以TOUGH2檢驗宜蘭平原南部裂隙型地熱概念模型

Abstract

本研究旨在評估深層地熱在宜蘭平原的潛力，並進一步建立三星至紅柴林區域地熱概念模型。目前綠能意識抬頭，地熱能源的開發技術日漸增強，宜蘭平原位處沖繩海槽張裂末端，周遭地區如龜山島岩漿活動、清水和土場等宜蘭周圍山區之溫泉露頭皆暗示宜蘭地區極具地熱發展潛力。目前對於宜蘭平原沖積層下之區域構造已存在初步概念模型，並有紅柴林三口一千米以上之深井井測資料，但模型仍缺乏深部地下水流及熱傳輸數值模式的驗證。基於前述，本研究利用GIS軟體彙整過去在三星周圍地區之地質資料、地球物理探勘及現地井溫資料，並搭配Python和PetraSim設置岩石及破碎帶之熱傳和水力參數，建置宜蘭裂隙主控型地熱的地熱概念數值模型。使用數值模擬套件TOUGH2 (Transport Of Unsaturated Groundwater and Heat) 計算在模型所設置之熱流和導水裂隙情景下，驗證當前地熱概念模型以及解釋紅柴林多口井中所量測到之溫度分布。 對比前人探勘成果，中央山脈盧山層逆衝於雪山山脈之乾溝層、四稜砂岩等地層之上，多數地層和褶皺走向為東西向。在蘭陽溪周圍存在傾向海槽中心之高傾角正斷層，同時透過震測剖面和地電阻結果的結合，三星至紅柴林區域可能存在多條南北向潛在走向滑移構造。 依地下水流及熱傳輸數值之結果，本研究認為宜蘭平原西南部區域的四稜砂岩受圳頭斷層截穿後，岩層破碎具有較高之滲透率；同時紅柴林一號井東側南北向之低電阻構造可能為本區域主要之熱流來源，熱液進入破碎的四稜砂岩中後與較冷之地下水混和，造成紅柴林二號井和耕莘井中地溫停滯，而混和後向東遷移之地下水造成宜蘭平原東南區域淺層普遍具有較高之地溫梯度。

This study evaluates the deep geothermal potential of the Ilan Plain and establishes a conceptual model for the Sanxing to Hongchailin area. With advancing geothermal technology, the Ilan Plain, located at the end of the Okinawa Trough, shows significant geothermal potential, as indicated by magmatic activity on Guishan Island and local hot springs. A preliminary model of the regional structure beneath the alluvial deposits, supported by data from deep wells over 1,000 meters in the Hongchailin area, exists but lacks validation. This study integrates geological data, geophysical surveys, and in-situ well temperature data with GIS software, using Python and PetraSim to set thermal and hydraulic parameters for rocks and fracture zones. The numerical simulation software TOUGH2 (Transport Of Unsaturated Groundwater and Heat) calculates heat flow and water-conducting fracture scenarios, verifies the current geothermal model, and interprets temperature distributions measured in Hongchailin wells. Compared to previous exploration results, the Lushan Formation of the Central Mountain Range thrusts over the Hsueshan Formation, with most strata and folds oriented east-west. High-angle normal faults are inclined toward the trough center around the Lanyang River, and the integration of seismic profiles and electrical resistivity results suggests the presence of several potential north-south trending strike-slip structures in the Sanxing to Hongchailin area. According to the results of groundwater flow and heat transfer modeling, the study suggests that the Szeleng Sandstone in the southwestern part of the Ilan Plain, intercepted by the Juntao Fault, exhibits higher permeability due to fractured rock layers. The low-resistivity structure to the east of HCL-1 may be a major source of heat flow in this region. Thermal fluids enter the fractured Szeleng Sandstone, mix with cooler groundwater, causing temperature stagnation in HCL-2 and GS Well, and migrate eastward. This migration leads to a generally higher geothermal gradient in the shallow southeastern Ilan Plain.