of slurry), which is technically incorrect. It is necessary to make sure the terms are defined prior to starting the treatment. ppg: … Most accurately, it is the pounds of proppant in a gallon of slurry, as opposed to ppa, pounds of proppant added to a gallon of fluid. However, it is commonly used interchangeably with “ppa.” Care should be taken to ensure the terms are defined prior to starting the treatment. ppt: … Denotes pounds of material per 1000 gallons. Screen-out: … The slurry (proppant laden fluid) dehydrates, due to leak-off, as it travels down the fracture. This dehydration concentrates the proppant in the slurry. The concentration can become so great that the slurry is no longer pumpable, or a proppant bridge is created in the fracture. Both conditions cause the fracturing pressure to increase. Screen-out occurs when the maximum surface treating pressure is reached and pumping is ceased. This can occur very rapidly within a few seconds or over several minutes. Shear Rate: … A value calculated as the velocity difference between two planes (rotational speed between bob/sleeve, frac faces, etc) divided by the distance between the two planes (gap between the bob/sleeve, frac faces, etc.). It is usually expressed in reciprocal seconds, sec-1 or 1/seconds. In viscometers, each bob and sleeve configuration (gap width) has a multiplier to convert rpm to shear rate. Sieve Analysis: … To determine the mesh size distribution of a proppant sample, pass the sample of proppant through a prescribed series of sieves (screens). The amount of proppant retained on each screen is used to calculate the % distribution. “Slaved Pumps”: … Most additives are based on clean volumes (no proppant). It is impossible to control all the additives manually during the job. So, the additive pump/flow meter rates are tied to (slaved) to a designated clean flow meter rate, usually the blender suction flow meter. Slurry Stage: … The proppant-laden portion of the frac treatment. Straps: … The physical volume measurement of chemicals/products in containers. This is done at the beginning, during and at the end of the job to track the volume of additives used.


Visco-Elastic Effect: … Fluids that exhibit properties of a fluid and a solid. Manifested in the cohesive properties of a crosslinked fluid that hold it together when trying to pour it out of a beaker (“lip”), or when the fluid climbs the spindle of a rotational viscometer.


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Note: It is intended that this document and all procedures contained within be customized for each specific fluid & proppant used in each field, and for each service company, using local & specific terminology for all equipment, products, and services. This will increase field ownership of the guidelines and avoid confusion during the course of a treatment. Throughout this document, generic placeholder names for field-specific, service company-specific, or trade name-specific products, equipment, and services are identified by underlined italicized type. All such occurrences should be replaced by the correct names. TABLE OF CONTENTS 1. General Guidelines and Principles 2. Pre-Job Preparation

2.1. Fluid Testing 2.2. Proppant Testing

3. Day of Job - Prior to Treatment 3.1. Fluid Testing 3.2. Proppant Testing

4. During the Treatment 4.1. Fluid Monitoring 4.2. Proppant Monitoring

5. After the Treatment/Stage 6. Additional Stages/Wells Conducted on Same Day Appendix 1. Service company fluid name Pumping Contingency Plans Attachments 1. Fluid & Proppant Quality & Metering QC Form for fluid name #1 2. Fluid Mass Balance Form 3. Proppant Quality Control Form for proppant size mesh proppant type 4. Specific Gravity vs. Polymer Concentration Chart for gelling agent name 5. Base Gel Hydration Chart for gelling agent name 1. GENERAL GUIDELINES AND PRINCIPLES: These guidelines are specific to the field name field. Notice must be given to all impacted BP and service company personnel before any alterations are made to these guidelines. These guidelines should be readily available in the treatment van during all fracture stimulations. 1.1. No visible leaks are permitted anywhere in the treating line, pumps, or wellhead

before pumping. The only permissible leak while pumping is a drip through a


chicsan "weep hole". If the drip becomes a continuous stream, pumping must be terminated immediately if it cannot be isolated.

