Table Of ContentComposition and Properties of Drilling
and Completion Fluids
Composition and
Properties of Drilling
and Completion Fluids
Sixth Edition
Ryen Caenn
H. C. H. Darley
George R. Gray
AMSTERDAM(cid:129)BOSTON(cid:129)HEIDELBERG(cid:129)LONDON
NEWYORK(cid:129)OXFORD(cid:129)PARIS(cid:129)SANDIEGO
SANFRANCISCO(cid:129)SINGAPORE(cid:129)SYDNEY(cid:129)TOKYO
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ThiseditionisdedicatedtothememoryofWalterF.Rogers,GeorgeR.“Doc”
Gray,andH.C.H.“Slim”Darley.Theyweretrulypioneersinthedevelopment
of drilling fluids technology and applications and through their combined
efforts, codified this technology through the six editions of this book. We also
dedicate this edition to the many hundreds of technologists who have labored
so long to improve our industry. We stand on the shoulders of remarkable
men and women.
Preface
Walter F. Rogers wrote and published the first edition of Composition and
Properties of Oil Well Drilling Fluids in December of 1948. The book devel-
oped from his efforts in teaching drilling fluids technology to new drilling
fluid engineers while he was with the Houston Chemical Laboratory of Gulf
Oil Corporation. He produced two more editions, the last published in 1963.
The third edition went through five printings, the last in September 1979.
Doc Gray and Slim Darley took over the editing efforts beginning with the
fourth edition in October 1980 and a second printing in August 1981. They
presented the subject matter in a different approach, reflecting that “drilling
fluid technology has expanded enormously in scope and sophistication.”
BythetimethefiftheditionwaspublishedinMarchof1988,DocGrayhad
passed away and Darley took over the editing chores. The fifth edition also
brought a name change to the book, now encompassing “completion fluids”
and dropping “oil well” from the title.
Thesixtheditionstillhasthelookandfeelofthepreviousedition.Chapters10
and 11 have been completely rewritten. A new chapter on Waste Management
has been added. Other chapters have had updated information and references
inserted where appropriate. Twenty-three years between editions is too long to
wait for updates. There are still chapters needing revision, which we hope will
be done as soon as possible.
Ryen Caenn
xvii
Chapter 1
Introduction to Drilling Fluids
Chapter Outline
Functions ofDrillingFluids 2 Drilling FluidSelection 19
CompositionofDrilling Fluids 2 Location 21
PropertiesofDrilling Fluids 5 Mud-MakingShales 21
Density 5 Geopressured Formations 22
Flow Properties 7 HighTemperature 22
Control ofFlow HoleInstability 23
Propertiesatthe Well 12 FastDrilling Fluids 24
Filtration Properties 14 RockSalt 24
pH 16 HighAngleHoles 25
Alkalinity 17 FormationEvaluation 25
CationExchangeCapacity: ProductivityImpairment 25
MethyleneBlueTest 17 MudHandlingEquipment 26
ElectricalConductivity 18 Solids RemovalEquipment 26
Lubricity 18 Optimization 33
Corrosivity 18 References 34
The successful completion of an oil well and its cost depend to a considerable
extentonthepropertiesofthedrillingfluid.Thecostofthedrillingfluiditselfis
relatively small, but the choice of the right fluid and maintenance of the right
propertieswhiledrillingprofoundlyinfluencethetotalwellcosts.Forexample,
the number of rig days required to drill to total depth depends on the rate of
penetration ofthebit,and ontheavoidanceofdelays caused by caving shales,
stuckdrillpipe,lossofcirculation,etc.,allofwhichareinfluencedbytheprop-
erties of the drilling fluid. In addition, the drilling fluid affects formation eva-
luation and the subsequent productivity of the well.
It follows that the selection of a suitable drilling fluid and the day-to-day
control of its properties are the concern not only of the mud engineer, but
also of the drilling supervisor, the drilling foreman, and drilling, logging, and
productionengineers.Drillingandproductionpersonneldonotneedadetailed
knowledge of drilling fluids, but they should understand the basic principles
governing their behavior, and the relation of these principles to drilling and
CompositionandPropertiesofDrillingandCompletionFluids.DOI:10.1016/B978-0-12-383858-2.00001-9
©2011ElsevierInc.Allrightsreserved. 1
2 CHAPTER | 1 IntroductiontoDrillingFluids
productionperformance.Theobjectofthischapteris,therefore,toprovidethis
knowledgeassimplyandbrieflyaspossible,andtoexplainthetechnicalterms
so that the information provided by the mud engineer may be comprehensible.
Aspiring drilling fluid specialists who have no previous knowledge of drilling
fluidsshouldalsoreadthischapterbeforegoingontothemoredetailedcover-
age in the subsequent chapters.
