Moore, Michael G.¹, Gillian M. Apps¹, Bryan C. Delph¹ 
(1) BHP Billiton Petroleum (Americas) Inc, Houston, TX

ABSTRACT: Controls on Lower and Middle Miocene Reservoir Sand Distribution in the Ultra-Deep Water Gulf of Mexico

The ultra-deep water Gulf of Mexico has yielded several major Lower and Middle Miocene oil discoveries including Atlantis, Mad Dog, Tahiti, and Thunder Horse. Major hydrocarbon accumulations are possible because of the large volumes of reservoir quality sand that have been transported more than 100 miles basinward of the shelf edge. 
Three large Lower and Middle Miocene submarine fan systems are recognized in the 200 mile long arc from northeast Walker Ridge to eastern Mississippi Canyon. The reservoir quality sand distribution in these large systems is controlled by a combination of sediment composition, pre-existing topography, and accommodation space created by salt tectonism. 
The Walker Ridge and Western Atwater Foldbelt (WAFB) systems both extend basinward of the terminus of the deep salt sheet and are controlled by a combination of limited accommodation space and paleotopography created by minor salt withdrawal and depositional topography. The thickness of the Middle and Lower Miocene is similar in the two systems but the WAFB system is relatively sand-rich and the Walker Ridge system is relatively sand-poor. 
The Mississippi Canyon (MC) system was deposited on top of thick salt leading to very thick deposits of Middle and Lower Miocene sediments in the salt withdrawal basins. The distribution of reservoir quality sand is controlled by the location of the withdrawal basins and the intervening salt highs. While the maximum sediment thickness of the MC system is about twice that of the WAFB system, the percentage of sand is similar in both systems.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.