From its discovery May 14, 1942 to January 1, 1965 Embar field produced 28,344,573 bbl 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 as it is incorporated with Martin San Andres field and Andector San Andres field. Up to 1,500 ft of sandstone and red shale of Tertiary, Cretaceous, and Triassic age overlie the Permian, which in turn is about 6,400 ft 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 Embar Ellenburger field beds no younger than Precambrian, Ellenburger, or basal Simpson are found.
The pre-Permian structure of 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 the earliest Permian. This structure is gently reflected through the Permian pay horizons owing to drape or to renewed uplift along the old axes. The Devonian is productive on the south flank of the Embar structure, owing to up-dip pinchout complicated by faulting.
Although analyses reveal that oils from the different horizons of Embar field are similar, the waters are distinctive. This does not damage the concept that the oils from the upper and lower Clear Fork, Devonian, and Ellenburger are probably from the same source. This source may have been dark shales of Pennsylvanian and Mississippian age which were preserved in structurally lower areas. It is theorized that migration may have started 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, then Permian strata, and/or fault planes, until it reached the Ellenburger and Devonian. From these horizons the oil may have gradually migrated vertically to the lower and upper Clear Fork horizons.
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Fluids in Subsurface Environments
Sourced from a 1964 symposium on The Geology of Fluids, this publication brings together an array of papers dealing with many aspects of the subject. Included are 18 papers covering basin-specific research as well as basic research on fluids in subsurface environments.