2 Introd to Drlg Flds.ppt Introd to Drlg Flds.ppt

© 2001 PetroSkills LLC, All Rights Reserved
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Drilling Fluid

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Definition
A fluid that makes possible the drilling of
oil and gas wells
Transportation of formation solids to the
surface
Control of subsurface formation pressure
Preservation of the borehole until protected
by casing

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Importance
Life blood of modern drilling operations
Facilitates drilling
Vital to the overall success of any well-
construction project
Averages less than 8% of tangible costs
Protects against formation damage
Responsible to the environment
Provides safe drilling environment

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Drilling Fluid Selection
Dominated by three Factors
Performance
overall success of the well-
construction process
Economics
must be affordable
Environmental
not harmful to the H.S.&E.
With an element of risk

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Historical Perspective
Development paralleled the drilling
industry
Percussion drilling
Soften rock for pulverizing
Suspend pulverized solids for bailing
Control formation pressure
Rotary Drilling
Circulate drilled solids from bore hole
Stabilize unconsolidated formations
….

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Early Chinese Rig
256 BC
Drinking water
Brine for salt
Fluid applications
soften the rock
bail out solids

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David & Joseph Ruffner
Brine
Spring Pole Rig
West Virginia
1806 - 1808
Steel bit

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Spring Pole Drilling
Belgium 1828
Kentucky 1828
Pennsylvania 1860’s

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Canada 1860’s
Lifting Tools
winches
cables

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“American Well”
1829
Burkesville, Kentucky
Drilling for salt brine
One of first American wells to produce a
consistent flow of oil
Thousands of gallons per day
Until about 1860
“American Medicinal Oil”

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Fauvelle
“A New Method of Boring for Artesian
Springs,” Journal of the Franklin Institute,
Vol. XII, 3rd Series, 1846
Hollow boring rod, consisting of hollow tubes
screwed end to end with a drilling tool of a
larger outside diameter attached to the lower
end.
Water circulated through the tubes and up
the annulus to clean the hole
Drilling by either percussion or rotation

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“Drakes Well”
Colonel E. L. Drake
1859
69 feet
Cable-tool
First commercial oil
well in America
Renewed interest in
rotary drilling

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P. Sweeney
United States Patent, 1866
Stone drill
Swivel head
Rotary drive
Roller bit
Water as a circulating
fluid to remove cuttings

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Hole Stabilization
Rotary drilling of mud making clays
Common in Louisiana and Texas during
1800’s
Showed the importance of mud to hole
stability
M. J. Chapman’s Patent Application, 1887
Stream of water with a quantity of plastic
material
Plaster the wall of the well and reduce caving
tendencies
Clay, bran, grain, and cement

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Spindletop
Captain Anthony Lucus
Spudded October 1900
Quick sand
Curt Hamill
Remembered when the drilling fluid is
thickened with clay it helps line the walls of
the hole
Nearby cattle herded into a pit containing
their water supply to produce a muddy fluid
Muddy fluid sealed of the quick sand

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Unstable Holes
Poorly consolidated sands in California
demanded attention
Clays from surface deposits often mixed with
water
Little attention paid to mud properties
heavy
thick

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“Mud-Laden” Fluid
1913
Enormous waste of natural gas in drilling with
the cable-tool method.
Used to seal each gas bearing formation by
drilling with the hole full
Definition
mixture of water with a clayey material that
will remain suspended for a considerable time
free from sand, lime, cuttings, and other
similar material

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“Mud-Laden” Fluid
Advantages
Reduction in number of casing strings
Protection of upper sands
Prevention of migration between casings
Recovery of casing
Protection of casing from corrosion

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Mud Density
B. K. Stroud, 1922
“They continue to go by the consistency of the
mud fluid rather than by its actual weight”
“drillers should frequently weigh samples of the
mud..”
Materials for increasing density
iron oxide (Fe2O3) to 1.86 specific gravity
• used successfully in several fields
galena, a pigment-grade barite
• fall 1922 used to make a heavy mud

