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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 73 (1989)

Issue: 1. (January)

First Page: 24

Last Page: 39

Title: Exploring for Subtle Traps with High-Resolution Paleogeographic Maps: Reklaw 1 Interval (Eocene), South Texas

Author(s): T. P. Bulling (2), J. A. Breyer (3)


With sufficient well control, high-resolution paleogeographic maps can be made using log curve shapes and sand-body geometry to interpret depositional environments within genetic increments of strata. High-resolution paleogeographic maps depicting the depositional history of the Reklaw 1 interval provide a basis for prospecting for subtle traps in the updip Reklaw trend in south Texas. The Reklaw 1 interval began with sand being carried southwestward by longshore currents to form the barrier bar that became Atkinson field. The hydrocarbons were trapped by the updip pinch-out of barrier-bar sand into lagoonal mud. Stratigraphic traps similar to Atkinson field could be present along depositional strike if the sand in the field were part of an extensive barrier-bar system. >

After the barrier bar formed, distributary mouth bars prograded seaward, depositing the bar-finger sands that became the Hysaw and Flax fields. Subtle structural traps could be present today where small up-to-the-coast faults associated with the Sample fault system cut the bar-finger sands downdip from established production. Farther down paleoslope, the distributary channels began to bifurcate and the distributary mouth bars coalesced to form a broad delta-front sheet sand. Burnell, Hondo Creek, and Runge West fields produce from this sheet sand at the unstable shelf margin. A rapid rise in relative sea level terminated the Reklaw 1 interval.

Many of the oil and gas fields still to be discovered in the United States are in mature petroleum provinces where much of the remaining oil and gas probably resides in subtle traps. High-resolution paleogeographic maps are the key to finding these subtle traps.

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