Abstract: Structural Overview of the Deepwater to Ultra Deepwater Northern Gulf of Mexico Area based on a Recent Regional Seismic Program

Abstract

This interpretation project is based on an extensive 2-D seismic program (known in the industry as Phase 45) that consists of 60,000 line miles, covering the central and western parts of the deepwater and ultra deepwater northern Gulf of Mexico region. This paper concentrates on the central part of the project area (Garden Banks, Keathley Canyon, Green Canyon and Walker Ridge) covering 38,000 mi 2 and utilizing a 4 by 4 mile recently acquired seismic grid. Four horizons have been interpreted: top and base salt along with the Discoaster surculus (DS - approximate top Pliocene) and Discoaster berggrenii (MDB - approximate top Miocene) horizons. Abundant well data, in the form of electric logs, micropaleontology and velocity data, were available in the northern Green Canyon and Garden Banks regions. All interpretation was performed on a workstation. The mapping of these horizons shows how salt geometry changes moving from north to south. Around the continental shelf break a series of coalesced but discrete allochthonous sheets with significant intersalt basins occur. To the south a virtually continuous salt sheet, with numerous suprasalt basins, develops out to the edge of the present day northern Gulf of Mexico salt province, marked, in part, by the Sigsbee Escarpment. In these distal parts of the salt province, particularly in the Walker Ridge area, there is comparatively little sedimentary cover above the salt except where suprasalt basins have locally depressed salt. These basins have both symmetric and asymmetric geometries. The Mio-Pleistocene section is oilen railed above the allochthonous salt in these basins and seems to override deeper Mio-Pleistocene identified outboard of, and carried beneath, salt.