RESERVOIR MONITORING BY TRACER TESTING DURING A LONG TERM CIRCULATION TEST AT THE HIJIORI HDR SITE

Abstract

A long-term circulation test has been conducted since 27 November 2000 at a hot dry rock (HDR) test site in Hijiori, Japan. During the test we carried out tracer test every two or three months for monitoring flow regime in the reservoir. Tracer reagents among potassium salts, sodium fluorescein, and naphthalene sulfonates were dissolved in 1 m3 of water and pumped in a deep reservoir at a depth of 2,200 m. Fluids from two production wells HDR-2a and HDR-3 were sampled and analyzed to obtain tracer response curves. A fiber-optic fluoremeter was also applied to obtain real time data of fluorescein concentration. Comparison of each tracer response curve suggests that the flow regime in the reservoir was severely affected by anhydrite precipitation in the production wells and also temperature draw down in the reservoir.