Faculty of EngineeringPetroleum Engineering & Gas Technology Department

Petroleum Reservoir Engineering Module Code: PTRL02H02Semester 2 - 2008/2009

Dr Taha MoawedEng. Ahmed Al ZahabyExample 1

A small gas reservoir with an initial bottom-hole pressure 3200 psia and bottom hole temperature 220 F. Its desired to inventory the gas in place at three production intervals .The pressure production history and gas volume factors in cubic feet per standard cubic foot at standard conditions of 14.7 psia

And 60 F are as the following :Pressure ,psiaCum. Gas Production MM Ft3Gas Vol. Factor,ft3/SCF

320000.0052622

2925790.0057004

25252210.0065311

21254520.0077360

a) Calculate the initial gas in place using production data at the end of each of the production intervals, assuming volumetric behavior (no water influx).b) Explain why the calculations of part (a) indicate a water drive.

c) Show that a water drive exists by plotting the cumulative production versus p/z.

d) Based on electric log and core data, volumetric calculations on the reservoir showed that the initial volume of gas in place is 1018 MMSCF. If the sand is under a partial water drive, what is the volume of water encroached at the end of each of the periods? There was no appreciable water production. Example 2

Given the following data for an oil field

A gas cap reservoir is estimated, from volumetric calculations, to have an initial oil volume N of 115 x 106 STB. The cumulative oil production Np and cumulative gas oil ratio Rp are listed in the following table as functions of the average reservoir pressure over the first few years of production. Assume that pi = pb = 3330 psia. The size of the gas cap is uncertain with the best estimate, based on geological information, giving the value of m = 0.4. Is this figure confirmed by the production and pressure history? If not, what is the correct value of m?