Study on fracture propagation of hydraulic and supercritical CO2 fracturing in different rock

Abstract

In this study, the performance of water-based fracturing fluids and supercritical CO2 in three types of representative reservoirs (sandstone, conglomerate, and shale) was investigated. The results showed that there are differences in fracture initiation pressures in different rocks, but the fracture initiation pressure of supercritical CO2 is lower than that of water regardless of the rock type. In sandstone reservoirs, supercritical CO2 induced more complex fractures than water, resulting in branching fractures. In conglomerate reservoirs, hydraulic fractures pass through the conglomerate and are flatter, whereas supercritical CO2 fractures pass through or around the conglomerate, and thus the fractures are more tortuous. Gravel stopped the fracture extension in both conditions. In shale reservoirs, supercritical CO2 can communicate natural fractures more effectively than water, thereby increasing the effective transformation volume. The study provides theoretical guidance for reservoir adaptation of supercritical CO2 fracturing.