Improvement of the Reservoir Model Using the Well-based Data and Geophysical Exploration Data in the Wasabizawa Field, Japan

Abstract

The Wasabizawa geothermal power plant in Akita prefecture, Japan has been in operation since May 2019 with a generation capacity of approximately 46 MW. Many geophysical surveys have been conducted prior to the beginning of the operation, and some geophysical data such as time-lapse gravity and self-potential are periodically observed during ongoing operation at the field. A three-dimensional numerical model of the reservoir developed prior to the beginning of the operation (Nakanishi et al., 2017) has been improved mainly based on the data of the new-drilled wells to be matched with the logging data and previous pressure transient tests (Kano et al., 2023). In this study, we conduct a production-reinjection history matching simulation which incorporates the operation history using the improved model, and compare the results with the data of the produced fluid, pressure histories of the observation wells, and the results of the previous and the latest geophysical surveys. That indicates that minor geological structures of the caprock could affect the fluid flow in the reservoir. Also suggested is the necessity for further consideration on the mass balance including recharge. We will also present the attempts to further improve the model mainly in regard to the minor geological structures based on the investigation. [Acknowledgement]The authors are grateful to Yuzawa Geothermal Power Corporation for their generous support on developing the model and conducting the history matching simulations. [References] Nakanishi et al. (2017) A Numerical Simulation Study of the Wasabizawa-Akinomiya Geothermal Field, Akita Prefecture, Japan. GRC Transactions 41, 2811-2825; Kano et al. (2023) Improvement of the reservoir model and history-matching simulation in Wasabizawa field. Presentation at 2023 Annual Meeting Geothermal Research Society of Japan, November 14-16, 2023, Gifu, Japan. Abstract Number B08, in Japanese.