Depositional Framework and Reservoir Distribution of Red Fork Sandstone in Oklahoma

John W. Shelton, Richard D. Fritz, Chris Johnson

The Middle Pennsylvanian Red Fork sandstone formed as a result of southward progradation across most of Oklahoma. The Red Fork is one of several cyclothemic (transgressive-regressive) sequences developed within the Desmoinesian Cherokee Group. Sea level changes and stability of the depositional area were dominant factors in determining the general stratigraphic characteristics of the Red Fork interval. Progradation was episodic, with sand deposition in the distal, more subsident part of the basin during lower sea level stands, and valley-fill deposition in the more stable areas during sea level rises.

Red Fork sandstone trends depict an alluvial-deltaic complex covering most of Oklahoma. The Red Fork consists primarily of alluvial-valley and plain (fluvial) bodies in the northern part of northeastern Oklahoma, alluvial-deltaic bodies in most of the remaining parts of the shelf area, and off-shelf submarine-fan and slope/basin-floor complexes within the deeper part of the Anadarko basin.

Determination of reservoir trend and genesis requires integration of rock data and log data, with logs calibrated to cores for estimating depositional environments and assessing diagenetic overprints.

Much of the oil and gas has been trapped in stratigraphic traps, some of which represent channelized sandstones with trends at high angles to the structural grain. Secondary chlorite, in particular, is associated locally with development of productive reservoirs showing microporosity, high water saturation, and correspondingly low resistivities.

AAPG Search and Discovery Article #91025©1989 AAPG Midcontinent, Sept. 24-26, 1989, Oklahoma City, Oklahoma.