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Bentonite: Its Origin
Large volumes in western U.S.
Formed during
Cretaceous Period Formed by volcanic
ash http://www.webcamcruise.com/USA%20Map_fichiers/usa_map.jpg
Bentonite Mining
Wyoming Sodium Bentonite High swelling clay
Ability to adsorb large quantities of water
Composed of many stacks of platelets like a stack of cards
Expands up to 20 times its volume
One inch3 covers 66 football fields
One inch high contains between 35,000-40,000 layers (stresses good mixing)
Venturi Pipe Hopper Jet
Bentonite going into hopper @ 200 mesh (74 Microns)
Bentonite platelets (1/2 Micron) mechanically separated by high velocity fluid from jet hopper
Venturi Style Mixing Hopper
Mixing System
Examples of Un-yielded Bentonite
This image shows a poorly mixed 40 Viscosity SUPER GEL-X poured over the screen on a Marsh Funnel
This image shows the un-yielded bentonite on your hand when dipping it into the mix tank
Most important block of fluid system!
Makes 95-99% of a drilling fluid!
Bad Water = Bad Drilling Fluids
Make-Up Water
Bentonite does not mix like it should
When we turn off the mixing equipment the bentonite settles and leaves water on the surface
It takes a lot more bentonite to get the same viscosity
The pump is making all kinds of noises when pumping the slurry
Polymer gets all stringy when we mix it
Do These Problems Sound Familiar?
Is there a problem with the Bentonite? Probably not.
Most likely the culprit is low pH (<9.5) and or
hardness (calcium)
When contaminants are present, the stack of cards does not want to separate and disperse
Make-Up Water
Effects of Soda Ash on Bentonite in Water
Soda ash increases the negative charge on bentonite
More water is adsorbed
Dispersion of clay platelets increases
Soda ash also promotes dispersion of the drill cuttings
+ + Na2CO
Bentonite Settles and Leaves Water on the Surface
Bentonite settling due to calcium in water
Check pH (7 is neutral)
HYDRAUL-EZ and polymers like a pH of approximately 9.5+
Raise the pH with soda ash (sodium carbonate). This also precipitates out calcium
Normal treatment is ¼ to ½ pound per 100 gallons of water
What to Do?
Check Mix Water pH with pH Strips
The pH Scale
Neutral (H+ = OH-)
100 10-1
10-2
10-3
10-4
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
10-14
0 1 Molar Hydrochloric acid (HCI) 1 Stomach Acid, Lime Juice
2 Lemon Juice
3 “Acid Rain” (2.5-5.5), Vinegar, Cola
4 Beer
5 Black Coffee, Tea
6 Normal Rain (5.6) 7 Pure Water, Saliva, Blood, Sweat
8 Seawater (7.8-8.3)
9 Baking Soda
10 Phosphate Detergents, Chorine Bleach
11 Household Ammonia
12 Washing Soda
13 Oven Cleaner
14 1-Molar Sodium Hydroxide (Na0H)
Incr
easi
ngly
Bas
ic (
H+ <
O
H- )
Incr
easi
ngly
Aci
d (H
+ >
O
H- )
pH Value H+ Concentration (Moles/Liter)
Bentonite Mixing
Reference: Audesirk, T., Audesirk, G., & Byers, B. 2003. Life On Earth. Third Edition. Prentice Hall. Upper Saddle River
Functions of HYDRAUL-EZ Drilling Fluid Cool bit & lubricate the hole
Control sub-surface pressure
Control fluid-loss, loss circulation, and frac-outs
Hold the hole open, stabilize the hole
Clean the hole, suspend & transport cuttings
Reduce torque associated with sticky soil
Characteristics of HYDRAUL-EZ Drilling Fluid
Density, Hydrostatic Head
Sand Content
Fluid Loss
Gel Strength
Viscosity
The resistance of a fluid to flow; the greater the resistance, the greater the viscosity or thickness
Measured with a marsh funnel and cup
Viscosity only tells us the thickness of a fluid
Two fluids with the same viscosity can be vastly different in terms of its ability to clean the hole
Viscosity
Units for Bingham Plastic Fluids We use the following units, typically, to describe the rheological behavior of drilling fluids
Plastic viscosity, PV (cp) Yield Point, YP (lb/100 ft2) Apparent Viscosity, AV (cp) Gel strengths (??)
