A 3D Network Model of Rock Permeability Impairment Due to Suspended Particles in Injection Water

摘要

A 3-D network model is used to simulate the impairment ofrnporous medium permeability during the flow of water withrnsuspended particles.rnDigitized 2-D images of the porous systems are obtained byrnpetrographic image analysis of rock thin sections.rnGeostatistical procedures are applied to construct 3-D virtualrnrealizations of the medium. The pore body and throat sizesrndistributions of the virtual medium and its connectivity,rnexpressed by the average coordination number, arerndetermined. Alternatively, these characteristics are obtainedrnby using capillary driven porosimetry data and empiricalrncorrelations. A regular cubic network of sites (pore bodies)rnand bonds (pore throats) that reproduces these characteristicsrnis structured.rnNetwork absolute permeability can be calculated by solving arnsystem of linear mass balance equations for the sites, alongrnwith equations of hydraulic conductivity for the bonds.rnRealistic permeability estimates are obtained.rnMotion and contingent capture of injected particles inside thernmedium are simulated. Both physicochemical interception andrnsize exclusion mechanisms of particle retention are modeled,rnthe former with the aid of two empirical parameters. Particlerncapture modifies the flow in the network, that is recurrentlyrncalculated, resulting in permeability decline as more particlesrnare retained.rnNetwork simulated data and their comparison with thosernobtained in laboratory tests are reported. Besides particle tornpore throat size ratio, concentration and flow velocity, otherrnimportant factors governing the permeability impairment are:rn1. medium coordination number and 2. shape of pore throats.