PETROLEUM TECHNOLOGY SKILL TEST

PETROLEUM TECHNOLOGY SKILL TEST 1 w w w. p m t u t o r. o r g

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1. Reserves are defined as the amount of oil in a reservoir and are classified as 3 P s, which are --------------? 2. The first well you drill is called? 3. What is Reservoir Engineering? 4. How would you identify a reservoir with a strong water drive? 5. What are the three classification used to describe the methods of recovering fluids from oil and reservoirs? 6. The injection of fluid such as water and gas to displace the oil is called? 7. ------------------ methods are used to recover residual oil left behind by increasing the volume of the reservoir contacted. 8. The categories found in tertiary recoveries are? 9. Given these data of petroleum sample from an Oil field with the following PVT properties: Temperature = 210 F Pressure = 4470 Psz Oil gravity = 25 API Gas gravity = 0.70 Producing Gas oil ratio = 0.64 msef STB Determine: I. Oil formation volume fraction Resbbl/STB II. Gas formation volume fraction III. Water formation volume fraction IV. Solution Gas oil ratio (mscf/stb) V. Oil Viscosity (cp) VI. Water Viscosity (cp) VII. Gas Viscosity VIII. Bubble point pressure (psia) IX. Under saturated oil compressibility X. Under saturated water compressibility 10. In the derivation of MBE (Material Balance Equation), what are (a) Underlying assumptions (b) Respective drive parameters (c) Limitations and uses? 11. Oil pore volume of reservoir = 300mmcuft Solubility of gas in crude = 0.42scf/STB 3 w w w. p m t u t o r. o r g

Initial bottom hole pressure p =3500 psia Initial bottom hole temperature T =105 F Saturation pressure of the reservoir = 2400 psia Formation volume factor @ 3500psia and 105 F = 1.33bbl/stb Determine: A. The Initial STB of oil in the reservoir. B. The Initial scf of gas in reservoir. C. The scf of gas remaining in the reservoir at 1500psia D. The total reservoir gas oil ratio (GOR) at 1500 psia. 12. Well head kind and configuration are determined by? 13. A well head comprises the following except one, which one? Casing head, Tubing head, Christmas tree, Stuffing box, Pressure gauge and Wildcart. 14. A pipeline reaching from the top of the ground to the oil-producing formation is called? 15. What keeps surface waters and loose earth from entering the well? 16. What is an equipment used to maintain surface contract of the well? It is usually made of steel, cast or forged and machined to a close fit forming a set to prevent well fluids from blowing or leaking at the surface. 17. Perforating with shaped charges rather than bullets is called? 18. A group of valves which controls the flow of oil and gas from a well due to its shape and large number of fitting branching is referred to in the petroleum industry as? 19. If a well is not producing by Natural flow, what is installed to supplement the formation pressure? 20. An artificial lift in surface equipment that impact an up and down motion to a sucker rod string to which is attached a piston (or plunger) pump submerged in the fluid of a well is called? 21. The most frequently conducted well test is called? 22. Modern separators uses other types of forces such as? 23. The prevention of hydrate formation in a separator is carried out by three methods, which are? 4 w w w. p m t u t o r. o r g

24. The number of tanks in a battery will vary, as will their size, depending on the daily production of? 25. Obtaining samples in storage tanks are done by either of which two methods? 26. Where is gas sampling done? 27. What is used to estimate reserves and production optimization performance? 28. Name the types of decline curve. 29. Causes of decline involves? 30. What units has changed the processes of measuring, sampling, testing and transferring oil from a tedious, time consuming business that require many man hours and error prone into an efficient operation? 31. A well that came in at 100b/f/day has declined to 80bbl/day at the end of the first year. Calculate: (a) the yearly and monthly decline rates and (b) the yearly and monthly continuous decline rates. (c) If the economic unit of the well is 2bbl/day, calculate the life of the well and its cumulative production. 32. What are the characteristics that a reservoir rock must possess? 33. What are the types of petroleum traps? 34. For oil and gas, the science of exactly shock waves on the surface that penetrate downward into the rock layers or finding traps is? 35. The actual location on which the well is to be drilled and selected by an operating company is called? 36. The various kinds of oil and gas wells are classified into? 37. What do Mobile rigs include? 38. The very basic needs of drilling a hole in the ground is? 39. List the modern techniques of drilling. 40. What is being used to enlarge the undersize hole by bits? 5 w w w. p m t u t o r. o r g

