The Transition or T-Zone is defined as an area where the water is too shallow for the acquisition of marine seismic data with towed streamers. These areas are located in shallow water near the shoreline and in marshes and lagoons where water depths are typically less than five feet. In a broader sense, the Transition Zone refers to the area of marshland and swamp that constitutes a swath of Southern Louisiana 30 to 50 miles wide, running parallel to the coastline.

Many of the Gulf Coast’s giant oil and gas discoveries have been made in the Transition Zone but the majority of these discoveries were made in the 1950s or earlier. Three-dimensional seismic data were notoriously of inferior quality in the Transition Zone because of the difficulties and cost of data acquisition across the land/sea interface. Additionally, data acquisition has been hindered by the presence of field facilities and infrastructure such as tank batteries, compressors, and pipelines. Because of the high cost of data acquisition, many of the earlier surveys were compromised either in terms of overall quality or due to the areally-limited extent where data were collected only on the crests and immediate flanks of salt domes, with little or no three-dimensional survey coverage between known fields.

The author will show examples of some notable successes among the independents and will try to demonstrate that there is substantial untapped potential remaining in the T-Zone. This potential is not just in the “ultra-deep” plays, but also in plays at conventional depths and even in the “ultra-shallow.” Trap styles, seismic data, and log data will be presented.