Louisiana Shelf:  Timbalier Bay and Bay Marchand Salt Domes

The configuration of the salt domes had come into question by the client.  The directive given to IGC was to determine the possibility and extent of the salt overhang. Several publications were available on the Bay Marchand and Timbalier Bay salt domes. All publications described the as deep seated salt domes. The top of salt was defined by approximately 320 well penetrations.  Only 1well with a base of salt occurs on Bay Marchand Dome. High amplitude gravity minima are associated to the two salt domes which is generally considered indicative of deep seated attached salt domes. However the 3D gravity based EarthModel interpretation of the domes determined:

  • Bay Marchand detached but shows welding on its North side with base/overhang depth ranging from 14,000’ in the south to 23,000’ in the north
  • Timbalier Bay is totally detached with a base/overhang depth ranging from 19,000’ on the west to 16,000’ elsewhere

The 3D EarthModel utilized:

Commercial land & water bottom gravity surveys.

Basement structure interpretation based on commercial aeromagnetic data.

Well salt tops

Well density logs

Well & seismic velocities


Configuration of the 3D EarthModel:

400 sq miles for Timbalier Bay and Bay Marchand domes

Total Model Area 8200 square miles

Total Model Depth extent 150,000 feet

All Horizons and Layers Gridded at 500 foot interval

  • 5 Non-Salt Control Layers
  • Bathymetry/Topography
  • Moho
  • Lower Crust
  • Magnetic Basement
  • Mid-Jurassic Sequence Boundary (MJS)
  • 2 Salt Control Layers
  • Autochthonous Salt from IGC Louisiana SaltWorks interpretation
  • Allochthonous Salt from IGC Louisiana SaltWorks interpretation
  • 25 Horizontal Density Layers