How can this possibly make any sense?
Marsh Funnel and Cup - Viscosity
Viscosity & Pump Performance Higher viscosity fluids will reduce the flowability of
cuttings
Higher viscosity fluids will drastically reduce pump performance
Higher viscosity fluids will increase pumping and material costs
Viscosity & Pump Performance Pump curves are based on clear water at sea level and under ideal conditions
Example 40 gpm pump with clear water, 26 viscosity
40 viscosity – 10-15% capacity = 34-36 gpm 60 viscosity – 25-30% capacity = 28-30 gpm 80 viscosity – 40-50% capacity = 20-24 gpm
Gel Strength Most important drilling fluid characteristic
The ability of HYDRAUL-EZ to form gels and suspend
cuttings in borehole
If drill cuttings are not suspended, they will pack off borehole and cause pressure buildup, fracturing, and stuck pipe
Two methods to increase the gel strength of a drilling fluid
1. Add more HYDRAUL-EZ, which also increases viscosity
(resistance to flow)
2. Add a gel strength enhancing polymer to HYDRAUL-EZ slurry HYDRAUL-EZ/polymer system - HYDRAUL-EZ with
SUSPEND-IT is most desirable since it forms a high gel strength, pump-able slurry
Gel Strength
If cuttings are flowing out of the hole, we know we have an open hole
If the hole is open, we don’t get stuck
HYDRAUL-EZ offers superior gel strength 0
5
10
15
20
25
30
35
40
45
10 MIN GEL
SUPER GEL-X
HYDRAUL-EZ
Gel Strength
One Minute Gel Strength @ 60 Viscosity
SUPER GEL-X HYDRAUL-EZ
Four Minute Gel Strength @ 60 Viscosity
SUPER GEL-X HYDRAUL-EZ
Ten Minute Gel Strength @ 60 Viscosity
SUPER GEL-X HYDRAUL-EZ
Gel Strength
No viscosity increase with HDD designed drilling fluids
Recommend SUSPEND-IT when coarse sands and gravel are anticipated
Fluid Loss Measure of amount of drilling fluid lost through a
permeable formation
Fluid loss can be measured with a filter press
Bentonite platelets shingle off wall of the hole and form a filter cake when slurry is pumped under pressure
This cuts off water to surrounding sand or gravel
Fluid Loss Two methods to “tighten” or reduce amount of fluid going into formation
Add more HYDRAUL-EZ, which increases platelets but
increases viscosity (resistance to flow)
Add fluid loss polymer to HYDRAUL-EZ slurry HYDRAUL-EZ/polymer system – HYDRAUL-EZ with SUPER PAC or REL PAC is most desirable since it forms a low solids pump-able slurry
HYDRAUL-EZ Drilling Fluid Seals Borehole Sidewall Bentonite Suspension
Hydrostatic
Pressure
Bentonite Particles Bentonite Filter Cake Formed by Clogging and Bridging
Soil Grains
Fine to Medium Sand
Water percolating through sand
Total saturation
Fine to Medium Sand
HYDRAUL-EZ and REL-PAC Drilling Fluid
MINIMAL Fluid Loss
Water or drilling fluid with poor fluid loss
HIGH Fluid Loss
Controlling Fluid Loss
Minimal Fluid Loss = Borehole Stability
Fluid Loss SUPER PAC and REL-PAC enhance the
performance of HYDRAUL-EZ
A thick filter cake does not
translate to a reduction in fluid loss
Modified Natural Polymer Used in Coarse Non-Reactive Soils
Manufactured in liquid and powdered form, cellulose polymers are used primarily to control fluid loss and stabilize difficult holes
REL-PAC and SUPER PAC – Dry and liquid cellulose polymers which are added to HYDRAUL-EZ systems to create superior borehole stability
Holding the Hole Open Maintaining a stable hole while drilling through soil, sand, gravel or other non-consolidated formations
Positive pressure of drilling fluid (filter cake, circulating pressure, hydrostatic pressure)
Similar to coffee grounds in a vacuum sealed can
Keys Filter cake Particle bridging character of the polymers in CETCO’s
formulations
Density/Hydrostatic Pressure of Boring Fluids
Borehole Stability Major function of HYDRAUL-EZ fluid is to keep the
hole open
Hole is held open by hydrostatic pressure from a HYDRAUL-EZ fluid pressing against a lower formation pressure – across a filter cake
The pressure difference need not be great, but must always be positive
What Is Loss Circulation?
