Numerical simulation and parameter analysis of liquid nitrogen cooling for high temperature granites

Liquid nitrogen stimulation has important application value in the fields of deep geothermal development, and unconventional oil and gas reservoir exploitation. It is difficult to experimentally observe the evolution of temperature and cryogenic-induced stress inside the rock during the cooling process. Numerical simulation complements the experimental difficulties. In this study, the liquid nitrogen cooling process of high temperature granite under different parameters is studied by numerical simulation. The results show that a higher heat transfer coefficient and model initial temperature enhance the heat transfer efficiency of the cooling process, thus resulting in more severe cryogenic-induced stresses. Young?s modulus and expansion coefficient are independent of the temperature distribution during the cooling process. Higher Young?s modulus amplifies stress under identical thermal contraction constraints. Higher expansion coefficients enhance the thermal strains and thermal strain incompatibility, thus elevating the cryogenic-induced stresses. This study will provide the theoretical basis for the application of liquid nitrogen in reservoir stimulation.