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Cementing

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Cementing

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Cementing

  1. 1. 5. CEMENTING Habiburrohman, B.Eng, M.Eng. 1
  2. 2. Cement Manufacture Dry Process CLAY WASH MILL STORAGE BIN SILOS LIMESTONE CRUSHER SILOS PULVERIZER DRYER OIL OR GAS GYPSUM HOPPERS PROPORTIONER GRINDER UNIT ROTARY KILNS CLINKER COOLERS CLINKER HOPPERS GRINDINGMILLS PACKAGING PLANT CEMENT SILOS COAL GYPSUM 2
  3. 3. Cement Manufacture Wet Process LIMESTONE PULVERIZER DRYER OIL OR GAS CLAY WASH MILL CEMENT SILOS PACKAGING PLANT GYPSUM HOPPERS WATER WET GRINDING MILLS STORAGE BASINS GRINDING MILLS CLINKER HOPPERS ROTARY KILNS CLINKER COOLERS COAL GYPSUM CRUSHER SILOS CORRECTION BASINS KILN FEEDERS STORAGE BIN 3
  4. 4. Cement Hydration 4
  5. 5. Clinker Grain Structure C3CS C2S C3A C4AF Silicates are approximately 80% of total material 5
  6. 6. Principle Components of Portland Cement • C3STricalcium silicate • C2SDicalcium silicate • C3ATricalcium aluminate • C4ATetracalcium alumino ferrite • C3S often used as model for cement hydration • All phases have a role in sequence of hydration events and impact setting process 6
  7. 7. Hydration Mechanisms • Four Main Hydration Phases: – Wetting SHARP EXOTHERMIC PEAK; LASTS < 5 MINS – Induction ACTIVITY SEEMS LOW; CEMENT REMAINS FLUID – Setting SUSTAINED EXOTHERMY; CEMENT THICKENS – Hardening LOW HEAT FLUX; STRENGTH STILL INCREASING 7
  8. 8. Heat Flow During Hydration % Hydration of Cement Heat Flow Acceleration Deceleration % Hydrated Cement Heat Flow Induction Period (Silicates Have Low Reactivity During This Period) Time Diffusion 40-50% Hydrated Cement Setting and Hardening Pre-induction Period (2%to 3% Hydration) min hours days 8
  9. 9. Hydration Mechanisms • Two main theories of hydration process –Protective Coating Theory –Delayed Nucleation Theory 9
  10. 10. Protective Coating Theory • On contact with water, C3S AND C2S react to form calcium silicate hydrate (C-S-H) gel • Initial surge or reactivity due to heat or hydration of free lime occurs • C-S-H external reactions inhibited by semi-permeable gel coat, but internal reactions continue • This is called the “dormant” or “induction” phases 10
  11. 11. Cement Hydration (C3S) MIXWATER C3S 2 OH-Ca2+ H2O 11
  12. 12. Cement Hydration (C3S) MIXWATER C3S Ca 2+ 2 OH - H2O C-S-H - Gel (Calcium Silicate Hydrate) 12
  13. 13. Protective Coating Theory • Osmotic pressure within C-S-H builds due to internal reactions • This causes C-S-H membrane to rupture • Materials released include Ca(OH)2. • Tubular growths of C-S-H (fibrils) form a network of interlocking with other hydration products 13
  14. 14. Cement Hydration (C3S) C3S C-S-H - Gel (Calcium Silicate Hydrate) MIXWATER Ca 2+ 2 OH - H2O 14
  15. 15. Delayed Nucleation Theory • C3A enters into reaction with gypsum to form ettringite (calcium-sulpho-aluminate-hydrate) • Ettringite coats C3A surface, reducing reaction until all gypsum present is consumed • Ettringite then converts to calcium aluminate hydrates 15
  16. 16. Cement Hydration (C3A) MIXWATER CaSO4 C3A 16
  17. 17. Cement Hydration (C3A) MIXWATER C3A CASH CaSO4 (Calcium Alumino Sulphate Hydrate) Ca 2+ + SO4 2- 17
  18. 18. Thickening Time • The viscosification that is observed from a consistometer test is the result of: – Interlocking effect of the hydration products – Consumption and immobilization of internal water • The rate of viscosity build-up to final set is influenced by: – Temperature – Additive chemistry 18
  19. 19. Oilwell Cement 19
  20. 20. Oil Well Cementing ? • CEMENTING • What is Oil Well Cementing ? • Oil well cementing is a process of mixing a slurry of cement and water and pumping it through the casing pipe into the annulus between the casing pipe and the drilled hole. • Cement plugs are also set in the wellbore to isolate zones e.g. loss zones, water bearing zones 20
  21. 21. Oil Well Cementing • Two general classifications of oil well cementing are :- 1. Primary Cementing 2. Secondary or remedial cementing 21
  22. 22. OBJECTIVES OF CEMENTING • Primary Cementing • Main objectives of primary cementing are :-  to support the casing pipe  to restrict the movement of formation fluids behind the casing • Cement also provides the following advantages :-  seal off zones of lost circulation (fractured formation)  protect the casing from shock loads during drilling deeper section  protect casing from corrosion 22
  23. 23. OBJECTIVES OF CEMENTING (continued) • Secondary Cementing • Most common secondary cementing jobs are :-  Circulation squeeze  plug back cementing  squeeze cementing 23
