Semi-Analytical Temperature and Stress Profiles for Nonisothermal CO2 Injection

Abstract

Reservoir cooling at the injection interval is expected if CO2 is used as a heat carrier fluid in multi-well enhanced geothermal systems. Cooling the reservoir near the well alters the stress field. The tensile fracture pressure is reduced at the injection well perforations when the temperature difference between injected fluid and the reservoir is large. In this work semi-analytical models are used to estimate the relative length-scales and magnitude of thermal, saturation, pressure and stress distributions for constant rate, nonisothermal CO2 injection into a porous medium that is initially water saturated. Advection-dominated radial flow is assumed so that the coupled two-phase flow and thermal conservation laws can be solved analytically. The resulting saturation and thermal profiles are then used in semi-analytical estimates of the pore pressure and in situ stress changes in the reservoir.