ABSTRACT

One of the largest gas fields in the South Louisiana Gulf Coast area, West Bastian Bay produces from beds of late Miocene age between 6,950 feet and 15,500 feet. Structurally, it is an anticline on the south, downthrown side of a fault whose throw exceeds 3,000 feet. The center of uplift has moved progressively northwestward a distance of two miles from its "X" Sand position near the southeast edge of the field. The fairly recent development of a new locus of uplift near the east edge of the field has given the field a double crest in uppermost Miocene beds. A small, long-quiescent fault with 60 to 100 feet of throw across the axis of the fold, and the east portion of an axial fault, separate the deep reservoirs in the northeast segment of the field from those in the other segments. The fact that gas columns in this area are thinner than elsewhere along the apex of the fold is believed due to the presence of the nearby East Bastian Bay field and to the eastward shaling out of the "W" and "X" Sands.