Problem 2

6.1

An undersaturated reservoir producing above the bubble point had an initial

pressure of 5000 psia, at which the oil volume factor was 1510 bbl/STB. When the

pressure dropped to 4600 psia owing to the production of 100,000 STB of oil, the

oil volume factor was 1520 bbl/STB. The connate water saturation was 25%, water

compressibility 32*10-6 psi¯¹, and based on an average porosity of 16%, the rock

compressibility was 4.0* 10–6 psi¯¹. The average compressibility of the oil

between 5000 and 4600 psia relative to the volume at 5000 psia was 17.00*

10-6 psi-¹.

Geologic evidence and the absence of water production indicated a volumetric

reservoir. Assuming this is true, calculate the OIP.