MINISTRY OF SCIENCE AND TECHNOLOGY DEPARTMENT OF TECHNICAL AND VOCATIONAL EDUCATION Sample Questions & Worked Out Examples For PE-03014 FUNDAMENTAL OF NATURAL GAS ENGINEERING B.Tech(First Year) Petroleum Engineering 3 Ministry of Science and Technology Department of Technical and Vocational Education Petroleum Engineering Sample Questions for PE 03014 FUNDAMENTALS OF NATURAL GAS ENGINEERING Chapter (1) 1*** Introduction 2** Describe Methane, Propane and n-Butane of hydrocarbon gas molecule structures ( 10 Marks ) Explain the characteristic of natural gas. (10 Marks) 3*** Describe other sources of gaseous fuel. 4 *** Describe constituents of petroleum. ( 20 Marks ) ( 20 Marks ) 5*** Describe possible pressure losses in complete system. 6*** Explain geological occurrence of natural gas. (20 Marks) 7.*** Explain modification by migration and burial. (10 Marks) 8.** Sketch the illustration of differential entrapment principle.(15 Marks) 9** Explain Liquefied natural gas.(5 Marks) 10*** Describe coal gasification. 11** (5 Marks) Explain substitute natural gas. (10 Marks) 12*** Describe gas from Devonian shale. (10 Marks) Chapter 2 Gas Properties 13.*** Explain the Boyle’s law.. (5 marks) 14.* Describe the ideal- or perfect-gas law. (10 marks) 15.** Explain charle’s law.(5 Marks) 16.* Explain Avogadro’s law. (5 marks) 17.*** DescribeBoyle’s law, Charle’s law and Avogadro’s law. (10 marks) 18.* Calculate the mass of methane gas contained at 1,000 psia and 68 F in a cylinder with volume of 3.20 cuft. Assume that methane is an ideal gas. 19.*** Calculate the density of methane at standard conditions.(5)Marks) 20.*** Explain Dalton’s law. (10 Marks) 4 21.** Explain Amagat’s Law. (10 marks) 22.*** What are the pseudocritical temperatures and pseudocritical pressures? Why are they used for? (10 marks) 23.* Compute the density of gas A with the composition shown at 1,200 psia and 80°F. Constituent Mole fraction (20 marks) Carbon dioxide 0.0040 Methane 0.9432 Ethane 0.0390 Propane 0.0117 Isobutane 0.0008 n-Butane 0.0013 1.0000 24.*** Explain the influence of nonhydrocarbon constituents on the degree of conformity to the theorem of corresponding state. (10 marks) 25.* Find the compressibility of a natural gas with a gravity of 0.65 at 1,500 psia and 160°F. (10 marks) 26.*** How do you determine the density of hydrocarbon liquids? (10 marks) 27.* Define the partial volume of a constituent. (10 marks) 28.** Explain about the characterization factor of hydrocarbons. (10 marks) 29.* Explain gas formation volume factor.(10 Marks) 30.*** Describe the following? (5 marks) (a) Density of liquids 31.*** Calculate the density of ethane at 900 psia and 110 F 32.** Calculate the mass of methane gas contained at 1,000psia and 68 F in a cylinder with volume of 3.20 cuft.(8 Marks) Chapter 3 Flow and Compression Calculations 33.** Describe the law of conservation of energy and explain it. (15 marks) 34.** Calculate the static bottom hole pressure of a gas well having a depth of 5800 ft. The gas gravity is 0.65 and the pressure at the wellhead is 2350 psia. The average temperature of the flow string is 118°F. (15 marks) 35.** A pipeline 100 miles long has an internal diameter of 13.35 in. The inlet pressure is 1400 psia and the pressure at the end of the line is 290 psia. The temperature of the flowing gas is 40°F, and its composition is as follows: (15 marks) Methane Mole % 75 Ethane 21 Propane 4 100 Calculate the volumetric flow rate measured at 14.68 psia and 60°F. 36.** Using the description of the pipeline given in the previous problem(35), calculate the storage capacity of this line in cubic feet of gas measured at 60°F and 14.68 psia when for unpacked conditions the pressure at the outlet end of the line is 400 psia and for packed conditions it is 900 psia. (15 marks) 5 Chapter 4 Gas-flow Measurements 37.* 38.** 39.** 40.** 41.* 42.** 43.