ABSTRACT: Leasing Opportunities, Environmental Constraints and Oil and Gas Plays on the Shawnee National Forest

RORICK, ANDREW HAMMOND, U.S. Department of Agriculture Forest Service, Harrisburg, IL

The 265,500-ac (107,500-ha) Shawnee National Forest is located in southernmost Illinois, United States, between 88 and 90 degrees west longitude and 37 and 38 degrees north latitude. Most of this area forms the southern rim of the Illinois basin; the southwestern portion is part of the eastern flank of the Ozark Dome. Strata from the Ordovician through Pennsylvanian Systems are exposed on the National Forest. The eastern half of the forest is structurally dominated by faulting associated with the Reelfoot rift and Rough Creek graben.

The Land and Resources Management Plan for the Shawnee National Forest has recently been published. It authorizes oil and gas leasing, exploration and development (for the first time in over 15 years), and itemizes the environmental constraints that will be placed on leases. To summarize them: of the 220,000 ac (89,000 ha) in the federal mineral estate, 194,000 (78,500 ha) are available for lease; 40% of that acreage will be subject to special stipulations for environmental protection that are more restrictive than standard federal lease terms, up to and including "no surface occupancy."

The USDI Bureau of Land Management will schedule a lease-sale auction of the federal mineral estate in the Shawnee National Forest for some time in the autumn of 1992.

Potential oil and gas plays within the Shawnee can be grouped generically (based on information provided by the Illinois State Geological Survey).

Stratigraphic, structural, and combination stratigraphic/structural traps in:
1. Pennsylvanian and Mississippian strata (the majority of the oil produced in Illinois derives from Mississippian sandstone reservoirs);
2. Devonian, Silurian and upper Ordovician strata (the upper Ordovician Galena Group are the oldest petroleum-producing rocks known in Illinois);
3. Lower Ordovician to Precambrian rocks in the Reelfoot rift (up to 22,000 ft (6700 m) deep); or
4. Faulted- and fractured-rock plays in strata of any geologic age (about 32 of Illinois oil fields are known to be associated with faulting);
5. Silurian reefs and reef drape (about 42 of Illinois oil fields are reef-related);
6. Traps associated with basement paleotopography in lower Ordovician to Precambrian rocks (there have been shows of oil reported from Knox dolomites in Union County).

AAPG Search and Discovery Article #91013©1992 AAPG Eastern Section Meeting, Champaign, Illinois, September 20-22, 1992 (2009)