41. The technique of allowing the drill string to be intentionally diverted to a given target is called? 42. What is the act of forcing a bit to seek a specific angle of travel? 43. What is the drilling of metal referred to as? 44. The dependability of a drill string is linked to 2 important facts, which are? 45. What is a formation capable of producing enough oil and gas to make it economically feasible for the operating company to complete the well called? 46. What is the question that an operating company asks after drilling a well? 47. What is the name of the step that is carried out in making these decision and in answering these questions? 48. What decisions are taken after careful consideration of data obtained by various tests ran on the formation (pay zone) by the operating company? 49. Calculate expected fracture pressure gradient in ppg, if pore pressure gradient p/d = 0.65psi/ft. 50. List the five types of bits you know. ANSWERS 1. Proved, probable, possible 2. Exploration well or wildcat well 3. This is the application of scientific principles to practically enhance the designing of oil and gas recovery from Reservoir. 4. (i) Recovery efficiency is 32 75% (ii) Pressure is maintained and water declines slowly (iii) GOR gradually increases (iv) Dry oil is produced until water breakthrough (v) Oil rate remains constant but gradually declines as water breaks through 5. Primary Recovery 6. Secondary Recovery 7. Tertiary Recovery 8. (i) Miscible fluid displacement e.g. Alcohol H20, CO2 + Oil (ii) Thermal recovery e.g. injecting O2 or steam (iii) Chemical recovery e.g. polymers and surfactants 9. (i) B0 = Oil formation volume and by standing co-ordination 6 w w w. p m t u t o r. o r g

B0 = 0.972 + 0.000147T 1.175 At T0 = 210 F = 650 R B0 = 0.972 + 0.000147 (650) 1.175 = 1.26 res bbl/stb (ii) Bg = Gas formation volume fraction res bbl/mscf Where By = 0.02829 Bg = 0.00504 OR - - - - - - - - - - (x) - - - - - - - - - - - - - (xx) Since Z = compressibility factor is a function of reduced temperature at reduced pressure i.e. Z = f (Tr, Pr) and by Hankinson and Philip correlation, Pc = 709.604 58.718 rg Tc = 170.491 + 307.344 rg Where rg = gas specific gravity Pc = Critical pressure in psi Tc = Critical Temperature in rankine ( R) rg = 0.1 Pc = 668.5 & Pr = Tc = 385.6 & Tr = Since Z = f (Tr, Pr) = f (1.74, 6.68) and from chart, Z is read as 0.95, substituting this into equation (xx) gives: Bg = = 0.0007176 = 0.7176 (where M = 1000) (iii) Water formation volume fraction res bbl/scf Bw = -1.485 10-5 p + 0.952 10A Where Bw = water formation volume fraction P = pressure T = 210 F A = 0.0001996 (T-100) 1.2676 = -1.04804 Bw = -1.485 10-6 (4470) + 0.952 10(-1.04804) Bw = 1.036rb STB (iv) Solution Gas-oil ratio (Rs) 7 w w w. p m t u t o r. o r g

Rs = Using standing correlation Rs = rg P+25.48 1.204 18.2 10 yg yg = 0.00091(T) 0.0125rAPI = 0.00091(210) 0.0125(25) yg = -0.1214 Rs = 0.7 4470 + 25.48 1.204-18.2 10-0.1214 (v) Oil viscosity Mo in centipoise (cp) Beggs and Robinson Head oil correlation Mod = 10 x 1.0 x = T -1.163 exp(6.9824 0.045658 rapi) x = (210) -1.163 exp(6.9824 0.04658(25)) = 0.669 Mod = 10 0.699 1.0 = 3.675 cp If mg = Molecular weight Nos = A Mod B A = 10.715 (Rs + 100) -0.515 = 0.333 B = 5.44 (Rs + 150) -0.338 = 0.546 Mos = 0.33 (3.675) 0.546 = 2.38cp (vi) Viscosity of water = Mw Mw = 4.33 0.07T + 4.73 10-4 T 2 1.415 10-6 T 3 + 1.56 10-9 T 4 T = 210 F W = 0.41 cp (viii) Bubble point pressure (Pb psia) Where Pb = 18.2 0.82 10 yg 1.4 = 18.2 0.83 10-0.1214-1.4 Pb = 4,453 psia (ix) Undersaturated oil compressibility (co) This is calculated with Vasquexz & Beggs Correlation co = 3Rsb + 17.2T 1.180rg + 12.6 (rapi) -1.433 P 10 5 8 w w w. p m t u t o r. o r g

