Abstract: A Petrophysical Model for Delta-Front Deposition in the Pennsylvanian Cross Cut Sandstone, Runnels County, Texas

HENDERSON, S. K., Halliburton Energy Services, Odessa, Texas andG. B. ASQUITH, Department of Geosciences and The Center for Applied Petrophysical Studies, Texas Tech University, Lubbock, Texas

Deltaic facies often exhibit different reservoir properties and, as a result, successful exploration strategies for productive sandstones depend upon the delineation of individual facies. Facies identification is relatively straightforward, provided adequate core and well control exist; however, in fields where cores are rare, identification of facies must rely heavily upon observed log signatures and reservoir geometry. Sediment characteristics, log responses, and sand body geometry are employed to depict the depositional setting of the Pennsylvanian (Missourian) Cross Cut sandstone in the TWP and Busher fields of Runnels County, Texas. A majority of the Cross Cut in these two fields is interpreted as delta-front sand that was deposited at the distal terminus of a prograding delta lobe. Longshore reworking has resulted in a sand body that is asymmetrical about the axis of the distributary mouth bar/channel trend.

The distribution of the delta-front Cross Cut sandstone with respect to its fluvial feeder system is explained through a depositional model that invokes progradational deposition followed by marine transgression. Log-derived relative sea level curves, together with petrophysical comparisons of shales underlying and overlying the Cross Cut sandstone, support a major progradational/transgressive event.

AAPG Search and Discovery Article #90936©1998 AAPG Southwest Section Meeting, Wichita Falls, Texas