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Drilling Muds Training Presentation
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Transcript of Drilling Muds Training Presentation
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)
Presenter
Presentation Notes
Sodium Wyoming bentonite is a very unique product with its platelet structure and tremendous surface area. Calcium bentonite, more commonly found in the United States, does not have the platelet structure of sodium bentonite (calcium bentonite looks like a needles instead of platelets under an electron microscope), therefore, calcium bentonite does not provide the gel strength and fluid-loss control.
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
Presenter
Presentation Notes
This photo points out shear points on a mixing system that help separate the bentonite platelets to create a colloid/drilling fluid. The mixing hopper is the first place where bentonite is introduced to high velocity which helps separate the platelets. Other shear points include the centrifugal pump, mixing guns (which are located inside the tank), shear filters, and even suction strainers.
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
Presenter
Presentation Notes
Poorly mixed bentonite can lead top low gel strength, poor fluid-loss control, and problems down hole. Check to insure that bentonite is properly sheared/mixed before adding polymers and additives which can coat the clumps of bentonite, preventing further mixing. A quick and easy way to see if the bentonite is properly yielded is to stick your hand in the mix tank and look for clumps of un-yielded bentonite. It the clumps are present, more mix time is needed.
Most important block of fluid system!
Makes 95-99% of a drilling fluid!
Bad Water = Bad Drilling Fluids
Make-Up Water
Presenter
Presentation Notes
Sodium Wyoming bentonite does not work with salt water (water with a chlorides level of over 1,000 ppm).� Calcium (which creates hard water) disrupts the electrical stability of bentonite clay, resulting in lower yield/viscosities, lower gel strength (suspension), and poor water loss (bore-hole stability).
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?
Presenter
Presentation Notes
Calcium/water hardness negatively effects bentonite, polymers and additives, and even surfactants (such as DrillTerge) and drill foam.
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
Presenter
Presentation Notes
Bentonite platelets will clump back together (referred to as flocculation) as a result of calcium disrupting the electrical stability (ionic charge) in bentonite platelets.
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
Presenter
Presentation Notes
The hydroxide ion (OH-) in soda-ash readily adsorbs on the silicate surfaces of bentonite platelets. The amount adsorbed increases with pH. The adsorbed hydroxide ion increases the surface charge on bentonite platelets. As a result, more water is adsorbed. The platelets swell and the platelets are more easily dispersed into individual particles by mixers.
Bentonite Settles and Leaves Water on the Surface
Bentonite settling due to calcium in water
Presenter
Presentation Notes
This photo is an example of what happens when bentonite is mixed with hard water (without using soda ash before mixing bentonite).
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?
Presenter
Presentation Notes
Add soda ash to the water tank while filling so that the calcium is neutralized/precipitated out, and the water is ready for mixing by the time the water truck arrives on the job-site.
Check Mix Water pH with pH Strips
Presenter
Presentation Notes
Test Procedure: Remove a test strip from the package (replace cap to protect the remaining test strips) and immerse in water for about 15 seconds. Match the color of the strip with the chart on the side of the package and read the pH of the water. pH strips can be purchased through your CETCO distributor.
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
Presenter
Presentation Notes
Problems can arise anytime one or more of these functions are not being addressed. An efficient horizontal direction drilling fluid performs all of these functions and the lowest possible viscosity (the reason Hydraul-EZ was developed).
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?
Presenter
Presentation Notes
Bingham Plastic Fluid - A viscoplastic material that behaves as a rigid body at low stresses but flows as a viscous fluid at high stress. It is used as a common mathematical model of mud flow in offshore engineering, and in the handling of slurries. A common example is toothpaste, which will not be extruded until a certain hydrostatic pressure is used on the tube. (wikipedia.org, 2008)
Marsh Funnel and Cup - Viscosity
Presenter
Presentation Notes
The marsh funnel has a fluid capacity of 1,500cc, and is 6” diameter at the top, 12” long, tapers to a 2” long tube, and has an orifice inserted at the bottom of the tube section. Test Procedure: Using your finger to cover orifice, pour the drilling fluid through the screen until the fluid level reaches the bottom of the screen. While holding the marsh funnel over the over the viscosity cup, remove finger from the orifice and carefully observe the time (in seconds) required to fill the cup to the quart level mark. The funnel viscosity is reported as the number of seconds. The Marsh funnel can be checked for calibration by using clear water. The one-quart drain time for clear water should be 26 seconds (@ a temperature of between 70° and 80°F) with a tolerance of plus or minus ½ second. Clean thoroughly after each use and inspect the orifice for obstructions.
