The primary production in the University Waddell field in Crane County, Texas, is obtained from Devonian siliceous carbonates. Since its discovery in 1948, the field has produced 42 million bbl of oil through primary and secondary production.

The field's structure is an asymmetric anticline created by the upthrown side of a reverse fault. The anticline dips steeply into the fault on the west side of the crest and dips gently away from it on the east. The seal and source rock for the field is the Woodford Shale (Devonian), a black pelagic shale. Updip migration from the Woodford provided the source for the three productive zones in the reservoir rock. Production is directly related to fracture porosity (7 to 12%) in beds with abundant replacement chert. Permeability through the productive zones is discontinuous and generally low (less than 5 md). The fractures in the Devonian siliceous limestones developed as a response to Pennsylvanian compression that created the reservoir structure.

The siliceous lithologies make up 60% of the Devonian sequence. The cherts are black, white, or gray and occur in brecciated or massive beds. Associated limestones are light-gray bioclastic packstones.

The chert is thought to be of secondary origin. The silica was derived from in-situ spiculites, locally reprecipitated as chert. A basinal environment is interpreted for the Devonian siliceous limestone and carbonate units. The Devonian carbonates deposited after the Silurian pelagic shales indicate a period of shallowing in the basin.

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