| 講演要旨(和文) | | 電力中央研究所が秋田県雄勝実験場で実施した高温岩体発電実験では、深さ1,000 mの坑井（OGC-1）の深さ710 m付近 と1,000 m付近の二箇所から水圧破砕により人工の貯留層を造成した。この貯留層の位置や広がりはAEの震源分布などから評価し、これらの貯留層を貫くよう生産井（OGC-2）を掘削した。二つの坑井間での初期の循環実験では圧入した水の回収率が低かったため、二つの坑井の水圧刺激を実施した。OGC-1の水圧刺激では、AEの震源は深さ900 m〜1,050 mの範囲で、OGC-1とOGC-2の間に集中し、下部貯留層内の亀裂の拡大や新たな亀裂の発生が生じたことが示唆された。また、水圧刺激後の循環実験中に実施されたトレーサ試験結果や、OGC-2の温度検層結果からも下部貯留層での亀裂拡大によるショートカットや温度低下が認められ、下部貯留層を循環水が優勢に流れたものと推定された。 |
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| | 講演要旨(英文) | | Two reservoirs (upper and lower) were created at different depths of a 1,000 m-deep injection well (OGC-1) in the Ogachi HDR project. The location and the size of these reservoirs were estimated by acoustic emission (AE) hypocenter distribution. A production well (OGC-2) was drilled according to the hypocenter locations to penetrate the reservoirs. Because of low water recovery rate during the initial water circulation test between the wells, hydraulic stimulation operations for improving hydraulic connection between OGC-1 and OGC-2 were conducted in 1994 and 1995. Hypocenters of AE observed these operations distributed around bottom of the wells. Comparing with the tracer tests and temperature logging results, the stimulation operations were effective to improve water flow connection between OGC-1 and OGC-2 and short circuit of the flow path had to occur in the lower reservoir. |
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