John J. Farrelly¹, Julie A. d'Ablaing¹
(1) BP-AMOCO, Houston, TX

Abstract: Into the Unknown, A History of the Discovery of the Giant Fields of the Western Mississippi Fan Foldbelt, Gulf of Mexico

Early interest in the stratigraphy and structuring along the central Sigsbee Escarpment has been pursued, resulting in the discovery of several giant accumulations within the Mississippi Fan Foldbelt, deepwater Gulf of Mexico. Initial work based upon mid 1980's 2D seismic indicated outboard and counter-regional dip, upon which the allochthonous salt canopy was riding and possibly masking large folds. In the first area wide sales, all but the exclusively subsalt features of the foldbelt were leased. Progress in assessing the foldbelt slowed with the price collapse of 1986. In 1987, Shell drilled the first foldbelt well, Atwater Valley 471 #1. The well mitigated the chief concern, reservoir, but was dry. By 1994 only four Trend features remained leased.

During 1993, BP Amoco's regional work suggested that potential of these large structures merited another look. In 1995 BP Amoco, in partnership with BHP, acquired several features that appeared to be a material.

Rumors of the 1995 Neptune discovery re-ignited industry interests. In 1998 two additional discoveries were made, Atlantis and Mad Dog.

One of the keys in exploring the area was imaging. Shallow salt sheets, seabed topography, and steep dip within the folds created a significant imaging challenge. Integrated teams addressed the issue aggressively, working with both proprietary 3D post-stack and pre-stack depth seismic volumes.

Recognition of the potential of the Trend, perseverance and technical innovation has unveiled a significant hydrocarbon province. Current work focuses on assessing these discoveries and progressing development options.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana