In 1996, a one-month circulation test (flow enhancement test; Exp.9601) was carried out with HDR-1 as an injection well and HDR-3 as production well at the Hijiori HDR site in Yamagata prefecture, Japan. There are two reservoirs (a shallow reservoir and a deep reservoir) in high temperature granite at the site. The shallow reservoir was located at the depth of about 1800 m with an injection well SKG-2 and the deep reservoir at the depth of about 2200 m with an injection well HDR-1. Both reservoirs were connected with HDR-2a and HDR-3 as production wells.

In 1995, we observed that water injected into HDR-1 flowed into the shallow reservoir from the deep reservoir at the initial period of a preliminary circulation test (Exp.9501)(Tenma et al., 1995). To examine this characteristic of the multi-reservoir system, the pressure of the shallow reservoir was monitored using SKG-2 during Exp.9601. Also, PTS (Pressure - Temperature - Spinner) logging was periodically carried out in production well HDR-3. Thus, we got the pressure and flow rate between SKG-2 and HDR-3 of the shallow reservoir.

Prior pressure and flow rate of the shallow reservoir were acquired both from PTS logging in the 1991 90-day circulation test (Exp.9102) data and the 1994 injection test (Exp.9403) for wells HDR-2a, HDR-3 and SKG-2.

With the combined data from Exp.9102, Exp.9403 and Exp.9601, we attempted to study the pressure - flow response between SKG-2 and HDR-3 of the shallow reservoir.

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