--> ABSTRACT: Exploring for Subtle Traps with High-Resolution Paleogeographic Maps, by T. B. Bulling and J. A. Breyer; #91030 (2010)

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Exploring for Subtle Traps with High-Resolution Paleogeographic Maps

T. B. Bulling, J. A. Breyer

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 forms the reservoir in Atkinson field. The hydrocarbons are trapped by the updip pinch-out of barrier-bar sand into a lagoonal mud. Stratigraphic traps similar to Atkinson field could be present along depositional strike if the sand in that field were part of a more extensive barrier-bar system. After the barrier bar formed, distributary-mouth bars prograded seaward depositing the bar-finger sands that are the reservoirs in Hysaw and Flax fields. Subtle structural traps co ld be present where small down-to-the-north faults associated with the Sample fault system cut the bar-finger sands downdip from the established production. Farther down paleoslope, the distributary channels began to bifurcate and the distributary-mouth bars coalesced to form a broad delt-front sheet sand. Burnell, Hondo Creek, and Runge West fields produce from this sheet sand near the unstable shelf margin. A rapid rise in relative sea level terminated deposition of the Reklaw 1 interval. Many of the oil and gas fields remaining 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 may be a key to finding these subtle traps.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.