AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Sequence to Architectural Element Framework of the Tuscaloosa Massive Sandstone, Eastern Gulf of Mexico Province, USA
(1) The Universtiy of Texas at Austin, Austin, TX.
The lower Tuscaloosa Sandstone (late Cretaceous) is a major hydrocarbon bearing fluvial/deltaic clastic unit located in the central and eastern U.S. Gulf Coast region. The lowest portion of the lower Tuscaloosa, in this area, is a coarse-grained conglomeratic sand often termed the Massive Sand. The Massive Sand has been an important interval in the production of hydrocarbons from the Tuscaloosa Sandstone. The growing importance of pre-Neogene Gulf of Mexico exploration plays suggests a need to revisit the various influences on the Tuscaloosa’s sequence framework and controls on its fairways, accommodation sinks, and probability for deep marine reservoirs in more distal locations. This study defines a sequence stratigraphic framework for the Massive Sand to better understand the location and nature of high net-to-gross depositional fairways located within each parasequence. The well-defined locations of these fairways are essential for improving prediction for the future exploration and production of hydrocarbons and may give some insight to the downdip location of associated deep offshore reservoirs being fed by these fairways.
An analysis of over 2500 well log suites, three core, regional seismic lines and, previously published data over a study area of about 45,000 km^2 in Mississippi and Alabama indicate there are three major third-order parasequences within the Massive Sand. The duration of these parasequences indicate a wide range of possible controls could have had an effect on their deposition including changes in base level due to sea level changes, tectonics, or a combination of both. The parasequences transition from stacked, blocky low gamma log motifs and coarse-grained core intervals in the north, which are interpreted as fluvial in nature to stacked, coarsening and thickening up log motifs southward, which are interpreted as increasingly shelf and shelf-edge deltaic in nature. Identified fairways show some degree of structural control and form potential low accommodation point source sites for sediments moving into deep water locations.