Unit 1 Overview of Drilling Fluids in oil and gas wells drilling.pptx

Drilling fluid for oil and gas drilling

1. Overview of Drilling Fluids By, Prof. M. H. Siddique Department of petroleum engineering Iit (ISM) Dhanbad

2. Contents Drilling fluids Function of Drilling fluids Properties of Drilling fluids Additives Treatments of drilling fluids Drilling fluid handling equipments

3. Drilling fluids Drilling fluid or most commonly know as “Mud” is a volume of fluid used during drilling operation for solids removal. Circulated from pump at surface to the drill string and bit in the sub-surface and back to the surface via the annulus. It serves many need of the drilling operation. It is analogous to blood in a living being body.

4. Basic Functions of Drilling Fluids Carry cuttings Cool and clean the bit Reduce friction or lubrication Maintain stability of uncased borehole Prevent inflow of the fluid in the borehole Suspend cuttings Provide information about the formation

5. Other functions Exert hydrostatic pressure against the formation fluid Transmit hydraulic energy to tools and bit Control corrosion Facilitate cementing and completion Inhibit gas hydrate formation Minimize impact on the environment

6. Functions in details Carry cuttings or transport cutting

7. Functions in details Cool and clean the bit Drill bit

8. Functions in details Reduce friction or lubrication

9. Functions in details Maintain stability of uncased borehole

10. Functions in details Prevent inflow of the fluid in the borehole Inflow Caving

11. Functions in details Suspend cuttings 1 2

12. Functions in details Provide information about the formation Types of formation Properties of inflow fluids (Oil, water or Gas) Fractured zone

13. Functions in details Exert hydrostatic pressure against the formation fluid Pressure, psi =  0.052  x Mud Weight ( ppg ) x TVD ( ft )  

14. Functions in details Transmit hydraulic energy to tools and bit

15. Functions in details Control corrosion Facilitate cementing and completion Inhibit gas hydrate formation Minimize impact on the environment

16. Questions Q1. Why do we need to check the properties of drilling fluid time to time? Q2. What is meant by underbalanced drilling and overbalanced drilling? Q3. Is rate of penetration dependent on drilling fluid circulation?

17. Types of Drilling fluids Drilling fluid systems have a continuous phase, which is liquid, and a discontinuous phase comprising solids . The continuous phase may be used to categorize drilling fluid types as gas , aqueous fluids or nonaqueous systems.

18. Water based fluids (WBFs): Water-based fluids (WBFs ): Most common technique Less expensive than oil-based fluids (OBFs ) Easily available Example: fresh water, seawater, brine WBMs used for pay-zone drilling different for non-pay-zone drilling Pay-zone drilling fluid are also called a non-damaging drilling fluid Design is Costly

19. Oil based fluids (OBFs): Oil-based systems was introduced in the 1960s to help in several drilling problems Increasing downhole temperatures Formation clays that react , swell , or slough after exposure to WBFs Stuck pipe and torque and drag Contaminants Examples: Oil-based fluids (OBFs) are used for formulated with diesel , mineral oil , or low-toxicity linear olefins and paraffins .

20. Pneumatic-drilling fluids : In place of drilling fluid, compressed air or gas can be used to circulate cuttings out of the wellbore Pneumatic fluids can be classified into three categories: Air or gas only Foam Aerated fluid Dry gases like air, natural gas , NO2 , CO2

21. Pneumatic-drilling fluids : Pneumatic fluids offer several advantages: Rapid evaluation of cuttings for the presence of hydrocarbons Little or no formation damage Significantly higher penetration rate of hard-rock formations

22. Drilling fluid Selection Criteria

23. Properties of Drilling fluids

24. Properties of Drilling fluids Density Viscosity, Gel strength Fluid loss control or Filtration pH Alkalinity Cation exchange capacity Electrical conductivity Lubricity Corrosivity

25. Properties of Drilling fluids Density( ρ ): Density is defined as mass per unit volume. It is expressed either in pounds per gallon ( Ib /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 on both the density and the depth; therefore, it is convenient to express density in terms of pounds per square inch per foot (psi/ ft ).

