Lessons in Tight Oil Production

An Unconventional Look at Unconventional Resources

David Foo FMC Technologies

([email protected]) April 15, 2015

CSUR Technical Lunch Presentation

• Review of Temperature Logging and Distributed Temperature Sensing (DTS)

• Preliminary Examples and Illustrations • Production logging (gas wells) • Water injection profiles • Frac tracing • Dynamic well behavior

• Tight Oil DTS Examples • Directive 51 Applications • Water injection profiles • Channels, Faults, and Other Problems

• Conclusions

Presentation Agenda

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Temperature Logging - Conventional

Source: Dresser Atlas Production, Interpretive Methods for Production Well Logs, Second Ed., 1982

Source: Dresser Atlas Source: Dresser Atlas Production, Interpretive Methods for Production Well Logs, Second Ed., 1982

Production logging of gas wells Logging of injection wells

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Instead of making measurements by stopping with an instrument at discrete, pre-determined points, Distributed Temperature Sensing (DTS) makes continuous measurements over the full length of the optical fiber. DTS is capable of detecting changes in temperature smaller than 0.01°C with 30 second time resolution. Distributed sensing is real time, so you get continuous monitoring at all points along the cable at all times. Record of dynamic well behavior allows quantitative analysis that is not possible with conventional temperature logs.

Distributed Temperature Sensing (DTS)?

Temperature Logging - Unconventional

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The DTS Data Acquisition System

• Fiber length: Can be used with fiber of 30km plus

• Detection Accuracy: Detect and position events to an accuracy of 1 meter at 100MHz • Distributed Monitoring: Possible to record data at each 1m interval along fiber

• Signal Bandwidth: Up to 200 MHz bandwidth possible along fiber • Communication infrastructure: Two way communications ready. Full diagnostics and health monitoring

• Remote Management: System parameters can be changed locally or remotely

• The entire system consists of only two parts: a standard communications fiber that is positioned on or in the vicinity of the object to be analysed and the analyser that is connected to one end of the fiber.

• The process was developed at the beginning of the 1980’s at Southampton University in the UK. The original DTS unit was developed to monitor insulation integrity of cryogenic fuel tanks on the Lockheed-Martin X-33 next generation space shuttle.

• Alternately used in Fire Detection and Suppression Systems

Standard Multimode Communications Fiber

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How DTS Works

= Raman Backscattering

= Laser Pulse

Optical Receiver

Pulsed Laser

Multimode Fiber Optic Line DTS Unit

Signal Processing

Anti-Stokes Signal (Strongly Temperature

Dependent)

Stokes Signal (Weakly Temperature

Dependent)

Directional Coupler

Spectrum of Backscattered

Incident Light

• Pulses of laser light are sent into an Optical Fiber • Immediately, some of the light scatters • Retained within the core of the fiber, the scattered light

is transmitted back to the source where it is captured and redirected into a highly sensitive receiver

• The returning light from the scattered light shows an exponential decay with time

• The constant speed of light allows the determination of the exact location of the source of the scattered light

• The analyzer determines the intensity of the Raman backscatter component at both the Stokes and anti-Stokes wavelengths, which is used to calculate the temperature of the fiber where the backscatter occurred

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Fibre Optic Wireline

Permanent (external) installation for new wells • Fibre can be permanently clamped on the outside of production casing • Bare fibre can be pumped down through integral joint string installed on the outside of

the production casing Limitation: there is presently no pass-through available for fibre in multi-stage frac’d wells Temporary (intervention) installation for existing wells Fibre can be contained inside slickline or braided wireline • 0.125 (1/8”) Triple Wall Dual Fibre • 0.25 (1/4”) Mono Conductor Dual Fibre Optic Braided E-Line • 0.375 (3/8”) Mono Conductor Dual Fibre Optic Braided E-Line For vertical wells, wireline fibre is run the same as conventional wireline For horizontal wells: • Wireline can be installed inside coiled tubing to run in horizontal wells • Electric wireline can be coupled with a tractor to run in horizontal wells

High temperature fibre (up to 315 C) is available for SAGD applications

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Conveyance Methods

Intervention • Standard Coil Tubing 1 ½” 6,200 ft (1,900 m) • High Temp Coil (315 oC) 1 ½” 6,200 ft (1,900 m) • Slickline 1/8” 16,400 ft (5,000 m) • Electric Wireline (tractor compatible) 1/4” 16,400 ft (5,000 m)

3/8” 24,600 ft (7,500 m)

External Installation • Permanently clamped on the outside of production casing • Pumped down through integral joint string installed on the outside of the production

casing

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Static Conditions: Using depth as the primary independent variable yields geothermal gradients, frac placement, caprock integrity, and hydraulic isolation. Dynamic Conditions: Using time as the primary independent variable shows heat flow along the well. Mass flows (production and injection profiles) can be inferred from this presentation.

