Some Keys to Exploration in the Forest City Basin
Marvin P. Carlson. Nebraska Geological Survey, University of Nebraska, Lincoln NE 68583-0996 [email protected]
Approximately 35 million barrels of oil have been produced from the pre-Mississippian formations within the Forest City basin. Most production has been obtained from the Hunton (Devonian) and Viola (Ordovician). Large areas of the basin remain unexplored, particularly in view of the small geographic extent of the producing fields. In addition, the vast majority of the drilling penetrated only to the top of the Hunton. One key to exploration is the source of the oil. Research has suggested scenarios including in-basin generation from the Simpson shales and vertical migration, long-distance migration from the Woodford (Chattanooga) of Oklahoma, and the possibility of an in situ origin within the reservoirs. Stratigraphic keys include the occurrence of most reservoirs in carbonates having a facies relationship with an overlying shale (Chattanooga/Hunton and Maquoketa/Viola). Northward across the basin, a carbonate buildup replaces these shale facies in both intervals. Original porosity has been enhanced by dolomitization. Other excellent potential reservoirs occur in the Mississippian, Silurian, and Simpson. Tectonic patterns, in both trend and timing, are important keys. Nearly all current fields have a structural component, often faulted. Regionally, structures both large and small appear to have resulted from rejuvenation of the original basement architecture. Keys to be utilized in exploration include origin and migration paths of the oil, location of porosity trends associated with the carbonate-facies buildups, and architecture of the underlying tectonic patterns controlling field structures. Integrating these keys for the region with more sophisticated exploration techniques should greatly enhance the production potential for the Forest City basin.
AAPG Search and Discover Article #90067©2007 AAPG Mid-Continent Section Meeting, Wichita, Kansas