26. Properties of Drilling fluids Density( ρ ): The specific weight ( γ ) of drilling fluids may range from that of air to up 20 lb /gal for heavily- weighted, water-based drilling fluids.

27. Properties of Drilling fluids Density( ρ ): The pore pressure depends on the depth of the porous formation, the density of the formation fluids, and the geological conditions . The hydrostatic pressure gradient of formation fluids 0.43 psi/ ft The problem of maintaining mud density high enough to control formation fluids, but not so high as to induce a fracture

28. Properties of Drilling fluids Density( ρ ):

29. Properties of Drilling fluids Density( ρ ):

30. Properties of Drilling fluids Density( ρ ):

31. Properties of Drilling fluids Density( ρ ): Q1.

32. Properties of Drilling fluids Density( ρ ): Q2.

33. Properties of Drilling fluids Viscosity and Gel strength Rheology is the study of the deformation and flow of matter . Viscosity is a measure of the resistance offered by that matter to a deforming force. Shear dominates most of the viscosity-related aspects of drilling operations . Retention of drilling fluid on cuttings is thought to be primarily a function of the viscosity of the mud and its wetting characteristics .

34. Properties of Drilling fluids Viscosity and Gel strength Shear viscosity is defined by the ratio of shear stress (τ) to shear rate ( γ ): The traditional unit for viscosity is the Poise (P), Drilling fluids typically have viscosities that are fractions of a Poise, so that the derived unit, the centipoise ( cP ). For Newtonian fluids , such as pure water or oil, viscosity is independent of shear rate. Drilling fluids are non-Newtonian , so that viscosity is not independent of shear rate .  

35. Properties of Drilling fluids Viscosity and Gel strength The most popular used to describe non-Newtonian fluid are the Bingham Plastic, Power Law, and Herschel Bulkley . The Bingham Plastic model is the simplest. It introduces a nonzero shear stress at zero shear rate : where is the plastic viscosity and the yield stress, that is, the stress required to initiate flow . The Bingham Plastic model is the standard viscosity model used throughout the industry, and it can be made to fit high shear-rate viscosity data reasonably well.  

36. Properties of Drilling fluids Viscosity and Gel strength When fitted to high-shear-rate viscosity measurements (the usual procedure), the Bingham Plastic model overestimates the low-shear-rate viscosity of most drilling fluids. The Power Law model (also called the Ostwald de Waele model) goes to the other extreme. The Power Law model can be expressed as follows: where K is dubbed the consistency and ‘n’ (0.5-1) the flow behaviour index. The Power Law model underestimates the low-shear-rate viscosity.  

37. Properties of Drilling fluids Viscosity and Gel strength To alleviate this problem at low shear rates, the Herschel- Bulkley model was invented. It may be thought of as a hybrid between the Power Law and Bingham Plastic models and is essentially the Power Law model with a yield stress [ Cheremisinoff ]:  

38. Properties of Drilling fluids Viscosity and Gel strength Marsh Funnel: This is usually calibrated to read 26 0.5 seconds when testing with fresh water .  

39. Properties of Drilling fluids Viscosity and Gel strength Apparent Viscosity (AV): The  apparent viscosity is reported as either the mud viscometer reading at 300 RPM (Θ 300 ) or one-half of the meter reading at 600 RPM (Θ 600 ). Plastic Viscosity (PV): Plastic Viscosity ( cP ) = Θ 600 – Θ 300 Yield Point (YP ): The yield point ( lb /100ft 2 ) is calculated as, YP = Θ 300 – PV Gel strength is the measure of maximum yield stress required to break the gel. Measured at 3 RPM Fann VG Viscometer

40. Properties of Drilling fluids Viscosity and Gel strength

41. Properties of Drilling fluids Fluid loss control or Filtration The ability of the mud to seal permeable formations exposed by the bit with a thin, low-permeability filter cake . For a filter cake to form, it is essential that the mud contain some particles of a size only slightly smaller than that of the pore openings of the formation. These particles, which are known as bridging particles, are trapped in the surface pores, while the finer particles are, at first, carried deeper into the formation. The bridged zone in the surface pores begins to trap successively smaller particles, and, in a few seconds, only liquid invades the formation. The suspension of fine particles that enters the formation while the cake is being established is known as the mud spurt . The liquid that enters subsequently is known as the filtrate .