** Describe two general classes of metering devices completely. (15 marks) Define orifice flow meter and Venturi flow meter. (15 marks) What is the effect of condensate in metered gas stream. (10 marks) Explain meter installation completely. (10 marks) Describe the mechanical pulsometer. (15 marks) Describe the pitot tube completely with representative drawing. (10 marks) Define the following. (15 marks) (a) Critical flow prover (b) Choke nipples (c) Volumetric meters 44.* What is a knowledge of the static bottom hole pressure of a gas reservoir? (5 marks) 45.** Calculate the static bottom hole pressure of a gas well having a depth of 6000 ft. The gas molecular weight is 19.5 and the pressure at the wellhead is 2400 psia. The average temperature of the flow string is 120°F. (15 marks) 46.** A pipeline 200 km long has an internal diameter of 14 in. The inlet pressure is 1450 psia and the pressure at the end of the line is 300 psia. The temperature of the flowing gas is 40°F, and its composition is as follows: (15 marks) Methane Mole % 60 Ethane 30 Propane 10 100 Calculate the volumetric flow rate measured at 14.68 psia and 60°F. 47.** Define pulsation completely. (5 marks) 48.** Discuss the following. (15 marks) (a) Pulsation (b) Pitot tube (c) Critical flow prover. 49.*** Compare between orifice flow meter and venturi flow meter. (15 marks) 50.*** Define pulsometer and explain meter installation completely. (15 marks) * = Must know, ** = Should know, *** = Could know 6 Ministry of Science and Technology Department of Technical and Vocational Education Petroleum Engineering Worked Out Examples for PE 03014 FUNDAMENTALS OF NATURAL GAS ENGINEERING 1. Define, Boyle’s law and Charle’s law. Boyle’s law: Boyle observed experimentally that the volume of an ideal gas is inversely proportional to the pressure for a given weight or mass of gas when temperature is constant. This may be expressed as V α 1/p or P V = constant. Charle’s law: While working with gases at low pressures, Charles observed that the volume occupied by a fixed mass of gas is directly proportional to absolute temperature, or Vα T or V / T = constant. 2. Calculate the mass of methane gas contained at 1,000 psia and 68 volume of 3.20 cuft. F in a cylinder with m = p M V / ZRT From fig 2.2 Z = 0.89 m = 1,000 x 16 x 3.2 / 0.89 x 10.73 x 528 m = 10.2 Ib 3. Describe the ideal- or perfect-gas law. The gas law relating pressure, temperature, and volume for a gas with molecules of zero size and without intermolecular forces is known as the ideal- or perfect gas law, PV = n RT where P = pressure V = volume n = number of moles R = gas constant T = absolute temperature Gases near atmospheric pressure follow the ideal-gas law; so pressure or volume can be predicted from temperature and mass within 5 per cent or better. If more precise prediction becomes necessary or if gases at high pressure are to be treated, the ideal-gas equation becomes inadequate. 7 One is to insert a variable correction factor, the compressibility factor z, into the ideal-gas equation. PV = znRT The gas law is general, and z may be either a graphical or a mathematical function of temperature, pressure, and the composition of the gas. 4. The diffusion coefficient for C14O2 in hydrogen at 100°C is 0.341 sq cm/sec. Compute the diffusion rate of 100°C through a conduit 3 mm×3 mm and 1.0 cm long, when hydrogen with 0.1 mole per cent C14O2 is in container I and hydrogen with 1.0 per cent C14O2 is in container II. dc dn sq cm 0.3 × 0.3sqcm 0.009 × 273 gram moles = − DA = (0.341 )( )( ) dt dx sec 1.0cm 22,414 × 373 cu cm = 9.0×10–10 gram mole/sec 5. Compute the density of gas A with the composition shown at 1,200 psia and 80°F. Constituent Carbon dioxide Methane Ethane Propane Isobutane n-Butane Constituent Carbon dioxide Methane Ethane Propane Isobutane n-Butane Mole fraction 0.0040 0.9432 0.0390 0.0117 0.0008 0.0013 1.0000 Mole Fraction y 0.0040 0.9432 0.0390 0.0117 0.0008 0.0013 1.0000 Mol wt 44 16 30 44 58 58 Computation of pseudocritical point Critical temp, °R Critical pressure, psia Lb/ mole Tc yTc Pc yPc 0.17 15.09 1.17 0.51 0.04 0.07 17.05 548 343 550 666 735 766 2.1 323.5 