New insights on supercritical CO₂ fracturing coal mass: a staged analysis method

Abstract

Abstract As a water‐less fracturing mining technology, supercritical CO 2 fracturing has attracted increasing attention in the mining industry. Based on detailed analysis of CO 2 phase behavior in the whole process of supercritical CO 2 fracturing, the whole cycle of supercritical CO 2 fracturing was divided into the supercritical CO 2 fracturing stage and the CO 2 phase transition–induced fracturing stage, and according to the characteristics of each fracturing stage, the fracturing mechanism of supercritical CO 2 was analyzed in stages, and the roles of the two stages in the life cycle of the entire supercritical CO 2 fracturing process were obtained. Through the laboratory test of supercritical CO 2 fracturing coal mass, the pressure–time curves during the whole process of supercritical CO 2 fluid fracturing were analyzed, and the rationality and correctness of the supercritical CO 2 fracturing staged analysis method proposed in this paper were verified. Based on the energy conservation theory and the state function equation of classical thermodynamics, the burst energy of the CO 2 phase transition–induced fracturing stage was estimated. By comparing the trinitrotoluene equivalent of phase‐transition energy with the trinitrotoluene amount of explosive explosion, it was proved that the CO 2 phase transition–induced fracturing stage was not negligible. The research results of this paper are of considerable significance for the full understanding of the supercritical CO 2 fracturing mechanism. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.