Uncertainty analysis of forecasting with the Ohaaki reservoir model using PEST

摘要: In 2017 the TOUGH2 numerical reservoir model of the Ohaaki geothermal field in New Zealand underwent a significant re-calibration. The model was updated with a new simplified geological structure with stronger agreement to the conceptual understanding of the field (Ratouis et al., 2017). This update marked a step change in the approach to model calibration by using a pure water model for rapid calibration, before conversion to a simulation (with slower run times) with gas added to capture the CO2 content which is important to match boiling conditions. Model run times and model accuracy improved considerably as a result.With the simplified geological structure and shorter run times, this model presented the opportunity to use PEST (Model-Independent Parameter Estimation and Uncertainty Analysis) to develop a set number of plausible alternative model solutions by varying selected parameter values within …