Inclusion of Formation & Water Expansion

Introduction

In recent years, the contribution of rock compaction and water expansion are now included in the general MBE.

Formation Expansion

The contribution of rock and water expansion are determined from the compressibility of formation and water as follows:

formation expansion =

Where:

Vf = Bulk volume of the hydrocarbon bearing zone

Vw water volume in the hydrocarbon bearing zone

cf = formation compressibility

cw = water compressibility

Knowing the definition of formation compressibility

And that the volume of water is related to Bulk volume via initial water saturation, we have:

Recalling some of our earlier work, we know that the initial hydrocarbon volume is:

Finally, the formation expansion term, after substitution, is:

formation expansion =

formation expansion =

The general MBE from Oil Material Balance is expanded to be:

+ + = + + + +