利用示蹤劑研究清水地熱區儲集層裂隙特性

近年來因應氣候變遷和溫室氣體的排放，政府規劃和發布2050年淨零排放的路徑。其中，綠色能源為重要的選項，而地熱能可當基載電力且用地小的特性，為重要的綠色能源選項之一。宜蘭清水地熱區為台灣開發最早的地熱區，位於中新世廬山層，主要由透水性差之板岩所組成。工業技術研究院和中國石油公司於1972年開始進行探勘研究，期間共鑽井19口，發現產能佳並在1981年建置了3MWe的地熱示範電廠，但最終因生產過程降壓熱水不足和管線結垢，而在1993年停止運轉。清水地熱電廠在2021年重新啟用，並綜合前人在野外地質、地球物理及地球化學上的調查結果，規劃利於電廠持續運作的措施。其中尾水回注為一項維持儲集層壓力以及補注儲集層熱水的重要技術。要確定回注井的佈置，其中一項直接且有用的技術為地化示蹤劑試驗。示蹤劑試驗是了解地下儲集層各種特性的簡單方法之一，提供傳統調查方法無法獲得的優勢流體流動網絡。鑽井擠注適量化學混合物的水體作為示蹤劑，進入地下後於其他生產井定時收取水體，並分析水體中所含示蹤劑的量，然後綜合地質背景建立地質模型以獲得地下流體及儲集層參數。本研究選用2,6 -萘二磺酸鈉，萘磺酸類常用於地熱示蹤劑，其符合熱穩定性佳、低偵測極限、低自然背景濃度、無吸收率、無毒性及低成本，適合用於清水地熱區的研究。採集之水樣利用高效液相層析儀進行分析，獲得示蹤劑濃度對時間的變化圖。利用示蹤劑突破曲線之特性包含峰值的位置、數量和突破時間等等形貌上的特徵進行定性分析，再使用動差分析法，估算其在裂隙介質中流體的平均滯留時間、掃略體積以及流動容量儲存容量圖等，並綜合兩分析方法特性了解清水地熱區之井間裂隙連通性，包含裂隙破碎程度與管道連通性。同時提供清水地區更為精確的井間裂隙參數，如異質性參數。並進一步綜合前人地質模型可以提供清水地熱區更高解析度的裂隙密度分布。結果顯示，各點位與IC-09井間連通性以往北及往西最低，往東南方向則有較好的連通性，綜合前人之裂隙量測與研究可發現點位連通性之方位大致與導水裂隙相符，且可提供更精細的導水裂隙延伸性。

關鍵字

地熱探勘；地化示蹤劑；儲集層模型；地熱發電

並列摘要

Geothermal energy is regarded as an important green energy in terms of it’s characteristics of base load power and small land occupy. The Chingshui geothermal field was built the first geothermal power plant which is located in south-west of Yilan Plain, Taiwan. Itis predominantly composed of slate, which is poor permeable. The Industrial Technology Research Institute (ITRI) and Taiwan CPC, drilled 19 wells with depths ranging from few hundreds to over three thousands meters and constructed a 3 MW geothermal power plant. It operated 12.5 years and shut down in 1993 due to pressure drop and scaling quickly in the wells. After re-evaluated by new data of geology, geophysics, geochemistry and well testing, this geothermal field constructed and operated a new geothermal power plantin 2021 However, to recharge fluid for maintaining pressure in reservoir for long term operations, the reinjection is an important technique. To understand reinjection efficiency and fluid circulation in fractures between wells, the tracer test is a relatively simple and useable method. In this research, use 2, 6-NDS chemicals as tracer to conduct a test in shallow wells, the R1, R5 and R3, deep well, the IC-19 21 as production wells, and the IC-09 as injection well in the Chingshui geothermal field. Then use the instrument, the high performance liquid chromatography (HPLC) to analyze the concentrations of tracer in samples and construct a breakthrough curve for every wells and outcrop. Meanwhile, use qualitative analysis to understand relationships between peaks in breakthrough curves and possible fracture connectivity; and quantitative analysis to understand the swept volume, flow geometry and heterogeneity. Finally, we combine all results to construct a fracture distribution conceptual model This conceptual model provides detailed fracture connectivity between wells and more information for the future deploy of reinjection well locations in the Chingshui geothermal field.

並列關鍵字

geothermal exploration ； Tracer test ； Reservoir conceptual model ； Geothermal power plant

參考文獻

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