報告書番号

U01004

タイトル（和文）

高温岩体発電のための貯留層亀裂構造評価（その3） --坑井壁面画像解析に基づくフラクチャの分布・性状評価--

タイトル（英文）

Estimation of Fracture Structure in Reservoir for Hot Dry Rock Geothermal Power (3) -Fracture Distribution and Characteristics Evaluated by Wellbore Wall Image Analysis-

概要 （図表や脚注は「報告書全文」に掲載しております）

OGC-3井の地質調査と坑壁を画像化する検層であるFMI，UBI検層から雄勝地点の地質，フラクチャおよび地圧について再検討を行った．その結果，OGC-3井の地質構成や天然のフラクチャの方向性は既存坑井と概ね同様であることがわかった．光ファイバー温度検層で抽出されたOGC-1井との導通箇所をFMI，UBI検層で調査し，導通フラクチャを同定した．その結果，深度960m付近に2本の主要な導通フラクチャがあることがわかった．深度1140ｍ付近の大量逸泥箇所のフラクチャの性状を明らかにし，その結果，これらのフラクチャの貯留層へ及ぼす影響評価の必要性を示した．坑壁画像から地圧を推定できるDTFやブレークアウトがOGC-3井ではほぼ全裸孔区間に亘って観測され，解析の結果，OGC-3井周辺の地圧は逆断層型で水平面内の最大主応力はほぼE-W方向と推定した．

概要 （英文）

Geology and fractures were investigated and re-evaluated using a newly drilled wellbore, OGC-3. It was clarified that the geology and the naturalfracture orientations, revealed by FMI and UBI logging, of the OGC-3 are almost the same with those of the other wells. The connected points to theOGC-1, revealed by optic fiber temperature logging, were investigated by FMI and UBI and the connected fractures were identified. It was revealed that there are two major connected fractures around 960m in depth of the OGC-3. Fractures were revealed around 1140m, where the largest lost circulation occurred. It was underlined that the influence of those fractures on the Ogachi reservoir should be carefully examined. Drilling-induced tensile fractures (DTF) and borehole breakouts, which indicate the underground stress, were observed throughout the entire open hole at the OGC-3. It was analyzed that the stress around the OGC-3 was reverse fault type and the maximum principal stress on horizontal plane was east-west.

報告者

キーワード