Geological characterisation of Australia’s first carbon dioxide storage site

Abstract

This is a PhD thesis by publication consisting of four journal papers and two chapters in books. Each manuscript details the geological characterisation that has underpinned scientific field research and operations at the CO2CRC Otway Project. This is Australia’s first site to geologically store carbon dioxide and has been operating in Victoria, Australia, since 2008. Site screening, planning, and development began four years prior to that. During the course of the past 14 years the project has achieved demonstrated storage in both a depleted gas field, and a saline aquifer, and investigated the dynamic processes and monitorability of both scenarios in a series of controlled field experiments. This has provided a unique opportunity to test and validate interpretations of the geological characteristics that are thought to influence storage efficacy and containment. The research presented in this thesis has the distinction of being able to test geological heterogeneity at both the core and field scale by comparing the core analysis and laboratory experiments with actual injection data. It shows that small scale geological influences, particularly vertical permeability, have an impact on capacity and trapping. Furthermore, the time-lapse monitoring datasets provide evidence to which the conformance of reservoir models are assessed. The body of work herein has established that valuable insights may be used to improve site characterisation before, during, and post-injection. This is particularly important for updating models to enhance reservoir management, as well as for predicting the longterm evolution and stabilization of injected CO2. This in turn will influence enduring monitoring strategies and the potential transfer of liability for many sites post-closure. The research presented here examines the whole of life site assessment process from site selection through to execution and completion. It dispels the myths that depleted fields have little uncertainty and risk because they have held hydrocarbons in the past and are already well characterised by the previous operators. Instead the findings show that characterisation for CO2 storage has very a different focus from that of petroleum exploration and development methods, and targeted data acquisition and integrated analysis is essential to reduce uncertainty. The study also shows that information gathered for CO2 storage site characterisation of a previously poorly characterised saline aquifer can have greater implications for the regional understanding of basin stratigraphy and geological controls on fluid migration. Thus the investigations may be of interest to those beyond just the carbon capture and storage research community.