Oil Quality and Value in the Deepwater Gulf of Mexico -- Its Influence on Exploration, Production, and Transportation Strategies

A. S. Kornacki, R. I. McNeil, S. J. Russell, P. O. Knigge, H. I. Halpern

The discovery of large oil and gas accumulations in the deepwater Gulf of Mexico demonstrates the petroleum potential of this frontier area. Because oil field development costs in the deepwater can exceed $1 billion, it is vital to understand how the properties of these oils influence their value and the methods used to produce and transport them.

In general, the shelf and slope areas of offshore Louisiana contain different types of crude oil. Most deepwater oil discoveries (e.g., Mars; Auger; Bullwinkle) contain sour crude (ca 1.0 - 2.5 wt% sulfur) that is enriched in asphaltenes, vanadium, and organic acids. Free bacterial gas is more common than free thermal gas in this sour oil province. The chemistry of these sour oils indicates that their properties principally are controlled by source effects: i.e., the deepwater oils are not simply immature or transformed varieties of sweeter shelf crudes. Deepwater oil discoveries in the Viosca Knoll lease area (e.g., Ram/Powell) and in the eastern Mississippi Canyon lease area (e.g., MC 383; MC 522), in contrast, contain sweet to marginally-sour crude. Although deepwater oils probably were generated by marine source rocks, these crudes contain unusual C₃₅₊ waxes.

The properties of deepwater oils influence how they will be produced and transported. Sour oils commonly contain high concentrations of water-soluble organic acids that may render toxic the brines produced with them. The presence of wax in deepwater oils requires special design considerations (e.g., pigging; wax inhibitors) for production and transportation systems in cold, deep water columns. Some deepwater oils will be more costly to refine -- the vanadium they contain "poisons" refinery catalysts, and their sulfur and organic acids can corrode refinery equipment operating at high temperatures.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995