Research on the Damage of Porosityand Permeabilitydue to Perforation on Sandstone in the Compaction Zone

A perforating hole is a channel through which the oil and gas in a reservoir pass into the production well bore. During the process of perforating due to explosion, the surrounding sandstone will be damaged to a certain extent, which will increase the well bore skin and lead to the decrease of production consequently. In this work a mechanical model of perforating damage is developed to describe the influences of perforating due to explosion on the porosity and permeability of the surrounding sandstone near the compaction zone. Based on this developed model, the important data related to the damage of sandstone, such as matrix effective stress, plastic deformation, volumetric strain, and so on, can be numerically simulated. Especially the behaviors of plasticity kinematic hardening at high strain rate due to impact loads, which are the important characteristics in the sandstone, is taken into account in this developed model. Both numerical and testing results show that the damage due to perforation in the sandstone can be accurately predicted by the developed model together with the porosity and peimeability evolving model of perforation in a compaction zone. As a practical application, a methodology for the analysis of damage of porosity and permeability around a perforation tunnel is supposed based on the developed model and the core flow efficiency test of interparticle pore spaced sandstone target in China Shengli Oilfield and the computed tomography test.