Measurement of Additional Skin Resulting From Perforation Damage

Abstract

Abstract Single shot laboratory flow tests were performed on perforated Berea and Gold sandstone cores to determine the additional skin caused by the presence of a perforation damage zone. A variety of underbalances, stresses and wellbore volumes were used. Whole core diametral and axial permeabilities were measured for each core tested. Cores were then perforated under simulated downhole conditions, and radial flow tests were conducted to determine the skin due to the perforation damage zone. Because these measurements gave no information on the distribution of permeability damage, further experiments were carried out using a radial flow permeameter to directly measure the permeability distribution. The radial flow permeameter confirmed the presence of a low permeability region around, but not always adjacent to, the perforation tunnel. Permeability damage at the outside of the cores due to the coring process was also determined. Although one set of experiments shot under identical conditions, at a low underbalance, showed a degree of randomness in the results, the following observations could be made: 1) For the conditions tested, there is no apparent stress effect on the perforation damage skin, 2) The size of accumulator attached to the wellbore affected the resulting skins, and 3) Results of single shot experiments should be used with extreme care.