The Utilization of Transient Output Measurement to Characterize Geothermal Reservoir Properties Using AWTAS for Well 2H-21 at Hatchobaru Geothermal Field, Japan

Abstract

The continuous measurement of mass flow rates during output testing from a geothermal production well 2H-21 of Hatchobaru geothermal field, Japan are relatively short. Field data from a horizontal discharge into a twin separator was used to evaluate and understand the transient behavior of the near-well characteristics. The data was recorded every second for: the pressure drop across the steam orifice plates, the pressure at the separators, and the water level at weir box. The atmospheric pressure was also measured daily. The valve opening was changed three times during the measurement to obtain the output curve of the well. The measured mass flow rates and pressure at the wellhead then were used as input data to wellbore simulator. The results of calculated well bottom pressures then were inputted into AWTAS (Automated Well-Test Analysis System) to evaluate the properties of the reservoir. Three different types of radial reservoir model were used including uniform porous media, dual porosity fracture/matrix model, and the fractional dimension model. The best match for the down-hole pressure data was achieved with the fractional dimension model.