Experimental study of the effect of temperature change in water-shale interaction on fracture generation and permeability change in shales under stress anisotropy

Water-shale interaction, as well as temperature change, can impact the generation of fractures and shale permeability. In most studies, experiments have been conducted to explore the role of water-shale interaction in fracture generation and permeability change without considering the effect of temperature change. To fill this gap, two sets of tests are conducted in this study. pressure differences of 750 psi, 2250 psi, and temperatures of 18.5 °C, 80 °C are employed. Two sets of sister core samples with artificial fractures are used. Fluids are injected at a flow rate of 2 ml/min under 18.5 °C. CT images are achieved to study fracture generation. The pressure change is recorded to study permeability change. The results show that temperature change is beneficial for fracture generation. The propagation of fractures is the result of the combination of water-shale interaction, stress anisotropy, and temperature change in the tests. Pressure data shows that shale permeability can be enhanced under the coupling effects from water-shale interaction, stress anisotropy, and temperature change. The results reveal that increasing temperature difference between the shale formation and fracturing fluid can facilitate the generation and propagation of fractures, thus, leading to the recovery of shale permeability.