影响岩溶热储采出温度的开采参数敏感性研究——以河南清丰地区为例

Sensitivity analysis of development parameters on the production temperature of karst geothermal reservoirs:A case study of the Qingfeng area in Henan,China

采出温度是影响地热能有效利用率的关键指标,采出温度越高,热储开发效果越好。岩溶热储作为一种重要的地热储层类型,其采出温度受到储层参数的影响。以河南清丰地热田奥陶系岩溶热储为例,通过建立热储地质模型并利用7口地热井资料,进行基于热流和井储耦合的数值模拟研究,探讨储层地质条件和回灌参数对采出温度的影响。研究结果发现,断层的存在加速了热储中低温区向生产井的扩散,导致热突破时间的提前。在开采后期,有断层情况下采出温度较高,且变化曲线斜率远高于无断层情况,表明断层有助于提高清丰地区热平衡时的采出温度,最终有利于增加采热量。目前,一般认为,注采井距越小采出温度越低。但是,当回灌速率高于50 kg/s时,随着开采时间的增加,采出温度呈现快速下降趋势,注采井距835 m下的采出温度甚至高于1000 m的情况。最后,确定清丰地区特定场景下的最优回灌参数组合为:回灌温度20℃、回灌速率50 kg/s、注采井距835 m。本研究结果将为清丰地区或其他类似岩溶热储开发方案的制定提供有益指导。

The temperature of produced geothermal water serves as a pivotal indicator influencing the efficiency of geo-thermal energy utilization,with a higher temperature corresponding to more effective geothermal reservoir exploitation.For karst geothermal reservoirs,recognized as a significant type of geothermal reservoir,the temperature of produced geothermal water is influenced by reservoir parameters.Focusing on the Ordovician karst geothermal reservoirs in the Qingfeng area,Henan Province,this study established a geological model of the reservoirs,followed by numerical simu-lations based on thermal flow and well-reservoir coupling using the data of seven geothermal wells.The purpose is to explore the effects of the geological conditions and reinjection parameters of geothermal reservoirs on the temperature of produced geothermal water.The results reveal that the presence of faults accelerates the diffusion of moderate-low-tem-perature zones toward production wells,leading to an early thermal breakthrough.In the late stage of geothermal exploit-ation,the temperature of produced geothermal water was higher in the presence of faults,and its curve exhibited a high-er slope compared to the case where faults are absent.This result indicates that faults contribute to an elevated temperat-ure of produced geothermal water during thermal equilibrium in the Qingfeng area,ultimately conducive to an increase in extracted heat.Presently,it is generally considered that a smaller spacing between production and reinjection wells(also referred to as the well spacing)is associated with a lower temperature of produced geothermal water.However,in this study,the temperature of the produced geothermal water exhibited a rapid downward trend with increasing exploita-tion time under reinjection rates exceeding 50 kg/s.Most especially,the temperature under a well spacing of 835 m was even higher than that under a well spacing of 1000 m.Finally,this study determined the optimal reinjection parameter combination for the specific scenario in the Qingfeng area,involving a reinjection temperature of 20°C,a reinjection rate of 50 kg/s,and a well spacing of 835 m.The results of this study will serve as a valuable guide for preparing schemes for the exploitation of karst geothermal reservoirs in the Qingfeng area or similar geological settings.