Simulation Study on the Influence of Reactions Between Granitic Hot Dry Rock Minerals and Water on Rock Non-Closed Crack Compressive Shear Initiation

The development of hot dry rock needs working fluids, and mineral reactions happen due to contact between hot dry rock minerals and fluids. Mineral reactions influence hot dry rock reservoir characteristics, whereas their impacts on hot dry rock mechanical properties lack understanding. In this study, a simulation study on the influence of reactions between granitic hot dry rock minerals and water on rock non-closed crack compressive shear initiation was conducted. High temperature (180 °C) and high pressure (24 MPa) mineral reaction experiments were performed to obtain reaction kinetics parameters. A model of non-closed crack compressive shear initiation induced by mineral reactions was established. Based on the model, the influences of mineral reactions on the compressive shear initiation of non-closed cracks were analyzed. Results show that the mineral reactions primarily contain feldspar dissolution and quartz precipitation, and their overall effect is crack enlargement. The crack enlargement reduces crack initiation potential for a crack inclination angle of α = 0°, while it increases crack initiation potential for α = 45° and 90°. The difference in crack initiation potential under various α values is attributed to the relative position of the crack to the maximum principal stress direction. This work reveals the influences of mineral reactions on hot dry rock reservoir crack initiation, contributing to achieving sustainable hot dry rock exploitation.