抄録
It is very important to grasp the flow conditions of geothermal fluid at the well inlet in order to investigate physical properties of the reservoir and consequently establish a technique for forecasting changes of the well output. However, at present, the data of temperature and pressure logs in discharging wells of the Otake and the Hatchobaru geothermal areas are rather rare. Almost all of the data are restricted to the ground surface measurements. In this paper, the relation between the fluid pressure, P1, and quality, x1, at the well inlet, and the saturated pressure at the flashing inception level, P'0, and variable well head pressures are calculated by means of the flow rate of steam-water mixture and the pressure measured at the well head, and also by the momentum equation. A plot of P1, and P0 for x1>∼0.1 (mean values of P1, P0 and x1, respectively) against the well inlet depth defines a region which, to some extent, can be used for the availability of the producttion well. The rise and fall of the flow characteristics of the production well is forecast by taking into account the change of the flow conditions at the well inlet with time.
