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Transcript of Intro to Drilling Fluids New
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Introduction to rilling Fluids
IDPT
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Introduction to Drilling FluidsIntroduction to Drilling Fluids –– WBM/OBMWBM/OBM
• Course Contents:
• Course Objectives,
• Basic Functions,
• Basic Properties,
• Water based and oil based muds,
• Performance Testing.
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• Course Objectives:
• At the end of this course,YOU will be able to:
• List functions & properties of drilling fluids,
• Understand the formation damage
• Describe different mud systems,
• Understand the performance testing of drilling muds
Introduction to Drilling FluidsIntroduction to Drilling Fluids –– WBM/OBMWBM/OBM
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IntroductionIntroduction
• The drilling fluid is a liquid or gas that is circulated downthe drillpipe through the bit and up to the surface. Untiltoday an oil or gas well cannot be drilled without thisbasic concept of circulation.
• A cycle is referred to as the time required for the pump tomove drilling fluid down to the hole and back to thesurface,
• The drilling fluid is a key part of the drilling process, andthe success of a drilling program depends on its design.
• A drilling fluid for a specific area must be individually
designed to meet specific requirements.
• In general drilling fluids will have many properties that arebeneficial to the operation, but also have some propertiesthat are not desirable. There is always a compromise.
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IntroductionIntroduction
• A service company provides mud engineering services on
rigs.
• Drilling fluid technology is dominated by three factors :
• Performance
• Economics
• Environmental concerns.
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HistoryHistory
• 1900 Water and Clays
No control of properties
• Weighting Agent (‘40’s) Water base muds
• Controlled Filtrate(‘50/’60’s) Cellulose polymers
• Polymers ( 70 ’s) PHPA systems
• Mineral oils(‘80’s) Formation compatibilty
• Synthetics (‘90’s) Environmental
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Introduction to Drilling FluidsIntroduction to Drilling Fluids –– WBM/OBMWBM/OBM
Section 1
Functions of Drilling Fluids
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FunctionsFunctions ofof DrillingDrilling FluidsFluids
• Basic functions;• There are at least ten important drilling-fluid functions :
• Remove cuttings from the bottom of the hole, transport them to the surface andrelease them.
• To cool and lubricate the bit and drillstring,• Coat the hole with a low permeability wall cake (filter cake),
• Control subsurface pressures,
• Hold cuttings and weight material in suspension when circulation is stopped,
• Support part of the weight of drill pipe and casing,
• Prevent or reduce to a minimum any damage to the surrounding formations,
• Allows information to be obtained about the formations penetrated,
• Transmit hydraulic horsepower to the bit,
• Control corrosion,
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FunctionsFunctions ofof DrillingDrilling FluidsFluids
• Remove cuttings from the bottom of the hole, transport them to thesurface and release them.
• Annular velocity is the key parameter to overcome the effect of gravity,
• Annular velocities between 100 and 200 ft/min are frequently used,• Annular velocity can be obtained from:
• AV=Pump rate (bbls /min) / Annular capacity (bbls / ft).
• Density and Viscosity also contribute to improving the carrying capacity of
a fluid,
• The cuttings and solids should be removed at the surface to obtain a
clean fluid to be pumped down the hole.
• Sand is very abrasive and if it is not removed it will damage mudpumps, lines, and tubulars.
• If the cuttings are not removed they will break down and fill the mud
with colloids which will deteriorate the properties of the mud.
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FunctionsFunctions ofof DrillingDrilling FluidsFluids
• Cool and lubricate the bit and drillstring:
• As the bit and drillstring rotate against the formation, a tremendous amount of
heat is generated,
• The drilling fluid absorbs the heat generated and carries it to the surface,
where it is released to the atmosphere,
• The drilling fluid should have some lubrication properties which will help
reduce the torque and drag.
• The lubrication occurs between the hole and the surface of the bit or
drillstring
• Drilling fluid can also lubricate the bearings of the bit, of the mud motor etc…
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FunctionsFunctions ofof DrillingDrilling FluidsFluids
• Deposit a low permeability/impermeable wall cake :
• A good drilling fluid should deposit a thin, low permeability filter cake on
the wall of the hole in front of permeable formations to consolidate the
formation and to retard the passage of fluid from the wellbore into theformation.
