Reliable CO2 injection procedures in carbonates
Increasing the confidence of future storage operators in injecting CO2 in deep saline formations
State of the art
Extensive experience of CO2 injection exists for enhanced hydrocarbon recovery (e.g. Weyburn, Canada), where reservoir history is typically available to help inform injection management. Injection into saline aquifers was only recently developed at the industrial scale (e.g. Sleipner, Snøvhit, In-Salah) but mainly within sandstone formations.
Experience in carbonate reservoirs for permanent storage of CO2 is limited, such as the Michigan Basin site within the US DOE RCSP validation phase (finished in 2009), the Cholla site in Arizona, USA, during which CO2 injection was not performed due to the lower permeabilities found during well drilling (WESTCARB, 2009), and the Williston Basin field demonstration (PCOR, 2009) in North Dakota, USA, in which up to 400t CO2 were injected into the Mission Canyon carbonate formation at more than 2400m depth. This site demonstrated the importance of fracture networks on migration of the injected CO2 plume given that the matrix permeability is typically lower than 0.5 mD and the same well was used for injection and oil production both before and after the test (with increasing values due to CO2 injection).
Field scale experiments complemented by well validated next-generation reservoir models are therefore urgently needed to better understand CO2 injection into fractured carbonate saline formations and to demonstrate our ability to safely inject and store CO2 at relevant scale.
Progress beyond the state of the art
The results from this task will increase the confidence of future storage operators in injecting CO2 in deep saline formations, especially carbonate formations, providing a higher understanding on the risks and cost-effectiveness.
Outcomes
Design and execution of cost-effective and innovative CO2 injection strategies (pulse, cold, ...), associated modelling and history matching activities, linked with Pressure management and site conformance, under real-life conditions. Demonstration of safe and environmentally sound CO2 storage.
