The First Two-Phase Tracer Tests at the Matsukawa Vapor-Dominated Geothermal Field, Northeast Japan

Abstract

As injection was practiced in the Matsukawa geothermal field, northeast Japan, the necessity of a tracer test emerged to evaluate the flow paths and recoveries of injected water. The Matsukawa reservoir being vapor-dominated, vapor-phase and two-phase tracers were considered for the first tracer test at this field. Sulfur hexafluoride, hydrofluorocarbons (vapor-phase tracers), and alcohols (two-phase tracers) were examined in terms of their practical use. The alcohols (methanol, ethanol, n-propanol and i-propanol) were selected since their properties were suitable for two-phase tracers.
The returns of alcohols were detected by five tests from 2000 to 2003 and smooth return curves were obtained. The flow paths and recoveries were evaluated from the tests. The results of the tests using mixed solutions of ethanol and i-propanol showed variation in the ethanol / i-propanol ratios and different peak times of ethanol and i-propanol, which could be caused by the process of boiling and two-phase flow in the vapor-dominated reservoir.