Abstract: The mathematical model of existing commercial black oil reservoir numerical simulator does not take variations in porosity and permeabilitywith pressure as amoderate sanding happens in unconsolidated sandstone reservoir into consideration and ignores impacts ofporousmedia deformation on production performance, whichmakes the development plan design and the prediction of
production behavior uncertain. In this paper, a coupled flow model in unconsolidated sandstone reservoir, taking account of influence of stress change on variations in porosity and permeabilitywith pressure, was presented.An explicitalgorithm to couple porous flow and the changes of porosity and permeability where flow calculations were performed every time step was used, and the changes of porosity and permeability were calculated only during selected time steps. The mathematicalmodel was numerically solved by differentialdiscrete. Based on BOAST II, program code was modified. The simulation of fluid-solid coupled flowwas implemented in unconsolidated sandstone reservoir. The results indicated that production performance predictingwith coupled flow was very different from thatwithout coupled flow in unconsolidated sandstone reservoir. Thiswork overcame difficulties that conventional black oil simulator was not well applied in unconsolidated sandstone reservoir.

Key words: unconsolidated sandstone reservoir, fluid-solid coupled flow, mode, l numerical simulation