TABLE OF CONTENTS Most reservoir engineering calculations involve the use of the material balance equation. Some of the most useful applications of the MBE require the concurrent use of fluid flow equations, e.g., Darcy's equation. Combining the two concepts would enable the engineer to predict the reservoir future production performance as a function of time. Without the fluid flow concepts, the MBE simply provides performance as a function of the average reservoir pressure. Prediction of the reservoir future performance is ordinarily performed in the following two phases:
Phase 1. Predicting cumulative hydrocarbon production as a function of declining reservoir pressure. This stage is accomplished without regard to:
Actual number of wells
Location of wells
Production rate of individual wells
Time required to deplete the reservoir
Phase 2. The second stage of prediction is the time-production phase. In these calculations, the reservoir performance data, as calculated from Phase One, are correlated with time. It is necessary in this phase to account for the number of wells and the productivity of each well.
The material balance equation in its various mathematical forms as presented in Chapter 11 is designed to provide with estimates of the initial oil in place N, size of the gas cap m, and water influx We. To use the MBE to predict the reservoir future performance, it requires two additional relations:
Equation of producing (instantaneous) gas-oil ratio
Equation for relating saturations to cumulative oil production
These auxiliary mathematical expressions are presented as...
