AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Reinterpretation of the “J” Basalt Reflector from Seismic Data Reprocessing Across the Coastal Plain of Southeastern Georgia: Potential Implications for Long-Term CO2 Sequestration
(1) Earth and Ocean Sciences, University of South Carolina, Columbia, SC.
(2) Earth Sciences and Resources Institute, University of South Carolina, Columbia, SC.
We present new results focused on the regional significance of the Jurassic basalt (“J” basalt) within the Late Triassic South Georgia Rift (SGR) basin and its potential as a seal for CO2 storage. The SGR basin which covers parts of Georgia, western Florida, southern Alabama and southern South Carolina, contains Triassic rocks that are deep enough to be classified as saline formations and are close to CO2 emission sources, making them promising for geologic CO2 sequestration.
The objective of this work is to identify and interpret subsurface reservoirs and seals as part of a basin-scale geological assessment for potential CO2 storage. Contrary to the paradigm that the “J” basalt is present beneath the Cretaceous sediments in southeastern Georgia and parts of the (SGR) basin, our seismic imaging results corroborated by interpretation from nearby Georgia well data provide evidence to suggest that no pre-Cretaceous rocks are above the SGR in southeastern Georgia.
This new seismic imaging involved reprocessing of 96-channel, 6s and 24 fold seismic reflection data (SEISData6) covering the Coastal Plain of southeastern Georgia. Reprocessing was enhanced by the use of residual statics in addition to the attempt to boost signal to eliminate the background noise. Of primary importance to our interpretation is the presence of a conspicuous, southeast-dipping reflector with seismic characteristics similar to those previously described as the “J” reflector. However, our interpretation and subsequent correlation with a nearby Georgia well log indicates that this high-amplitude and fairly continuous reflector corresponds to the base of the Coastal Plain sediments and the transition to the underlying Triassic sediments. The “J” basalt, widely recognized in the 1980’s as a distinct and prominent geologic marker that is either below or at the base of the Coastal Plain, does not appear to be present in the study area. Absence implies either a restricted spatial distribution of the “J” basalt or uplift and erosion, possibly associated with fault reactivation. Our results further underscore the need for improved understanding of the geographical extent of the “J” basalt throughout the SGR basin. We conclude that the absence of the “J” basalt reflector from the study area does not preclude subsurface storage of CO2. Substantial evidence abounds for the occurrence of diabase and shale that could serve as effective seals for potential CO2 storage within the SGR basin.