1.2. No more than ¼ " mushroom on any hammer union wing (frac iron or suction/discharge hose connections) is allowed. Any iron with loose metal burrs or splitting mushrooms will not be used and should be ground off at the service company district shop as soon as possible.

1.3. Before implementation of any change to the procedures or products listed in these guidelines or appendices, the proposed change must be reviewed and approved through the BP MOC (Management of Change) process.

1.4. The gel hydration unit and blender must be fully operational and functional prior to beginning the treatment. This is to include all turbine flow meters, magnetic flow meters, additive flow meters, pumps, and densometers.

1.5. All additives must be added in the automatic mode. 1.6. All equipment, including additive pumps and proppant delivery system, must be

capable of accurately delivering the desired rates and concentrations before dispatching equipment to location.

1.7. All additive rates and volumes are to be pumped within +/- 5% of the design rate. The accuracy of all additive pumps and meters must be proved on location, prior to the job, to within +/- 5% of the required design rate.

1.8. In order to obtain a more accurate measurement of stage additive rates and volumes, all additive flow lines and manifolds are to be fully primed prior to taking beginning job chemical straps.

1.9. Each hydraulic fracturing fluid formulation and breaker schedule must be supported by Fann 50 (or similar cuette type viscometer) test data. All tests are to be conducted using a B5 Extended Bob at a constant shear rate of 100 sec-l. The data is to be presented at 100 sec-1. BP and service company design engineers must approve any changes to the design not validated by Fann 50 tests.

1.10. The additive variance guidelines given in the appendices, "Pumping Contingency Plans" are based on fluid testing results presented by service company labs located in location name, dated effective date.

1.11. If samples obtained during the treatment appear "bad", do not immediately change additive concentrations in an attempt to correct the fluid properties. First take another sample, and then follow the contingency plan in Appendix 1 Section 4.

1.12. Refer to the Appendix and Attachments for the pumping contingency plans for the specific fluid systems data, and the applicable QA/QC Forms and Mass Balance Spreadsheets.

1.13. All data gathered during this QA/QC process is to be transferred to the BP QA/QC form by the service company mass balance technician, and is to be included in the Final Treatment Report.

The purpose of these procedures is to take job execution out of the job evaluation process. The frac design engineers must be able to evaluate performance results of a frac design without worrying about whether the job was pumped as designed. Following these guidelines ensures that we "Pump the Job as Designed and Prove It."


2. PRE-JOB PREPARATION 2.1. Fluid Testing

a. All fluid formulations require Fann 50 tests using materials from the same production lots to be used in the frac treatment. These tests should be repeated every time a different chemical or a new production lot is used.

b. If possible, water analysis and fluid pilot tests are to be completed prior to the day of treatment and recorded in BP QA/QC Form Sections I and II. The pilot test data can be from the district lab or from previous treatments using the same chemical production lots.

c. Base gel viscosity, base gel pH, crosslink stability, crosslink pH, and crosslink time tests are to be conducted on each tank or on a composite water sample, per stage or per job as appropriate. Additionally, the gel concentrate specific gravity and polymer concentration must also be recorded.

d. When obtaining water samples from frac tanks, all BP and OSHA guidelines must be strictly followed regarding working at heights and avoiding spills. Working within those guidelines, make every effort to collect representative water samples from each frac tank.

e. Documentation of pre-job test results conducted by the service company district lab are to be on location and appropriately recorded in BP QA/QC Form Sections I and II in the "Pad Lab Pilot" Column.

