ABSTRACT

The studied area includes Townships 22-24 North, Ranges 13-19 West in contiguous portions of Woods, Woodward, and Major Counties, Oklahoma. The objectives of the study are: (1) the reconstruction of the paleotopography on the Hunton erosional surface; (2) the delineation of possible porosity-permeability trends within the Hunton Group; (3) the determination of the relationship of structure, porosity-permeability trends, and paleotopography to the accumulation of petroleum; (4) completion of detailed field studies of the major Hunton producers in the area.

The Hunton Group in the area of investigation consists dominantly of dolomite and dolomitic limestones and ranges in thickness from 17 feet to 407 feet. The Hunton Group is divisible into three Zones (A, B, and C) on the basis of electrical and gamma ray log characteristics related to a lithological zonation. In general, it is believed that only the Silurian portion of the Hunton Group is present in this area. The Hunton Group lies with apparent conformity on the underlying Ordovician Sylvan shale and is unconformably overlain by the Kinderhook-Woodford shale sequence.

The structural configuration of the Sylvan shale is that of a southwesterly dipping homocline modified by several south plunging structural "noses". Three small faults and one structural closure are the only features which break the fairly regular surface. This same structuring is reflected at the Hunton level.

As defined by variations in the thickness of the Kinderhook-Woodford shale sequence, a dendritic stream system was developed upon the Hunton surface during the post-Hunton, pre-Woodford hiatus. These streams channeled deeply in the Hunton Group, removing substantial thicknesses of strata and outlining a well-developed paleo-drainage pattern.

The best porosity and permeability in the Hunton Group are in the basal portion of Zone A. Near the subcrop edge of this interval and near faulting the porosity and permeability are particularly well developed. This zone accounts for most of the Hunton production in the area.

A combination of structure, porosity-permeability development, and paleotopography have resulted in the formation of several petroleum accumulations in the Hunton Group. Ten fields in the area are producing or have produced from the Hunton. As of January, 1972 the cumulative production from the Hunton fields in the area was approximately five million barrels of oil and 58 billion cubic feet of gas. This production is dominantly from the basal portion of Zone A where it subcrops beneath the Hunton unconformity. The area has the potential for many other similar type accumulations.