Calling it “the last green splotch,” a Bernstein Research E&P resource report about the Illinois Basin concludes that “it is the only remaining oil-producing basin without a well-established resource play” such as Williston Basin’s Bakken and Three Forks or the Denver Julesberg Basin’s Niobrara play.

“It is an oil-producing basin with a legacy of conventional, but not large, production,” according to the report.

Bernstein also notes that evaluating the basin is difficult because “Indiana and Illinois have extremely poor data reporting for oil and gas in comparison with states like Texas, Oklahoma, North Dakota, and even Pennsylvania and Ohio. This poor reporting hampers easy research.”

About the Illinois Basin

The Illinois Basin includes most of Illinois and Indiana, western Kentucky and small areas of southwestern Ohio and northwestern Tennessee. According to a 2007 USGS assessment of undiscovered oil and gas resources, there is a mean of 214 million barrels of oil, a mean of 4.65 trillion cubic feet of natural gas, and a mean of 24 million barrels of natural gas liquids.

The total petroleum systems (TPS) identified in the basin are the Precambrian to Cambrian, Ordovician Ancell/Maquoketa; Devonian to Mississippian New Albany; and Pennsylvanian coal and shale. The Precambrian to Cambrian TPS, however, encompasses both source rocks in the Cambrian Eau Claire Formation and older, hypothetical source rocks in the deeper parts of the basin.”

Illinois Basin Targets

The Bernstein report singled out unconventional drilling targets in the basin and a theoretical Ordovician shale:

• Mississippian: Ste. Genevieve, St. Louis, Warsaw, McClosky, Tar Springs, Palestine, Salem, Cypress, and Waltersburg (similar in concept to a Mississippi Lime in Oklahoma).

• First Devonian: New Albany shale, pursued typically as a gas target (analogous to Barnett).

• Second Devonian: Lingle or perhaps Geneva or Boyle Dolomite (Grand Tower Formation), directly underlying New Albany shale as an oil target (analogous to Bakken/Three Forks).

• Silurian: slightly older rocks deeper/below New Albany but believed to be sourced from New Albany. This play is also referred to as the Hunton play.

• A second potential source rock – Maquoketa shale – is the same age (Ordovician) as Utica shale.

“The New Albany shale was pursued as a shale gas play. We see relatively little focus on the play, which failed to compete with other more prolific shale gas plays. More interestingly, a Devonian dolomite below the New Albany (analogous in age and geometry to the Bakken) is being pursued.

“If the opportunity is truly analogous to Bakken wells in the 1,000-5,000 feet depth range, then perhaps 400,000 to 800,000 acres of opportunity at F&D costs below $20/barrel could be present.”

The report continues, “An emerging Miss Lime in the Illinois Basin may also succeed. Hydraulic fracturing of the overlying Mississippian formations above New Albany, in analogy to the Miss Lime of Oklahoma, could also be pursued with unclear economics, but potentially not dissimilar from the Devonian dolomite.”

According to HIS Inc., a CountryMark Energy Resources discovery in Vigo County, Ind., #1 Hulman Farms, was tested in Middle Devonian Lime and flowed approximately 400 bbl. of oil per day. The venture was drilled to 1,600 ft.

According to Bernstein, the majority of hydrocarbon-generative potential lies in New Albany, and its maximum thickness is near the point where Illinois, Indiana, and Kentucky meet. Four billion barrels of petroleum have been produced through 1996 with an additional 8 billion barrels left in conventional reservoirs (11.5 billion barrels of original oil in place).

“We also note that the New Albany has generated 140 billion barrels of oil with typical API gravity average 38 degrees with 0.3% sulfur. As a result, the region is home to a significant resource.”