長期循環試験, 第2期及び第3期の数値シミュレーション結果から推定される肘折貯留層の生産及び抽熱特性について : 二層貯留層を用いた高温岩体発電システムの開発に関する研究(第2報)

概要

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At the Hijiori Hot Dry Rock (HDR) field in Yamagata prefecture, the Long-Term Circulation Test (LTCT, Term 2 and Term 3) was conducted from December 23, 2001 to August 31, 2002. The test used two injection wells SKG-2 and HDR-1, and two production wells HDR-2a and HDR-3. At the beginning of this test, water was injected at a constant flow rate of 8.35 kg/s into SKG-2 and HDR-1. The ratio of injection flow rate at wells, HDR-1: SKG-2 was changed from 1:1 to 3:1 during the test, and production flow rate of HDR-2a decreased from 8 kg/s to 6kg/s. Production rate in HDR-3 remained almost constant during the test.Because of difficulties in obtaining a match between the simulated and measured pressure of HDR-1 in the Term 1 of LTCT, the Bed-of-Nails model for fracture flow was modified. We re-developed a simple multi-reservoir model and simulated the test data using the FEHM (Finite Element Heat and Mass transfer) code developed at Los Alamos National Laboratory. In addition, to estimate the productivity and the heat extraction of the multi-reservoir system during the long-term circulation, we studied four different injection scenarios by changing the ratio of injection rate or wells. The two most important conclusions of the calculation are:1) Production flow rate of HDR-2a decreased under the influence of decrease the injection rate of SKG-2, and2) one of these four scenarios is recommended because of its high recovery and thermal output.
2004-07-25