FUNCTIONS OF DRILLING FLUIDS
Manyrequirementsareplacedonthedrillingfluid.Historically,thefirstpurpose
ofthedrillingfluidwastoserveasavehiclefortheremovalofcuttingsfromthe
borehole,butnowthediverseapplicationsfordrillingfluidsmaketheassign-
mentofspecificfunctionsdifficult.
Inrotarydrilling,theprincipalfunctionsperformedbythedrillingfluidareto:
1. Carrycuttingsfrombeneaththebit,transportthemuptheannulus,andper-
mit their separation at the surface.
2. Cool and clean the bit.
3. Reduce friction between the drilling string and the sides of the hole.
4. Maintain the stability of uncased sections of the borehole.
5. Prevent the inflow of fluids—oil, gas, or water—from permeable rocks
penetrated.
6. Formathin,low-permeabilityfiltercakethatsealsporesandotheropenings
in formations penetrated by the bit.
7. Assistinthecollectionandinterpretationofinformationavailablefromdrill
cuttings, cores, and electrical logs.
In conjunction with the above functions, certain limitations—or negative
requirements—are placed on the drill fluid. The fluid should:
1. Notinjuredrillingpersonnelnorbedamagingoroffensivetotheenvironment.
2. Notrequireunusualorexpensivemethodsofcompletionofthedrilledhole.
3. Not interfere with the normal productivity of the fluid-bearing formation.
4. Not corrode or cause excessive wear of drilling equipment.
COMPOSITION OF DRILLING FLUIDS
Drilling fluids are classified according to their base:
● Water-basemuds.Solidparticlesaresuspendedinwaterorbrine.Oilmay
be emulsified in the water, in which case water is termed the continuous
phase.
● Oil-basemuds.Solidparticlesaresuspendedinoil.Waterorbrineisemul-
sified in the oil, i.e., oil is the continuous phase.
● Gas. Drill cuttings are removed by a high-velocity stream of air or natural
gas. Foaming agents are added to remove minor inflows of water.
CompositionofDrillingFluids 3
Inwater-basemudsthesolidsconsistofclaysandorganiccolloidsaddedto
providethenecessaryviscousandfiltrationproperties,heavyminerals(usually
barite, added to increase the densitywhen needed), and solids from the forma-
tion that become dispersed in the mud in the course of drilling. The water
contains dissolved salts, either derived from contamination with formation
water or added for various purposes. Further details are given in Table 1.1.
Thesolidparticlesmaybeconvenientlydividedintothreegroupsaccording
to size: (1) colloids, from about 0.005–1micron (1micron= 0.001mm),
which impart viscous and filtration properties; (2) silt and barite (sometimes
called “inert solids”), 1–50microns, which provide density as just discussed
but are otherwise deleterious; and (3) sand, 50–420microns (assuming a
40-mesh screen on the shale shaker), which, apart from bridging large open-
ingsincertainveryporousformations,isobjectionablebecauseofitsabrasive
qualities.
TABLE1.1 Classification of DrillingFluidsAccordingto Principal
Constituent
Gas Water Oil
Drygas:Air,naturalgas, Freshwater Oil:Dieselorcrude
exhaustgas,combustion
gas
Mist:Dropletsofwateror Solution:Trueandcolloidal,i.e., Oilmud:Astableoil-base
mudcarriedintheair solidsdonotseparatefrom drillingfluidcontains:
stream. wateronprolongedstanding. 1.Water-emulsifying
Foam:Airbubblessur- Solidsinsolutionwithwater agents
roundedbyafilmofwater include: 2.Suspendingagents
containingafoam- 1.Salts,e.g.,sodiumchloride, 3.Filtration-controlagents
stabilizingsurfactant. calciumchloride Containscuttingsfromthe
Stablefoam:Foamcon- 2.Surfactants,e.g.,detergents, formationsdrilled.
tainingfilm-strengthening flocculants Maycontainbariteto
materials,suchasorganic 3.Organiccolloids,e.g., raisedensity.
polymersandbentonite. cellulosicandacrylic
polymers
Emulsion:Anoilyliquidmain-
tainedinsmalldropletsinwater
byanemulsifyingagent,e.g.,
dieseloilandafilm-stabilizing
surfactant
Mud:Asuspensionofsolids
(e.g.,clays,barite,smallcut-
tings)inanyoftheaboveliquids,
withchemicaladditivesas
requiredtomodifyproperties.