  24. 24. OBJECTIVES OF CEMENTING (continued) • Secondary Cementing • Circulation squeeze • Cement slurry is circulated into the annulus through perforation, which are at the top and the other at the bottom of desired interval • Reason for circulation squeeze are :-  supplementing a faulty primary job  extending the casing protection above the cement top 24
  25. 25. OBJECTIVES OF CEMENTING (continued) • Secondary Cementing • Plug back cementing • Hole is plugged by cement in order to initiate a new drilling operation • Plug back is carried out for a number of reasons:  Abandonment of the hole  Sidetracking the hole  Seal off lost circulation  Shutting off of water or gas encroachment 25
  26. 26. OBJECTIVE OF CEMENTING (continued) • Secondary Cementing • Squeeze Cementing • Squeeze cementing involves forcing the cement slurry under pressure into open holes or channels behind the casing or into perforation tunnels. • The operation is performed during drilling, completion and workover operations 26
  27. 27. OBJECTIVE OF CEMENTING (continued) • Secondary Cementing • Main purposes of squeeze cementing :- • Supplementing a faulty primary cementing job • Repairing casing defects • Stopping lost circulation in open hole during drilling • Shutting off old perforation for recompletion • Reducing water cut in a producing well 27
  28. 28. API Classification of Cements • A wide range of the properties of the slurry (viscosity, density, and fluid loss) and the set cement (strength, permeability & porosity) are required to meet the down hole temperature & pressure and other conditions • API provides specs covering eight classes of oil well cement designated as class A, B, C, D, E, F, G and H 28
  29. 29. API Classification of Cements • API Class A and B cements  Intended for use in wells from the surface to the depth of 6000 ft and 16 - 70 deg C  The recommended water to cement ratio according to API is 0.46 by weight (5.2 gal/sack or 19.71 ltr/sack) • API Class C  Is a high strength cement and used for oil wells from surface to a depth of 6000 ft (16 - 77 deg C temperature) 29
  30. 30. API Classification of Cements • API Class D, E and F  As a basic and regarded as retarded cement  Intended for use from surface up to 16,000 ft depth  Premium cement because of high cost  Resistant to surface water 30
  31. 31. API Classification of Cements • API Class G and H  Regarded as basic cement; chemically similar to class B  Intended for use from surface up to 8000 ft depth  Can be modified by adding accelerator or retarder to suit wide range of depth and temperature  The recommended water to cement ratio according to API for class G cement is 44% (5 gal/sack or 18.9 ltr/sack) and class H cement is 38 % (4.3 gal/sack or 16.3 ltr/sack) • The most common cement used in Malaysia is class G produced by Pan Malaysian Cement (PMC) in Pasir Gudang 31
  32. 32. Cement Additives • The of API cement above are used for wells with moderate bottom hole conditions • It is necessary to modify cement properties to meet specific well conditions such as deep wells, HPHT, lost circulation zones, etc by adding chemicals • The chemicals can be classified as follows :-  Accelerators – reduce thickening time  Retarders – increase thickening time  Fluid Loss reducers – control amount of fluid loss to formation  Weighting materials – increase/decrease density  Lost circulation materials – seal off lost circulation zo3n2e.
  33. 33. Cement Additives – Accelerator • The accelerator is used to reduce the thickening time and set the cement faster by accelerating the hydration of chemical compound of cement. • Liquid cement (known as cement slurry) will harden faster by adding accelerator • Common Accelerators used are Sodium Chloride, Calcium Cholride and Calcium Sulphate (gypsum) 33
  34. 34. Mechanism of Accelerators MIXWATER C3S Ca 2+ 2 OH - H2O C-S-H - Gel INCREASED PERMEABILITY 2 Cl - INCREASE RATE OF OH- EFFLUX BY COUNTER-DIFFUSION OF CL-Hydrate morphology and ion flux
  35. 35. Mechanism of Accelerators SECONDARY CaS04 MIXWATER C3A CASH CaS04 PRECIPITATION INCREASED Ca 2+ + SO4 2- pH LOWERED Accelerated nucleation
  36. 36. Cement Additives – Retarder • The retarder will increase the thickening time or prolong the time of cement to set. • It is necessary since more time is needed to place cement in deeper wells or to combat the thickening time reduction in high temperature environment • Common retarder are saturated NaCl, lignosulfonate and its derivatives, cellulose derivative and sugar derivatives 36
  37. 37. Mechanisms of Retarders MIXWATER d+ NET POSITIVE CHARGE ON CEMENT PARTICLE H2O 2 OH - Ca 2+ LARGE ORGANIC MOLECULE WITH NET NEGATIVE CHARGE HINDERS MOVEMENT OF IONS ETC. ACROSS GEL MEMBRANE SO3 - SO3 - SO3 - ADSORPTION AND STERIC HINDERANCE
