Effect of stimulation in hot dry rock reservoirs from carbon dioxide blasting-induced cracking

Abstract

Carbon dioxide blasting provides a new technical idea and way to stimulate hot dry rock reservoirs. To explore the effect of carbon dioxide blasting-induced cracking on dry-hot rock reservoirs, a numerical simulation for the action range of carbon dioxide blasting-induced cracking of hot dry rock was carried out. Considering the cooling effect of drilling fluid on the hot dry rock reservoir near the wellbore in the actual mining process, the fitting functions with temperature difference as a variable were adopted to set the material parameters of the reservoir in the damaged area, and the temperature distribution functions of the reservoir near the wellbore after well washing were adopted to set the temperature field of the reservoir in the damaged area. The blasting load was set by the relevant theories and formulas of explosive blasting. Combined with COMSOL software, the process of carbon dioxide blasting to stimulate hot dry rock reservoirs was simulated. The results showed that there were multiple stress concentrations in the process of the dry hot rock cracking caused by carbon dioxide blasting, the compressive stress concentration near the blast hole produced the crushing zone, and the tensile stress outside the crushing zone formed the fracture zone. In addition, the initial temperature of the reservoir and the thickness of the pressure plate would affect the effect of carbon dioxide blasting fracturing to stimulate dry and hot rock reservoirs. The initial temperature had a great influence on the scope of the blasting crushing zone and had little influence on the scope of the fracture zone. The thickness of the pressure plate had little influence on the scope of the crushing zone, which mainly affected the distribution of the blasting fracture zone. The research results could provide a theoretical support and a reference for the subsequent exploitation and utilization of dry-hot rock geothermal energy.

Keywords

• hot dry rock
• reservoir stimulation
• carbon dioxide blasting
• geothermal energy
• numerical model