Theoretical fundamentals, critical issues, and adequate formulation of effective shale gas and condensate reservoir simulation
The issues of relevance to describing the storage and movement of hydrocarbon gas and condensate, and water through extremely low permeability shale formations are reviewed. The shale rock is viewed as a heterogeneous quad-media continuum system. Each system has different wettability, storage, transport, and connectivity characteristics. The hydrocarbon storage is considered as being in the free gas, adsorbed gas, and dissolved gas. The alteration of fluid properties and flow behavior under pore confinement are emphasized. For gas transport the effective mean-radii and apparent permeability as a function of pore-size distribution and gas adsorption are examined. The nonequilibrium fluid distribution effect produced by tortuous narrow flow paths is discussed. It is emphasized that these form the essential phenomena that must be taken into account for effective simulation of shale gas and condensate reservoirs.