Comparison of heat extraction from production wells in the shallow and the deep reservoirs at the Hijiori HDR Test Site using FEHM Code

Abstract

From November 27, 2000, a two-year circulation test (Long-term circulation test; LTCT) was started with HDR-1 as an injection well, and HDR-2a and HDR-3 as production wells 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 the injection well SKG-2 and the deep reservoir at the depth of about 2200 m with the injection well HDR-1. Both reservoirs were connected with HDR-2a and HDR-3 as production wells (Fig. 1).

In the second half of the LTCT, the test that HDR-1 and SKG-2 are injection wells, and HDR-2a and HDR-3 are production wells will be planned. It is important for this test that the flow distribution in a multi-reservoir system is examined.

Aiming to grasp the characteristic of the multi-reservoir system, we make both reservoir models. And we will combine these models in order to examine the performance of this system. As part of estimation of this system, we compare the ability of heat extraction from both reservoirs using numerical models. As the results, the ability of heat extraction of HDR-2a is higher than that of HDR-3 in the deep reservoir. But, that of HDR-2a is almost similar that of HDR-3 in the shallow reservoir.