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One of America's oldest oil and gas provinces, the Illinois basin encompasses approximately 60,000 square miles and spans 4 states — Illinois, Indiana, Kentucky, and Tennessee.
Production of oil and natural gas in the Illinois basin was concentrated in the late 19th and early 20th centuries, in an era when technology options were limited. Production has been primarily shallow oil - several billion barrels.
The majority of remaining hydrocarbon resources in the basin exists in unconventional settings — primarily in coal seams, Devonian-age shales, and low-permeability (tight) gas sands — and previously untapped deeper formations. Below 6,000 feet is virtually unexplored.
Estimated gas-in-place is 86 Tcf in Devonian shale and 21 Tcf in Coal Seams. To date, fewer more than 600 Shale wells and 100 CBM wells have been drilled. Development of gas production has been impeded by an under-developed gas pipeline infrastructure and inaccessible production data. | 
