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ABSTRACT: Submarine-Fan Delta Depositional Environment of the Pennsylvania Redfork Sandstone

Active exploration and development drilling for the Upper Pennsylvanian Red Fork sandstone has been going on since 1979 in the western part of the Anadarko basin of Oklahoma. The fine-grained, low-permeability gas and gas condensate reservoir produces at depths ranging from 12,000 to 14,000 ft from stratigraphic traps. Although drilling generally has been continuous through the years, producing the Red Fork play is very sensitive to gas price because of drilling depths and reservoir characteristics. The play is now mature, but because of the complex submarine-fan depositional environment, it is not easy to predict the good-quality reservoir sandstone.

Isopach maps, log shapes, lithologic information, and seismic data are all used to define the facies within the fan. In the Red Fork, most of the sand was deposited in the middle fan with the best reservoirs found in narrow channels of the suprafan lobes. Quality of the reservoir rock in the levee facies deteriorates significantly away from the channel. The gross morphology of interpreted suprafan lobes in the Red Fork arc compared to and show a similarity with the modern Mississippi submarine fan and suprafan lobes seen in the outcrop.

Using two-dimensional and three-dimensional seismic data to map the suprafan lobes and channel systems has proven very challenging in the Red Fork; however, careful integration of all well information with the seismic data will yield the best interpretation. Changes in amplitude are used to help define the presence or absence of sandstone and the relative quality of the reservoir.

AAPG Search and Discovery Article #90991©1993 AAPG Mid-Continent Section Meeting, Amarillo, Texas, October 10-12, 1993.