The role of heterogeneity in CO2 storage in a depleted gas field: History matching of simulation models to field data for the CO2CRC Otway Project, Australia

Abstract

The first stage of the CO2CRC Otway Project, located in south-eastern Australia, has stored 65,445 tonnes of CO-rich gas in the depleted Naylor Gas Field. Comparisons have been made between simulations using the nonisothermal multi-phase flow simulator TOUGH2/EOS7C and the accumulated field data up to and beyond the end of injection. The geological models and the derived simulation models have been able to fit most of the key features of the field data, including the downhole pressure measurements and the arrival time at the observation well. When fitting to the downhole pressure only, the observed arrival time was in the range of uncertainty of the model predictions. The use of multiple geostatistical realisations of heterogeneity demonstrates the importance of capturing the range of uncertainty in the geology and the consequent scatter in forward predictions. Thus the storage of CO in the Naylor depleted gas field is shown to be adequately modelled by numerical simulation, and this increases confidence in the suitability of similar depleted gas fields for underground storage.