Study Of Formation Parameter Variation For Waterflooding Sandstone Reservoir Based On Pore-scale Network Modeling

During the process of waterflooding in unconsolidated sandstone reservoirs, the permeability and porosity of the reservoir will change gradually with injected water flushing, which exerts a very significant influence on reservoir development. Therefore, revealing the mechanism and law of reservoir parameters changing could provide a useful guidance for tapping the potential of remaining oil, establishing plans of tertiary recovery and improving the effect of water flooding.Particle release and capture have been studied through force analysis by taking into full consideration of the electrostatic force and hydrodynamic force. Critical flow velocity of particles releasing from the pore-throat surface and the judging criteria of particle in fluid redeposit on the pore-throat surface are obtained from theoretical derivation. Subsequently, pore-throat is simplified to a single capillary, and pore-throat size changing, resulted from particle depositing in a pore-throat, is simulated by lattice Boltzmann method. A network simulation method, which can simulate reservoir parameters changing during the process of water flooding in unconsolidated sandstone reservoirs is established. This method is based on the constructed random network model, instead of the pore-throat in actual reservoir, and takes into account the mechanism of particle release, capture, migration and distribution. Laws of reservoir parameters changing under different geological features and development characteristics conditions have been investigated by means of the network simulation method.Study results reveal that pore-throat sizes will progressively increase in the process of water flooding on account of particle constantly changing in the pore-throat, and the permeability and porosity of a reservoir will also increase by degree with injected water flushing. When considering the existence of suspended particles in injected water, formation damage will take place in consequence of injected particles depositing in the pore-throat, which lead to the reservoir permeability reduce gradually. At last, laws of reservoir parameters changing under different influencing factors are studied through the sensitivity analysis.