Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Topic overview Do you want to know about Link til PDF-fil med dypere teori og lab.øvinger Clays in Drilling Fluids Clays in Drilling Fluids ? PrehydrationPrehydration ? Clay Mineral Groups Clay Mineral Groups ? Fundamental Building Units Fundamental Building Units ? or are you stuck in the mud ? IntroductionIntroduction to Introduction Clay Chemistry

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids The group of minerals classed as clays play a centrale role in many areas of petroleum technology such as: Drilling and formation stability Drilling fluid technology Reservoar productivity Since the elements that constitute the clays account for more than 80% of the mass of the earth (Al 8%, Si 27.7%, O 46.6%), it can be readily realized that every stage of drilling a hole brings contact with clays. There are over 400 mineral and rock names to describe clay minerals. 1: Introduction Physical Phenomena in Clays Physical Phenomena in ClaysPhysical Phenomena in Clays Physical Phenomena in Clays. Click on the text above and you will enter a very interesting web-page.

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Basic Features There are a number of features of the clay minerals that distinguish them as a group: Fine size (less than 2  m) Large surface area Chemical reactivity of the surface Composed of the same chemical components

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids 2: Fundamental Building Units Clay is composed essentially of silica, alumina and water. Lesser quantities of iron, magnesium, sodium and potassium. Fundamental building units of clay minerals: Octahedral layer Tetrahedral layer

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Tetrahedral Layer In each tetrahedral unit, a silicon atom is located in the centre of a tetrahedron, eqidistant form four oxygen atoms, or hydroxyls, if needed to balance the structure. The silica tetrahedral groups are arranged to form a hexagonal network, which i repeated infinitely to form a sheet of composition Si 4 O 6 (OH) 4. The figure is viewed from below, to show the hexagonal structure with a ”hole” in the centre.

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Octahedral Layer This unit consists of two sheets of closely packed oxygens or hydroxyls in which aluminium, iron or magnesium ions are embedded in octrahedral coordination When Aluminium is present, only two thirds of the possible positions are filled to balance the structure – gibsonite – Al(OH) 3 When magnesium is present, all the positions are filled and the structure is brucite – Mg(OH) 2 Often in clays, this layer contains more than one metal ion.

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Structures of Clay Minerals Tetrahedron and octahedral units Layers Structure The fundamental units of tetrahedral sheets and octahedral sheets can combine with the hydroxyl group of the tetrahedral layer contributing to the octahedral layer. Different combinations of these units and chemical modification of the basic structure give rise to the range of clay minerals with different properties.

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids 3: Clay Mineral Groups There are over 400 mineral and rock names to describe clay minerals. We will restrict our attention only to a few minerals that are most common and most applicable minerals to petroleum technology: Montmorillonite Kaolin Micas Chlorite These clay minerals are built up by different ratios of silica layer to octahedral layer. The most important groups is: 2:1 layer 2:1:1 layer 1:1 layer

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Kaolin The origin of Kaolin is often hydro-termal alternation of feldspars, or from volcanic ash, and is extensively found in Shales and marine deposits. 1:1 structure balanced charges within the structure very strong hydrogen bonding between the basic building units: - no swelling occurs - natural crystals consist of about 100 unit layers stacked one upon the other Diagrammatic sketch of the structure of Kaolin.

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Micas Micas are a 2:1 lattice type mineral. ion substitution is mainly in the tetrahedral layer where si is replaced with Al the charge deficiency is ballanced by potassium ions - successive sheets are strongly bound together - non expanding structure Different types of micas are Muscovite, Biotite and Illite The micas found in sedimentary shale sections is normally classed as Illite Diagrammatic sketch of the structure of Muscovite. From

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Chlorite Clorite are a 2:1:1 lattice type mineral the charge deficiencies in mica layer is ballanced by kations - successive sheets are strongly bound together - non expanding structure Chlorite tends to be associated with old sediments Diagrammatic sketch of the structure of Chlorite. From

