Initially Saturated (Gas Cap Present)

Introduction

To begin, we define “m“ as the ratio of gas cap size to the oil volume size

Re-arranging, we get:

Now, lets begin with:

Original Hydrocarbon in pore space = Current Hydrocarbon and water in pore space

Original Oil (with solution Gas) + (Original Gas Cap) = Oil (with solution gas) + Free gas + water

1. Gas Material Balance

Initially

Total Gas Original = Total Gas Remaining (Free+ Solution Gas) + Gas Produced

gives:

Ensure Free Gas is in terms of reservoir volumes:

2. Substitute Back to Original MBE

Original Oil (with solution Gas) + (Original Gas Cap) = Oil (with solution gas) + Free gas + water

Re-arrange, collect “like-terms“ etc gives:

A=

B =

C =

D =

E =

F =

G =

3. And Finally:

The generalized MBE is:

A + B + C = D + E + F + G

+ + = + + +

References:

• Northern Alberta Institute of Technology, Course Notes, PETE 2320, 2020.