4 CHAPTER | 1 IntroductiontoDrillingFluids
Theactivityofthecolloidalfractionfundamentallyisderivedfromthevery
small size of the particle (and consequent high surface area) relative to its
weight. Because of this high specific surface, the behavior of the particles is
governed primarily by the electrostatic charges on their surfaces, which give
risetoattractiveorrepulsiveinterparticleforces.Claymineralsareparticularly
activecolloids,partlybecauseoftheirshape—tinycrystallineplateletsorpack-
etsofplatelets—andpartlybecauseoftheirmolecularstructure,whichresultsin
high negative charges on their basal surfaces, and positive charges on their
edges. Interaction between these opposite charges profoundly influences the
viscosityofclaymuds atlow flowvelocities,andisresponsiblefortheforma-
tion of a reversible gel structure when the mud is at rest.
Claysastheyoccurinnaturearecomposedofvariousclayminerals,suchas
montmorillonite,illite,andkaolinite,ofwhichmontmorilloniteisbyfarthemost
active.Otherminerals,suchasquartz,feldspar,calcite,etc.,mayalsobepresent,
inboththecolloidalandsilt-sizeranges.Whenclaysaremixedwithwater,the
viscosityoftheresultingmudperunitweightofclayaddeddependsonthepro-
portionofthevariousclayandothermineralspresent.Commercialclaysthatare
usedindrillingmudsareratedbytheiryield,whichisdefinedasthenumberof
42-gallonbarrels(0.16m3)ofmudwithanapparentviscosityof15centipoises
producedbyaton(2000lb;907kg)ofclay.Figure1.1showsthatWyomingben-
tonite,whichcontainsabout85%montmorillonite,hasbyfarthegreatestyield.
Similarly,inthedrillingwell,theriseinmudviscosityperfootofholedrilledis
muchgreaterwhendrillinginrichformations,suchastherecentmontmorilloni-
ticsedimentsoftheGulfCoast,thanwhendrillinginleanformations,suchasthe
siltyshalesoftheMid-Continent.Intheformercase,theviscositymustbekept
within bounds by chemical treatment, dilution, or mechanical separation of
drilled solids at the surface. In the latter case, the silts must be removed by
mechanical separation, and the necessary rheological and filtration properties
mustbeobtainedbyaddingcommercialclays.
Clay colloids are sometimes supplemented, or even entirely replaced, by
organic colloids when required by particular problems. For instance, if clays
areflocculatedbysolublesaltswithconsequentlossofrheologicalandfiltration
control, salt-resistant colloids (such as pregelatinized starch or cellulosic poly-
mers) are added to salt water, or to salt-contaminated muds. Cellulosic, poly-
acrylic, and natural gum polymers are also used in low-solid muds to help
maintain hole stability and to minimize dispersion of drill cuttings into the
mud. These polymers consist of long chains of unit cells, which are adsorbed
on the surface of the cuttings, protecting the cuttings from disintegration. The
viscouspropertiesofthesepolymersaremainlyduetomechanicalinterference
betweenthechains,whichdonotbuildgelstructures(exceptinthecaseofone
polymer whose chains can be crosslinked by chemical bonding).
The colloidal fraction of one type of oil-base mud consists of oxidized
asphalt. Viscous and filtration properties are obtained in another type (known
as invert emulsion) by tightly emulsifying substantial quantities of water. Gel
PropertiesofDrillingFluids 5
Weight in pounds per cubic foot
63.7 67.5 71.2 75.0 78.7 82.5 86.2 90.0
Weight in pounds per gallon
8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0
60
ntripoises 4500 *Wyoming bentonite Premium drilling clay Common drilling clay Low yield drilling clay
e
osity in c 30
Visc
20
10
0
0 5 10 15 20 25 30 35 40 45 50
Percent solids by weight Specific gravity of solids=2.4
200 10075 50 40 30 25 20 18 16 14 12 10 9 8
Yield (15 Centipoise mud) in barrels per ton
2 4 6 8 10 12 14 16 18 20 25 30
Percent solids by volume
10 20 30 40 50 75 100 150 200 250
Pounds solids per barrel of mud
*A good salt clay in salt water approximates the bentonite yield curve in fresh water.
FIGURE1.1 Typicalclayyieldcurves.(From“PrinciplesofDrillingFluidControl.”Courtesyof
PetroleumExtensionSerive,UniversityofTexas,Austin.)
structures may be obtained by adding clays treated with surfactants so as to
make them dispersible in oil, and similarly treated lignite may be added to
obtain improved filtration properties, if these are required.
PROPERTIES OF DRILLING FLUIDS
Density
Density is defined as weight per unit volume. It is expressed either in pounds
per gallon (lb/gal) or pounds per cubic foot (lb/ft3), or in kilograms per
cubic meter (kg/m3), or compared to the weight of an equal volume of water,
as specific gravity (SG). The pressure exerted by a static mud column depends