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
Presenter
Presentation Notes
Pullback and or back-ream speed is determined by the amount of fluid one can deliver to the cutting head. The reamer is not only cutting soil, but mixing soil and drilling fluid to creat a flowable mixture that can exit the bore-hole. An 80 viscosity drilling fluid cuts the pump performance in half, reducing the amount of fluid to the reamer, making it easier to “out-run the drilling fluid.”
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
Presenter
Presentation Notes
As mentioned earlier in this presentation, two drilling fluids can have the exact same viscosity, but be totally different in their ability to clean the bore-hole (gel strength) or maintain bore-hole stability (control fluid loss). This demonstration shows how two fluids with the same viscosity can have different gel strengths. The same demonstration can be done with a high-yield bentonite and hard water mix verses a high-yield bentonite mixed in the same water pre-treated with soda ash.
Four Minute Gel Strength @ 60 Viscosity
SUPER GEL-X HYDRAUL-EZ
Ten Minute Gel Strength @ 60 Viscosity
SUPER GEL-X HYDRAUL-EZ
Presenter
Presentation Notes
A simple way to determine of the gel strength of a drilling fluid is up to the demands of a project (soil conditions) is to use a clear container (such as a clear plastic cup or a water bottle with the top cut off), pour in the drilling fluid, and mix in soil collected from the entry pit. If it settles in the cup, it will settle down hole and more gel strength is needed to adequately do the job.
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
Presenter
Presentation Notes
Bentonite platelets create a membrane/barrier for which hydrostatic pressure is applied, to create bore-hole stability. Fluid-loss is a measure of the effectiveness of that membrane or barrier.
Fine to Medium Sand
Water percolating through sand
Total saturation
Presenter
Presentation Notes
Water percolates through the porous sand (no water-loss control). If one drills their finger through the sand, the hole closes up as soon as the finger is removed (like digging a hole in the sand on a beach).
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
Presenter
Presentation Notes
When a drilling fluid with good fluid-loss control such as Hydraul-EZ and Rel-PAC is poured over dry sand, one can see a dramatic difference in results over the sand and water demonstration. The thin wet layer is where the bentonite platelets and hydrostatic head of the fluid created an impermeable membrane/barrier (the wall cake) which stabilizes unconsolidated soils such as sand.
Controlling Fluid Loss
Minimal Fluid Loss = Borehole Stability
Presenter
Presentation Notes
Borehole stability can only be achieved through good fluid-loss control. In this demo, the drilling fluid was removed after the hole was drilled.
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
Presenter
Presentation Notes
PAC is an acronym for poly anionic cellulose (plant fiber) which when combined with a bentonite drilling fluid creates superior fluid-loss control.
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
Presenter
Presentation Notes
Rel-Pac and Rel-PAC Xtra-Low offers an almost unlimited shelf-life and will not be damaged by freezing. Supper-PAC and Super-PAC Xtra-Low blends in easier and is more compatible with drilling fluids recycling systems. Super-PAC and Super-PAC Xtra-Low can also be poured down the drill stem (8 to 12 ounces) when a reduction in return flow is detected.
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
Presenter
Presentation Notes
A very important function of drilling fluids is to help hold the hole open. Construction drilling is often done through unconsolidated or poorly consolidated formations, such as soils, sand, and gravel. Why do these holes not fall in? How do drilling fluids hold these holes open? The pressure of the drilling fluid, encapsulated by the filter cake, against the formation, helps hold the hole open. The coffee grounds in a vacuum-packed package of coffee are hard. They appear to be consolidated, solid – nothing loose about them. However, when the vacuum seal is broken, the grounds lose their strength and are obviously loose. The atmospheric pressure held the grounds firmly compacted. A good drilling fluid through a sand bed does the same thing. The filter cake formed by the drilling fluid provides a seal; the pressure -- circulating pressure and hydrostatic pressure – of the water against that seal helps hold the hole open.. Also, very high molecular weight polymers help bridge sand grains by bridging flocculation. The extremely long polymer chains bridge across several sand grains, helping to knit them together. More in a later chapter. If the pores in the sand bed or gravel bed are too large for a filter cake to form – the mud flows through the pores – then controlled particle size solids or lost circulation material may need to be added.
Density/Hydrostatic Pressure of Boring Fluids
Presenter
Presentation Notes
This illustrates how fluids of different densities interact and their effect on hydrostatic head. Diet soda contains no sugar, therefore is lighter than regular soda.
