LAUSR

Abstract As a new potential economic and effective fracturing method, supercritical carbon dioxide (SC-CO2) waterless fracturing technology can be implemented to alleviate problems such as water sensitivity and reservoir pollution. Further, it reduces emissions, which is an advantage that is being extensively studied. In SC-CO2 fracturing, fracturing pump injection parameters, physical property changes of fracturing fluid, and the geometry size of fractures influence the temperature–pressure field. Based on an experimental regression, the calculation formula of SC-CO2 friction coefficient in fractures is obtained. Considering the physical characteristics of SC-CO2, the change in internal energy and flow work of fracturing fluid, and filtration and fracture characters, the unsteady temperature–pressure field model of SC-CO2 in wellbores and fractures is established. The model is applicable for any known fracture geometry. For a fixed position in the wellbore, with the increase of fracturing time, the temperature of the fracturing fluid rapidly drops and the pressure gradually increases; for a fixed position in the fracture, the temperature of the fracturing fluid gradually drops and the pressure gradually increases. The temperature difference between the fracturing fluid and the filtration zone gradually decreases from the fracture opening to end. As the fracturing time and fracturing fluid flow rate increases, the rock cooling distance of SC-CO2 fluid increases with fracturing time and flow rate of the fracturing fluid. By incorporating the unsteady temperature–pressure field model in wellbores and fractures with SC-CO2 fracturing, theoretical guidance for the phase state control in SC-CO2 fracturing fractures and the hydraulic parameter design of SC-CO2 fracturing is attained.