A realistic transport model with pressure dependent parameters for gas flow in tight porous media with application to determining shale rock properties

摘要

Shale gas recovery has seen a major boom in recent years due to theincreasing global energy demands; but the extraction technologies are veryexpensive. It is therefore important to develop realistic transport modellingand simulation methods, for porous rocks and porous media, that can complimentthe field work. Here, a new nonlinear transport model for single phase gas flowin tight porous media is derived, incorporating many important physicalprocesses that occur in such porous systems: continuous flow, transition flow,slip flow, Knudsen diffusion, adsorption and desorption in to and out of therock material, and a correction for high flow rates (turbulence). This producesa nonlinear advection-diffusion type of partial differential equation (PDE)with pressure dependent model parameters and associated compressibilitycoefficients, and highly nonlinear apparent convective flux (velocity) andapparent diffusivity. An important application is to the determination of shalerock properties, such as porosity and permeability, by history matching of thethe simulation results to data from pressure-pulse decay tests in a shale rockcore sample [Pong K., Ho C., Liu J., Tai Y. Non-linear pressure distribution inuniform microchannels. ASME Fluids Eng. Div. (FED) Vol. 197, 51--56, (1994)].The estimates of the rock porosity and the permeability from our modelsimulations are realistic of shale rocks, more realistic than obtained fromprevious models, and illustrates the potential of the modelling strategypresented here in producing accurate simulations of shale gas flow in tightreservoirs.