Changing Stratigraphic Models to Create New Opportunities: An Example Contrasting the Texas Woodbine and Louisiana Tuscaloosa

Robert J. Bunge
Santos USA Corp, Houston, TX

Despite the exploration maturity of the onshore Gulf of Mexico basin, ample opportunities may still be created by re-evaluating the stratigraphy of the Mesozoic and Paleozoic. Areas prime for re-evaluation are often part of broad regional trends where exploration is being done on older 2D data, and drilling is being pushed into deeper settings. Through regional work and acquisition of new data, the understanding of stratigraphy in these areas is being rewritten and exploration opportunities are being created. A good example of this is the Woodbine-Tuscaloosa trend of Texas and Louisiana.

Deep Tuscaloosa production has primarily come from deltaic sediments deposited in a growth fault setting basinward of the lower Cretaceous carbonate shelf margin. This prolific hydrocarbon province is often projected to continue all of the way across Louisiana and into Texas in the age equivalent Woodbine Formation. There has been a flurry of recent exploration activity in the downdip Woodbine Formation, as companies try to extend Tuscaloosa style deposition into the Woodbine. However, regional work conclusively shows that the Woodbine and Tuscaloosa are strikingly different. The Tuscaloosa was deposited off a shelf break style margin with high clastic influx, while the Woodbine was deposited on a ramp margin with low clastic influx.

Despite the ramp style margin and low clastic influx, new seismic also provides new insight into sedimentation, suggesting that deposition may have been in significantly shallower water than previously believed. This creates new exploration targets in the Woodbine, as well as more consistent sea level around the Gulf during the Cenomanian.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005