Residual gas saturation revisited

摘要

The determination of residual gas saturation in gas reservoirs from long spontaneous and forced-imibibition tests is addressed in this paper. it is customarily assumed that when a gas reservoir is over- laying an aquifer, water will imbibe into the gas-saturated zone with the onset of gas production. The process of gas displacement by water will lead to forced imbibition in areas of high drawdown and spontaneous imbibition in areas of low draw- down. It is further assumed that in the bulk of the reservoir, spon- taneous imbibition will prevail and the reservoir will be water-wet. A final assumption is that the gas behaves as an incompressible Fluid. All these assumptions are challenged in this paper.