Research on the Characteristics of Supercritical CO2 Shock Fracturing Flow Field Based on Numerical Simulation

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ABSTRACT: Unconventional oil and gas have significant resource potential and economic value. Based on the technical method of extracting unconventional oil and gas through supercritical carbon dioxide (SC-CO2) shock fracturing proposed by the research team, a SC-CO2 shock fracturing tool has been developed. Based on computational fluid dynamics and the finite element method, a three-dimensional model was established to simulate the flow field of SC-CO2 shock fracturing. Numerical simulations were conducted to obtain the spatiotemporal distribution patterns of pressure, temperature, and velocity. The results show that under impact load, the maximum stress strain and maximum temperature of the tool occur at the nozzle wall, with a maximum equivalent stress of 409.25 MPa and a maximum total deformation of 0.075 mm, meeting the strength requirements. The SC-CO2 fluid is released through the nozzle, resulting in drastic changes in the flow field temperature, pressure, and velocity, causing a backflow phenomenon and continuously impacting the reservoir. The research results can provide a reference for the development of SC-CO2 shock fracturing tools. 1. INTRODUCTION Currently, with the advancement of global oil and gas resource exploration and development, unconventional oil and gas have shown significant resource potential and economic value (Wang et al., 2016). However, unconventional reservoirs have issues such as high seepage resistance and poor connectivity (Middleton et al., 2017), leading to high development costs. Therefore, it is necessary to enhance the reservoir, and hydraulic fracturing is the most widely used reservoir modification technology (Li et al., 2024). However, in the development of unconventional oil and gas, water-based fracturing fluid systems face technical challenges such as hydraulic fractures being controlled by formation stress; high water demand and low utilization efficiency (Shahbazi et al., 2020); clay swelling due to water sensitivity, blocking reservoir flow channels, and damaging the reservoir (Ahamed et al., 2019); incomplete flowback contaminating groundwater, and high wastewater treatment costs (Li et al., 2015), which restrict the development and utilization of unconventional oil and gas resources (Wu et al., 2022).