2.2. Proppant Testing a. Weight tickets for each truckload of proppant are to be reviewed with and

provided to the BP onsite supervisor prior to the treatment. b. Record the weight and type of proppant in each proppant field bin, by

compartment, in Section VI of the QA/QC Form. In the event it is necessary to split loads in order to fill the proppant field bin, use the first column for the entire field bin. If possible, load a known weighed amount (25,000-50,000 pounds) into at least one compartment in order to perform a densometer check during the initial stages of the job as outlined in Section 4.2 of these guidelines. If possible, continuously track the proppant remaining in the field bin to know exactly the amount in each compartment. If that is not possible, estimate the amount in each compartment before pumping for monitoring during the job In the event it is necessary to split loads in order to fill the proppant field bin, then use the first column for the entire field bin.

c. All proppants used for BP must meet or exceed the standards as described in API RP 56 and 60, ISO/WD/l3503-2 , and in Section 2.2g below. The ISO guidelines also address proppant sampling and testing specifications to be used on BP jobs.

d. Every proppant supplier must submit their product to be tested by StimLab or FracTech. The tests are to include those described in API RP 56 as well as standardized industry fracture permeability and conductivity measurements. If a proppant to be pumped is not in the StimLab


Proppant Database, the information must be supplied directly to BP for approval prior to use.

e. Each load of proppant delivered to location must have the following sieve analysis performed, prior to delivery to location. The mesh size distribution requirements are detailed later in this section. - Take three samples from a moving stream of proppant for every

20,000 pounds of proppant, or for each compartment on a truck bulk transport, whichever is greater.

- Combine the samples from each 20,000-pound batch or compartment.

- Conduct a sieve analysis on each combined sample and record the results on the designated Proppant QA/QC Forms. The results of these analyses must be available on location and must be reviewed with the BP Foreman prior to pumping.

- Calculate the "sieve average" of all truckloads, and enter it in Section VII of the BP QA/QC Form in the "Ave. Truck Load Composite" column

f. All proppant sieve analysis are to include the following sieve series: 16, 20, 25, 30,35, 40, 50, and Pan.

g. All 20/40 mesh proppant must meet the following minimum required total weight percent for proppant coarser than the 30 mesh critical screen: - 20/40 Versaprop: >70% - 20/40 PR 6000: >65% - 20/40 EconoProp: >50% - 20/40 Unimen (Northern White) Sand: >25% - (Other proppant types and minimum required total weight percent

coarser than the critical sieve can be found in Section 1-3.1 of the QA/QC Manual)

h. No load of proppant is to be delivered to a BP location that is outside the above listed guidelines unless BP grants specific permission.

i. Results from the sieve analysis of samples collected on location, or elsewhere, that do not follow API & ISO sampling guidelines will be considered estimated data. The sieve data from the individual truckloads determined in Section 2.2e. will determine the proppants' acceptability.

3. DAY OF JOB - PRIOR TO TREATMENT: 3.1. Fluid Testing

a. Water analyses must be completed on all water in every tank prior to the job, before beginning fluid preparation.

b. Conduct on location pre-job pilot test using on-site chemicals and composite water sample from tanks to be used for that stage or job. To ensure a representative water sample is taken, be sure to flush the valves before catching a sample or take the samples from the top of the tanks provided the proper safety and environmental precautions are taken as to spills and working at heights. If anything other than fresh water is in the


frac tanks, care must be taken not to spill any on the ground during sampling.

c. BP QA/QC Form Section I: Perform and record water analysis as listed in Section I, if not conducted in the district lab prior to the job.

d. BP QA/QC Form Section II "Pad Pre-Job Pilot": The calibration of the Fann 35 should be verified prior to every job. Use standard "Calibration Oil" with a viscosity of 25-50 cp (close to base gel viscosity) at 300 RPM with an RIB1 configuration. Measure the temperature of the calibration oil and record it in the cell labeled "Actual Oil Temp F." Measure the viscosity of the calibration oil and record it in the "Actual Oil Visc. @ 300 rpm" cell. Then refer to the calibration oil suppliers' chart of oil viscosity versus temperature. Record the Standard Viscosity at Actual Temperature in the "Standard Oil Visc. @ 300 rpm @ Actual Temp" cell. The "Visc Corr" cell calculates the difference between the "Actual Viscosity" and the "Standard Viscosity." All subsequent Fann 35 readings should be corrected by that value. Measure and record slurry gel concentrate specific gravity, slurry gel polymer concentration based on specific gravity (refer to appropriate LGC Specific Gravity vs. Polymer Concentration Chart), base gel viscosity, (refer to appropriate Polymer (LGC) Loading vs. Temperature vs. Linear Gel Viscosity chart), base gel pH, final crosslink pH, crosslink stability, and crosslink time tested on composite water sample. If composite sample tests are out of compliance, test each tank as necessary to identify the source of the water problem.