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Montmorillonite Montmorillonite is the most common mineral in the group of minerals called the smectites.smectites The essential feature is expandable (swelling) structure: -very large surface area -ionic substitution in the octahedral layer -negative ionic character at the mineral surface -attractive forces for the adsorption of polar molecules such as water Expandable montmorillonite can exist in substantial quantities in shales as a result of volcanic ash falling into a marine environment. Diagrammatic sketch of the structure of Montmorillonite-Bentonite (Smectite). 5m5m Smectite From

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Bentonite Bentonite is a soft clay substance composed essentially of clay minerals of the smectite (montmorillonite) group. Bentonite is mined throughout the world but is abundant in Wyoming, USA and Greece. Bentonite is remains of volcanic materials. Uses of Bentonite: well-drilling mud binder and digestive aid in animal feed absorbent material for cat litter sealing agent for reservoirs, lagoons and other engineering projects binder in foundry sand ceramic cosmetics, facial/body masks and more

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids 4: Prehydration Clay in dry state exist in face-to-face stacks like a deck of playing cards, the packets begins to change when the clay is exposed to water. negative ionic character at the mineral surface provides attractive forces for adsorpsion of polar water molecules Na + at the mineral surface will associate with a charge deficient area on one sheet and dispersion in water will create separated sheets Ca 2+ cannot effectively assosiate with two negative charge sentres on one sheet and must bind 2 sheets together The volume of the clay will increase, and the clay minerals will disperse into the water phase. Click here to watch video Hydration of Calcium Montmorillonite and Sodium Montmorillonite.

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Video Left Beaker Montmorillonite clay (Bentonite) exposed to fresh water. Right Beaker Montmorillonite clay (Bentonite) exposed to sea water. Total time is 5 hours What does this experiment shows ? experiment shows experiment shows

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids The Experiment Shows In fresh water clay sheets will seperate and as a result the clay swells. In sea water the hydration of the montmorillonite reduces due to the effect of salt. The force causing the sheets to seperate are electrostatic repulsive force between negatively charde particles. These forces are decreased as the conductivity of the water is increased by the addition of salts.

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids 5: Clays in Drilling Fluids Clays play a significant role in drilling fluids, particularly the water based. They may be added intentionally to control viscosity and fluid loss. In most water based drilling fluids there is a rapid build up of clay minerals from the formation. The association between clay particles are important as they affect important properties (viscosity, yield, fluid loss). The mechanisms are deflocculation, flocculation, aggregation and dispergation.deflocculationflocculationaggregation dispergation END

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Dispersed System A system in which the breakdown of the aggregates is complete is called a dispersed system. Effect of Clays in Drilling Fluids: Viscositynormal Yieldnormal Fluid lossnormal

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Flocculated System A system may be described as flocculated when there are net attractive forces for the particles and they can associate with each other to form loose structures. Effect of Clays in Drilling Fluids: ViscosityHigh YieldHigh Fluid lossHigh

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Deflocculated System A system of suspended particles is described as deflocculated when there is an overall repulsive force between the particles. This is normally achieved by creating the conditions in which the particles carry the same charges. In clay systems this is normally a net negative charge. Effect of Clays in Drilling Fluids: Viscositynormal YieldLow Fluid lossLow

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Aggregated System A clay aggregate is an assemblage of clay sheets. The aggregate may be disaggregated by hydration and or mechanical shear. The aggregates themselves may be flocculated or deflocculated. Effect of Clays in Drilling Fluids: ViscosityLow YieldLow Fluid lossHigh

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids Developers Topic expert and coordinator Skule Strand Petroleum Technology Dept. Stavanger University College NORWAY Module made by Student Hege Anita Handeland Petroleum Technology Dept. Stavanger University College NORWAY

Home DevelopersReferences 1: IntroductionIntroduction 2: FundamentalFundamental Building Units 3: Clay MineralClay Mineral Groups Clay Chemistry 4: PrehydrationPrehydration 5: Clays inClays in Drilling Fluids References IDF International Drilling Fluids Limited 1982 Technical Manual