= 3(745) + 17.2(210) 1.180(0.70) + 12.61(25) -1.433 4.470 10 5 co = 1.378 10-5 psi -1 10. A-Underlying assumptions (i) Reservoir is considered to be tank of constant value (ii) The temperature and pressure and rock and fluid properties are not space dependent (iii) Equilibrium is also attained e.g. between oil and solution gas 11. A = STOIIP (N) Stock tank oil initial in place = Vp = pore volume Boi = oil formation volume fracture initial N = = 40mmSTB 12. Well conditions 13. Wildcart 14. Oil well 15. Surface string 16. Well Head 17. Jet perforation 18. Christmas tree 19. Artificial lift 20. Beaming pumping 21. Potential test 22. Centrifugal and Impact force 23. (i) Heating the gas stream (ii) Removing water vapour from gas by using an antifreeze agent (iii) The use of liquid absorbents 9 w w w. p m t u t o r. o r g

24. The well or wells and the frequency of pipeline output 25. Thief-sampling method or bottle sampling method 26. Field 27. Decline curve: it is primary used for forecasting future production 28. Constant percentage declines (exponential), Harmonic and hyperbolic decline curves. 29. When more H20 and gas are produced, production declines (BHP, GOR, WOR) and changes in (i) the drainage area (ii) Changes in PI (productivity index) (iii) Changes in efficiency in vertical and horizontal flow. 30. Lease Automatic Custody Transfer (LACT) 31. Year decline rate = Q = Q0(1-da) Where da = annual decline rate Q0 = Initial production rate at t0 = 0 Q = Production at the point of decline Q = Q0(1-da) - - - - - - - - - - -(1) Q = 80 bbl/day, Q0 = 100 bbl/day On substitution in - - - - - -(1), we have: 80 = 100(1 - da) = 1 da 10 w w w. p m t u t o r. o r g da = 1 0.8 = 0.2 = 20% Monthly deconsecrate (1 - dm) 12 = 1 da - - - - - - - - - - -(2) Substituting for da in - - - (2) results in: (1 - dm) 12 = 1 0.2 1 dm = (0.8) 1/12 dm = 1 - (0.8) 1/12 = 1 (0.8) 0.085 = 0.0184 dm = 0.0184 100 = 1.84% per month Year continuous decline rate (ba) exp (-ba) = 1 da exp (-ba) = 1 0.2 -ba = In (1-0.2)

ba = = 0.223 Monthly continuous decline rate (bm) ba = 12bm 0.223 = 12bm bm = = 0.0186 Using 1 year as the time, Q = Q0exp (-bt) Q = 100 365 Q = 2 bbl/day = economic life of use Q = 2 365 Therefore, 2 365 = 100 365 (-bt) Recall ba = 0.223 2 365 = 100 365 exp (-0.223t) Exp (-0.223t) = = 0.02 0.223t = In (0.02) t = In 11 w w w. p m t u t o r. o r g = 17.5 years Economic life of the well = 17.5yrs 32. Porosity, permeable, exist in a special way 33. Structural and stratigraphic traps. Structural traps are formed because of a deformation in the rock layer that contains the hydrocarbon e.g. are fault and antic lines. 34. Seismology 35. Drill site 36. Exploration well and development well 37. Jack-ups, submersibles, semi submersibles and a drill ship 38. Rotation, Circulation and hosting and housering 39. Rotary drilling and Coiled tube drilling 40. Reamer 41. Directional Drilling

42. Whip stocking 43. Milling 44. Inspection and Maintenance 45. Pay zone 46. Does this well contain enough oil or gas to make it worthwhile to run the final production string of casing and completing the well? 47. Formation evaluation 48. Production Casing and complete the well or to plug and abandon the well 49. Where Pf(min) = fmin = min fracture pressuring D = fmin = D = Depth fmin = Pfmin/D = = 14.7ppg Pf/d(max) = fmax = 1 + 0.52 = 15.8ppg 50. Fish tail, milled tooth, tungsten carbide teeth roller cutter, drag bit, roller bearing, journal bearing 12 w w w. p m t u t o r. o r g