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Commercialization
Patent issued to B. K. Stroud in 1926 for the use
of weighting materials such as barium sulfate
and iron oxide
Assigned to National Pigments and Chemical
Company a subsidiary of National Lead Company
Sold paint grade barite.
Barite mining operations at El Portal California
Patent application for bentonite as a suspending
agent, by P. E. Harth, 1929

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BENTONITE
California Talc Company
Producer and marketer of clays and an
agent in the sale of brand bentonite as an
admixture for cement
Successful in stopping severe caving at
Kettleman Hills, California
1929
California Talc began the sale of
“Plastiwate” 95% barite and 5 % bentonite

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Mud Company
Patent situation with Phillip Harth led
California Talc to discontinue sales of
Plastiwate

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Continuing Development
By 1931
The application of bentonite to wall building
and filtration control
By 1940
Mud testing, density, viscosity, filtration,
……
Thinners
Filtration control agents Lost circulation
material

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Solving Problems for Drilling
Weight materials
Thinners
Filtration control
Lubricants
Corrosion inhibitors
Lost circulation
materials
Viscosifier
Shale stabilizers
Defoamers
Commercial
chemicals
Polymers
Emulsifiers
Oil-base fluids
Synthetic-base
fluids

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Functions of Drilling Fluids
Provide wellbore stability
Transport cuttings & cavings to surface
Suspend solids
Control subsurface pressure
Cool and lubricate bit and drill string
Help suspend weight of drill string and casing

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Functions of Drilling Fluids
Transmit hydraulic energy to downhole
tools
Provide a medium for wire line logs
Minimize formation damage
Protect drill string and casing from
corrosion

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Wellbore Stability
Stabilize water sensitive formations
Minimum fluid loss to formation
Impermeable wall cake
Minimum wellbore pressure
Chemically inhibitive environment
Minimize hydraulic erosion
Control drilling fluid circulation rates
Non-turbulent flow
Minimum frictional pressure in bore hole

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Wellbore Stability
Balance formation stress
Matrix pressure
Pore pressure
8000 ft
HP HP
FP
 
FP
+ +
+
8000 ft
Mud off sands and
gravels
Minimize erosion
Provide firm wall cake

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Transport Cuttings & Cavings
Transport efficiency sufficient to prevent
solids buildup inside the wellbore
To prevent stuck pipe
To prevent excessive torque and drag on
the drill string
Effective at both high and low mud flow
rates

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 Rock fragments
 Cavings
 Drilled cuttings
 Mud solids
 Foreign objects
• Particles wedge between drill string and bore hole wall

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Drillstring contact with borehole wall
– Fluid loss prevented by
pipe wall contact
– Thick sticky wall cake
– Differential pressure builds
up across area of contact
Excessive wellbore pressure
High rate of fluid loss to formation

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Suspend Solids
Provide quick gel strengths sufficient to
prevent solids from settling inside the
wellbore when not circulating
To prevent excessive wellbore pressure
when circulation is restarted
To prevent stuck pipe
To assist with running formation logs
Provide fragile gel strengths to allow
circulation to be restarted at low pressure

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Suspend Solids
Stuck pipe
Lost circulation
High ECD
Low density out
and high density
in

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Control Subsurface Pressure
WBP < FPP
HP
FPP
WBP > FPP
Fluid density sufficient to
control pore pressure

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Cool and Lubricate
Minimize friction
Between drill string and casing
Between drill string and formation
Between drill string and formation solids in
high angle holes
Prevent sticking of mud and solids to the
drilling assembly

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Transmit Hydraulic Energy
Provide a low viscosity at high shear rates
and fluid densities to maximize delivery of
pressure at optimum flow rates to down-
hole drilling tools.

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Minimize Formation Damage
Prevent precipitation of salts in pore spaces of
the formation
Prevent the migration of small solids into the
formation
Prevent the swelling of interstitial solids
Preserve the initial formation Wettability
Build a non damaging removable wall cake

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End

2 Introd to Drlg Flds.ppt Introd to Drlg Flds.ppt

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