COMER, JOHN B., and NANCY R. HASENMUELLER, Indiana Geological Survey, Bloomington, IN, WAYNE T. FRANKIE, Illinois State Geological Survey, Champaign, IL, and TERENCE HAMILTON-SMITH, Kentucky Geological Survey, Lexington, KY

ABSTRACT: Gas Potential of New Albany Shale (Devonian-Mississippian) in the Illinois Basin

A study to update and evaluate publicly available data relating to present and potential gas production from New Albany Shale in the Illinois basin was conducted cooperatively by the Indiana, Illinois, and Kentucky geological surveys (Illinois Basin Consortium), and was partially funded by the Gas Research Institute. Deliverables included a plate of stratigraphic cross sections and six basin-wide maps at a scale of 1:1,000,000 showing (1) major structural features, (2) core locations, (3) structural elevation of the top of the formation, (4) total thickness, (5) average initial production/
initial open-flow from producing gas fields, and (6) vitrinite reflectance (Ro).

The New Albany Shale is an organic-rich brownish black shale present throughout the Illinois basin. Gas potential of the New Albany Shale may be great because it contains an estimated 86 tcf of natural gas and has produced modest volumes since 1858 from more than 60 fields, mostly in the southeastern part of the basin. Reservoir beds include organic-rich shales of the Grassy Creek (Shale), Clegg Creek, and Blocher (Shale) members. Limited geologic and carbon isotope data indicate that the gas is indigenous and thermogenic. Tmax data suggest that, statistically, gas generation begins at Ro values of 0.53% and may begin at Ro values as low as 0.41% in some beds.

New Albany Shale reservoirs contain both free gas in open-pore space and gas adsorbed on clay and kerogen surfaces. Natural fracturing is essential for effective reservoir permeability. Fractures are most common near structures such as faults, flexures, and buried carbonate banks. Based on limited data, fractures and joints have preferred orientations of 45-225 degrees and 135-315 degrees . Commercial production requires well stimulation to connect the well bore with the natural fracture system and to prop open pressure-sensitive near-borehole fractures. Current stimulations employ hydraulic fracture treatments using nitrogen and foam with sand as a propping agent.

AAPG Search and Discovery Article #90995©1993 AAPG Eastern Section Meeting, Williamsburg, Virginia, September 19-21, 1993.