Chemical Industry and Engineering Progress ›› 2023, Vol. 42 ›› Issue (2): 711-721.DOI: 10.16085/j.issn.1000-6613.2022-0754

• Energy processes and technology • Previous Articles     Next Articles

Numerical simulation of heat extraction in single-well enhanced geothermal system based on thermal-hydraulic-chemical coupling model

GUO Zhipeng1,2(), BU Xianbiao2, LI Huashan2, GONG Yulie2, WANG Lingbao2()   

  1. 1.School of Engineering Science, University of Science and Technology of China, Hefei 230026, Anhui, China
    2.Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou 510640, Guangdong, China
  • Received:2022-04-26 Revised:2022-09-08 Online:2023-03-13 Published:2023-02-25
  • Contact: WANG Lingbao

基于热-流-化耦合作用的单井增强地热系统性能分析

郭志鹏1,2(), 卜宪标2, 李华山2, 龚宇烈2, 王令宝2()   

  1. 1.中国科学技术大学工程科学学院,安徽 合肥 230026
    2.中国科学院广州能源研究所,广东 广州 510640
  • 通讯作者: 王令宝
  • 作者简介:郭志鹏(1997—),男,硕士研究生,研究方向为地热能开发利用。E-mail:guozp@ms.giec.ac.cn
  • 基金资助:
    国家重点研发计划(2019YFB1504104);中国科学院洁净能源先导科技专项(XDA 21000000);国家自然科学基金(42102336)

Abstract:

The minerals dissolution and precipitation in geothermal water has a significant impact on geothermal resource development. Based on the control equation of water-SiO2 reaction rate, a thermal-hydraulic-chemical (THC) coupling numerical model of single-well enhanced geothermal system (SEGS) was established. The accuracy of flow heat transfer model and solute transport model was validated by the analytical solution. The coupling relationships between reservoir temperature, SiO2 concentration, reaction rate and fracture width were simulated and analyzed. Based on the discrete fracture model, the effects of injection mineral concentration and injection flow rate on the heat transfer performance of SEGS were investigated. The results showed that, ① mineral precipitation caused by over-saturated injection and mineral dissolution caused by under-saturated injection occured at a certain distance away from the injection section, the evolution of fracture aperture was distributed as a band at a fracture plane, and the peak value of reaction rate moved to the periphery with time; ② the maximum differences between injection pressures and production temperatures obtained from the coupling model of TH and THC were 2.12MPa and 4.66℃, respectively. Under-saturated injection reduced the injection pressure and accelerated the attenuation of production temperature, while over-saturated injection was the opposite; ③ when the SiO2 concentration increased by 0.005mol/kg, the average injection pressure increased by 0.5MPa and the average recovery temperature increased by 0.4℃. When the injection flow increased from 8kg/s to 12kg/s, for over-saturated injection, the injection pressure increased by 7.2MPa and the production temperature decreased by 8.58℃ after 30 years; for under-saturated injection, the injection pressure increased by 5.14MPa and the production temperature decreased by 10.43℃.

Key words: geothermal energy, thermal-hydraulic-chemical coupling, porous media, permeability, mineral concentration

摘要:

地热流体中的矿物溶解沉淀对地热资源开发具有重要影响。本文基于水-SiO2反应速率控制方程,建立了单井增强地热系统(SEGS)热-流-化(THC)耦合数值模型,利用解析解验证了流动换热模型和溶质运移模型的准确性,模拟分析了储层温度、SiO2浓度、反应速率和裂隙宽度之间的耦合关系。基于离散裂隙模型,分析了注入矿物浓度和注入流量对SEGS取热性能的影响。结果表明:① 过饱和注入引起的矿物沉淀与欠饱和注入引起的矿物溶解均发生在远离注入段的一定距离处,裂隙宽度的改变呈带状分布,反应速率峰值随时间推移向外围移动;② 由热-流(TH)与热-流-化(THC)耦合模型得出的注入压力和采出温度最大相差2.12MPa和4.66℃。欠饱和注入降低了注入压力,加快了采出温度的衰减,过饱和注入则与之相反;③ 注入流体中的SiO2浓度每增加0.005mol/kg,30年平均注入压力增加0.5MPa,平均采出温度增加0.4℃。将注入流量从8kg/s提高至12kg/s,对于过饱和注入,系统运行30年后的注入压力提高7.2MPa,采出温度下降8.58℃;对于欠饱和注入,注入压力提高5.14MPa,采出温度下降10.43℃。

关键词: 地热能, 热-流-化耦合, 多孔介质, 渗透率, 矿物浓度

CLC Number: 

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