Evaluation and Optimization of Fracturing Effects of Carbonate Geothermal Reservoirs in Typical Target Areas in Xian County, Hebei

Abstract

In order to evaluate the effect of hydraulic fracturing in carbonate geothermal reservoirs in Xian County, this study used COMSOL finite element multi-field coupled numerical simulation software to develop a geological model using 2D seismic data. By considering the influence of seepage on the heat transfer process of geothermal reservoirs, we then developed a coupled seepage-heat transfer model for fault-containing geothermal reservoirs. Combined with the "one extraction, one reinjection" well injection mode, the temperature and flow field changes under different fracturing effects during heat extraction in a typical thermal reservoir were analyzed and compared, and the optimal fracturing conditions evaluated. The main conclusions are: (1) Under a water injection temperature of 50℃, the recommended extraction and reinjection well-spacing is 700 m, and the optimal fracturing permeability is 5.77 × 10-16. When the operation time is 100 years, the temperature at the bottom of the heat extraction well drops 1℃ from the initial temperature, and no thermal breakthrough is produced. (2) Faults within the strata will form a dominant seepage channel with a length of about 500 m, with the reinjection water seeping from outside the channel between the extraction and reinjection wells, forming an elliptical seepage channel on both sides. (3) At the recommended well-spacing, the heat extraction wells are still 200 m away from the tail of the seepage dominant channel, and the extension surface of the convex cold front is reduced.