• The differential pressure will result in fluid invasion, which in absence of
a filter cake would force mud or filtrate into the formation,
• The loss of mud or high filtrate volume is likely to cause formation
damage,
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FunctionsFunctions ofof DrillingDrilling FluidsFluids
• Control subsurface pressure :
• Mud hydrostatic pressure must be sufficient to prevent an influx ,
• The mud density ( mud weight) is the controlling factor:• Hydrostatic pressure exerted by the mud column:
Hydrostatic pressure (psi ) = (Vertical depth ft. )(mud weight lb/gal )(0.052)The mud gradient in (psi/ft) = (mud weight lb/gal )(0.052)
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FunctionsFunctions ofof DrillingDrilling FluidsFluids
• Hold cuttings and weight material in suspension when circulation is
stopped:
• This is achieved with good thixotropic properties of the fluid.
• Thixotropy is the ability of a fluid to develop gel strength with time when it isallowed to stop at rest, but will also allow it to return to its fluid state by applying
mechanical agitation to it.
• Support part of the weight of drill pipe and casing:
• As a well is drilled deeper, the weight of the drill string and casing string
becomes a critical factor.
• The mud helps reduce the weight of the drill string and casing string as these
are buoyed up by a force equal to the weight of mud displaced.
• Increasing the mud weight increases the force of buoyancy.
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FunctionsFunctions ofof DrillingDrilling FluidsFluids
• Avoid damage to productive zone :
• The fluid used to drill the production zone will have an important impact onwell productivity ,
• Loss of production results from:
- Swelling clays
- Reservoir pores blocked with solids and/or micro-emulsion droplets.
• Allows information to be obtained of the formations penetrated
• The properties of the fluid should not interfere with the logging program, theyshould facilitate obtaining the desired information.
• For example, the mud should have a defined/known resistivity so that whenlogs are run the resistivity of the formation can be derived.
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FunctionsFunctions ofof DrillingDrilling FluidsFluids
• Transmit hydraulic horsepower to the bit :
• The drilling fluid is the medium to transmit hydraulic horsepower to the bit,
• The flow properties of the mud exert a considerable influence on hydraulics.
They should be optimized to obtain good hydraulics.• Optimum hydraulics will promote high penetration rates.
• Protect the drill pipe against corrosion :
• The drilling fluid should be non corrosive,
• Corrosion rates will increase as pH decreases.
• Corrosion can lead to :
- premature Wash out
- premature pump failure
- premature surface leaks.
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Introduction to Drilling FluidsIntroduction to Drilling Fluids –– WBM/OBMWBM/OBM
Section 2
Properties of Drilling Fluids
P tiP ti ff D illiD illi Fl idFl id
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• Density
• The primary performance requirement for a drilling fluid is
pressure control
• The density of any mud is directly related to the amount andaverage specific gravity of the solids in the system,
• The control of density is important in that the hydrostatic
pressure exerted by the column of fluid is required to contain
formation pressure and to aid in keeping the hole open,
• The density of drilling fluids should be dictated by
formation pressures,
• The pressure exerted by the fluid column should behigher than the formation pressure.
PropertiesProperties ofof DrillingDrilling FluidsFluids
P tiProperties fof D illiDrilling Fl idFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Density
• The control of density is important,
• The density will need adjustment during well operations,
• Weighting material such as Barite will be used due to its high
specific gravity ( 4.2 sg),
• Under circulating conditions the effective pressure is increased
by the circulating pressure,• The Equivalent Circulating Density
ECD = (depth x 0.052 x mud density(ppg)) +Pann
depth x 0.052
PropertiesProperties ofof DrillingDrilling FluidsFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Viscosity
• Viscosity is defined as the resistance of a fluid to flow.
• It is routinely measured in the field using the Marsh funnel and it is
the timed rate measured in seconds of what it takes one quart offluid to flow through the funnel. (water = 27s)
• As penetration increases, inert solids and contaminants enter the
mud system and can cause the viscosity to increase.
• The Marsh Funnel can be used to determine if the viscosity is in
the proper range.
PropertiesProperties ofof DrillingDrilling FluidsFluids
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• Rheology
• Rheology is the science of the deformation of materials ( if they are
solid ) or of their flow ( if they are liquid ) under applied stress.• In the case of drilling fluids Rheology is the study of the
characteristics that define the flow and gelation properties of a drilling
fluid.