Loss circulation refers to the total or partial seepage of drilling fluid into the formation through crevices or porous media
Not to be confused with frac-outs which refer to fluid breaking through the surface
Coarse Unconsolidated Formations Sand
Gravel
Partial and or gradual loss of return flow
may be experienced in coarse soil conditions.
Utilize a drilling fluid with good fluid-loss control such as a HYDRAUL-EZ/PAC polymer fluid (soda ash is also important to get maximum yield out of HYDRAUL-EZ)
Reduce the mud weight as much as possible by good solids control practices and checking mud properties frequently
Driller-Created Loss Circulation Problems
High solids/high density drilling fluids increase hydrostatic pressure on formations Example: Mud Weight X 0.052 X Depth = Hydrostatic Pressure 9.0 pound mud @ 200’ depth: 9.0 X 0.052 = 0.468 X 200’ = 93.6 PSI of Hydrostatic Pressure on the Formation 14 pound mud @ 200’ depth: 14 X 0.052 = 0.728 X 200” = 145.6 PSI of Hydrostatic Pressure on the Formation
Driller-Created Loss Circulation Problems
Failure to adequately transport cuttings to the surface
Inadequate gel strength and or annular ascending velocity to transport cutting to the surface, and suspend cuttings when circulation is stopped can result in the bridging of drill cuttings around the drill stem which can block return flow, over pressure, and fracture the formation
Driller-Created Loss Circulation Problems
Failure to control the hydration of reactive soils
Reactive clays can swell up and create blockages that prevent return flow from exiting the bore and over-pressure the formation causing fractures and loss circulation
Utilize synthetic polymer for controlling reactive soils
Driller-Created Loss Circulation Problems Hole Swabbing
Thick, poorly-yielded bentonite drilling fluids (not using soda ash) along with a failure to utilize modified natural polymers (PAC polymers) to control water-loss can result in high fluid-loss conditions
A thick ineffective filter cake can cause swabbing (suction) of the hole, when downhole tooling is pulled, resulting in hole collapsing and loss circulation problems
Barrel Yield Describes the number of barrels of a given viscosity bentonite slurry that can be made from a ton of clay
SUPER GEL-X High Yield Bentonite = 200-220 bbls HYDRAUL-EZ HDD specialty bentonite = 165-185 bbls PREMIUM GEL API grade = 90 bbls
Examples 210 bbls x 42 gal = 8,820 gallons of slurry 185 bbls x 42 gal = 7,770 gallons of slurry 90 bbls x 42 gal = 3,780 gallons of slurry
Five Steps to a Successful Borehole Soil
Identification
Drilling Fluids
Bits & Reamers
Planning
Volume
Successful Borehole
PLAN for SUCCESS! Time is Money! Planning Phase Saves Time
Jobsite Layout Needs:
Manpower Equipment Needs (Tooling, Vacs, Recycling) Product Needs
Jobsite Water Source (Fire Hydrant) Disposal Options
CETCO Online Calculation Guides
Why Use a Software Based Mud Program? Allows for more accurate bidding of jobs
Ensure you have the correct products on the job-
site
Ensure you have proper quantity of products on the job
Printed report can be used with your submission
Engineers are using this to assist in specs
Sample Input Screen
Five Steps to a Successful Bore - Soil Identification Coarse Soils Sand, Gravel, Cobble, Rock, typically use bentonite or bentonite/polymer system
Fine Soils Clay and silts, typically use polymer or bentonite/polymer system
Soil Identification Reactive (Fine Soils)
Clay Shale
Non-Reactive (Coarse Soils)
Sand Gravel Cobble Rock
Five Steps to a Successful Bore - Drilling Fluids
There are no universal soils and there are no universal drilling fluids
Match the drilling fluid to the soil type
Use bentonite as a base for all soil conditions
