Abstract: Depositional Facies and Porosity Development at Coon Creek Field (Newman "Big Lime"), Leslie County, Kentucky

Stephen O. Moshier, Michael E. Stamper

Coon Creek field is a significant petroleum reservoir in the "Big Lime," Middle to Upper Mississippian Newman equivalent, in southeastern Kentucky. Initial production from select wells has exceeded 600 bbl of oil/day at drilling depths averaging 915 m (3300 ft). Facies patterns, dolomitization, porosity, and structure in this carbonate reservoir have been delineated by geophysical logs, subsurface mapping, and examination of cores and cuttings. The reservoir is set within a localized paleotopographic low on the unconformable surface of the underlying siliciclastic Borden Group; the Borden surface can express rapid relief of over a 10% grade within less than 300 m. Transgression across the exposed Borden surface resulted in the deposition of a complex system of carbonate lithofacies. C inoidal dolostones, representing shallow subtidal skeletal bars and banks, form the basal Big Lime (1.5-6 m thick). They are overlain by an atypical facies (30 m thick) of bryozoan grainstones/packstones, crinoid grainstones, and mixed skeletal wackestones/mudstones. The bryozoan facies are characterized by unfragmented fenestrates cemented by radiaxial-fibrous calcite. Stratigraphic distributions indicate the bryozoan facies were broad buildups with crinoidal flank and cap deposits and muddy skeletal off-mound facies, similar to deeper water Waulsortian mounds in other basins. Pellet and ooid grainstones represent moderate- to high-energy subtidal shoal deposits that covered the mound complex.

Hydrocarbon production is restricted in this field to the crinoid-bryozoan facies complex within the basal 30 m. Reservoir porosity and permeability have been enhanced by selective dolomitization of grainstones and fracturing related to postdepositional reactivation of basement faults.

AAPG Search and Discovery Article #90984©1994 AAPG Annual Convention, East Lansing, Michigan, September 18-20, 1994