e. Bacteria Test Section II.l & II.m: As noted above, the initial linear gel viscosity and temperature have been recorded in Sections II.f and II.g. After one-two hours, measure and record the viscosity and temperature of the sample in Sections II.l and II.m. Compare to the results to the initial reading. Less than 2 cp reduction in viscosity is acceptable. A loss in viscosity of 2 cp or more usually indicates bacterial degradation. Re-run the test on each frac tank to determine the extent of the contamination. Do not use any contaminated tanks. If the tanks have bacteria, the problem cannot be remedied by simply adding more gel.

f. After the hydration unit has been gelled take another sample and repeat the test as in the "Pad Pre-Job Pilot" and record in Section II "Pad Pre-Job Hyd. Tank Pilot".

g. Zero the Pre-Gel Blender Driver Suction Totalizer prior to filling. Fill the Pre-Gel Blender to the 3,000 gallon (70 bbl) mark and record volume in BP QA/QC Form Section III "Fill Test". Record and compare the Pre Gel Blender suction flow meter totalizer reading to the known 3000-gallon Pre-Gel Blender volume and/or with volume from the frac tank. Be sure to account for Pre-Gel Blender suction manifold plumbing. No more than 5% error is permitted. This flow meter now becomes the anchor flow meter to calibrate the other flowmeters to during the Loop Test.

h. Conduct Loop Test of all four TFM's (Turbine Flow Meters) and record results in the BP QA/QC Form Section III. Be sure to simultaneously zero all totalizers after desired rate is attained. Conduct test at a minimum rate


of 20 BPM (or actual rate if possible), for at least 5 minutes (100 bbls). Record BPM and totals for each TFM. No more than 5% variance is acceptable: Variance = 100 X (Max rate - Min rate)/Min Rate. Each loop test is to be charted and results recorded on BP QA/QC Form and included in the Final Treatment Report.

i. Conduct additive flow meter test on each Pre-Gel Blender and Downhole Blender additive pump to be used, including back-ups. Record the results on BP QA/QC Form, Section IV. No more than 5% error is acceptable.

j. The Downhole Blender Suction TFM is the designated clean rate for proportioning all additive rates.

k. Witness and record the beginning and ending straps of all the additives for each treatment. Record the information on BP Mass Balance Sheet.

l. Conduct Pre-Gel Blender/Hydration Tank Fill Test: BP QA/QC Form Section V. Verify gel flow meter as follows: - Record beginning strap of slurry gel. - Zero slurry gel totalizer. - Add prescribed amount of slurry gel to gel the hydration tank - Re-strap slurry gel and compare to slurry gel totalizer. NOTE: Since the amount of gelling agent is small relative to the size of the

gel compartment, a strap error of +/-10% is acceptable. 3.2. Proppant Testing:

a. Collect proppant samples from each compartment of each proppant field bin. Combine the samples and conduct a sieve analysis on a composite sample. Enter the sieve analysis in BP QA/QC Form Section VII. "Location Pre-Job Composite". This sieve analysis only verifies that the correct type and mesh size of the proppant is on location. The mesh size distribution criterion is established by the sieve analysis of each truckload as described above in Section 2.2.

b. Prior to pumping, the BP Foreman and service company treater should review the following proppant quality criteria: - Visually inspect the proppant hopper after it is filled to ensure the

proppant is of the correct type. - Examine the proppant samples from the field bin and check

against the stimulation procedure to ensure the proppant is of the correct type and size.