Data is a 3 dimensional array: depth, time, temperature How to Look at DTS Data

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Wellbore Leaks

Leaking casing collars

This well had a leak so the operator ran a casing inspection log but casing inspection tools do not see defects in the collars. After pressuring up the well, a small amount of fluid leaked through the collars. The fluid that leaked was slightly cooler than the formation at that depth, so the leaks showed up as faint lower temperature anomalies. The operator later ran a packer and confirmed the locations of the leaks.

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• Vertical gas well – production allocation • Horizontal gas well - frac placement • Tight oil producer - frac placement and production • Tight oil producer - water problem remediation • Tight oil producer to injector conversion (Directive 51) • Oil injector - thief zone • Tight oil injector - channel with remediation • Open hole injectors – miscellaneous issues

Unconventional Wells - DTS Logging

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Vertical Gas Well – Production Log

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DTS Production Log (Example)

At what depth should the horizontal well be drilled?

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Inflow from traditional Prod. Logging Downhole Conditions

Uncemented Completions Differential temperature map showing that some of the

fracs opened next to the swell packers and others did not.

Packer Packer Packer Packer Packer Packer Packer Packer Port Port Port Port Port Port Port Port

Low temperature anomalies due to Joule Thompson effect (source of flow – location of frac)

Less distinct low temperature anomalies may indicate more complex fracs

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Frac Placement (logged after 4 days of flowback)

Frac Stage 14 13 12 11 10 9 8 7 6 5

Fracs 7 and 12 screened out

Flowed back for 4 days after a hot water frac, thermal anomalies persist at each frac

Frac Treatment – Thermal “Fingerprint” (Viking)

CHAT Log

DTS

Dynamics of Flow in a Horizontal Well (Viking)

Shut In

Flowing

Direction of flow

Time

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Water Problem at Oil Producer

Low temperature anomaly indicates water influx

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Water Injection Profiles

Low temperature at certain depths indicate points of injection

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Injection Conversion DTS Survey (Horizontal Section)

Minor thermal anomalies

12 14 7

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Water Injection Analysis

No obvious persistent thermal anomalies

Injection profiles

• Warmback rate depends on injected fluid amounts

• Differential temperature plot shows results better

• Result matches quantitative analysis

• Middle stages take most of the injection

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Injecting Hot Fluid

“Valleys” indicate points of injection

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Injection Well DTS Survey (Entire Well)

Extremely steep thermal gradient over very short distance

No temperature difference between injection and shut in at toe

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Thief Zone DTS Survey (Thief Interval)

Extremely steep thermal gradient over very short distance

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Thief Zone Analysis

Over 50% of injection in 10m of the horizontal leg

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The problem: with horizontal production wells, how do you optimize injection geometry to maximize secondary recovery?

Vertical Injector

Channeling in Horizontal Injection Wells

Channeling in Horizontal Injection Wells (cont.)

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Wave Fronts

Storage

Material Balance

Channeling in Horizontal Injection Wells (cont.)

• Set a packer in the lateral to redirect injection water away from stages 7 and 8.

• The well was set up as a dual injector, with injection down the tubing to stages 1 through 6 and injection down annulus to stages 7 and 8.

Before

After

Workover to Fix Channel in Horizontal Injection Well

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Water Injection Profiles - Open Hole Injection

In open hole horizontal injection wells, there is no other technology that will provide an injection profile.

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Warmback Analysis: temperature changes after shut in indicate areas of injection.

Qualitative: white and blue colors indicate areas of injection.

Wave Fronts: fluid velocity decreases along well indicating areas of injection.

Water Injection Profiles – Possible Effect of a Fault

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Warm Back Analysis: temperature changes after shut in indicate areas of injection.



Water Injection Profiles – Possibly Off Depth

Well TVD

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Warm Back Analysis: temperature changes after shut in indicate areas of injection.



Water Injection Profiles – Possibly Off Depth

Well TVD High point – no injectivity

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Water Injection Profiles – Offset Injector

Cooler at toe (effect of offset injector)

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Conclusions – DTS Technology

• DTS logging provides well insights through qualitative analysis in many applications.

• DTS is often the only technology that can provide an answer to certain production questions.

• DTS can be used for similar applications to conventional temperature logs, but it is often faster and provides greater insight.

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Conclusions – Tight Rock Production

• Frac placement can be determined in both oil and gas wells, and complex frac geometry can often be detected. Fracs often do not line up with frac ports.

• Frac stages for any well anticipated to be put on injection should be as uniform as possible.

• Wells producing from tight rock may exhibit unusual flow characteristics. • Horizontal production wells are often plagued by water, but isolation of the

water producing interval and eventual repair is possible. • Reservoir heterogeneities are common and the effect that they have on

permeability are profound. • Uniform injection profiles are rare and will become more rare through time. • In general, when dealing with horizontal waterflood projects, avoid

trajectories that intersect faults or come close to abandoned wells.

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Acknowledgements Trevor Meador, Teresa Cheng, Greg McLeod, Steve Wierenga, Mahlon Lisk (all of FMC Technologies) Crescent Point Enerplus CSUR

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Questions? [email protected]

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Lessons in Tight Oil Production