Interpretation of a Pressure Interference Test of the Sumikawa Geothermal Field

Abstract

In reservoir engineering, pressure interference testing is a fundamental tool for establishing reservoir connectivity and for computing interwell properties. An interference test consists of the discharge (and/or injection) of one or more wells, and the measurement of the resulting pressure disturbance in shutin observation wells. These pressure records reflect the spatially-integrated properties of the reservoir in the region between the discharging well and the observation well(s), and thus provide direct information regarding average reservoir properties on a large scale which are unobtainable by any other technique. A large-scale reser~oir interference test at Sumikawa was performed in the fal~ of 1986 by Mitsubishi Metal Company under NEDO's program "Development of Geothermal Reservoir Evaluation Technology" (Maeda, et a1., 1987). Well S-4 (see Figure 1 for well locations) was discharged starting at 11:20 local time on September 2, 1986 and was shutin at 16:30 hours on November 3, 1986; the liquid fraction of the discharge was simultaneously reinjected into Well S-2. Four observation wells (0-5T, S-3, N60-KY-l and N60-KY-2) were equipped with capillary-tube type pressure gauges. No pressure measurements were made in either the production well (S-4) or ' the relatively shallow disposal well (S-2).