Characteristics of Carbonate Reservoirs in Kentucky

Patrick J. Gooding
Kentucky Geological Survey, University of Kentucky, Lexington, KY

Carbonates comprise more than 70 percent of the sedimentary record in Kentucky and have considerable significance and economic and scientific importance. They contain most of the fossil record and provide information that permits reconstruction of past environments. Carbonates serve as reservoir rocks to most of Kentucky's petroleum reservoirs and are host rock for many minerals.

Understanding carbonate reservoirs through the examination of cores is often challenging because of the complexity of carbonate diagenesis. This examination provides a better understanding and greater knowledge of those reservoirs and the nature and characteristics of the environments and the depositional history. It also provides a better understanding of the origin and occurrence of hydrocarbons, tectonic setting, diagenesis, paleoclimate, paleogeography, and rock properties of the reservoir.

Carbonates from Kentucky's reservoirs were deposited in a variety of marine environments ranging from tidal flats to reefs to deep marine. They are important oil and gas reservoirs and the most prolific producers of hydrocarbons in Kentucky. The original texture and porosity of the reservoir carbonates are highly variable because of the wide range of environments in which they were formed. Porosity types, texture, fabric, grain composition, and carbonate types vary considerable depending on the depositional setting.

Effects of tectonics; fractures and faults, sedimentation, and stratigraphic cycles can be observed in the reservoir cores. In addition, variation in minerals, dissolution features including karst and solution collapse breccias, patterns, colors, bedding, hydrothermal activity, and compaction can also be observed. The effects of diagenesis, including compaction, cementation, and dolomitization, can also be recognized.