The Woodbine Kurten field trap is a stratigraphic sand lens surrounded by shale. This field is a significant discovery in Brazos, Grimes, and Madison Counties, Texas. Structure plays only a minor role in oil entrapment. The sand was deposited in a structural and topographic low demonstrated by comparing maximum pay sand thickness with a computer trend surface residual thick derived from Austin to Buda isopach map.

Sand migration southward down the East Texas trough was deflected westward by the Angelina-Caldwell flexure and caught in a sag at the Kurten field locality. The higher Madisonville nose to the northeast has essentially no sand at the crest. Structural elevation at Madisonville and on the Angelina flexure only serves to limit sand deposition.

Many porosity pod-type fields may result by looking for sags near a sand-shale regional boundary.

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