Characterization of Fractured Geothermal Reservoir Using Sinusoidal Flow-Rate Pressure Interference Test

Abstract

Sinusoidal pressure transient test is one of the periodically changing flow-rate methods to evaluate complicated reservoirs. We have carried out numerical simulation studies to examine optimal sinusoidal flow periods and resulting pressure transient behaviours of an observation well. Threedimensional porous and double porosity ("MMC") reservoir models are used. Differences between the pressure response of the porous-medium and the fractured-medium models are discussed. It appears possible to predict whether a reservoir medium between two wells is porous or fractured, when hydraulic difkivity of several different sinusoidal flow-rate periods can be estimated from a time lag of the pressure interference at an observation well. An example of pressure interference data observed at the geothermal field in Japan is also presented.