单井闭循环地热系统可持续开发潜力数值模拟

Numerical simulation on the sustainable development potential of a single-well closed-cycle geothermal system

为了提高地热系统的产热量、实现地热能高效可持续开发的目标,需要明确储层温度恢复在地热系统间歇运行过程中的作用及其重要性。为此,以吉林省松原市某实际供热场地的单井闭循环地热系统为研究对象,利用物联网技术进行地热系统智能监测与数据采集,采用TOUGH2-WELL模拟程序模拟了单井闭循环地热系统可持续开发的潜力;进而将实测、模拟数据进行拟合来确定精确的模型参数,通过改变注入温度和注入流速来探究最佳的开采方式。研究结果表明:①在现有开采模式下,地热系统运行30年后产热量下降17%;②若将注入温度由25℃提高到31℃,则出水口温度下降幅度变小,产热量降低10.5%;③若将注入流速从8 kg/s提高到20 kg/s,出水温度虽然降低约4℃,但岩层的热恢复情况较好,产热量增大2.67%。结论认为:①在保持注入温度不变的情况下,提高注入流速,系统长期运行后生产水温下降幅度较小,岩层的热恢复情况好,更有利于地热能的持续开采;②在保持注入流速不变时情况下,地热系统在长期运行后注入温度越高,出水温度下降幅度越低,储层热恢复情况越好。

In order to improve the heat production rate of a geothermal system and achieve efficient and sustainable development of geothermal energy, it is necessary to determine the action and importance of reservoir temperature recovery in the intermittent operation process of the geothermal system. by taking the single-well closed-cycle geothermal system at one real heating site in Songyuan City of Jilin Province as the research object, this paper performed intelligent monitoring and data acquisition on the geothermal system via the internet of things technology and simulated the sustainable development potential of the geothermal system by using the TOUGH2-WELL simulator program. Then, the measurement data and the simulation results were fitted to determine the precise model parameters. Finally, an optimal production mode was explored by changing injection temperature and injection rate. And the following research results were obtained. First, under the current production mode, the heat production rate of the geothermal system will be cut down by 17% after 30 years of operation. Second, if the injection temperature is increased from 25 ℃ to 31 ℃, the decline amplitude of water outlet temperature gets smaller and the heat production rate decreases by 10.5%. Third, if the injection rate is increased from 8 kg/s to 20 kg/s, the water outlet temperature decreases by about 4 ℃, but the reservoir temperature recovery is better and the heat production rate increases by 2.67%. In conclusion, if the injection rate is increased while the injection temperature is kept constant, the production water temperature of the system decreases less after long-term operation and the reservoir temperature recovery is better, which is more conducive to the sustainable production of geothermal energy. In addition, if the injection rate is kept constant, the higher the injection temperature after longterm operation, the smaller the decrease amplitude of water outlet temperature and the better the reservoir temperature recovery.