A Closer Look at Salt, Faults, and Gas in the Northwestern Gulf of Mexico with 2-D Multichannel Seismic Data

The sedimentary wedge of the northern Gulf of Mexico (GOM) is extensively deformed and faulted by salt tectonics. It is also an area of biogenic and thermogenic gas and gas hydrate accumulation. To understand the interplay of salt tectonics, gas, and sedimentary history, we studied a dense grid of 2D multichannel seismic data covering an area of 33,800 km2 in the northwestern GOM, with an average grid spacing of 3.3 km. Salt is abundant in the study area. The distribution varies throughout the region from large diapirs and massifs in the east, to small isolated salt bodies in the west. Salt migration affects local topography and local bathymetric highs are salt diapirs and lows are areas of salt withdrawal. Two different styles of faulting are found within the study area. In the West, faults are longer, linear and trend NE-SW. They are parallel to slope which implies some degree of gravitation sliding. In the central and eastern part of the study area, faults are localized on salt bodies, resulting from diapirism. Acoustic blank zones caused by gas in the sediment column are common. Areas of gas enriched sediment found near the surface are assumed to contain biogenic gas. Vertical acoustic wipeout features, (aka "gas chimneys",) vent deeper thermogenic gas. While there is a high abundance of gas, little evidence of bottom simulating reflectors (BSR), a widely accepted indicator of gas hydrate, has been found.