PropertiesProperties ofof DrillingDrilling FluidsFluids
P tiProperties fof D illi gDrilling Fl idFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
Rheology-Characterisation of Fluids;
A
2 Platelets
F
-The resistance or drag force is the shear stress
v
v + dv
-The difference in the velocities divided by the
distance is called the shear rate
PropertiesProperties ofof DrillingDrilling FluidsFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Shear Stress – the force required to overcome a fluid’s resistance toflow, divided by the area that the force is acting on:
Force causing the shearing Unit : lb / 100 ft2
Surface area of the platelet
• Shear rate – the relative velocity of the fluid layers divided by theirnormal separation distance
Difference of velocity between 2 platelets Unit : sec-1
Distance between 2 platelets
P i f D illi Fl id
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Rheology Models ;
Shear rate
Shear
stress
Newtonian
BinghamPower Law/Non Newtonian
P iP i ff D illiD illi Fl idFl id
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Newtonian Fluids – no particles larger than a molecule – water. Shear Stress
is directly proportional to shear rate.
• Shear Stress = coefficient of viscosity * shear rate
τ = μγ
• Coefficient of Viscosity = Shear Stress / Shear Rate
The units of the coefficient of viscosity are : Centipoise, cP
P tiP ti ff D illiD illi Fl idFl id
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PropertiesProperties ofof DrillingDrilling FluidsFluids
Non-Newtonian Fluids (anything other than a Newtonian fluid) - Bingham
Plastic Model
• A model which has been used often to characterize the flow properties of
drilling mud is the Bingham plastic model.
• τ = τy + μpγ
( The shear stress is equal to the shear stress at zero shear rate + the
rate of increase of shear stress with increasing shear rate * shearrate.)
•The
τy ( shear stress at zero shear rate ) is called the yield point andthe μp ( rate of increase of the shear stress with increasing shear rate )
is called the plastic viscosity.
P tiP ti ff D illiD illi Fl idFl id
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Plastic Viscosity and Yield Point
• Measurements of the plastic viscosity and yield point areessential in determining the cause of abnormal viscosities indrilling fluids.
• Plastic viscosity is the part of flow resistance caused bymechanical friction (interaction of solid particles).
• High concentration of solids leads to friction which will in turnincrease the plastic viscosity. Decreasing the size of solids at
constant volume also increases the plastic viscosity becausethere is an increase in surface area which increases friction.
• The yield point, the second component of resistance to flow ofa drilling fluid, is the measurement of the electro-chemical or
attractive forces in a mud. These forces are a result ofnegative and positive charges located near the surface of theparticles.
P tiProperties fof D illiDrilling Fl idFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Measuring Viscosity with the Fann V-G Meter
•The commonly used Fann V-G (viscosity-gel),or direct indicator
viscometer, is specially designed to measure the rheological
properties of the drilling fluid in the field.
• The instrument has a torsion spring-loaded bob which gives a
dial reading proportionnal to torque and analogous to the shear
stress.
•The speed of rotation rpm,is analogous to the shear rate.
•Instrument constants have been built in so that plastic viscosity
and yield point readings are obtained from dial readings for two
rotor speeds, 300 and 600 rpm.
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PropertiesProperties ofof DrillingDrilling FluidsFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Gel Strength ( lb/100 ft2);• Gel strength measurements denote the thixotropic properties of the
mud. They are the measure of the attractive forces under static or
non flow conditions.
• Yield point, on the other hand is the measure of attractive forces
under flowing conditions.
• Gel strengths are classified as progressive ( strong ) or fragile (
weak ) type gels. A progressive gel starts low, but increases
consistently with time; whereas, a fragile gel, may start high initially
but only increase slightly with time.
• Progressive gels are undesirable because they may create
problems such as excessive pump rates to break circulation, lost
circulation, hole swabbing, etc.
PropertiesProperties ofof DrillingDrilling FluidsFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Gel Strength ( lb/100 ft2
)
PropertiesProperties ofof DrillingDrilling FluidsFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Non-Newtonian Fluids – Power Law Model
• The Power Law Model is a more versatile approach to describe the flowproperties of a non-Newtonian fluid.
• The equation for the power law model is: τ = Κγn
Where: τ = Shear stress
Κ = Consistency Index
γ = Shear rate (sec-1)
n = Power Law index
• The K and the n are constants representing characteristics of a particularfluid.
• K is a consistency index indicative of the pumpability of the fluid
• n is the Power Law Index indicating the the degree of non-Newtonian behavior over a given shear rate range.
• As a fluid becomes more viscous, K increases; as a fluid becomesmore shear thinning, n decreases.
PropertiesProperties ofof DrillingDrilling FluidsFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Rheology and flow regimes;
• In 1833, Osborne Reynolds conducted experiments with
various liquids flowing through a glass tube.• The type of flow in which all the fluid motion is in the
direction of flow, is now called laminar flow,
• A rapid, chaotic motion in all directions in the fluid is
called turbulent flow,
• A fluid’s flow at extremely low flow rates is plug flow,
• The flow can alternate back and forth between laminar
and turbulent, it is a transitional flow.
