The Reelfoot Rift / Exploration Assessment of Hydrocarbon Potential Based Upon Seismic, Geopotential and Sedimentary Characteristics

T. Joshua Stark
Hess Corporation, Houston, TX, [email protected]

The Reelfoot Rift is an element of the East Continent Rift Complex, a major belt of deformation modifying the Eastern Midcontinent with rift segments of both Precambrian and Cambrian age. While evidence is inconclusive, it is speculated that the Reelfoot Rift initiated during Keweenawan extension and was modified during Grenvillian collision. Renewed extension during the Middle Cambrian opening of the Iapetus Ocean resulted in rifting inboard of the craton margin and the syn-tectonic deposition of thousands of feet of primarily marine rift-fill sediments. It is interpreted that organic-rich shale source rocks equivalent to the Cambrian-aged Rogersville Shale (Conasauga Group) were emplaced within deep depocenters of the rift during syn-tectonic fill. The Rogersville Shale has been recognized in the Rome Trough by the USGS as a source rock linked with production from Cambrian-aged sediments of the Rome Formation and the Conasauga Group.

During late-stage rift subsidence (Upper Dresbachian / Lower Franconian), a major lowstand of the North American craton resulted in the deposition of an 830’ thick (gross) turbidite sequence within the deep depocenter of the Reelfoot Rift. Subsequent compression during the Alleghenian Orogeny inverted an interior margin fault upon the eastern flank of the depocenter, forming an eastward-vergent inversion anticline with over a vertical kilometer of structural development covering approximately 150 square miles. Analysis of geophysical logs suggests the presence of both tight sandstone porosity (avg. 5%) and hydrocarbon charge.

In addition, significant potential may be developed within Bonneterre Formation boundstone complexes forming along the rift margin. Observed test flow rates of formation fluids from these carbonate build-ups suggest the presence of reservoir quality P&P characteristics. Numerous structural and stratigraphic targets, evident from a regional seismic grid (3400 line miles 2D), also remain untested in this frontier province.

AAPG Search and Discovery Article #90154©2012 AAPG Eastern Section Meeting, Cleveland, Ohio, 22-26 September 2012