Effect of the Perforation Damage on Well Productivity

This paper reveals new information on the reduction in productivity caused by the crushed zone surrounding a jet perforation tunnel. A Berea sandstone sample was perforated according to a slightly modified API RP 43 Recommended Practice Standard Procedure for perforation, using a 3.5 gr. RDX type charge. The crushed zone was identified using a scanning electron microscope, SEM. The crushed zone was divided into a number of cells both radially (away from the shot center) and longitudinally (along the perforation tunnel). Porosity and permeability of each cell were obtained using image analysis. The permeability value of each cell was arranged around the perforation tunnel according to their original orientations. U sing a black oil simulator, productivity of a well was found and compared to one where no permeability reduction was assumed for the crushed zone. In addition, the Dykstra-Parsons relation was employed to estimate permeability values for a suite of 20 cells. The estimated values were then oriented around the perforation tunnel in ascending, descending, and randomly orders. Productivity of the well was obtained for each permeability orientation. A 55% permeability reduction around the perforation tunnel, as the result of the perforation process, led to a 60% reduction in well productivity. Also, ascending orientation of the permeability around the perforation tunnel resulted in a higher well productivity than descending or random orientation.