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
Presenter
Presentation Notes
Major function of boring fluid is to keep hole open. Hole is held open by hydrostatic pressure from boring fluid pressing against a lower formation pressure – across a membrane (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
Presenter
Presentation Notes
Because of the shallow depths (below 100’) involved in horizontal directional drilling, loss circulation problems due to high solids drilling fluids are rare.
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
Presenter
Presentation Notes
One does not need a degree in geology to be able to classify soil as either reactive (fine) or non-reactive (coarse) soils. Simply stir a sample of the soil into a clear container of water and see what happens. Reactive soils will swell, stick to whatever one is stirring with, and or thicken up the water like a malt. Non-reactive soil will settle to the bottom leaving thin dirty water on top.
Soil Identification Reactive (Fine Soils)
Clay Shale
Non-Reactive (Coarse Soils)
Sand Gravel Cobble Rock
Presenter
Presentation Notes
Once the soil conditions are identified (the entry pit provides a great opportunity for soil sampling), a drilling fluids mix can be designed.
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
Presenter
Presentation Notes
Bentonite drilling fluid is the starting point. From there, we very the amount of bentonite (less bentonite for finer soils), and then polymers and additives are added to enhance the desired properties of a drilling fluid in order to address specific problems inherent to the various soil conditions encountered.
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
Presenter
Presentation Notes
ClayCutter works differently from conventional synthetic polymers in that it actually disrupts the ionic charge/molecular attraction of the clays causing the clay to break down. Unlike conventional thinners, ClayCutter has a minimal adverse effect on bentonite drilling fluid. When drilling through alternating soil conditions such as clay and sand, one no longer has to juggle the mixture; simply run a sand mixture (Hydraul-EX and Rel-PAC or Super-PAC) and add Clay Cutter when needed.
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
Presenter
Presentation Notes
PAC polymers provide superior fluid-loss control and are also good for inhibiting reactive clays.
Reducing Fluid Loss REL PAC
40 Viscosity HYDRAUL-EZ fluid
40 Viscosity HYDRAUL-EZ fluid with REL PAC
Presenter
Presentation Notes
The Xtra-low versions of Rel-PAC offer the same great fluid-loss control while not increasing the viscosity of the drilling fluid.
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
Presenter
Presentation Notes
Products such as ClayCutter provide a tremendous advantage when drilling through multiple soil conditions such as sand and clay. One can run a sand mixture of Hydraul-EZ and Rel-PAC, and add ClayCutter to handle the clay zones. Sand mixture: (25 to 30 pounds of Hydraul-EZ and ½ pound of Rel PAC per 100 gallons) Add ClayCutter at ½ to1 gallon per 1,000 gallons of drilling fluid for clay sections.
Example: Difficult Conditions
Presenter
Presentation Notes
Problem: Contractor drilling through multiple highly reactive clay zones, sand, and a buried creek bottom with cobble and flowing water. First 2 attempts resulted in stuck product line so the CETCO distributor and regional manager was called in to assist. Success was achieved with using a clay conditions recipe of 15 lbs of Hydraul-EZ and 16 ounces of Insta-Vis Plus per 100 gallons, and drill terge on the clay sections and a 35 pounds of Hydraul-EZ with 1 pound of Suspend-IT and 1 pound of Rel-PAC per 100 gallons on the river bottom, and a less viscous sand mixture for the remainder of the bore. The key is identifying the soil conditions as well as the problems that are inherent in these soil conditions, and utilize the correct drilling fluids products and additives to address these problems.
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
Presenter
Presentation Notes
A common mistake made by contractors is to save the good stuff (polymers and additives) for the back-ream and or pull-back. Doing so can lead to high differential; sticking caused by either clay or sand binding the drill stem creating excessive torque long before the reamer hits the dirt. This can also lead to more frack-outs due to a loss of annular space needed to flow returns (containing drill cutting) out of the bore-path.
Avoid Creating Bottlenecks in the Bore Path
Rotate the bit through sections where push-steering corrections were performed to maintain annular spacing
Presenter
Presentation Notes
This driller created bottle neck impedes the flow of returns (causing frac-outs, damaging pavement) and also adds to the overall differential torque (robbing the rig of power needed to turn reamers).
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
Presenter
Presentation Notes
Sprial or fluted reamers have lots of surface area for clay to stick and build up on, which can prevent return flow from exiting (causing pressure build-up, frac-outs, and surface damage).
