Gas Flowing Material Balance (GFMB)

Accurate estimation of reservoir reserves is fundamental to reservoir engineering. Among the various methods, the material balance approach—relying on actual reservoir performance data—is widely regarded as the most reliable for calculating initial hydrocarbon volumes.

Traditionally, this method involves shutting in multiple wells to determine average reservoir pressure. However, this process is often logistically complex and may not yield sufficiently accurate pressure measurements.

The flowing material balance method provides a practical alternative. By incorporating concepts such as boundary-dominated or pseudo-steady state flow, and utilizing flowing pressures and production rates, it enables reserve estimation without the need for well shut-ins.