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    青海共和盆地干热岩人工储层示踪试验研究

    Tracer test study on artificial reservoirs in hot dry rock geothermal systems in the Gonghe Basin, Qinghai

    • 摘要:
      研究目的 干热岩是一种清洁、储量巨大的地热资源,从2019年开始,中国地质调查局在青海共和持续实施中国首例干热岩发电并网工程。干热岩储层致密,需压裂形成一定渗透性的连通缝网,形成容纳一定规模换热、导水储层,但高温硬岩人工储层研究还相对较少。
      研究方法 人工储层的成功建造和井间有效连通是干热岩成功开发的核心,示踪试验是研究上述问题、刻画储层水文地质条件的有效手段,本文以青海共和盆地干热岩试采场地为研究对象,选取荧光素钠、溴化钠作为示踪剂,分别在规模压裂改造前后开展示踪试验。
      研究结果 规模压裂改造前示踪剂回收率、换热体积等均较低,改造后储层裂缝更复杂,储层连通性更好,示踪剂回收率达到14.14%,裂缝换热体积增大至27倍,裂隙相对均质,有效减少了热突破风险。
      结论 示踪实验可以定量化评价干热岩人工储层压裂改造效果,研究成果对于干热岩示踪试验的开展和高温硬岩热储的科学开发具有指导意义。

       

      Abstract:
      This paper is the result of geothermal survey engineering.
      Objective Hot dry rock is a clean and vast geothermal resource. China Geological Survey has been continuously implementing China's first hot dry rock geothermal power generation and grid connection project in Gonghe, Qinghai since 2019. Hot dry rock reservoirs are dense and require fracturing to form a permeable interconnected fracture network, creating a reservoir capable of accommodating a certain scale of heat exchange and water conduction. However, research on artificial reservoirs in high−temperature hard rock is relatively limited.
      Methods The successful construction of artificial reservoirs and effective inter−well communication are the core of successful hot dry rock development. Tracer tests are an effective means to study the above issues and characterize reservoir hydrogeological conditions. This study focuses on the hot dry rock test site in the Gonghe Basin of Qinghai, selecting sodium fluorescein and sodium bromide as tracers, and conducting tracer tests before and after large−scale fracturing.
      Results Before large−scale fracturing, tracer recovery rate and heat exchange volume were relatively low. After the transformation, reservoir fractures became more complex, reservoir connectivity improved, and the tracer recovery rate reached 14.14%. The heat exchange volume of fractures increased to 27 times, and the fractures became relatively homogeneous, effectively reducing the risk of heat breakthrough.
      Conclusions Tracer experiments can quantitatively evaluate the effectiveness of hot dry rock artificial reservoir fracturing. The research results have guiding significance for the conduct of hot dry rock tracer tests and the scientific development of high−temperature hard rock thermal storage.

       

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