API REPORT 86-36-1987 THE EFFECTS OF STRESS AND PORE PRESSURE ON PENETRATION OF JET PERFORATORS IN BEREA SANDSTONE - FINAL REPORT (INCLUDES ERRATA AND ADDENDA)
"INTRODUCTION This report covers results of the first phase of a new multi-phase API-sponsored program on jet perforator performance. The overall objectives of the program are to establish better criteria for oil-well perforator performance and to improve predictions of penetration depth and flow performance down hole. In this first phase@ we report the results of experiments on the effect of stress on penetration depth. Based on the premise that down-hole stresses might degrade perforator penetration and flow performance@ Saucier and Lands (1977) studied the effect of stress on jet perforator performance. They fired 3.2-g charges into 2.75-inch-diameter Berea Sandstone cores and found reductions in rock penetration of up to 38%. Concerned that boundary conditions might affect the experiments@ the API PRAC committee sponsored work at GOEX to extend these tests to larger targets and charge sizes. This study also found significant reductions in penetration with stress@ up to 50% (Siggers@ 1982@ and Hayes@ 1984.) In recent internal work@ Schlumberger Well Services repeated these tests using large 30x3Ox36-inch blocks of Berea Sandstone and a specially-designed stress apparatus@ described below. Much smaller penetration reductions@ on the order of 10%@ and of marginal statistical significance were observed. This apparent discrepancy with earlier results suggested differences either in the test procedures or in the charges tested. This@ combined with API's program objectives@ led to the phase-I studies reported here. The specific objectives of the program's first phase were a) to determine the cause of apparent differences between recent Schlumberger results and earlier tests. b) To compare tests with and without pore pressure and to verify the ""effective stress"" law. c) To begin collection of rock properties data for later correlations of penetration with rock type@ and d) to attempt correlations of stress-induced penetration reductions with other stress-dependant rock properties. To achieve these objectives@ three test procedures were used on two different charge sizes from different manufacturers. The three test procedures were@ a-Berea ""slab"" tests performed under surface conditions using multi-shot guns according to proposed API Sec. ill standards; b-""Stressed block"" tests@ using multi-shot guns fired into 3Ox3Ox36-inch blocks of sandstone stressed in a large three-axis load frame; c--single-shot experiments in stressed 8-inch diameter cylinders of sandstone. Rock samples were characterized by density@ porosity@ uniaxial elasticity and ultimate strength@ and longitudinal- and shear-wave acoustic velocities as a function of pressure."
API REPORT 86-36-1987 history
1987API REPORT 86-36-1987 THE EFFECTS OF STRESS AND PORE PRESSURE ON PENETRATION OF JET PERFORATORS IN BEREA SANDSTONE - FINAL REPORT (INCLUDES ERRATA AND ADDENDA)