Water-base Drilling Fluids

Water-based drilling fluids, regardless of the name assigned to them, usually contain clays, water soluble chemicals (including salts), a pH control additive (hydroxyl source), and one or more organic polymers, surfactants, and deflocculants.

In order for drilling fluid engineering to be a science and not an art, a basic understanding of the chemistry involved is required. This chapter attempts to provide the chemical background to the reactions that take place in the fluid.

By adoption of this approach the engineer will be well equipped to deal with variations in the fluid properties which may occur from time to time. If the basic chemical concepts are well understood, then the causes of any problems can be better identified and dealt with.

The Structure of Matter

The properties and reactions of materials can be related to the basic structures of the atoms and molecules of which they are formed. The difference between water and diesel, bentonite and sand, and so on, arises from their physical and chemical properties which are best understood in these terms.

Vortex formation in fluid

Elements and Compounds

An element is a chemically unique substance which cannot be split up into a simpler chemical form by chemical means. The names of the various elements are usually written as abbreviations to simplify chemical notation. A full list of elements and their symbols is given in Table 1.

Table 1. Known Elements and Atomic Weights

ElementSymbolAtomic NumberAtomic WeightElementSymbolAtomic NumberAtomic Weight
ActiniumAc89227*MercuryHg80200.59
AluminumAl1326.9815MolybdenumMo4295.94
AmericumAm95243*NeodymiumNd60144.24
AntimonySb51121.75NeonNe1020.179
ArgonAr1839.948NeptuniumNp93237.0482
ArsenicAs3374.9216NickelNi2858.71
AstalineAt85210*NiobiumNb93237.0482
BariumBa56137.33NitrogenN714.0067
BerkeliumBk97247*NobeliumNo102259*
BerylliumBe49.01218OsmiumOs76190.2
BismuthBib83208.9808OxygenO815.9994
BoronB510.81PalladiumPd46106.4
BromineBr3579.904PhosphorusP1530.9738
CadmiumCd48112.41PlatinumPt78195.09
CaesiumCs55132.9054PlutoniumPu94244*
CalciumCa2040.08PoloniumPo84209*
CaliforniumCf98251*PotassiumK1939.0983
CarbonC612.011PraseodymiumPr59140.9077
CeriumCe58140.12PromethiumPm61145*
ChlorineCl1735.453ProtactiniumPa91231.0359
ChromiumCr2451.996RadiumRa88226.0254
CobaltCo2758.9332RadonRn86222*
CopperCu2963.546RheniumRe75186.2
CuriumCm96247*RhodiumRh45102.9055
DysprosiumDy66162.50RubidiumRb3785.467
EinsteiniumEs99254*RutheniumRu44101.07
ErbiumEr68167.26SamariumSm62150.4
EuropiumEu63151.96ScandiumSc2144.9559
FermiumFm100257*SeleniumSe3478.96
FluorineF918.9984SiliconSi1428.0855
FranciumFr87223*SilverAg47107.868
GadoliniumGd64157.25SodiumNa1122.9898
GalliumGa3169.72StrontiumSr3887.62
GermaniumGe3272.59SulphurS1632.06
GoldAu79196.9665TantaiumTa73180.9479
HafniumHf72178.49TechnetiumTc4398.9062
HeliumHe24.0026TelluriumTe52127.60
HolmiumHo67164.9304TerbiumTb65158.9254
HydrogenH11.0079ThalliiumTl81204.37
IndiumIn49114.82ThoriumTh90232.0381
IodineI53126.9045ThuliumTm69168.9342
IridiumIr77192.22TinSn50118.69
IronFE2655.847TitaniumTi81204.37
KryptonKr3683.80TungstenW74183.65
LanthanumLa57138.9055UraniumU92238.029
LawrenciumLr103260*VanadiumV2350.941
LeadPb82207.2XenonXe54131.30
LithiumLi36.941YtterbiumYb70173.04
LutetiumLu71174.97YttriumY3988.9059
MagnesiumMg1224.305ZincZn3065.38
ManganeseMn2554.9308ZirconiumZr4091.22
MendeleviumMd101258*

Atomic weights quoted are the 1969 values based on carbon 12 and include the IUPAC revision 1971 Values marked * are for the most stable or most common isotopes.

Elements can combine together to form compounds. A compound has different chemical and physical properties than those of the simple mixture of elements from which the compound is formed. Thus hydrogen and oxygen are both gases and remain gases when they are mixed together. However, if they are chemically combined, they form water, which is a liquid. When elements combine together, they do so in a fixed ratio by weight, which always remains constant for one particular compound.

Atoms and Molecules

An atom is the smallest particle of an element which can exist and still retain the same chemical properties of that element. Atoms are the basic building bricks of matter from which all things are constructed. They are the smallest units of matter which can undergo chemical change.

A molecule is the smallest particle of a compound which can exist and still retain the same chemical properties of that compound. Molecules consist of atoms chemically bonded together in a precise arrangement. A molecule of water consists of two atoms of hydrogen combined with one atom of oxygen to give a chemical formula of H2O. When the elements hydrogen and oxygen combine to form the compound water, each molecule of water consists of two atoms of hydrogen bonded to one atom of oxygen.

 

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