煤-热共采模式下地热水非常规开采数值模拟研究

Numerical simulation on unconventional mining of geothermal water in coal-heat co-mining mode

在我国“碳达峰、碳中和”时代背景下,开展矿井地热水资源开发利用实现煤-热共采的研究具有重要战略意义。然而,目前煤-热共采技术尚不成熟,针对矿井地热水抽采的研究还需进一步补充。因此,基于煤-热共采理论及技术框架,提出了一种地热水井下非常规开采方法。分析了矿区热储形成机制,采用热储体积法对矿区地热水资源量进行了估算,评价了矿井地热水开发潜力。同时,数值模拟了地热水非常规开采模式下的热储温度场及生产井水温变化。分析了生产井群参数对热储层温度场及生产井水温的影响,并与常规地热水生产方法进行了对比。最后,讨论了矿井地热水开采利用所产生的社会、经济效益。结果显示:①矿区地热水静态可采量为1.14×10^(17)J,折合标煤3.9 Mt。动态可采量为2.95×10^(16)J/a,折合标煤1.01 Mt/a。②生产井水温受回灌水温的影响较大,与回灌方式的关系不大,且回灌水温对生产井水温的影响主要体现在生产后期。③随着生产速率的增加,生产井群热突破时间提前,且在热突破点之后的温降速率加快。④均衡生产对生产井的服务年限具有有益作用。⑤通过调整非常规开采模式的生产策略可实现生产井群的协调开采,延长生产井群的开采期限,使其平均温降速率小于常规开采模式下的生产井温降速率。⑥矿井地热开发系统建成后,可实现煤矿17万m^(2)的供暖及全矿职工的洗浴,每年减少燃煤10327 t,减少CO_(2)排放量26900 t,为企业创造693.8万元的经济效益。因此,针对水热型高温矿井,实施井下地热水非常规开采具有一定的可行性。通过合理布置生产井群分布,科学制定生产策略,可实现矿井地热水的高效开采。

It is strategically significant for the mine in operation to investigate the development and utilization of geothermal water resources for realizing coal-thermal co-mining in the context of“carbon peaking and carbon neutral”in China.However,currently the coal-thermal co-mining technology is immature,and a further research is needed for the geothermal water extraction in operating mines.Thus,this paper presented an unconventional method for the underground mining of geothermal water based on coal-thermal co-mining theory and technical framework.In the studied mine area,the formation mechanism of thermal reserves was analyzed,the amount of geothermal water resources was estimated by the thermal reserve volume method,and the potential of geothermal water development was evaluated.Simultaneously,the thermal reservoir temperature field and production well water temperature variation were numerically simulated under the unconventional mining mode of geothermal water.The effects of production well-group parameters on the thermal reservoir temperature field and production well water temperature were analyzed and compared with the conventional method of geothermal water production.Finally,the social and economic benefits generated by the mine geothermal water mining and utilization were discussed.The results show that:①The static recoverable reserves of geothermal water in the mine is 1.14×10^(17)J,equivalent to 3.9 Mt of standard coal.The dynamic recoverable reserves is 2.95×10^(16)J/a,equivalent to 1.01 Mt/a of standard coal.②The water temperature of the production well is influenced by the temperature of the recharge water,with less relation to the recharge method.Meanwhile,it is affected by the temperature of the recharge water on the production well water temperature mainly in the late production period.③The thermal breakthrough time of the production well-group is advanced and the cooling rate is increased after the thermal breakthrough point with increasing production rate.④Balanced production has a beneficial effect on the life of producing wells.⑤Adjusting the production strategy of the unconventional mining mode can realize the coordinated mining of the production well-group and extend the life of the production well-group,resulting in a smaller average cooling rate than the conventional mining mode of the production wells.⑥Once the mine geothermal development system has been completed,the heating area of 170000 m^(2)in the coal mine and the bathing of all mine employees can be realized,reducing coal burning by 10327 t and CO_(2)emission by 26900 t per year,creating economic benefits of 6.938 million RMB for the enterprise.Therefore,it is feasible to implement unconventional mining of underground geothermal water for hydrothermal high-temperature mines.And the efficient mining of geothermal water in mines can be realized by reasonably arranging the distribution of production well-group and scientifically formulating the production strategy.