Polymers & additives are added to bentonite drilling fluids to match soil conditions
Polymer Additives Designed as additives for HYDRAUL-EZ & SUPER
GEL-X drilling fluids, not a replacement
First used as drilling fluids in the late 1930’s
Specifically designed for a particular drilling situation
Three basic categories; synthetic, modified natural, and natural polymers
Synthetic Polymers - Used in Reactive Soils
Manufactured in liquid and powdered form; they can be tailor made to fit any function
Functions: Viscosifiers Clay and shale inhibitors Lubricants Borehole stabilizers Very shear sensitive
Synthetic Polymers ACCU-VIS and INSTA-VIS PLUS
– Liquid polymers to increase viscosity and inhibit hydration of clay and shale
INSTA-VIS DRY – Dry polymer for stabilizing borehole and coating clay and shale
Clay & Water (Reactive Soils)
Mixing clay with water
Clay will hydrate causing sticking and swelling
Polymer and water
Polymer coats clay particles and delays hydration
CLAY CUTTER A concentrated, non hazardous,
proprietary clay inhibitor that can be used with either polymer or HYDRAUL-EZ drilling fluid systems
An ideal additive for reactive clay soils
Will greatly reduce or eliminate clay cuttings from sticking to each other and to the drilling tools. Swelling of the bore will be reduced or eliminated
Rotation and pullback pressures will be significantly reduced
Can be used in antifreeze tank for easy spot treatment
CLAY CUTTER Breaks Down Reactive Soils
Adding CLAY CUTTER to granular bentonite and water
Granular bentonite/reactive soils are broken down (instead of being encapsulated) and in a more flowable state
Modified Natural Polymer (Used in Coarse Non-Reactive Soils)
Manufactured in liquid and powdered form, cellulose polymers are used primarily to control fluid loss and stabilize difficult holes
REL-PAC and SUPER PAC – Dry and liquid cellulose polymers which are added to HYDRAUL-EZ systems to create superior borehole stability
Reducing Fluid Loss REL PAC
40 Viscosity HYDRAUL-EZ fluid
40 Viscosity HYDRAUL-EZ fluid with REL PAC
Natural, Biodegradable Polymers
No viscosity increase
with HDD designed drilling fluids
Increases gel strength
SUSPEND-IT is recommended when coarse sands and gravel are anticipated
Example: Alternating Clay & Sand
Sand
Reactive Clay
Example: Difficult Conditions
Pilot Hole Use drilling fluids and additives both ways: if you
need it back-reaming, you will need it on the pilot hole
Maintain an open bore path and steady flow
Avoid over-steering
Avoid Creating Bottlenecks in the Bore Path
Rotate the bit through sections where push-steering corrections were performed to maintain annular spacing
Five Steps to a Successful Bore Bits & Reamers
No universal soils
No universal drilling fluids
No universal bits & reamers
Match downhole tooling to the soil type
Bits Duckbill Roller Cone Geo-Head
Reamers
Barrel/Packer Spiral/Fluted Winged/Open Roller Cone/Hole Opener
Bit Selection – The Proper Bit is Critical for a Successful Pilot Hole
Reamer Selection Reamer should always be a minimum of 1 ½ times
the diameter of the product line to prevent getting stuck and frack outs.
Reamer selection is critical for a successful bore
Like fluids, reamers need to be matched to soil
types
Reamers should not restrict the pump’s capacity or annular flow
Spiral or Fluted Reamer Versatile type of
reamer Used in sand, silty
soils, and rocks & cobbles
Avoid using spiral or
fluted reamers in clay
Spiral Reamer In Clay
Winged or Open Reamer Used in reactive soil
conditions (i.e. clays) Minimal surface area for
clay to stick and cause blockage of annular flow
Good chopping action
(required in reactive soils)
Barrel Reamer or Packer
Used in uniform soils and loose sands
Used with high viscosity to maintain borehole stability
Makes a great boat anchor!
