1. A representative bottom-hole liquid sample has been analyzed in the laborator
ID: 884592 • Letter: 1
Question
1. A representative bottom-hole liquid sample has been analyzed in the laboratory to determine the solution gas and formation volume factor as a function of pressure. The initial reservoir bottom-hole pressure and bottom-hole temperature are 3600 psia &160oF respectively; so all measurements in the laboratory were made at 160oF. The following data, converted to practical units were obtained from the measurements:
Pressure
psia
Solution gas SCF/STB at
14.7 psia and 60oF
Formation Volume factor
Bbl/STB
3600
567
1.310
3200
567
1.317
2800
567
1.325
2500
567
1.333
2400
554
1.310
1800
436
1.263
1200
337
1.210
600
223
1.140
200
143
1.070
Based on the data above do the following:
a. If the reservoir contains 250 MM reservoir barrels of oil initially, what is the initial number of STB in place?
b. If initial water saturation is 0.23 what is the initial volume of dissolved gas in an acre-ft of the reservoir?
c. If the reservoir pressures drops to 1200 psia how much reservoir volume would a 1000 STB oil occupy (with its dissolved gas)?
Pressure
psia
Solution gas SCF/STB at
14.7 psia and 60oF
Formation Volume factor
Bbl/STB
3600
567
1.310
3200
567
1.317
2800
567
1.325
2500
567
1.333
2400
554
1.310
1800
436
1.263
1200
337
1.210
600
223
1.140
200
143
1.070
Explanation / Answer
a) N =V0 / Boil
= 250 MM bbl /1.31 bbl/STB Boil = Formation volume factor at 3600 psia
= 190.84 MM.STB
b) solubility of gas = 0.23 SCF/STB/psia / 3600 psia
= 0.000064 SCF/STB
c)
With gas solubility of 0.000064 SCF/STB/psia, and initial Roil =0.23SCF/STB/psiaSCF/STB
at 1200 psia, the R = 0.23(3600-1200) = 552 SCF/STB
So the gas dissolved in oil is (190.84 - 1 ) MM STB* 552 SCF/STB = 104791.68 MM.SCF
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