PropertiesProperties ofof DrillingDrilling FluidsFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
Velocity Profile ( Sliding motion )Velocity is maximum at the center
• Rheology - Laminar flow;
PropertiesProperties ofof DrillingDrilling FluidsFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Rheology - Turbulent flow;
Velocity Profile ( Swirling motion )Average particle velocity is uniform
PropertiesProperties ofof DrillingDrilling FluidsFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Rheology - Reynolds number
• Reynolds number takes into consideration the basic factors
of pipe flow :• Pipe, diameter, average velocity, fluid density and fluid
viscosity,
• Re= Velocity* pipe diameter* density / fluid viscosity
• Laminar < 2000- Transition - 3000 <Turbulent
The particular flow regime of a drilling fluid duringdrilling operations can have a dramatic effect on parameters
such as pressure losses, hole cleaning and hole stability.
PropertiesProperties ofof DrillingDrilling FluidsFluids
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PropertiesProperties ofof DrillingDrilling FluidsFluids
• Filtration ;• There are two types of filtration - dynamic and static.
• In dynamic filtration, the flow tends to erode away the filter cake as
it is deposited; while in the static case, the cake continues to
become thicker with time.
• There is no way to measure dynamic filtration in the field, so
measurements done by the mud engineer are confined to tests
done under static conditions.
• For filtration to occur, the permeability of the formation has to be
such that it will allow passage of fluid between the pore openings.
• As the fluid is lost, a build up of the mud solids is formed on the wall
face. ( Wall Cake ). The solids that form the mud cake are both
native solids found in the formations drilled and different kinds of
solids added at the surface (fluid loss control additives).
• In order to obtain the best possible filter cake, careful consideration
should be given not only to the base materials used, but on the
particle size distribution.
PropertiesProperties ofof DrillingDrilling FluidsFluids
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• Filtration ;• The following problems occur from improper filtration control :
• Tight spots in hole causing excessive drag.
• Greatly increased pressure surges when moving pipe due todecreased hole diameter – further exacerbated by poor
rheology.
• Differential pressure sticking of the drill string due to increased
area of contact of pipe in a thick filter cake and rapid build-up ofsticking force in high permeability cake.
• Primary cementing problems due to poor displacement of
dehydrated mud and excessively thick filter cakes.
• Formation evaluation problems from excessive filtrate invasionand thick filter cakes.
• Excessive formation damage from mud filtrate.
PropertiesProperties ofof DrillingDrilling FluidsFluids
PropertiesProperties ofof DrillingDrilling FluidsFluids
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• Filtration;• Drilling fluids used to drill the production zone have an impact
on well productivity due to the compositions and properties of
drilling and completion fluids,
• Filtration control, bridging and filtrate chemistry are the mostimportant properties for minimizing formation damage.
• How easy it is to remove the filter cake prior to production
ope t esp o gg u ds
PropertiesProperties ofof DrillingDrilling FluidsFluids
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• Filtration schematic;
Pore Throat
Fluid phase
Pore Blocking
Agent
Filter
Cake
pp gg
PropertiesProperties ofof DrillingDrilling FluidsFluids
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• Filtration control;• The formation of a thin tight filter cake will protect against high
drilling fluid filtrate invasion into the formation.
• Filtration control is achieved in drilling fluids by the addition ofbentonite clay, fluid-loss control polymers, lignite, resins, calcium
carbonate,etc.
• A common practice is to further reduce the filtration rate of the
drilling fluid before the reservoir formation is drilled.
• In many cases the reservoir formation is drilled with special clean (
clay free ) Drill-In fluids to prevent emulsions from forming and
plugging the formation. These fluids are formulated by polymers
and properly sized blocking inert solids such as Calcium
Carbonate.
pp gg
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SolidsSolids ContentContent
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SolidsSolids ContentContent
TheThe effecteffect ofof densitydensity onon PVPV -- YPYP
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TheThe effecteffect ofof densitydensity onon PVPV YPYP
SolidsSolids controlcontrol
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SolidsSolids controlcontrol
SolidsSolids controlcontrol
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SolidsSolids controlcontrol
Introduction to Drilling FluidsIntroduction to Drilling Fluids –– WBM/OBMWBM/OBM
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Section 3
Types of Drilling Fluids
Introduction to Drilling Fluidsg WBM/OBM/
TypesTypes ofof DrillingDrilling FluidsFluids
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ypyp gg
• Water-based muds;
• The majority of drilling fluids are water based.