- Examine the weight tickets to ensure the correct amount of proppant is on location.

- Examine the pre-job sieve analysis of each truckload of proppant to ensure all proppant is within specifications as listed above in Section 2.2.

c. If 100 mesh sand is to pumped in the pad, do not cycle the gates on the proppant bins until all the 100 mesh is in the hopper. This avoids contaminating the 100 mesh with larger proppant, which could cause a premature screen-out.


4. DURING THE TREATMENT 4.1. Fluid Monitoring

a. Provide real time monitoring of all additives and proppant. First preference is to display additives in concentration. If this is not possible, then display the additives in rates. On the additive plot, scale each additive concentration or rate such that +/-5% variance is easily detectable.

b. Conduct and record additive mass balance for each of the fluid systems on the appropriate Mass Balance Spreadsheet.

c. Guidelines for strapping tanks and chemical totes: - Since many jobs are small, the amount of chemical pumped may

be too small to accurately measure early in the job. These strap measurements should be taken, but primarily used to determine if the additives are being pumped. At least 3-4 gallons (0.25-0.50 inches) must have been pumped from the large chemical totes to determine an accurate volume & rate. For small jobs, the critical additives, buffers and cross linkers should be placed in the smaller liquid additive tanks on the blender or in small totes.

- Schedule the timing of the straps so that a sufficient volume of the additive has been pumped to provide accurate measurement is so that good decisions can be made regarding material balance and rate variance throughout the job.

- If treatment time is less than 45 minutes, perform 1-2 straps during the job. At least 1 strap should be performed during the pad to ensure that all additives are in compliance, prior to starting the proppant.

- If treatment time is greater than 45 minutes, stagger the additive straps to allow time to record the data and take another strap if the reading appears erroneous or outside the guidelines.

- If the additive volume/rate is outside the design guidelines, take another strap immediately. If it is still outside the design guidelines, do another "bucket test" to verify the flow rate. If the "bucket test" verifies the error, correct the flow rate by adjusting the additive concentration by the percentage indicated. If any additive rate is not within +/-5% of the design range, refer to the variance guidelines in Appendix 1 for the appropriate action.

4.2. Proppant Monitoring

a. Check the Downhole Blender and Wellhead Densometer against a known pumped volume of proppant. Record in BP QA/QC Section VI. If possible, put one load of proppant in a single compartment and empty it during the first part of the job. Initially, load the belt and hopper from another compartment. When the compartment is empty, compare the sand totalizer to the weight ticket to verify the accuracy of the densometer. Adjust the densometer if necessary or compensate for the % error by


increasing or decreasing the "proppant multiplier" to correct the proppant concentration.

b. As per API RP 56, catch one (1) sample midway through each compartment. Conduct a sieve analysis on a composite sample and record sieve results in Section VII. POST-JOB COMPOSITE. As before, the results of the sieve analysis should be viewed only as a confirmation of the proppant type and mesh size.

5. AFTER THE TREATMENT/STAGE 5.1. Calculate mass balance of all additives. Record on BP Mass Balance Form and

include in the Final Treatment Report. 5.2. Compare the blender proppant totalizer to the proppant weight tickets for

accuracy. Conduct an inspection of each field bin compartment to determine the amount of proppant remaining in the bins. If pumping additional stages on the same well, adjust the densometer by the appropriate % error to bring it into compliance with the weight tickets.

5.3. Complete the BP QA/QC Form and enter it into service company computer. Include the QA/QC Form in the Final Treatment Report.

5.4. Note any additive volumes/rates outside design range (per sensitivity tests) and take corrective action to bring into compliance. Corrective action should be noted on the Job Evaluation Form or listed as an action item for follow-up before next stage or job.

6. ADDITIONAL STAGES/WELLS CONDUCTED ON SAME DAY 6.1. Start another BP QA/QC Form. Only record data as required below. 6.2. Conduct pilot test on fluid after gelling Pre-Gel Blender/Hydration Tank and

record in Sections I and II. If additional water has been delivered, conduct appropriate water analysis and record in Section I of the BP QA/QC Form.