42. Properties of Drilling fluids Fluid loss control or Filtration

43. Properties of Drilling fluids Fluid loss control or Filtration API Filter press Filtrate Mud cake

44. pH : Defined as the negative logarithm (to the base 10) of the hydrogen-ion concentration, pH units decrease with increasing acidity by a factor of 10 . The optimum control of some mud systems is based on pH, as is the detection and treatment of certain contaminants. A mud made with bentonite and fresh water, for example, will have a pH of 8 to 9. Contamination by cement will raise the pH to 10to 11, and treatment with an acidic polyphosphate will bring the pH back to 8 or 9 . mitigation of corrosion

45. Alkalinity Alkalinity measurements are made to determine the amount of lime in lime treated muds . The mud is titrated to determine the total amount of lime, soluble and insoluble, in the system ( Pm). The filtrate is titrated to determine the amount of lime in solution (Pf). The amount of undissolved lime is calculated from PmPf . Measurements of the alkalinity of water samples, and of filtrates of very lightly chemically treated muds, can be used to calculate the concentration of hydroxyl (OH ), carbonate (CO3), and bicarbonate (HCO3) ions in solution.

46. Alkalinity

47. Cation exchange capacity: The methylene blue test serves to indicate the amount of active clay in a mud system or a sample of shale. The test measures the total cation exchange capacity of the clays present and is useful in determination of solids content as an indication of the colloidal characteristics of the clay minerals. Similarly , shale cuttings can be characterized and some estimations can be made regarding mud-making properties and possible effects on hole stability. Organic materials , if present in the sample, are destroyed by oxidation with hydrogen peroxide . The sample is titrated with standard methylene blue solution until the adsorptive capacity is satisfied, as shown by the appearance of a blue color in the water in which the sample is suspended. If other adsorptive materials are not present in significant amounts, the bentonite content can be estimated, based on an exchange capacity of 75 milliequivalents per 100 grams of dry bentonite .

48. Cation exchange capacity:

49. Electrical conductivity The resistivity of water muds is measured and controlled, whenever desired, to permit better evaluation of formation characteristics from electrical logs. The determination of resistivity involves the measurement of resistance to the flow of electrical current through a sample of known configuration. In the direct-reading resistivity meter, the resistance measurement is converted to resistivity in ohm meters. The electrical stability test is used as an indication of the stability of emulsions of water in oil (oil muds): A probe fitted with electrodes is immersed in the sample; the voltage imposed across the electrodes is increased until a predetermined amount of current flows; and the voltage at this breakdown point is reported as the emulsion stability.

50. Electrical conductivity

51. Lubricity: One of the functions of the drilling fluid is to lubricate the drill string. The requirement for lubrication is especially critical in directional and crooked holes , and in avoidance of wall-sticking. The Timken lubricant tester has been modified and a method devised to furnish comparative results on which to base recommendations for treatment of the mud.

52. Questions? Q1. What is the difference between viscosity and lubricity? Q2. How we estimate formation using resistivity log? Q3. What do you mean by logging while drilling?

53. Additives

54. Additives Alkalinity and pH Control Designed to control the degree of acidity or alkalinity of the drilling fluid. Most common are lime , caustic soda and bicarbonate of soda . Bactericides Used to reduce the bacteria count. Paraformaldehyde , caustic soda, lime and starch preservatives are the most common. Calcium Reducers These are used to prevent, reduce and overcome the contamination effects of calcium sulfates (anhydrite and gypsum). The most common are caustic soda, soda ash, bicarbonate of soda and certain polyphosphates . Corrosion Inhibitors Used to control the effects of oxygen and hydrogen sulfide corrosion . Hydrated lime and amine salts are often added to check this type of corrosion . Oil-based muds have excellent corrosion inhibition properties. De foam ers These are used to reduce the foaming action in salt and saturated saltwater mud systems, by reducing the surface tension.

