Thermo-coupled FSI analysis of high-temperature heterogeneity rocks subjected to jet impingement

Abstract

Jet impingement is an efficient rock breaking method in the development of geological resources. In high-temperature formations, thermal stress induced by the temperature difference interacts with fluid pressure and impact forces, thus further enhancing the efficiency of rock failure. Meanwhile, the inherent heterogeneity of rocks influences stress distribution and failure characteristics of rocks as well. To elucidate this intricate process, a multi-physics coupling model is developed in the present study, in which the finite-discrete-element method (FDEM) and Weibull distribution are employed to describe the mechanical response and heterogeneity of rocks. The evolution of temperature, stress, and crack propagation are computed to reveal rock failure mechanisms under different formation conditions and jet parameters. The findings indicate that increasing jet pressure markedly increases jet velocity, improves heat transfer efficiency, and changes the transition from heat conduction to convective heat transfer. Thereby, greater thermal stress is induced, which is accompanied by the application of increased jet pressure on the rock surface. The combined effects of these two factors result in an initial decrease followed by a subsequent increase in crack length. Although rock temperature has fewer effects on jet velocity, the heat transfer efficiency also increases at elevated temperatures resulting from the variation of temperature differences. Correspondingly, thermal stress and crack length rise continually. Moreover, heightened heterogeneity exacerbates rock damage. In this research, thermal stress exerts pronounced effects on crack length once rock temperature exceeds 200 °C on the whole. However, the heightened rock heterogeneity can lower the critical temperature threshold for the propagation of cracks. The results of this investigation provide an in-depth insight into the rock failure mechanism influenced by multi-physics coupling.