Frac-Outs and Bulging Pavement
No space between formation and drill pipe for drilling fluid to return
Reamers such as fluted and spiral ball up with clay and restrict flow to exit side
Drilling fluid has nowhere else to go but into the formation
Annular space is maintained through proper drilling fluid additives and good drilling techniques
- Open type of back reamers reduce balling of clays and provide a chopping/mixing action while allowing for fluid to flow to the exit side
Preventing Frac-Outs Frac-outs occur when the circulating pressure in the wellbore exceeds the formation strength Build-up of solids in drilling fluid lead to really high
mud viscosities, low pump rates, and/or “out-running mud”
Solution is more drilling fluid and or higher circulation
rates to reduce solids content in returns
A Little Bit of Volume and Pressure Can Cause a Lot of Damage
Damage Repair is Costly
Five Steps to a Successful Bore Volume
Provide sufficient volume to maintain a flowable slurry
Calculate drilling fluid volumes based on hole size and soil type
Determine backream time based on pump capacity
Don’t Forget an Important Rule of Thumb In HDD
Hole diameter must be at least 1 ½ times the diameter of the product line
Calculating Drilling Fluid Volumes Volume of hole = Diameter2 ÷ 24.52 = gals/ft
Example: 8” backream and 200 ft bore 8x8=64 ÷24.52=2.61 gals/ft
200 ft bore x 2.61 gals/ft = 522 gals (based on 1:1 ratio)
Requirements for different soils
Sands: 2-3 x volume of hole Clays: 3-5 x volume of hole
Calculating Drilling Fluid Volumes Estimating bore time based on pump capacity
Example: 200 ft bore x 8” hole; sandy soils 2.61 gals/ft x 2= 5.22 gals x 200 ft=1,044 gallons
Using 10 ft drill stem we need 52.2 gallons per stem:
Pumping 20 gpm takes between 2.5 and 3 minutes per 10 ft. rod. Pumping 30 gpm takes between 1.5 and 2 minutes per 10 ft. rod. Pumping 40 gpm takes between 1 and 1.5 minutes per 10 ft. rod.
* Given above examples, reaming time should vary between 25 and 60
minutes.
HDD Pumping Volume Requirements Hole dia.
(in.) Gal/ Lin. Ft.
= (dia2 ÷24.5) Coarse Soils (Sands) 2 to 3 X Vol. Of hole
Fine Soils (Clays) 3 to 5 X Vol. of Hole
2 0.16 0.32 to 0.48 0.48 to 0.8
4 0.65 1.3 to 1.95 1.95 to 3.25
5 1.02 2.04 to 3.06 3.06 to 5.10
6 1.47 2.94 to 4.41 4.41 to 7.35
7 2.00 4.0 to 6.0 6.0 to 10.0
8 2.61 5.22 to 7.83 7.83 to 13.05
9 3.30 6.60 to 9.90 9.90 to 16.5
10 4.08 8.16 to 12.24 12.24 to 20.4
12 5.87 11.47 to 17.61 17.61 to 29.35
14 8.0 16 to 24 24 to 40
16 10.44 20.88 to 31.32 31.32 to 52.2
18 13.22 26.44 to 39.66 39.66 to 66.10
20 16.32 32.64 to 48.96 48.96 to 81.6
24 23.49 46.98 to 70.47 70.47 to 117.45
30 36.73 73.467 to 110.19 110.19 to 183.65
36 52.88 105.76 to 158.64 158.64 to 264.4
Let the Exit Flow Be Your Guide
Five Steps to a Successful Borehole
Soil Identification
Drilling Fluids
Bits & Reamers
Planning
Volume
Successful Borehole
Up Your Odds for Success! Utilize drilling fluids as a tool to avoid trouble
instead of an aid to get you out of trouble
Take advantage of the information available on the CETCO website @ http://www.cetco.com/DPG/
Utilize the CETCO HDD Estimator: http://www.cetco.com/DPG/HDD.aspx
Putting it All Together Functions of Drilling Fluid Characteristics of
a Drilling Fluid Cool bit & Lubricate the hole
Control sub-surface pressure
Control fluid loss, loss circulation, and frac-outs
Hold the hole open (stabilize the hole)
Clean the hole (suspend & transport cuttings)
Reduce torque associated with sticky soil
Density, Hydrostatic Head
Sand Content
Fluid Loss
Gel Strength
Viscosity
INSTA-VIS PLUS
SUPER PAC XTRA-LOW REL-PAC XTRA-LOW
SUPER GEL-X
SUPER PAC REL-PAC
HYDRAUL-EZ
CLAY CUTTER CLAY CUTTER DRY
PROSHOT
ACCU-VIS
INSTA-VIS DRY
DRILL-TERGE
SUSPEND-IT