地熱因可做為基載電力而為國家重點發展對象，傳統型地熱發電除了足夠的熱源外亦需充沛的水源與裂隙系統，這些嚴苛的條件使得開發充滿不確定性與挑戰。增強型地熱系統由於可人為製造裂隙及注水循環取熱，被視為未來極具潛力的發電方式。本研究以員山一號井岩屑為材料，將具代表性之不同深度岩屑與超純水、溪水、溫泉水放入水岩反應裝置進行195°C下72、168與720小時水岩反應，模擬EGS可能的流體與圍岩變化，並額外加入除氧劑DEHA探討除氧劑功效。以多功能水質計、離子層析儀、感應耦合電漿光學發射光譜儀分析水岩反應前後水質與離子濃度變化。並將反應前後的岩屑樣本進行掃描式電子顯微鏡與能量頻譜分析儀及X光繞射分析儀觀察礦物的溶解與生長。結果顯示：圍岩內的黃鐵礦含量是水岩反應流體變化的關鍵變因。四稜砂岩層富含黃鐵礦，氧化態流體分解黃鐵礦，會降低流體pH值並增加硫酸根離子濃度，並產生二次沉澱使岩屑表面被紅棕色之氧化鐵覆蓋；隨深度增加，岩屑內黃鐵礦漸減，pH值變化越不明顯。在短期添加除氧劑可以有效阻止黃鐵礦之氧化，但若將反應時間拉長至720小時則會失去效果，若想維持除氧劑之效果須不斷的投入以維持有效劑量。水岩反應後流體的鈉、鉀等離子濃度上升，源於長石與黏土礦物的溶解。石膏沉澱則可對應長時間反應後流體鈣離子濃度下降。氧化鐵與石膏、碳酸鈣、含鐵礬類、硫酸鋇、矽酸鹽類礦物是後續EGS營運管理時，儲集層可能的產物。此外若無流體酸化影響石英地質溫度計，可用於後續儲集層溫度監測；然而添加除氧劑則可能導致溫度略微低估。;Geothermal energy is an important renewable energy resource because it can provide stable baseload power generation. However， conventional geothermal systems require sufficient heat sources， water supply， and fracture networks， making their development highly uncertain. Enhanced Geothermal Systems (EGS)， which create artificial fractures and fluid circulation for heat extraction， have therefore emerged as a promising alternative. This study investigated fluid–rock interactions relevant to EGS development using drill cuttings collected from Yuanshan Well No. 1. Representative cuttings from different depths were reacted with pure water， stream water， and hot spring water at 195°C for 72， 168， and 720 hours. An oxygen scavenger， diethylhydroxylamine (DEHA)， was also added to evaluate its effectiveness in suppressing oxidation reactions. Water chemistry changes were analyzed using ion chromatography and inductively coupled plasma optical emission spectrometry， while mineralogical alterations were examined using scanning electron microscopy with energy-dispersive spectroscopy and X-ray diffraction. The results show that pyrite abundance is the primary factor controlling geochemical evolution during water–rock interaction. Pyrite oxidation in pyrite-rich Szuling Sandstone lowered fluid pH， increased sulfate concentrations， and promoted the formation of secondary iron oxide precipitates on rock surfaces. The influence of pyrite oxidation became less significant with increasing depth due to decreasing pyrite content. DEHA effectively inhibited pyrite oxidation during short-term experiments but lost effectiveness after longer reaction periods， indicating that continuous added would be necessary for long-term operation. Elevated concentrations of sodium and potassium were attributed to the dissolution of feldspars and clay minerals， whereas gypsum precipitation corresponded to decreasing calcium concentrations during longer reactions. Iron oxides， gypsum， calcite， iron-bearing alum minerals， barite， and silicate minerals were identified as potential secondary minerals that may affect reservoir performance during EGS operation. In addition， in the absence of significant fluid acidification effects， quartz geothermometer may serve as a useful tool for long-term reservoir temperature monitoring. However， the addition of oxygen scavengers may result in slight underestimation of reservoir temperatures derived from quartz geothermometric calculations.
