Anadarko Basin
Our Anadarko Basin wells produce from a variety of sands and carbonates in both stratigraphic and structural traps. During 2008 we drilled 19 gross (11.5 net) wells with a 90% gross (84% net) success rate.
Anadarko Woodford. We owned 117,000 net acres in the emerging Anadarko Woodford shale play of western Oklahoma as of August 2009. This includes 93,000 net undeveloped acres acquired in 2008. The remainder is held by production. Our acreage is strategically positioned within the window of thermal maturation for natural gas along the eastern flank of the Anadarko basin, extending across portions of Grady, Canadian, Blaine, Custer and Dewey counties. The Woodford shale underlying this acreage ranges from 75 to 250 feet thick, at depths ranging from 10,000 to 15,000 feet.
Industry peers began drilling horizontal Woodford shale wells in Canadian County in August 2007; as of year-end 2008, there were 17 rigs drilling in the play. Announced results have included initial daily production rates up to 8,300 Mcf of natural gas equivalent per well. Our economic model for the play is based on reserves of 5 Bcf to 7 Bcf per well. We have drilled 2 gross (1.9 net) horizontal Woodford wells in the play, and both are currently being completed.
Anadarko Atoka. As of year-end 2008, we owned 44,938 gross (27,566 net) acres in the emerging Anadarko Atoka Shale play of western Oklahoma and the Panhandle of Texas. Our acreage is focused in Ellis County, Oklahoma and Lipscomb County, Texas.
We sought acreage in the Atoka along trend with the development of the Novi Lime formation. The significance of the Novi Lime is that it serves as both reservoir and drilling conduit for the horizontal wellbore. Natural gas-charged Atoka shales surrounding the Novi Lime can be fracture-stimulated and produced from a wellbore in the Novi Lime. The Atoka shales range from 75 feet to 125 feet thick and are present throughout our properties.
As of February 23, 2009, 37 horizontal Atoka wells have been completed by industry peers, with initial production rates of up to 7,500 Mcfd. We drilled 2 gross (2 net) horizontal Atoka wells in 2008, 1 of which had a short lateral section. The 2 wells were productive, but not sufficiently to be considered economic.
Illinois Basin
We drilled 19 gross (17 net) wells in the Illinois Basin during 2008, developing fields and expanding our reserve base. Our production there is primarily crude oil from units comprised of shallow sand formations under water injection.
Michigan Trenton-Black River
Our Trenton-Black River project in and around Hillsdale County, Michigan continues to produce excellent results guided by proprietary 3-D seismic techniques. As of year-end 2008, we had completed 7 gross (5.8 net) operated wells in the play with 6 gross (4.9 net) of the wells completed as Trenton-Black River producers and 1 well temporarily abandoned. These producing wells were assigned average estimated recoverable reserves of 490 MBoe per well. Combined, these wells were producing an average of 550 gross barrels of oil per day during December 2008. Three of the 6 wells are capable of flowing in excess of the 200 barrels-per-day allowable set by the Michigan Department of Environmental Quality, and 3 are restricted by natural gas flaring restrictions, which will be removed once the wells are connected to a natural gas pipeline. A natural gas gathering pipeline has been installed and processing facilities are under construction to enable these flare-restricted wells to produce up to the 200 barrels of oil per day allowable rate.
At year-end 2008, we had approximately 65,418 gross (52,110 net) acres leased in the play and approximately 40 square miles of 3-D seismic on our acreage. During 2008, we acquired 20 square miles of 3-D seismic on our Chicago/Norad project. Interpretation of the seismic data identified up to 14 potential drilling locations. Four of these locations have been selected and permitted for drilling. We plan to acquire an additional 6.5 square miles of 3D seismic data during 2009.