6.3. Obtain beginning additive straps on all chemicals. 6.4. Only repeat the "Bucket Test" on additive pumps that are outside the acceptable

variance range of 5%. Record in Section IV. 6.5. If the Pre-Gel Blender and/or Downhole Blender are powered down between

stages, or there is evidence that any of the TFM's were out of compliance by more than 5%, conduct "Bucket Tests" and "Loop Test" before beginning the next stage or job. Record in Sections III and IV.


APPENDIX 1: Service Company Fluid Name Pumping Contingency Plans Fluid Name Additive System: Product Trade Name Additive Function/Description product name Gelling agent product name Crosslinker product name pH buffer product name Surfactant product name Catalyst product name Un-encapsulated Breaker product name Encapsulated breaker product name Biocide product name KCI substitute product name Other additives as appropriate Contingency Plans For Additive and/or Proppant Delivery Problems Critical proppant volumes and rate accuracy percentage "set points" for decisions (e.g. "1/3 of proppant pumped" or "+/- 10%") should be customized for each specific field, service company, and fluid system. The following contingency plans are offered as a starting point for the development of field-specific contingency plans. 1. Unplanned shutdowns 1.1. During the Pad:

a. Refer to the hydraulic fracture simulator output for estimated pad leak-off rate. Multiply the estimated downtime by the predicted fluid loss rate at that point in the frac schedule, and pump that much extra fluid once the job commences again. If sufficient extra fluid is not available on location, stay shut down until fluids can be replenished, and start the job over. Be sure to perform all QA/QC tests on the new fluid delivered to location before starting to pump again.

b. If the pad leak-off rate is not available, and less than half of the pad has been pumped, assume half of the pad pumped thus far has leaked off, add this volume to the remaining pad, and continue the job as designed when ready.

c. If the pad leak-off rate is not available, and greater than half of the pad has been pumped, remain shut down. Redesign the job based on the available materials on location with the first priority being that the new design will not be significantly different that the original design. Do not reduce the Pad Volume by more than 20% from the original design without consulting the BP/service company frac design engineers. If adequate materials are not available to do this then restock and perform the original job at a later date.


1.2. During proppant with less than 1/3 of the proppant pumped: a. In order to determine what pumping schedule modifications need to be

made, re-run frac simulator and make adjustments accordingly. In the absence of such information, use the following guidelines: - If the problem can be resolved within 5 minutes, continue the job

as designed as long as pressures allow. - If the problem cannot be resolved within 5 minutes, then over flush

by 200% of cumulative slurry volume of base liquid or foam. Remedy the problem and start the job over.

1.3. During proppant with more than 1/3 of the proppant pumped: a. In order to determine what pumping schedule modifications need to be

made, re-run the frac simulator and make adjustments accordingly. In the absence of such information, the following guidelines are to be followed.

b. If the problem can be resolved within 10 minutes, continue the job as long as pressures allow. Anticipate a wellbore (quick!) screenout. If the job screens out, shut down. Do not reduce rate to continue pumping while trying to squeeze more proppant in.

c. If the problem cannot be resolved within 10 minutes, the job will likely be difficult to finish. Two options exist: - If the possibility of leaving the pipe full of proppant is an acceptable

outcome, proceed with the job, expecting a wellbore screenout. - If a screenout is not acceptable, immediately go to flush. If ±80% of

the proppant is placed, this is often the best option. 2. Unable to achieve the design pump rate 2.1. During the pad:

a. If because the treating pressure is too high, shut down, record ISIP and determine if the problem is underestimated frac gradient, excess perforation friction, near well bore tortuosity, or excessive fluid friction. Consult BP/service company engineers for resolution. Adjust pad volume as described in Section 1.1. Consider redesigning job at a lower treatment rate.

b. If due to equipment failure, shut down, remedy the problem and start the job over.

