George E. King, Amoco Production Research
Perforating through multiple strings of casing is one of the most difficult design problems in recompletions. The overlap of casing sections may occur in the middle of a series of pay zones as the result of drilling breaks, hole problems or pressure control. Tests in surface targets have provided information that is useful in design for perforating two and three strings of casing as well as addressing problems of perforating in large diameter casing and the thick cement sections of hole wash-outs. In the surface tests, large deep penetrating charges in large diameter guns with minimum gun-casing clearance were found to create the most consistent penetration through multiple strings of casing. Information presented includes evaluation of deep penetrating and big hole charges, charge variances, perforation plugging by debris, and effect of clearance on penetration. Entrance hole information in each string is presented on some targets.