Possible Future Petroleum Provinces of United States Western Gulf Basin--Pleistocene: ABSTRACT

Abstract

Hydrocarbons in sediments of Pleistocene age have been found in 56 fields located mainly offshore from Louisiana. The Pleistocene section of the western Gulf basin has potential for significant additional reserves of hydrocarbons. The sequence consists of 3 gross depositional facies, in ascending order, (1) deep-water bathyal sediments, (2) neritic sediments, and (3) continental deposits. The maximum thickness of the Pleistocene exceeds 10,000 ft near the outer edge of the continental shelf in the western Gulf basin. The lithologic characteristics, facies, and types of traps in which the accumulations are present are similar to those of the underlying Pliocene and Miocene beds, which contain major reserves. The greatest potential is in an area of 15,000 sq mi on the outer continental shelf offshore from Louisiana and Texas. In this area, the overall objective section, the neritic interbedded sandstone and shale facies, is from 3,000 ft to more than 8,000 ft thick. Approximately 1/3 (4,300 sq mi) of this area is in an early stage of development, and 2/3 (10,700 sq mi) is unexplored. Most of the reserves found to date are in the continental and neritic facies of the lower Pleistocene. The area of greatest potential is indicated by several factors. Potential source and reservoir rocks of the Pleistocene neritic facies are similar to those of the older, highly productive Tertiary section. Structural and stratigraphic conditions favoring the entrapment of oil occur as commonly in the most favorable Pleistocene area as in nearby areas of prolific Tertiary fields. The area of favorable stratigraphy on the outer continental shelf is underlain by many diapiric structures. Significant discoveries from marine Pleistocene sediments in recent years afford direct evidence that the section is a major objective for future exploration. In the past, this section as a potential source of hydrocarbons has been downgraded by some workers because of its relatively young age. Drilling and producing capabilities are now sufficiently advanced to permit economical operations over most of the continental shelf. However, major hydrocarbon reserves are required to justify the extremely high operating expenses in the deep-water area. The continental slope of the Gulf of Mexico offshore from Texas and Louisiana is also underlain by a large volume of Pleistocene sediments, but its potential cannot be assessed at our current state of knowledge. End_of_Article - Last_Page 1789------------