• The base liquid can be :
• Fresh water,
• Sea water,
• A specific brine base (NaCl, KCl, formate based)
• Special additives are used to build a water based mud in orderto achieve the rheological and filtration control parametersrequired to drill each individual hole section.
TypesTypes ofof DrillingDrilling FluidsFluids
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ypyp gg
• Water- based muds and additives ;
• Clay materials,
• Viscosity control additives,• Viscosifiers,
• Thinners,
• Filtration control additives,• Density control additives .
TypesTypes ofof DrillingDrilling FluidsFluids
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ypyp gg
• Clay materials ;
• Bentonite is used in drilling fluids for viscosity and fluid
loss control,
• Different grades of bentonite :
• Wyoming bentonite, pure sodium montmorillonite,
• API Bentonite, montmorillonite treated with polymers,
• OCMA Bentonite, calcium bentonite treated with soda
ash to replace the calcium with sodium,
• Commercial clays are graded according to their yield.
(Yield is defined as the number of barrels of 15 centipoisemud that can be obtained from one ton of dry material )
TypesTypes ofof DrillingDrilling FluidsFluids
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yp g
TypesTypes ofof DrillingDrilling FluidsFluids
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• Clay materials ;,
• The yield of a clay will be affected by the saltconcentrations of water. Clay is hydrated in fresh water or
drill water. The higher the salt content the lower the yield.
• Hydration is reduced by the presence of Calcium andMagnesium ions, therefore a chemical treatment (Soda
Ash) of the base water will be necessary prior to hydration,
• Salt water gel (attapulgite) or prehydrated gel will be usedwith salt concentration. This product is rarely – if ever – used.
TypesTypes ofof DrillingDrilling FluidsFluids
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• Viscosity control additives ;,
• Organic Polymers such as Xanthan, PAC or CMC areviscosifiers with long chains molecules :
• Poly-anionic Cellulose polymer,
• Carboxyl Methyl Cellulose polymer,
• Chemicals thinners (dispersants) will reduce the viscosity
of drilling fluids:• Phosphates, lignites, lignosulfonates, tannins or
synthetic thinners may be used.
TypesTypes ofof DrillingDrilling FluidsFluids
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• Filtration control additives ;,
• Clays such as Bentonite support filtration building a cake,
• Organic Polymers such as starch will swell and is a veryeffective fluid loss control additive.
• Temperature stability is limited to 250 ° F,
• Low viscosity CMC and PAC are also good for forming a
filter cake,• PACs work with salinity( max 60,000ppm) and
temperature stability is limited 350 ° F.
TypesTypes ofof DrillingDrilling FluidsFluids
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• Density control additives ;,
• Limestone: Mud weight equivalent ( 12ppg)
• Calcium Carbonate, CaCo3 , Specific Gravity: 2.7• Barite: Mud weight equivalent ( 20ppg)
• Barium Sulfate, BaSo4, Specific Gravity : 4.2
• Hematite: Mud weight equivalent ( 25ppg)• Ferrous Oxide, Fe2O3, Specific Gravity: 5.0
• Galena: Mud weight equivalent (32ppg)
• Lead Sulfide, PbS, Specific gravity : 7.4
TypesTypes ofof DrillingDrilling FluidsFluids
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• Water- based muds;
• The diverse class of water- based mud needs to beclassified :
• Non inhibitive muds
• Where no inhibition is required to control hydratable ordispersible formations
• Inhibitive muds:• Where inhibition is required to control hydratable or
dispersible formations
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• Non inhibit ive muds;
• The simplest water based muds, are usually inexpensive.
• Non inhibitive muds , lightly treated are used for :
• Top hole sections,
• Non reactive formations.
• The main components of these fluids are :
• Native formation clays, commercial bentonite,polymers
• Organic thinners - lignites.
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• Inhibitive muds;
• Inhibitive muds reduce the chemical interaction betweenthe mud and the formation,
• The use of inhibitors in water based drilling fluidsminimize the swelling (hydration) of clays and reactive(dispersible) shales,
• The diverse inhibitors used are :
• Polymers,
• Cations (such as potassium from KCl)
• Glycols.
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• Polymer muds;
• Polymers, naturals,synthetics are routinely used for:
•Viscosity
• Filtration control,
• Shale inhibition.
