Well Performance Diagnostics and Forecasting Using the Gudrun Wellbore Simulator - Case Studies from Kawerau, New Zealand

Abstract

Ngati T?wharetoa Geothermal Assets Ltd. (NTGA) relies on real-time wellhead data trends and periodic downhole wellbore surveys to understand and forecast geothermal fluid supply availability and reinjection capacity. This paper illustrates the use of Gudrun, the standalone wellbore simulator application of the Volsung geothermal reservoir simulation software package. Here we have applied Gudrun for well performance diagnostics and are using it for forecasting future well performance based on future reservoir conditions.
Wellbore models were developed for a production and an injection well from the Kawerau Geothermal Field, calibrated with wellbore data and history-matched with continuous wellhead data to determine model performance. The calibrated wellbore models were used to forecast well performance using expected reservoir and wellhead conditions. The wellbore model forecasts provide insight into well performance and reservoir changes and are useful proxies for field performance forecasting while developing a full-field numerical reservoir model. Ongoing investigation is also carried out to determine whether mismatches between the wellbore model forecast and actual wellhead performance could be used as basis for optimising the wellbore downhole monitoring program.