The team of Denbury Resources, Inc., Southern Company, Geological Survey of Alabama, Alabama Agricultural and Mechanical University, University of Alabama, University of Alabama at Birmingham, and University of North Carolina at Charlotte have entered into a cooperative agreement with the U.S. Department of Energy, National Energy Technology Laboratory, to demonstrate enhanced oil recovery using carbon dioxide, to increase the oil yield and extend the productive life of the Citronelle Oil Field in Mobile County, Alabama. The announcement of the project by the Department of Energy may be found at http://www.netl.doe.gov/publications/press/2006/06050-DOE_Awards_EOR_Project.html.
Enhanced oil recovery using carbon dioxide (CO2-EOR) is a well-established method for increasing oil recovery from the Permian Basin oil fields of Texas and New Mexico and in the Williston Basin of North Dakota and Montana. Denbury Resources has also been successful in applying the technology in Mississippi oil fields. Typically, an additional 15% of the original oil present in a reservoir at the start of production can be recovered using CO2-EOR. Denbury Resources estimates that 36 million barrels of oil will be recovered from the Citronelle Field using this technique. When oil production is complete, the reservoir and adjacent formations can provide sites for storage of carbon dioxide produced from combustion of fossil fuels in power plants and other processes generating CO2. The Southern Company is evaluating the capacity of such reservoirs as possible locations for permanent sequestration of CO2 separated from coal and natural gas combustion products at its power plants.
The Citronelle Field is an ideal site for CO2-EOR and sequestration, both from the reservoir engineering and geological perspectives. The field is mature and water-flooded, with existing infrastructure including deep wells, and consists of fluvial-deltaic sandstone reservoirs in a simple structural dome. Because of the presence of the regionally extensive Ferry Lake Anhydrite seal, four-way structural closure, and lack of faulting, it is naturally stable with respect to CO2 storage. However, the geology of the heterogeneous siliciclastic rocks in this field is very different from those where CO2-EOR has been applied commercially, such as in the carbonate strata of the Permian and Williston Basins. The demonstration will introduce CO2-EOR for tertiary oil recovery from Alabama’s uniquely structured energy resources and realization of the benefit from additional U.S. petroleum production.
The work will also provide the operators of other similar oil fields and producers of CO2 with the means to refine estimates of the yield from CO2-EOR and the capacity of depleted oil reservoirs for sequestration of CO2. The reliability of simulators with which to assess the oil yield and capacity of a given geologic formation for CO2 sequestration and the rate at which CO2 can be introduced into the formation will be improved. The simulation will be integrated with visualization of the migration of oil, water, and CO2, making the results accessible to reservoir engineers, geologists, planners at electric utilities, and climate change modelers, with or without specialized training in geology and petroleum engineering.
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