Water
Shale
Polymers
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• High cation concentrations fluids;
• A cation is a mud inhibitor, such a salt, added to a drillingmud to minimize the hydration of formations.
• Cations exchange occurs.
• Inhibitor Cations :
• Sodium
• Calcium• Potassium
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• Inhibition;
Ion ExchangeLimit Hydration
Na+
Na+
Na +
Na+
Water
Water + KCl
K+
K+
K+
Na+
Na+
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• Water-based muds;
• Spud muds,
• Polymer muds,
• Lignosulfonates muds,
• Lime and calcium mud,
• KCl muds,
• Salt saturated muds,
• Glycol muds.
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• Oil base mud;
• Oil-based drilling fluids are :
• Highly inhibitive,• Resistant to contaminations,
• Stable at high temperatures and pressures,
• Highly lubricious,• Non corrosive.
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• Invert Emulsion;
• The basic components of an oil base mud include :
• Oil,
• Water / Brine,
• Emulsifier,
• Oil wetting agents,
• Fitration control agents
• Viscosifiers
• Weighting agent
A chemical emulsifier must be addedto prevent the water droplets tosettle out of the emulsion. Theemulsifier also permits water
originally present in the rockdestroyed by the bit to emulsifyeasily
A chemical wettability reversal agent isadded to make the solids in themud preferentially wet by oil ratherthan by water. Otherwise the solids
will be absorbed by the waterdroplets and cause high viscositiesand eventual settling of barite
• The volume percentage of oil and water are expressed as anoil / water ratio .
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• Invert Emulsion;
Emulsifier
Water droplets
Oil External phase
Introduction to Drilling FluidsIntroduction to Drilling Fluids –– WBM/OBMWBM/OBM
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Section 4
Performance Testing
PerformancePerformance TestingTesting
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• API drilling fluids tests;
• Drilling fluids are continually measured and adjusted at
the wellsite.
• Basic physical and chemical tests serve to monitor the
drilling fluid conditions.
• American Petroleum Institute issues recommended
practices for testing procedures and equipments,
• API RP 13B -1 water based
• API RP 13B -2 oil based drilling fluids
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• Standard API tests;
• Tests common to water and oil based muds:
• Mud weight – mud balance• Filtration – API filter press, HTHP Filter press
• Water ,Oil and Solids – API retort
• Viscosity and Gel strength• Marsh Funnel
• Viscometer – Fann 6 speed VG meter
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• Formulas and units;
• Density : the primary performance requirement for a drilling
fluid is pressure control,
• The mud weight is the measure of the density of the
drilling fluid expressed as :
• pounds per gallon (lb/gal, ppg)
• pounds per cubic foot (pcf)
• kilograms per cubic meter.(kg/m3)
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• Formulas and units;
• Filtration : API Filter Press,
• Darcy law application,• Time 30 min,
• Atmospheric temperature,
• Pressure 100 psi,• Volume of filtrate,
• Cake analysis.
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• Formulas and units;
• Liquid and Solid content :
• A carefully measured sample of mud is heated in a 50 mlretort kit until the liquid components are vaporised,
• The vapors are then condensed and collected in a
measuring glass,
• The volume of liquid ( oil and/or water is directly read asa percentage,
• The volume of solids (suspended and dissolved) is
calculated by substraction of 100%.
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• Formulas and units;
• Rheology is tested with the Fann V-G meter .
• The commonly used V-G(viscosity-gel),or direct indicator
viscometer, are specially designed to facilitate the use of the
Bingham plastic Model in conjunction with drilling fluids in the
field.
• The instrument has a torsion spring-loaded bob which givesa dial reading proportionnal to torque and analogous to the
shear stress.
• The speed of rotation, rpm,is analogous to the shear rate.
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• Formulas and units;
• The determination of viscosities are obtained from the dial
readings at 600 rpm and 300 rpm .
• The datas are used to calculated:
• Apparent viscosity : Fann 600/2 ( cp )
• Plastic viscosity : Fann 600- Fann 300 ( cp )
• Yield Point: Fann 300 – Plastic Viscosity ( lbs /100ft2)
• Gel Strength - 10 Sec and 10 min
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• Formulas and units;
• Sand control:
• The percentage of sand in the mud is measured by using
a 200 mesh sieve and a graduate tube,
• The glass measuring tube is filled with mud to the scribe
line, water is then added up to the next scribe line,
• The fluid is filtered through the sieve,
• The sand % retained on the sieve is calculated washing
the sieve with a funnel and allowing the sand to settle.