  38. 38. MMeecchhaanniissmmss ooff RReettaarrddeerrss C-S-H - Gel INSOLUBLE PRECIPITATE HINDERS MOVEMENT OF IONS ETC. ACROSS GEL MEMBRANE MIXWATER CEMENT GRAIN d+ H2O Ca 2+ 2 OH - PRECIPITATION THEORY
  39. 39. Mechanisms of Retarders MIXWATER Ca 2+ NUCLEATION THEORY CEMENT GRAIN d+ 2 OH - H2O C-S-H - Gel CRYSTAL GROWTH POISONERS ATTACH TO CRYSTAL GROWTH NUCLEI AND PREVENT CRYSTAL GROWTH
  40. 40. Mechanisms of Retarders MIXWATER Ca 2+ Ca 2+ COMPLEXION THEORY CEMENT GRAIN d+ 2 OH - H2O C-S-H - Gel CHELATING AGENTS SEQUESTER IMPORTANT IONS FROM INTERSTITIAL WATER AND CHANGE ION BALANCE ACROSS GEL MEMBRANE Ca 2+
  41. 41. Cement Additives – Fluid Loss • Fluid loss additives are used to control amount of liquid loss from cement slurries to the surrounding environment. • These additives control the fluid loss by one of the following mechanisms :-  Increasing the particle size distribution of the slurry so that it holds or traps the liquid in it  Making the interstitial slurry water viscous which increased resistance to flow through porous formation  Forming an impermeable film or miscells within filter cake  Common fluid loss additives are organic polymers, dispersants and synthetic polymers 41
  42. 42. Mechanisms of Fluid Loss Additives VISCOSIFICATION OF MIXWATER MIXWATER WALL BUILDING AND PORE PLUGGING ADSORPTION AND RESTRICTION OF WATER MOBILITY SOLIDS PLUG PORES AND BUILD MAT ADSORPTION, PORE FILLING, WALL BUILDING
  43. 43. Mechanisms of Fluid Loss Additives WALL BUILDING AND PORE PLUGGING VISCOSIFICATION OF MIXWATER THE PRESENCE OF FOAMED GASES CREATES MULTIPHASE FLOW AND RESTRICTS FILTRATION MIXWATER OF FLUIDS THROUGH THE FILTER CAKE MULTIPHASE FLOW PHENOMENA
  44. 44. Cement Additives • Weighting Materials • Most stable cement slurries have densities in range of 15.5 - 17.5 lb/gal.Weighting materials are used to increase the density of cement slurry depending on the requirement • Weighting Reducing Materials The weight of cement slurry can be reduced by :- • Adding material that increases the water content such as clay and silicate materials • Using light weight materials such as pozzolan, gilsonite or nitrogen 44
  45. 45. Cement Additives – Weighting Materials (continue) • Light weight cement is used on weak formation or loss circulation zones • The weight of cement slurries can be increased by adding barite, illmenite or hematite 45
  46. 46. Cement Additives – Lost Circulation Materials • The lost circulation materials are used to combat cement lost into very permeable, cavernous or fractured formations • The lost circulation materials prevent the loss of cement by one or more of the following mechanisms  Preventing fracture inducement by reducing hydrostatic pressure as in lightweight cement  Cure the lost circulation by forming a low permeability bridge across the permeable opening • Common LCM can be classified as fibrous, granular and flakes 46
  47. 47. Special Problems • Strength Retrogression – Silica flour / sand prevents detrimental reactions at > 230 °F – Up to 210 °F : hydration products differ only in morphology and microstructure – Above 210 °F: amorphous silicate hydrates form. Size range from x-ray amorphous to highly crystaline – Above 230 °F: onset of retrogression, large crystals, low strength, high permeability – Up to 300 °F : 35% silica sand or flour prevent formation of di-calcium silicate hydrate (orthorhombic phase). – Above 300 °F: 35% silica flour as increased surface area required for inhibition.
  48. 48. Special Problems • Gas Migration Control – Agents that minimize slurry depressurization or that decrease gas mobility in the cement paste (eg. by permeability reduction) during liquid to solid transition • (BA-10, BA-29, BA-56, BA-58L, BA-86L, FL-45LS, FLAG-56, BA-100L, BJ BLUE)
  49. 49. Special Problems • Lost Circulation – Agents which induce thixotropy can help prevent or cure losses by reducing wellbore hydrostatic or by building high flow resistance in the fractures • Microannuli/Poor Bonding – Agents which induce expansion after initial set, or materials that impart adhesion or improve elastic modulus may help provide better isolation
  50. 50. Free Water Control Additives • Under downhole conditions, it is important to control: – Free water – Slurry stability • Problems – Zonal isolation – Collapsed casing (steam) in geothermal wells • Applications – Horizontal, deviated and slimhole environments – Geothermal wells. • Products – Impart strength to gel structure of cement FWC-2, FWC-10, FWC-47, FWC-47L, BJ BLUE
  51. 51. Free Water Channels Free water Channel Measured Free Water 45° Cement Slurry
  52. 52. END 52

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