Regional Deep Water Salt Geology, Offshore Nova Scotia, Canada

Abu Chowdhury and Landis Newbanks
TGS-NOPEC Geophysical Company, Houston, TX

A pre-stack depth migration project has been undertaken to better image the deep-water salt and associated geology offshore Nova Scotia Canada. A regional 28,000 kilometers of 6 kilometer by 6-kilometer grid, 2 dimensional seismic data is being used. Seismic stacking velocities from the pre-stack time migrated volume were used to create a velocity model with which to migrate the sediments. The top salt is interpreted from the reflection character and geometry of the sediment migration data. The sections below are then migrated with salt velocity in an attempt to image the base salt that is subsequently interpreted from seismic character, regional geology and flatness of common image gathers. Salt interpretation from time data, water bottom multiples, top salt multiples, and cross- line interpretation picks posted in depth domain are integrated into the interpretation.

The pre-stack, depth-migrated data clearly reveal both autocthonous and allocthonous salt within the area. The Mesozoic and lower Tertiary sequences are also well recognized. The allocthonous salt bodies are locally rooted. Deflated autocthons loaded predominantly by Cretaceous sediments commonly exhibit rollover structures. Diapiric salt structures and salt canopies are common in the area. The salt canopies commonly show Roho structures with the leading edges prograding down slope. The salt movement is influenced by the deposition of pre-Tertiary sediment wedge that is significantly expanded in the Nova Scotia basin compared to the US offshore Gulf of Mexico. In majority portion of US Gulf, the relatively thick Tertiary sediment influx plays a key role in mobilizing salt.

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