結晶岩地下水水資源開發之力學評估：以臺灣和平與金門為例
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2017
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台灣本島與金門離島地區時常可以看到缺水的訊息，因此需要一些解決的方案，比如製造人造雨、抽取地下水與地球物理探勘尋找地下水層等。目前利用地層裡的裂隙與現地應力場的關係來找尋地下水源是前人尚未著墨的一環，其方法對於結晶岩非常適用，因結晶岩孔隙率少，蓄水量較低，但通常其裂隙孔隙率較高，含水量相對較高，所以，裂隙的分布與其活動性對於結晶岩地下水的水資源開發與使用相當重要。因現地應力場會影響裂隙的生長方式與是否再活化，故本研究以臺灣花蓮和平變質花崗岩以及金門花崗岩與片麻岩為例，整合地表與井下裂隙分布之位態以及現地應力資料，以地質力學觀點評估裂隙的滑動與擴張趨勢，進而評估潛在導水裂隙的分布與位態，以利後續水資源開發。
花蓮和平地區位處於臺灣大南澳片岩的太魯閣帶，主要岩層為晚古生代至中生代變質花崗岩與大理岩，僅有少數沖積層、金門島位處於福建沿海的平潭東山變質帶，絕大多岩層為中生代花崗岩與片麻岩，僅有少數沖積層。因為地層岩性、海島地形、氣候環境與人為開發之關係，金門地下水水資源相對匱乏。
前人於臺灣花蓮和平地區以岩心進行非彈性應變回復實驗，結果顯示為東北-西南拉張的正斷層應力場，地表裂隙統計位態以東西向與東北-西南為主，而井下裂隙則是與平行葉理面的位態居多。整合前人金門水力破裂實驗與本研究岩心直徑變形分析結果，其整合應力場為325度擠壓的走向滑移應力場，其最大、次大與最小應力場梯度依序為37.39、25.77、21.78MPa/km。地表裂隙統計位態主要以東西向和東北-西南向的走向為主，以及少數的其他方向，井下裂隙位態則是以東西向和西北-東南向為主。
裂隙的產生以及再活化與現地應力場有密切關係，若裂隙因現地應力產生或活化並連通則可能成為導水裂隙。同時藉由地溫梯度異常處來尋找導水裂隙位置。並利用現地應力場可以計算裂隙的滑動趨勢與擴張趨勢，位於擴張趨勢值為0.8以上的高擴張趨勢裂隙是有助於流體流動。
金門地表地區於南雄(NS-1)法線投影位態042˚/ 32˚、新塘(ST-1)裂隙法線投影位態150˚/ 61˚與峰上裂隙法線投影位態123˚/ 90˚三組高擴張趨勢的裂隙與金門淺層地下水流向方向一致，此三組裂隙為導水裂隙。金門一號井(BH01)、金門二號井(BH02)與金門四號井(BH04)等三口井下裂隙與井測微流速資料進行比對，結果顯示金門一號井(BH01)井下於0~80m、193m、350m與400~500m，金門二號井(BH02)井下0~70m，金門四號井(BH04)井下0~80、350與440~500m等深度有大量不同位態的裂隙存在，微流速資料也在這些深度有明顯改變，故這些深度為導水裂隙。
和平井下於149.5m有地溫梯度異常並有平行葉理之鏽染裂隙，此結果與井下電阻率與孔隙率進行比對，149.5m的裂隙可能是具有高可信度的導水裂隙。
和平井下裂隙大部份位於0.6~0.8之間的擴張趨勢，裂隙寬度相對於其他擴張趨勢值的裂隙寬。
將滑動趨勢加入抗張強度後，進而定義出剪切趨勢，和平井下構造在剪切趨勢的現今應力場並不會產生滑動，演算和平井下裂隙的可能生成環境。參考前人資料顯示有兩種生成深度，其一為地下3.17km處，最大應力、次大應力與最小應力分別為84.49MPa、64.29MPa與55.19MPa，液壓範圍為60MPa。其二為地下9.5km處，最大應力、次大應力與最小應力分別為253.08MPa、192.66MPa與165.40MPa，液壓範圍為161MPa。
綜合上述結果，金門地表、井下與和平井下區域皆有導水裂隙。利用張裂趨勢計算得知和平井下裂隙生長環境，以利後續水資源開發。
Taiwan Island and the Kinmen Islands region can often see information about the lack of water so need to rainmaking, extraction of groundwater and geophysical exploration to find the groundwater layer for solutions. This research selected crystalline rocks in Hoping and Kinmen areas of Taiwan. Then, to integrate data of fractures distribution, attitude and in-situ stress from surface survey and underground study by geomechanics for estimating the tendencies of slip and dilation of fractures. Understanding the characteristics of potential fluid conduits is useful the exploitation of groundwater resources. Intact crystalline rocks of low porosity possess lower water storage. Conversely, fractured crystalline rocks contain higher groundwater resources. Therefore, knowledge of distribution and characteristics of fractures is important to the exploitation of groundwater resources in crystalline rocks. Hoping is located in the NE Taroko belt of the Tananao metamorphic complex in Taiwan mountain belt. The formations in downstream area of Hoping River contain late Paleozoic to Mesoic meta-granites and marbles, and few alluvium strata. Kinmen island closed to SE Chain is located in Pingtan-Dongshan Metamorphic Belt of Late Yanshan orogeny. The formations contain Mesozoic granite, gneiss, various dikes, and some alluviums. Because of lithology, island topography, climatic characteristics and