Abstract:

The balance of exploitation and reinjection is an effective model for the sustainable development and utilization of hydrothermal geothermal resources. In order to simulate the temperature and pressure response of geothermal reservoir under different exploitation and reinjection scenarios, and to provide theoretical support for the sustainable development of geothermal resources, a mathematical model of Jixian system carbonate geothermal reservoir in Rongcheng geothermal field in Xiongan New Area was established by using numerical simulation technology. Firstly, COMSOL software was used to simulate the exploitation history data of existing geothermal wells in 300 km2 area. The simulation results are in good agreement with the monitoring data. Then, on this basis,the variation trends of temperature and pressure field of Jixian geothermal reservoir in the future 50 years under the single well exploitation model were predicted. Finally, according to the the declining trend of water level, the reinjection scheme was established, and the influence degree of different well spacing on the temperature field and pressure field of geothermal reservoir was analyzed. The results show that in the non-reinjection mode, the buried depth of water level decreases to 150 m in about 40 a, and the water level decreases about 1.13 m/a. The geothermal doublet system of  “one exploitation and one reinjection” scheme is adopted, and the well spacing is considered to be 600, 800 and 1 000 m respectively. Although increasing the well spacing reduces the number of arranged wells, it increases the exploitation amount and prolongs the thermal breakthrough time, so that more heat can be exploited. In practical engineering, the well spacing should be optimized by numerical simulation method to ensure the increase of production and prolong the thermal breakthrough time, so as to extract more heat.

Key words: numerical simulation, COMSOL, reinjection, Rongcheng geothermal field, carbonate rock, Xiongan New Area