Experimental investigation on the seepage characteristics and temperature–permeability (T–P) model of sandstone after different temperature treatments.

In order to study the effect of high temperature on the permeability characteristics of the surrounding rock of the geothermal well, the steady-state method was used to conduct experiments on the permeability of sandstone under different stress states under the action of 200 °C, 400 °C, 600 °C and 800 °C. The correlation between permeability and different temperature, seepage pressure and confining pressure was studied, and a temperature–permeability (T–P) model was established based on the principle of effective stress. The experimental results show that: (1) The reduction rates of density and wave velocity increase sharply from 0.57% and 15.08% at 600 °C to 1.79% and 45.68% at 800 °C and when the temperature was equal to 800 °C, the mass loss rate and the volume increase rate reached 0.96% and 1.36%, respectively. (2) The permeability increases gradually with temperature, and the permeability below 600 °C has a small increase, and the permeability between 600 and 800 °C will have a step change. (3) The permeability of sandstone decreases gradually with the negative exponential relationship of confining pressure after high temperature treatments. (4) Based on the experimental data, the rationality of the T–P model is verified. The results of the study can provide reference value for the stability assessment of the geothermal well envelope. [ABSTRACT FROM AUTHOR]