55. Additives Emulsifiers Added to a mud system to create a homogeneous mixture of two liquids (oil and water). The most common are modified lignosulfonates , fatty acids and amine derivatives . Filtrate Reducers These are used to reduce the amount of water lost to the formations . The most common are bentonite clays , CMC ( sodium carboxyl methyl cellulose ) and pre-gelatinized starch . Flocculants These are used to cause the colloidal particles in suspension to form into bunches , causing solids to settle out. The most common are salt , hydrated lime , gypsum and sodium tetra phosphates . Foaming Agents Most commonly used in air drilling operations. They act as surfactants, to foam in the presence of water. Lost Circulation Materials These inert solids are used to plug large openings in the formations, to prevent the loss of whole drilling fluid. Nut plug (nut shells) , and mica flakes are commonly used. Lubricants These are used to reduce torque at the bit by reducing the coefficient of friction. Certain oils and soaps are commonly used .

56. Additives Pipe-Freeing Agents Used as spotting fluids in areas of stuck pipe to reduce friction, increase lubricity and inhibit formation hydration. Commonly used are oils , detergents , surfactants and soaps . Shale-Control Inhibitors These are used to control the hydration, caving and disintegration of clay/shale formations . Commonly used are gypsum , sodium silicate and calcium lingosulfnates . Surfactants These are used to reduce the interfacial tension between contacting surfaces (oil/water, water/solids, water/air, etc .). Weighting Agents Used to provide a weighted fluid higher than the fluids specific gravity . Materials are barite (BaSo4) , hematite , calcium carbonate and galena .

57. Treatments of Drilling fluid

58. Treatments of Drilling fluid Reinjection safely into the formation Sealing safety landfill MTC technology Stabilization/solidification treatment Electrochemical technology Chemical oxidation technology Microbial treatment

59. Treatments of Drilling fluid Water-based drilling fluid waste treatment Reinjection safely into the formation

60. Treatments of Drilling fluid Water-based drilling fluid waste treatment Sealing safety landfill To prevent the landfilled drilling fluid waste from coming into contact with the surrounding environment, particularly to prevent groundwater pollution. Sufficient antiseepage treatment is also needed. First , a layer of organic soil is laid at the bottom and around the landfill pit, then a layer of plastic is laid , and finally, the pit is covered with a layer of organic soil . In addition, a solidified layer can also be placed at the bottom and around the pit to further prevent leakage.

61. Treatments of Drilling fluid

62. Treatments of Drilling fluid Water-based drilling fluid waste treatment MTC Technology MTC technology converts drilling fluid waste into cementing fluid by adding blast furnace slag and other additives to drilling fluid waste to reuse the pollutants . It eliminates the pollution caused by the efflux of drilling fluid waste and provides the drilling fluid waste with new uses. In addition, MTC cementing fluid has good compatibility with drilling fluid .

63. Treatments of Drilling fluid Water-based drilling fluid waste treatment Stabilization/solidification treatment Solidification/solidification technology involves solidification additives (cement, blast furnace residue, hydrated lime, etc .) that are added to the drilling fluid waste . Through the action of gelling, cementation, and curing, the solid components react with the binders to form gel-like hydration products that are typical of calcium silicate hydrate (CSH ). After a certain period, the drilling fluid waste forms a soil like solid ( pseudosoil ), and this material is buried in place or used as building paving materials. Stabilization/solidification technology is more reliable for drilling fluid waste that has high organic content, pH, and heavy metal content .