Spiral Reamer In Clay
Presenter
Presentation Notes
As noted in this photo, because of the clay build-up, there is no channeling for drilling fluids returns to flow to the exit side and all cutting surfaces are caked over (trying to cut clay with 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!
Presenter
Presentation Notes
Packer and or barrel reamers restrict annular return flow to the exit side, and the large amount of surface area is an open invitation for clay build-up. However, these style reamers are good for pigging a hole after a ream is completed to insure the hole is clean and ready for pull-back, or to get the drill stem back to the exit side in order to connect the reamer.
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
Presenter
Presentation Notes
Drilling fluid is always looking for the path of least resistance. Why not make that path of least resistance the exit pit?
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
Presenter
Presentation Notes
A common problem in shallow horizontal drilling is frackouts – raising the asphalt on parking lots or mud volcanoes in the middle of roads. Breakouts occur when the circulating pressure in the wellbore exceeds the formation strength -- in shallow unconsolidated soils, when the circulating pressure exceeds the overburden pressure. Nearly always this problem is caused by the operator being stingy with the circulation of drilling fluid. To avoid making up more drilling fluid, he circulates the fluid very slowly, even if he is drilling rapidly. The drilling fluid near the bit builds up in solids content, the viscosity goes sky high, the backpressure gets very high and the viscous “mud” breaks out somewhere on the surface. Higher solids content tends to affect the Plastic Viscosity most, which makes the mud more viscous at all shear rates. The solution is to increase circulation rates to reduce the buildup of solids. One of the real selling points of CETCO drilling products is that they are tolerant of high drill solids. (They start out at very low solids contents.) These fluids can be made more tolerant of drill solids by adding surfactants, thinners and other polymer additives. These products coat the drill solids and prevent a large increase in Yield Point.
A Little Bit of Volume and Pressure Can Cause a Lot of Damage
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On this project, it started to rain and the driller got in a hurry on the final ream/pullback which resulted in the driller outrunning the mud (returns became too thick to adequately flow out of the exit side) and damaged pavement (road raised over 6”). Reamer was 8’ below the pavement.
Damage Repair is Costly
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Damages such as this hurt your companies pocket book and reputation. Total cost of repairs: Over $9,000.00
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
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Just like drilling fluids, bits, and reamers, pumping volume requirements will vary depending upon soil conditions.
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
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Anytime this rule of thumb is ignored, the odds for success are greatly reduced!
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
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It goes back to what we all learned as children; To dig a hole in the ground, dirt must be removed, and drilling fluid is the means of transporting drill cutting out of the bore-hole. Drill cuttings and drilling fluid are being slurred up into mixture that must flow out of the bore-hole in order to make room for the product line. If the drilling fluid/drill cuttings mixture does not have enough drilling fluid, it will not flow and the results can vary from raised roadways to stuck or stretched product line.
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
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The more reactive the soil conditions, the more drilling fluid required to flow it out of the bore-path. Do the math to determine if you working within the operating parameters of the equipment. For example: Using a JT3020 drill with a 24” reamer, 400’ bore in reactive soil Pump volume requirements = 70.47 to 117.45 gallons per foot of hole 400’ X 70.47 gallons per foot (absolute lowest volume in reactive soil) = 28,188 total gallons (704.7 gallons per 10’ rod) 28,188 gallons ÷ 22 gallons per minute (pump capacity) = 1,281.27 minutes or 21.35 hours of pullback time, not including breaking and making connections, filling up the mix tanks with water, and mixing drilling fluid (better pack a lunch).
Let the Exit Flow Be Your Guide
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From the pilot hole to the final ream/pullback, the return flow is the closest thing we have to real-time data coming from the bit or reamer. All of the pumping calculations and drilling fluid recipes are estimations, but the return flow will tell the real story of: What the actual soil conditions are (and show unexpected changes in soil conditions) How the drilling fluid is interacting to the soil (suspending cuttings, controlling clays) Actual pump volume requirements (too little volume or too much pullback speed will result in the returns being too thick to flow adequately while thin returns may indicate that one can speed up the pullback process).
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
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There is a direct connection between the functions of drilling fluids, drilling fluid characteristics, and the CETCO products developed to help perform these functions and provide these desired drilling fluid characteristics in order to successfully complete a drilling project. Having a thorough understanding of how to match the drilling fluids to the various soil conditions encountered, will dramatically increase the odds for success.