21.4 7.8 0.6 1.0 356.4 1073 673 708 617 528 551 Reduced temperature, T/Tc = (80 + 460)/356.4 = 1.51 Reduced pressure, P/Pc = 1200/674.9 = 1.78 Gas gravity = 17.05/29.0 = 0.588 From Fig.2.16, at Tr = 1.51 and Pr =1.78, compressibility factor z = 0.84 Density of natural gas = Alternative calculation: 17.05 × 1200 × 520 = 4.2 lb/cu ft 379 × 14.7 × 540 × 0.84 4.3 634.7 27.6 7.2 0.4 0.7 674.9 8 ρ= 1 P 1200 × 17.05 × 1 × 1 = = = 4.2 lb/cu ft V znRT 0.84 × 1 × 10.73 × 540 6. Describe the law of conservation of energy and explain it. The basic energy relationship of any fluid-flow process stems from the law of conservation of energy, which states merely that the energy of the fluid entering the conduit minus the energy dissipated in the conduit through irreversible effects plus any work energy added to the fluid is equal to the energy of the fluid leaving the conduit. This is expressed by the well-known thermodynamic-flow equation for a unit mass of fluid in transit between two points, such as 1 and 2 of Fig. 3.1(sketch it). v2 g + ∆X = q −W 2gc gc where ∆H = H2 – H1 = the increase in enthalpy between the initial and final states, v2 ∆ = difference in kinetic energy (v = velocity, ft/sec) of flowing fluid, 2gc ∆H + ∆ (sq ft)(ft - lb force)(sec 2 ) (sec 2 )(ft − lb mass)(ft) g = acceleration of gravity, ft/sec2 gc = 32.174, conversion factor, [ft-lb mass/(ft)(lb force)](ft/sec2) ∆X = X2 – X1 = difference in elevation, ft q = heat absorbed by system from surroundings, ft-lb force/lb mass w = work done by the fluid while in flow, ft-lb force/lb mass 7. A pipeline 100 miles long has an internal diameter of 13.35 in. The inlet pressure is 1400 psia and the pressure at the end of the line is 290 psia. The temperature of the flowing gas is 40°F, and its composition is as follows: (15 marks) Methane Mole % 75 Ethane 21 Propane 4 100 Calculate the volumetric flow rate measured at 14.68 psia and 60°F. To work out the problem as shown in illustrative problem after Eq. (3.35) 8. Using the description of the pipeline given in the previous problem(35), calculate the storage capacity of this line in cubic feet of gas measured at 60°F and 14.68 psia when for unpacked conditions the pressure at the outlet end of the line is 400 psia and for packed conditions it is 900 psia. To work out the problem as shown in illustrative problem after Eq. (3.52) 7. What is the effect of condensate in metered gas stream. 9 Gas in transit to market seldom contains condensate, but gas flowing from high-pressure wells may contain substantial amounts of hydrocarbon condensate as well as some water. Tests were made (Fig.4.7) on a horizontal and on a vertical meter run to determine the effect of the presence of condensate with subsequent separation and measurement of the two phase streams. Studies of P-V-T data on gases that enter the two-phase region showed that the compressibility factor gave an adequate representation of the composite density of a two-phase stream even though liquid were present. 7. Describe mechanical pulsometer. The mechanical pulsometer shown in the Fig.4.20(Draw a sketch) consists of two cylindrical volumes, A and B, separated by a sylphon bellows C. The two volumes separated by the bellows are connected to the inlet (upstream) side and outlet (downstream) side of the meter connection. A coil spring A is mounted in the chamber connected to the highj-pressure tap. The tension on the spring is adjusted by handwheel E with the degree of movement indicated by scale F. Electrical contacts in volume B permit adjustment of spring tension so that the bellows is at a fixed position. The tension on the spring is gradually increased until the contact is broken, indicating that the bellows has come to a standard position and that the spring tension offsets the maximum differential pressure occurring at any time. The scale F may be calibrated by a manometer placed across the connections with steady pressure. gggggggggggggggggggggggggggg
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