human development, groundwater resources become a serious issue in Hoping and Kinmen, Taiwan. Previous studies had conducted experiments of anelastic strain recovery on retrieved cores in Hoping. The results show that the maximum principal stress is vertical and the horizontal minimum stress is in NE-SW orientation, indicating a normal faulting stress regime with NE-SW extension. Most fractures are in E-W and NE-SW orientations that fractures of borehole are more attitude than parallel foliation plane. Results of hydraulic fracturing experiments and Diameter Core Deformation Analysis(DCDA) in Kinmen display the maximum and intermediate stress is in NW-SE orientation and vertical, respectively, suggesting strike-slip faulting regime with NE-SW extension. Most fractures are in E-W and NE-SW orientations and some are in other orientations. The stress field gradient are 37.39 MPa/km, 25.77 MPa/km and 21.78MPa/km. The re-activation of fracture are closely related to the in-situ stress field. If the fracture produce open filling fluid conduits by the stress. Then, position of depth of open filling fluid conduits search by anomaly geothermal gradient. However, the in - situ stress field can calculate the slip tendency and dilation tendency. The dilation tendency value is more than 0.8 to contribute the fluid to flow. The fracture of high dilation tendency are the same with shallow groundwater flow direction that is termed open filling fluid conduits. The pole attitude of open filling fluid conduits of Kinmen are 042˚/ 32˚ on Nanxion-1, 150˚/ 61˚ on ST-1 and 123˚/ 90˚ on Fengshang. Three borehole fractures were compared with the groundwater resistance logging data that display different attitude of fracture on BH01 at 0-80m, 193m, 350m, 400-500m, on BH02 at 0-70m and on BH04 at 350m. Hoping have anomaly geothermal gradient and weathered fracture of parallel foliation on borehole at 149.5m. This results are high credibility open filling fluid conduits on 149.5m from porosity and resistivity of borehole. On borehole fracture of Hoping are dilation tendency between 0.3 and 0.65. The results of extension tendency show that borehole fracture of Hoping don’t effect in-situ stress field to produce to extension. Slip tendency and tensile strength could define the shear tendency. Borehole fracture of Hoping didn’t produce slip on in-situ stress field. Previous studies had maximum stress of 84.49MPa, intermine stress of 64.29MPa and minimon stress of 55.19MPa on borehole of 3.17km that the hydraulic pressure range is 60MPa. Another and 83.98MPa. Another result are maximum stress of 253.08MPa, intermine stress of 192.66MPa and minimum stress of 165.40MPa on borehole of 9.5km that the hydraulic pressure range is 161MPa. Analysis of well logging data and tracer experiments will provide further insights into evaluating the existence as well as the distribution and attitude of fluid conduits. The results establish the basis for exploitation and utilization of groundwater resources in Hoping and Kinmen areas, Taiwan.
