Borehole parameter optimization for supercritical carbon dioxide phase-transition fracturing

Abstract

Abstract In recent years, supercritical carbon dioxide phase-transition fracturing (SCDPTF) has extensively been used in rock engineering as an environmentally friendly rock breaking technology. It is important to improve the energy efficiency and rock breaking effect by examining the SCDPTF borehole parameters. In this study, SCDPTF was first analyzed by numerical simulations. Based on the numerical simulation results, field tests were subsequently performed to determine the optimal borehole parameters. The results indicate that the rock mass around the borehole under the carbon dioxide phase-transition fracturing load can be divided into a crushing zone, a cracking zone, and a vibration zone. The radius of the crushing zone was ~0.297 m and that of the cracking zone was ~1.399 m, respectively. The optimal minimum burden line was 1.8 m, and the optimal borehole spacing was 2.5 m, respectively. The abovementioned results could provide effective guidance for the parameter design of SCDPTF.