Analytical and Numerical Models for the Design under CO2 Fracturing of Rock

CO2 fracturing is an effective carbon-neutral technology for underground space engineering construction. Currently, the rock damage caused by different stages of CO2 fracturing is not well understood, and studying the rock fracturing mechanism under complex conditions is challenging. There is an urgent need to propose a theoretical model that considers the cumulative damage effect during the fracturing process. Therefore, an analytical model to estimate crushed and fractured radius, considering damage effects. A numerical model based on the particle flow model was also developed to simulate CO2 fracturing. The methods are validated by comparing with the results from physical model. Then, the CO2 fracturing design was investigated. The analytical model fairly estimated the radius of crushed and fractured zones. Numerical analysis demonstrated that fractures extend toward the control hole if it is close enough to the fracturing hole. The analytical model showed that the borehole diameter has a much larger effect on the size of the crushed zone than on the fractured zone. The findings provide a reference for optimizing CO2 fracturing parameters.