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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 47 (1963)

Issue: 12. (December)

First Page: 2077

Last Page: 2077

Title: Embar Field, Andrews County, Texas: ABSTRACT

Author(s): Jacob L. Williams

Article Type: Meeting abstract


From its discovery, May 14, 1942, to January 1, 1963, the Embar field produced 26,543,022 barrels of oil from pays in the Grayburg, upper Clear Fork, lower Clear Fork, Devonian, Fusselman, and Ellenburger. San Andres production on the Embar structure is not included in this figure since it is incorporated with the Martin San Andres field. Up to 1,500 feet of sandstone and red shale of Tertiary, Cretaceous, and Triassic age cover the Permian which in turn is about 6,400 feet thick and directly overlies a major unconformity. Beds ranging in age from Pennsylvanian to Precambrian are present beneath this unconformity, but within the limits of the Embar Ellenburger field, beds no younger than Precambrian, Ellenburger, or basal Simpson are found.

The pre-Permian structure of the Embar field is an anticlinal fault block which is part of a much larger anticlinorium. The structure was peneplaned following its uplift in late Mississippian or early Pennsylvanian time and again in late Pennsylvanian or earliest Permian. This structure is faintly reflected through the Permian pay formations because of drape or renewed uplift along the old axes. The Devonian is productive on the south flank of the Embar structure in updip pinchouts complicated by faulting. Although analyses reveal that oils from the different formations in the Embar field are similar, waters are distinctive. This does not damage the concept that the oil from the upper and lower Clear Fork, Devonian, and Ellenburger are probably from the same source. This source may ha e been dark shales of Pennsylvanian and Mississippian age which were preserved in structurally lower areas. It is theorized that migration may have begun in post-Clear Fork time when all the present reservoirs were covered. From the source beds the oil may have followed the unconformity at the base of the Permian strata, then fault planes, until it reached the Ellenburger and Devonian. From these formations the oil may have gradually migrated vertically to the lower and upper Clear Fork beds.

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Copyright 1997 American Association of Petroleum Geologists