Page 32 - Petroleum Production Engineering, A Computer-Assisted Approach

Guo, Boyun / Computer Assited Petroleum Production Engg 0750682701_chap02 Final Proof page 21 22.12.2006 7:08pm

PROPERTIES OF OIL AND NATURAL GAS 2/21
where 2.2.5 Oil Compressibility
‘‘Oil compressibility’’ is defined as
8:33
ð 0:43þ API Þ
A ¼ 10 (2:9)
1 @V
and c o ¼ , (2:17)
m od ¼ viscosity of dead oil (cp). V @p T
where T and V are temperature and volume, respectively.
Standing’s (1981) correlation for saturated crude oil is
expressed as Oil compressibility is measured from PVT labs. It is often
used in modeling well-inflow performance and reservoir
a
b
m ob ¼ 10 m , (2:10) simulation.
od
where m ob ¼ viscosity of saturated crude oil in cp and Example Problem 2.1 The solution GOR of a crude oil is
600 scf/stb at 4,475 psia and 140 8F. Given the following
7
4
a ¼ R s (2:2 10 R s 7:4 10 ), (2:11) PVT data, estimate density and viscosity of the crude oil at
the pressure and temperature:
0:68 0:25 0:062
b ¼ þ þ , (2:12) Bubble-point pressure: 2,745 psia
10 c 10 d 10 e
Oil gravity: 35 8API
5
c ¼ 8:62 10 R s , (2:13) Gas-specific gravity: 0.77 air ¼ 1
3
d ¼ 1:10 10 R s , (2:14) Solution Example Problem 2.1 can be quickly solved
using the spreadsheet program OilProperties.xls where
and Standing’s correlation for oil viscosity was coded. The
3
e ¼ 3:74 10 R s , (2:15) input and output of the program is shown in Table 2.1.
Standing’s (1981) correlation for unsaturated crude oil is
expressed as 2.3 Properties of Natural Gas
m o ¼ m ob þ 0:001(p p b )(0:024m 1:6 þ 0:38m 0:56 ): (2:16) Gas properties include gas-specific gravity, gas pseudo-
ob
ob
critical pressure and temperature, gas viscosity, gas
Table 2.1 Result Given by the Spreadsheet Program OilProperties.xls
OilProperties.xls
Description: This spreadsheet calculates density and viscosity of a crude oil.
Instruction: (1) Click a unit-box to choose a unit system; (2) update parameter values in the Input data section;
(3) view result in the Solution section and charts.
U.S. Field
Input data units SI units
Pressure (p): 4,475 psia
Temperature (t): 140 8F
Bubble point pressure ( p b ): 2,745 psia
Stock tank oil gravity: 35 8API
Solution gas oil ratio (R s ): 600 scf/stb
Gas specific gravity (g g ): 0.77 air ¼ 1
Solution
141:5
g o ¼ ¼ 0.8498 H 2 O ¼ 1
API þ 131:5
62:4g o þ 0:0136R s g g
r o ¼ h q ffiffiffiffi i 1:175 ¼ 44.90 lb m =ft 3
g g
0:972 þ 0:000147 R s þ 1:25t
g o
A ¼ 10 (0:43þ8:33=API) ¼ 4.6559
A
1:8 10 7 360
m od ¼ 0:32 þ ¼ 2.7956 cp
API 4:53 t þ 200
4
7
a ¼ R s (2:2 10 R s 7:4 10 ) ¼ 0.3648
5
c ¼ 8:62 10 R s ¼ 0.0517
3
d ¼ 1:10 10 R s ¼ 0.6600
3
e ¼ 3:74 10 R s ¼ 2.2440
0:68 0:25 0:062
b ¼ þ þ ¼ 0.6587
10 c 10 d 10 e
a
m ob ¼ 10 m b od ¼ 0.8498 cp 0.0008 Pa-s
m o ¼ m ob þ 0:001( p p b )(0:024m 1:6 þ 0:38m 0:56 ) ¼ 1.4819 cp 0.0015 Pa-s
ob
ob