Taiwan Island and the Kinmen Islands region can often see information about the lack of water so need to rainmaking, extraction of groundwater and geophysical exploration to find the groundwater layer for solutions. This research selected crystalline rocks in Hoping and Kinmen areas of Taiwan. Then, to integrate data of fractures distribution, attitude and in-situ stress from surface survey and underground study by geomechanics for estimating the tendencies of slip and dilation of fractures. Understanding the characteristics of potential fluid conduits is useful the exploitation of groundwater resources. Intact crystalline rocks of low porosity possess lower water storage. Conversely, fractured crystalline rocks contain higher groundwater resources. Therefore, knowledge of distribution and characteristics of fractures is important to the exploitation of groundwater resources in crystalline rocks. Hoping is located in the NE Taroko belt of the Tananao metamorphic complex in Taiwan mountain belt. The formations in downstream area of Hoping River contain late Paleozoic to Mesoic meta-granites and marbles, and few alluvium strata. Kinmen island closed to SE Chain is located in Pingtan-Dongshan Metamorphic Belt of Late Yanshan orogeny. The formations contain Mesozoic granite, gneiss, various dikes, and some alluviums. Because of lithology, island topography, climatic characteristics and human development, groundwater resources become a serious issue in Hoping and Kinmen, Taiwan. Previous studies had conducted experiments of anelastic strain recovery on retrieved cores in Hoping. The results show that the maximum principal stress is vertical and the horizontal minimum stress is in NE-SW orientation, indicating a normal faulting stress regime with NE-SW extension. Most fractures are in E-W and NE-SW orientations that fractures of borehole are more attitude than parallel foliation plane. Results of hydraulic fracturing experiments and Diameter Core Deformation Analysis(DCDA) in Kinmen display the maximum and intermediate stress is in NW-SE orientation and vertical, respectively, suggesting strike-slip faulting regime with NE-SW extension. Most fractures are in E-W and NE-SW orientations and some are in other orientations. The stress field gradient are 37.39 MPa/km, 25.77 MPa/km and 21.78MPa/km. The re-activation of fracture are closely related to the in-situ stress field. If the fracture produce open filling fluid conduits by the stress. Then, position of depth of open filling fluid conduits search by anomaly geothermal gradient. However, the in - situ stress field can calculate the slip tendency and dilation tendency. The dilation tendency value is more than 0.8 to contribute the fluid to flow. The fracture of high dilation tendency are the same with shallow groundwater flow direction that is termed open filling fluid conduits. The pole attitude of open filling fluid conduits of Kinmen are 042˚/ 32˚ on Nanxion-1, 150˚/ 61˚ on ST-1 and 123˚/ 90˚ on Fengshang. Three borehole fractures were compared with the groundwater resistance logging data that display different attitude of fracture on BH01 at 0-80m, 193m, 350m, 400-500m, on BH02 at 0-70m and on BH04 at 350m. Hoping have anomaly geothermal gradient and weathered fracture of parallel foliation on borehole at 149.5m. This results are high credibility open filling fluid conduits on 149.5m from porosity and resistivity of borehole. On borehole fracture of Hoping are dilation tendency between 0.3 and 0.65. The results of extension tendency show that borehole fracture of Hoping don’t effect in-situ stress field to produce to extension. Slip tendency and tensile strength could define the shear tendency. Borehole fracture of Hoping didn’t produce slip on in-situ stress field. Previous studies had maximum stress of 84.49MPa, intermine stress of 64.29MPa and minimon stress of 55.19MPa on borehole of 3.17km that the hydraulic pressure range is 60MPa. Another and 83.98MPa. Another result are maximum stress of 253.08MPa, intermine stress of 192.66MPa and minimum stress of 165.40MPa on borehole of 9.5km that the hydraulic pressure range is 161MPa. Analysis of well logging data and tracer experiments will provide further insights into evaluating the existence as well as the distribution and attitude of fluid conduits. The results establish the basis for exploitation and utilization of groundwater resources in Hoping and Kinmen areas, Taiwan.
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和平, 金門, 滑動趨勢, 擴張趨勢, 剪切趨勢, Hoping, Kinmen, Slip tendency, Dilation tendency, Shear tendency