2.2. During the proppant stages: a. If enough fluid and additives are on location, extend the stages

proportionally to actual versus desired rate. E.g.: If the actual rate is 50 BPM and the design rate is 60 BPM, then extend each prop stage 17%.

b. If possible, rerun frac simulator to alter proppant schedule as necessary to achieve desired frac geometry.

c. If there are enough materials on location, continue with the job as planned.

d. If there are critical design goals that must be accomplished, e.g., a final prop concentration, resin coated proppant tail-in, etc., it is recommended


those be started earlier than designed (reduce or omit a middle stage) in the event the well should screen out early.

3. Unable to achieve the design proppant concentration 3.1. If the design proppant concentration exceeds the capacity of the blender or

proppant field bin, reduce the pump rate to a point where the desired proppant concentration can be maintained. Rerun the frac simulator to determine what changes, if any, are necessary to the proppant schedule.

4. Loss of automatic control for additive pumps (Auto-Remote / Auto-Local /

Manual-Local) 4.1. Definitions:

a. Auto-Remote: The treatment van computer is controlling all additive rates. This is the preferred method of additive control. If the equipment is not so configured, do not begin the job until it is fully functioning.

b. Auto-Local: The blender, hydration unit, and/or chemical additive unit are being fed a clean rate and are proportioning the additives automatically. This is the next best method in the event the equipment cannot be configured to operate in Auto Remote, or if Auto Remote capabilities are lost at some point late in the job.

c. Manual-Local: The unit operator controls the additive rates manually. This is the least preferred method because of the difficulty in attempting to operate the unit as well as manually control many different additives. It should be employed only as a last resort once the point of no return has been passed in the treatment, as defined in the following pumping contingency plans.

4.2. If automatic control of one or more additive pumps is lost: a. Before the start of the job: Do not begin the treatment until the problem is

resolved. Correct the problem before beginning the job. b. During the pad: Shut down and resolve the problem before continuing.

Consider pad volume replacement to account for shut down as described in Section 1.1.

c. During proppant with less than 1/3 of the proppant pumped: Over flush by 200% of cumulative slurry volume. Remedy problem and start over.

d. During proppant with more than 1/3 of the proppant pumped: Continue to control additive as closely as possible and complete the treatment as scheduled.

5. Bad Gel Samples (Poor Crosslink Quality or Time, Poor Viscosity, etc) 5.1. If repeated gel samples are unsatisfactory and all quality control processes have

been rigorously followed: a. Verify that the sampling point is in the dynamic fluid stream. b. Check sample pH


c. Check the plumbing to ensure that all additives are rigged up correctly and that there are no leaks.

d. Check the additive flowmeter readings in the frac van for additive rate control accuracy.

e. Strap the tank of the suspect additive. Check the strap against the mass balance calculations and flowmeter totalizer.

f. Perform another bucket test on the suspect additive. If the "bucket test" identifies an inaccurate add rate, correct the flow rate by adjusting the additive concentration by the percentage error indicated.

g. If the problem with the gel samples cannot be resolved after following the above procedures then: - If during the pad, abort the job, remedy the problem, and start over. - If during the proppant with less than 1/3 of the proppant pumped,

abort the job, and overflush by 200% of cumulative slurry volume pumped. Remedy the problem and start over.

- If during the proppant with more than 1/3 of the proppant pumped, continue to investigate and attempt to remedy the problem. Continue the treatment.

6. Loss of down stream dirty densometer 6.1. If during the Pad, shut down and remedy the problem before continuing. Pump

additional pad as described in Section 1.1. 6.2. If during proppant with less than 1/3 of the proppant pumped, over flush by 200%

of cumulative slurry volume of base liquid or foam. Remedy the problem and start the job over.

6.3. If during proppant with more than 1/3 of the proppant pumped, complete the job using the Blender proppant screw rpm control mechanism.

