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.
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