Geological storage of CO2 in disused oil and gas reservoirs is one of the potential techniques to reduce CO2 emissions into the atmosphere because of the economic benefits that incremental oil recovery can bring in a tight energy market. However, the acceptance of this new paradigm will require a perception of geological storage as a safe and environmentally sound practice. Therefore, it is necessary to make CO2 storage predictable to avoid any negative impacts to the environment or society and implement a carbon emissions market. In the short-term, or injection stages, the main trapping element is a competent caprock, and its performance is a vital component of the risk assessment of any CO2 storage project. Geomechanics plays a key role in the performance assessment of the caprock and the reservoir as the hydraulic integrity of this system must be ensured both during the exploitation and production stages (pre-CO2 injection), and during CO2 injection in any CO2-EOR storage project. Phase One of the IEA Weyburn CO2 Monitoring and Storage Project offered an unique opportunity to conduct a geomechanical performance assessment of a caprock system overlying a large scale CO2-EOR storage project.
The IEA GHG (International Energy Agency, Greenhouse Gas R&D Programme) Weyburn CO2 Monitoring and Storage Project (Weyburn Project), coordinated through the Petroleum Technology Research Centre in Regina, Saskatchewan, was initiated to study the potential for geological storage of CO2 in a depleting oil field in southeastern Saskatchewan and to investigate methods of monitoring the movement of CO2 in the subsurface to: 1) enhance the effectiveness of the miscible flood; 2) determine the potential of the reservoir to serve as a vessel for long-term (ca. 5,000 years) storage of the anthropogenic CO2; and 3) to determine the economic feasibility of longterm storage.