For large-scale carbon dioxide (CO2) injection and storage, saline formations offer vast storage capacity, often in multiple geologic formations, or multiple storage reservoir horizons within a single formation. Challenges for characterizing CO2 storage reservoirs in specific saline formations may include limited subsurface data, unproven geologic traps and lack of any production infrastructure available for injection and monitoring operations. Active oil fields offer advantages for CO2 sequestration in saline formations that address such challenges. Advantages of active oil fields include proven structural traps and reservoir seals; confirmed saline storage horizons; existing field data including geophysical well logs, seismic data, core data, formation water analyses and reservoir pressure tests; existing infrastructure for access and monitoring; and potential use of CO2 in enhanced oil recovery. Such advantages are substantial, but active oil fields can also present unique hurdles for CO2 storage in saline formations. These include old and incomplete well data and geophysical logs; confirming the integrity of cement through the saline formation and confining unit (if located above the oil reservoir); and remediating existing wells.

The Southeast Regional Carbon Sequestration Partnership (SECARB) Phase III Anthropogenic Test is a large-scale demonstration of integrated CO2 capture, transport and storage planned for Citronelle field, in Mobile County, Alabama.1 Anthropogenic CO2 from a coal-fired electric generating plant, Alabama Power’s Plant Barry, will be captured and transported to Citronelle field.2 During 2011 to 2014, up to 182,500 tonnes of CO2 will be injected annually into the Lower Cretaceous Paluxy Formation, a saline formation that contains multiple reservoir sandstones and is located above the oil reservoir. This paper describes the initial characterization effort, which used all available field and regional data, to build a reservoir framework for the Paluxy Formation at Citronelle for initial assessment of injectivity, storage capacity and fate of injected CO2. The initial characterization of the Paluxy Formation demonstrates a successful approach for estimating key saline reservoir parameters including porosity, permeability, sand thickness and continuity from an incomplete existing data set in an active oil field. A robust geologic data collection effort is planned for the CO2 injection and observation wells to be drilled at the Anthropogenic Test site during 2011. The new data will be integrated with the existing Paluxy data set at Citronelle field to validate, refine and expand the initial characterization of the CO2 storage reservoir sandstones.

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