ANALYSIS OF RESERVOIR PROPERTIES AND CONTROLS IN THE COTTON VALLEY GROUP OF JONES COUNTY, MS

The Cotton Valley Group is an oil and gas system in the Upper Jurassic to Lower Cretaceous (152-140 Ma) in the Mississippi Interior Salt Basin and the Gulf coast region. Projected by the USGS to contain 30 million barrels of oil and over 600 billion cubic feet of gas, the Cotton Valley continues to be a productive hydrocarbon system both in Mississippi and regionally. This research investigates the controls on reservoir properties in a productive gas field in Mississippi. Using core and thin section analysis, this project will develop a depositional model for the Cotton Valley Group in the study area, and evaluate the diagenetic processes that have influenced the porosity and permeability of productive reservoirs in Glade Crossing Field.

Three sets of rock core samples, obtained from three wells at depths exceeding 16000 ft, were analyzed at the core sample and thin section scales. The core was logged to determine general lithologies, degree of lithification, grain size, texture, color, mixing, bioturbation, trace fossils, etc. Zones of interest, often intervals of consolidated sand or siltstone and adjacent gradational changes and contacts, were further studied at the pore scale through the analysis of thin sections. Reservoir analysis, basin characterization, and planned heat transfer studies will be conducted using samples generously provided by Venture Oil and Gas, Inc.

An additional objective of analyzing reservoir properties, such as porosity, permeability, and diagenetic alteration, is to improve understanding of the geothermal energy potential of the study area and other Cotton Valley wells in Jones County, Mississippi. Geothermal energy production is dependent upon identifying, producing, and maintaining natural hot water systems within subsurface basins.

This research will contribute to: understanding of the Late Jurassic to Early Cretaceous development of the Gulf of Mexico and Mississippi Interior Salt Basin, depositional environments and processes active during Cotton Valley deposition, hydrocarbon reservoir quality as determined by porosity and permeability, diagenetic alteration and its impacts on reservoir quality, heat flow as determined by geothermal gradient and thermal conductance of subsurface materials, and potential for geothermal energy production from the Cotton Valley.