Experimental study on the true triaxial fracturing of tight sandstone with supercritical CO2 and slickwater

Abstract

Under the effect of the goal of carbon peaking and carbon neutrality, the use of supercritical CO2 has gradually become a research hotspot as a new waterless fracturing fluid, supercritical CO2 fracturing is expected to become an effective techniques to solve the problem of fracturing fluid backflow in low pressure sandstone reservoirs. The outcrop of the Shaximiao Formation in the Sichuan Basin was selected as the research object, the true triaxial fracturing experiments with supercritical CO2 and slickwater were carried out by the large true triaxial fracturing experimental equipment, the computed tomography (CT) scanner and three-dimensional laser scanner to investigate the initiation, propagation patterns, fracture tortuosity and fractal dimension of fractures produced in tight sandstone via supercritical CO2 and slickwater fracturing and to clarify the influences of the different fluids, displacement rates, and in-situ stress differences on the propagation of fractures in tight sandstone. The results showed that the supercritical CO2 fracturing had a lower fracturing pressure and a longer rock fracturing time than slickwater fracturing. Furthermore, the supercritical CO2 fracturing produced fractures with greater tortuosity and fractal dimension as well as a more complex spatial morphology. In addition, the increase in the displacement rate and the decrease in the in-situ stress difference for supercritical CO2 fracturing was more conducive to the multi-point initiation and reorientation of the hydraulic fractures, increasing the complexity of the reservoir fractures and improving the flow effect. It can provide the important theoretical foundation for the creating plans for supercritical CO2 fracturing of tight sandstone with the experimental knowledge.