Tracer Tests for Evaluation of Flow in a Multi-Well and Dual Fracture System at the Hijiori HDR Test Site

Abstract

A long-term circulation test was conducted for around two years from 27 November 2000 at the hot dry rock (HDR) test site in Hijiori, Japan. During the test we carried out tracer tests every two or three months to monitor the flow regime in the reservoir. Tracer reagents including potassium salts, sodium fluorescein, and naphthalene sulfonates were injected into injection well HDR-1 in a single well injection stage and into HDR-1 and SKG-2 during a dual injection stage. Fluids from two production wells HDR-2a and HDR-3 were sampled and analyzed to obtain tracer response curves. A fiber-optic fluorimeter was installed in the sampling lines at surface to obtain real time data of fluorescein concentration. Comparison of the tracer response curves suggests that the flow regime in the reservoir was affected severely by pressure difference between injection and production wells.