Geophysical Characterization for Potential Carbon Dioxide Sequestration in the Black Warrior Basin of Alabama

The southeastern US is a leading producer of carbon dioxide emissions in large part due to the high number of coal-fired power plants in the region. As part of a Department of Energy (DOE) National Energy Technology Laboratory (NETL) funded geological characterization project we have collected a number of geophysical data sets that characterize the Black Warrior Basin in the vicinity of the Alabama Power Gorgas Steam Plant in Walker County, Alabama. These geophysical data sets are important for extending the results from our 8000-foot characterization hole throughout the basin. Two 5-mile seismic reflection profiles processed through pre-stack time migration image the Cambrian through Pennsylvanian stratigraphy in the basin. The major injection targets in the saline reservoirs of the Hartselle Sandstone, Tuscumbia Limestone, Stones River Group and Knox Group. Initial examination of the data show that it is well suited for techniques such as Amplitude Versus Offset (AVO) analysis and inversion with the downhole data. Multiple offset vertical seismic profiles (VSP) image the formations close to and at multiple azimuths away from the drill hole. These VSPs also provide an important link to the seismic reflection profiles, which pass a little less than a mile to the north of the drill hole. Three shallow microseismic wells in the vicinity of the main drill hole have 3-component geophones cemented at depths of 50, 150, and 250 foot. These wells, designed to record small magnitude seismic events resulting from low-volume water injection, are important for characterizing the local fracture pathways and stress fields. Downhole gravity data complements the usual suite of downhole tools by imaging density variations deeper into the formations and ensuring that the identified saline reservoirs are not locally discontinuous.