Abstract: The Stratigraphy and Petroleum Potential of the Lower Miocene, Offshore Galveston, and Jefferson Counties, Texas

By

Howard W. Kiatta
George Mitchell & Associates, Inc
Houston, Texas 77002

Lower Miocene sediments in the Southeast Texas coastal area can be divided into two distinct productive trends. The basal Miocene interval from the top of the Oligocene Discorbis upward to the Robulus charnbersi is a predominantly regressive marine sequence which reflects the gradual progradation of Miocene sands into this area. The overlying sequence from Robulus chambersi to Amphistegina (B) consists of deltaic and delta-related sediments which reflect continued marine regression and the encroachment of a large Lower Miocene delta system.

In the nearshore Galveston and High Island areas, the basal Miocene interval contains a series of attractive objective sands, most of which are above the abnormally pressured zones and occur at depths of less than 9500 feet. Further offshore, the younger Amphistegina (B) sands become more favorable exploration objectives.

Several Lower Miocene biostratigraphic zones are identifiable throughout the area of interest, and an attempt is made to relate each zone to particular lithologic conditions or depositional environments.

Because of the general southward movement of the Miocene shoreline and a relatively limited supply of sand, prospective Miocene sand trends in the Southeast Texas offshore occur in narrow "belts" which are approximately parallel to the present coastline. The identification of these favorable trends is essential to a successful exploration program in this area.

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