Hydraulic Communication Tests at the Ogachi HDR Site, Japan

Abstract

Hydraulic communication tests between an injection wellbore and a production wellbore were conducted in 1992, 1993, and 1994 at the Ogachi Hot Dry Rock (HDR) site in Akita prefecture, Japan. This testing, conducted by the Abiko Research Laboratory of Central Research Institute of Electric Power Industry (CRIEPI) included injection testing of two fracture zones which spread out from tow open hole intervals at depths of 720 m and 1000 m.

From the data obtained during hydraulic testing, reservoir parameters for Ogachi site (transmissivity and coefficient of storage) were calculated using an automatic inversion analysis based on the nonlinear least squares method. However, to avoid the lical minimum solutions, initial values for these two reservoir parameters were selected using trial and error curve matching method.

For the upper fracture, derived in 1992, the resulting transmissivity and coefficient of storage were 2.97x10-5 m2/s and 1.31x103 respectively. For the combined fractures, derived in 1993, the transmissivity and coefficient of storage were 7.5x10-5, respectively.

Temperature profile changes of the production wellbore during the circulation period can be observed easily by using an optical fiber temperature measurement cable (Distributed Temperature Sensor. DTS). From these profile changes, the places where fracture zones had penetrated the production wellbore can be determined.