Relationships Among Fracture Porosity, Regional Structure, Dolomitization, and Hydrocarbon Production, Mississippian "Big Lime," Kentucky

Bruce R. Moore, Stephen O. Moshier

The Mississippian "Big Lime" (Newman Formation subsurface equivalent) has been a prolific producer of natural gas in southern and eastern Kentucky and neighboring states. The productive areas have been associated with broad anticlinal structures, but the majority of the production is from areas with no dominant structural traps. Broad synclinal regions in the thinnest portions of the unit often have the best production.

There is a definite relationship between fracture porosity and gas production. Successful wells are almost always located at fracture intersections or on prominent fractures, currently being located through the use of low-altitude infrared scanning and computer analysis.

The basal dolomite zone of the "Big Lime" is the best producing zone, with production increasing with dolomite thickness. The possibility exists that the thickest dolomite in this zone is along fractures and at fracture intersections. Therefore, previous isopach maps of dolomite thickness from widely spaced subsurface data may be inaccurate. The fracture system may have provided a migration pathway for subsurface dolomitizing solutions, and therefore may be the true control of production. Studies leading to better understanding of the distribution of dolomite in the "Big Lime" and variations in dolomite recrystallization textures and stable isotope composition are proceeding to test these relationships.

AAPG Search and Discovery Article #91041©1987 AAPG Eastern Section Meeting, Columbus, Ohio, October 7-10, 1987.