--> Abstract: Two Decades of Oklahoma Coalbed-Methane Activity, 1988-2008, Brian Cardott, Article #90097 (2009)

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Two Decades of Oklahoma Coalbed-Methane Activity, 1988-2008

Brian Cardott1

1 Oklahoma Geological Survey

The Oklahoma coalbed-methane (CBM) play began with vertical wells to the Hartshorne coal (middle Pennsylvanian) in the Arkoma Basin in 1988. The play expanded to the northeast Oklahoma shelf in 1994. The first horizontal CBM wells were drilled in the basin in 1998. Through December 2008, 5,594 CBM completions were reported in Oklahoma—2,580 in the basin and 3,014 on the shelf. A peak of 677 CBM wells per year occurred in 2005.

Operators have targeted 14 coal beds on the shelf and 5 coal beds in the basin. The coals are high volatile bituminous to semianthracite rank. Of 1,519 horizontal CBM wells, 1,501 were in the basin and 18 were on the shelf, with laterals from 14 to 5,771 ft. Twenty-one wells perforated both the McAlester and Hartshorne coals, while an unknown number of wells in the basin were multiple-coal completions to both the upper and lower Hartshorne coal beds. On the shelf, 961 CBM wells were multiple-coal completions with two to nine coal beds. Of that number, 188 CBM wells were reported as completed to “Pennsylvanian” coals since 2000, complicating the identification of coal names, number, and depth intervals of coal perforations. About 290 wells on the shelf are commingled with noncoal lithologies including black shales such as the Excello, Little Osage, Nuyaka, and Oakley. Much of the gas from the Mulky-only CBM wells on the shelf is coming from the Excello Shale.

In general, coals in the basin are deeper, thicker, have higher initial gas rates, and have lower initial produced-water rates compared to CBM wells on the shelf.

 

 

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