Fangjian 'Jack' Xue¹, Joel S. Watkins²
(1) Schlumberger, Houston, TX
(2) Texas A&M University, College Station, TX

Abstract: Deep potential in the inner Louisiana shelf, Gulf of Mexico

Cenozoic depocenter shifting through the Gulf Coast area created a lithofacies "sandwich" pattern in productive section beneath the present-day inner western Louisiana shelf. In Early Miocene, the inner western Louisiana shelf was a slope environment which received large amounts of sand-rich lowstand deposits from a source located in the western Louisiana lower coast. In Middle Miocene, this area was sediment-starved and dominated by deepwater shale deposits due to shift of the depocenter to the east of the Mississippi Delta. In Late Miocene and Pliocene, this area received thick sand-rich highstand deltaic deposits due to a westward shift of the main depocenter.

This lithofacies "sandwich" pattern is reflected in seismic imagery. The pattern has significant impact on hydrocarbon exploration and development in this area. Shallow, high seismic amplitude Upper Miocene and Pliocene deltaic sands are the main drilling targets. Most exploration drilling was terminated within mid-depth Middle Miocene shales with weak seismic amplitudes. The deep, high seismic amplitude Lower-Middle Miocene lowstand sands are rarely drilled. The fact that the deep Miocene oil and gas pools found in offshore areas are mainly in submarine fan sediments with porosity between 20-35% below 15000ft implies the economic potential in deep Miocene deposits. With the improvement of geological understanding and technologic capability, the deep Miocene lowstand deposits beneath the inner shelf, the analog to the Plio-Pleistocene lowstand deposits on the slope, will become important targets in future Gulf of Mexico exploration.

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