Marine Sedimentation and Oil Accumulation on Gulf Coast: ABSTRACT

Abstract

The sands of the Gulf Coast are prolific petroleum reservoirs. Deposition of these sands has taken place during a series of advances and retreats of the sea. A resume of the sedimentation and depositional conditions occurring in a advance, or transgression, and in a retreat, or regression, is presented. The resulting stratigraphic sequences, the marine overlap and marine offlap are discussed under ideal conditions, and illustrated by electrical log profiles. Particular reference is made to possibilities for petroleum accumulation as influenced by stratigraphic conditions. Sands deposited in a transgressive sea, such as the Cockfield, upper Wilcox (Sabinetown), Marginulina-upper Frio, and lower Miocene sands, are believed to present conditions favorable for the migration, accumulation, and recovery of oil. Although sands deposited in a regressive sea, such as parts of the Rockdale (Wilcox), lower Yegua, Vicksburg-lower Frio, and Catahoula, are not considered theoretically as favorable, local structural or environmental conditions may effect excellent reservoirs. The compound features representing a invasion followed by a retreat, or the reverse, are also considered and electrical log profiles presented. The economic significance in petroleum geology of the resultant sand wedges and shale wedges is discussed. End_Page 930------------------------------ It is suggested that both local and regional studies of producing horizons be made in the light of the theory of the marine overlap. End_of_Article - Last_Page 931------------