64. Treatments of Drilling fluid Water-based drilling fluid waste treatment Electrochemical technology Electrochemical technology is generally divided into electrocoagulation (EC), electro-oxidation (EO), and microelectrolysis (ME) technologies EC utilizes an electrode potential difference to dissolve aluminium or iron on anodes and generate high-activity polyaluminium or polyiron flocculants in situ, which can agglomerate and settle pollutant particles or separate them by air flotation . EO refers to the direct oxidation and degradation of organic matter by the application of a direct current to a waste liquid containing organic pollutants; the organics capture electrons from the anode, and low- valent metal ions are oxidized to high- valent metal ions by obtaining electrons. Then, the organic matter is indirectly degraded by high- valent metal ions.

65. Treatments of Drilling fluid Water-based drilling fluid waste treatment Chemical oxidation technology Chemical oxidation technologies include essential oxidation and advanced oxidation technologies such as NaClO , H 2 O 2 which use oxidants or external energy to oxidize and remove organics. Advanced oxidation technology mainly involve the production of highly active free radicals (• OH and SO4-•, etc.) by different means (high temperature and high pressure, electricity, sound, light irradiation, catalyst , etc .)

66. Treatments of Drilling fluid Water-based drilling fluid waste treatment Chemical oxidation technology

67. Treatments of Drilling fluid Water-based drilling fluid waste treatment Microbial treatment Microbial treatment technology involves the use of microorganisms to treat and remediate waste drilling fluid. By introducing engineered bacteria or by domesticating and cultivating native bacteria, TPHs and organics in drilling fluid waste are converted into small molecules and are finally degraded into CO2 and H2O. Microbial degradation mainly includes two categories: aerobic degradation and anaerobic degradation. Aerobic degradation converts alkanes, alkenes , and aromatics into CO2, H2O, and NH3 through aerobic and facultative microorganisms that use molecular oxygen as a hydrogen acceptor. Anaerobic degradation means that under anaerobic conditions , some anaerobic microorganisms use nitrate, sulphate , etc., as electron acceptors and organic matter as electron donors to degrade THPs and organic matter.

68. Drilling fluid Handling Equipments

69. Drilling fluid Handling Equipments Portable Mud handling truck

70. Drilling fluid Handling Equipments

71. Drilling fluid Handling Equipments Solid handling capacity of various equipments

72. Drilling fluid Handling Equipments Solids Removal Equipment The advantages of doing so may be summarized as follows: 1. Less barite and mud additives required. 2. Better Theological properties because the reduction in plastic viscosity increases the YP/PV ratio, thereby promoting shear thinning. 3. Lower plastic viscosity facilitates the removal of entrained gas, hence lower mud densities can safely be carried. 4. Faster drilling rates, because of lower viscosity and drilled solid content. 5. Less risk of sticking the pipe, because of thinner filter cakes. 6. Less bit wear.

73. Drilling fluid Handling Equipments Solids Removal Equipment Double deck shakers Hydrocyclones Dewatering Surplus Mud Downhole solids control

74. Drilling fluid Handling Equipments Solids Removal Equipment Double deck shakers:

75. Drilling fluid Handling Equipments Solids Removal Equipment Hydrocyclones Desanders Desilters Mud cleaner

76. Drilling fluid Handling Equipments Solids Removal Equipment Dewatering Surplus Mud Dewatering Removes nearly all colloidal particles, producing nearly clear water that can be reused or often disposed to ground Provides cost savings related to fluid disposal and replacement Reduces unwanted liquid waste and mud dilution Ensures environmental compliance in areas of strict regulations 

77. Drilling fluid Handling Equipments Solids Removal Equipment Downhole solids control A sub, which is placed directly above the bit, contains a high efficiency cone that separates the mud into two fractions: a heavy fraction containing the removed solids, which is directed through two upjets into the annulus; and a lighter fraction that passes on to the bit. In two field tests, increases in penetration rate up to 58% and improved bit life were obtained when drilling in shale.

78. Questions Q1. What would you do if you noticed that the well started to leak? Q2. Why drilling fluids are always considered to be toxic ? Q3. What properties of drilling fluid will change most at high pressure and high temperature?