PERMEABILITY REDUCTION DUE TO GRAIN CRUSHING AROUND A PERFORATION

The permeability reduction around a perforation cavity is analyzed as the result of grain crushing due to the perforation process. The poroe lastic solution of a plane wave emanating from a cylindrical cavity is used to derive expressions for the intergranular stresses responsible for grain-crushing phenomena. These phenomena are examined on the bas is of Herizian contact theory of fracture and micromechanical descript ions of granular assemblies assisted by discrete element simulations. Results are presented for hydrostatic loading conditions for compariso n with existing experimental results, and for uniaxial strain conditio ns as an approximation to the stress field around the perforation. The analysis can be applied to the prediction of the extent of the permea bility-reduced zone and used for estimating the permeability reduction around the perforation.