ABSTRACT

Oil and gas production in South Texas occurs in four arcuate trends in the northwest flank of the Gulf Coast geosyncline. These trends commonly are called the Carrizo-Wilcox, Jackson-Yegua, Frio-Vicksburg, and Miocene trends, with more emphasis placed on their hydrocarbon content than their correct stratigraphic nomenclature.

The trends occur within the subsurface formations of the Gulf Coastal Plain. They represent subsurface zones where hydrocarbons have accumulated because of either (1) optimum coincidence between the occurences of suitable reservoir rocks and structural anomalies, or (2) sufficient changes of physical properties within the reservoir rocks. The reservoir rocks most commonly are sand lithofacies.

Cross sections published by the Corpus Christi and the San Antonio Geological Societies are very useful in analyzing these trends. They show the occurrences of sand facies along depositional strike and up-and downdip, to which oil and gas production can be related.

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