Reservoir Simulation Study of the Onikobe Geothermal Field, Japan

Abstract

This paper presents the results of a numerical modeling effort to construct the mathematical model of the Onikobe reservoir with an improved quality, thereby permitting more accurate forecasts of reservoir performance, and facilitating efficient reservoir management. The steady "natural state model of the field was developed by a natural state simulation. After matching of measured and calculated temperature and pressure distributions, a further calibration of the model was carried out by matching the known and calculated enthalpy histories of the existing wells. MINC (Multiple Interacting Continua) scheme to represent the naturally fractured reservoir was introduced to these history calculations, with equivalent steady properties. The thermal effects of reinjected water on the production wells could be reproduced by the simulation. These calculations indicate that the average fracture spacing of the reservoir nearby southern reinjection area was around 100m.