A Modeling Study of the Oguni Geothermal Field, Kyushu, Japan

Abstract

A numerical model of the Oguni liquid-dominated geothermal reservoir is presented. The steady .natural. state of the field was described by an unsteady heat-up calculation of 250,000 years duration. Next, the effects of several shallow small-diameter wells which have been operating in the area for the last thirty years were taken into account. The final state of this calculation represents present-day conditions. Comparisons of computed stable reservoir temperatures, pressures, and natural surface discharges with measurements are favorable. Finally, the model was employed in a series of forecasts to estimate the electrical capacity of the field and to design optimum exploitation strategies. These calculations indicate that the Oguni field is capable of supplying 250 tons per hour of steam (separated at 160?C) for more than thirty years.