7. Base gelling agent (product name) problems 7.1. Loss of gel pump:

a. If during the pad, abort the job. b. If during proppant with less than 1/3 of the proppant pumped, abort the

job and over flush by 200% of cumulative slurry volume of base liquid. c. If during the proppant with more than 1/3 of the proppant pumped, review

the effective stimulation at that point and determine if it is satisfactory or over-flush by 200 bbls and attempt the treatment again.

7.2. Loss of gel hydration unit (equipment name) concentration for more than 2 minutes: a. If during the pad stage, and if equivalent gel loading if off by more than

10% of design gel loading, abort the job. Remedy the problem and start from the beginning.

b. If during the proppant stages with less than 1/3 of the proppant pumped, and if equivalent gel loading is off by more than 15% of target, abort the


job and over flush by 200% of cumulative slurry volume pumped. Remedy problem and start from beginning.

c. If during the proppant stages with more than 1/3 of the proppant pumped, adjust buffer and cross linker loading according to equivalent gel loading and continue job as scheduled.

8. Loss of crosslinker (product name) add rate control: 8.1. If during the pad, and crosslinker rate variance is more than +/- 10%, abort job,

remedy problem and start over. 8.2. If during the proppant stages with less than 1/3 of the proppant pumped, and

crosslinker rate variance is more than +/- 10%, overflush by 200% cumulative slurry volume of base liquid or foam. Remedy problem and start over.

8.3. If during the proppant stages with more than 1/3 of the proppant pumped, maintain additive rate as close to design as possible and continue treatment.

9. Loss of buffer (product name) add rate control: 9.1. If during the pad, and buffer add rate variance is more than +/- 5%, abort job,

remedy problem, and start over. 9.2. If during the proppant stages with less than 1/3 of the proppant pumped, and

buffer add rate variance is more than +/- 10%, overflush by 200% cumulative slurry volume of base liquid or foam. Remedy problem and start over.

9.3. If during the proppant stages with more than 1/3 of the proppant pumped, maintain additive rate as close to design as possible and continue treatment.

10. Loss of surfactant (product name) add rate control: 10.1. If during the pad, and surfactant add rate variance is more than +/- 5%, abort job,

remedy problem and start over. 10.2. If during the proppant stages, with less than 1/3 of the proppant pumped, and

surfactant add rate variance is more than +/- 25%, overflush by 200% cumulative slurry volume of base liquid or foam, remedy problem and start over.

10.3. If during the proppant stages, with more than 1/3 of the proppant pumped, maintain additive rate as close to design as possible and continue treatment.

11. Loss of catalyst (product name) add rate control: 11.1. If during the pad, and variance is more than +/ - 10% of target rate, abort job,

remedy problem and start over. 11.2. If during the proppant with less than 1/3 of the proppant pumped, and add rate

variance is more than +/- 25% of target rate, overflush by 200% cumulative slurry volume of base liquid or foam. Remedy the problem and start over.

11.3. If during the proppant with more than 1/3 of the proppant pumped, and rate is lost or is >25% out of range, add an extra 2-4 pounds/l000 gals encapsulated breaker.


12. Loss of encapsulated breaker (product name) add rate control: 12.1. If during the pad, and add rate variance is more than +/ - 10% of target rate,

abort job, remedy problem and start over. 12.2. If during the proppant stages with less than 1/3 of the proppant pumped, and add

rate variance is more than +/- 25% of target rate, overflush by 200% cumulative slurry volume of base liquid or foam. Remedy problem and start over.

12.3. If during the proppant stages with more than 1/3 of the proppant pumped, and breaker add rate is lost, add breaker manually to blender tub and continue the job.

13. Loss of un-encapsulated breaker (product name) add rate control (usually

only added during last 15-20 minutes of the treatment): 13.1. If lost or outside guidelines, continue the job as scheduled. Compensate by

increasing the encapsulated breaker by an equivalent loading.

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QAQC MANUAL - Onshore Hydraulic Fracturing Manual_V1_Jul04