Coal-Bed Natural Gas Production and Gas Content of Pennsylvanian Coal Units in Eastern Kansas
Published:December 01, 2009
K. David Newell, Timothy R. Carr, 2009. "Coal-Bed Natural Gas Production and Gas Content of Pennsylvanian Coal Units in Eastern Kansas", Unconventional Energy Resources: Making the Unconventional Conventional, Tim Carr, Tony D’Agostino, William Ambrose, Jack Pashin, Norman C. Rosen
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Middle Pennsylvanian coal units in eastern Kansas produce commercial quantities of coal-bed natural gas. Annual coal-bed natural gas production in 2008 was 49.1 billion cubic feet (Bcf) (13% of state output); cumulative production since 2000 is 165 Bcf. Coal beds are commonly less than two feet thick and are mostly produced by vertical wells at 80- to 160-acre spacing. Wells usually have comingled gas production from several coal beds. The main producing region is a fourcounty area (Labette, Montgomery, Neosho, and Wilson counties) in southeastern Kansas immediately north of the Oklahoma state line. Most wells are not prolific; their average maximum production rate is approximately 67 mcf/day, peaking about 14 months after initial production. Decline rates are low, as some coalbed natural gas wells have produced 15 years and beyond. North-northwest–south-southeast trending production fairways can be defined by mapping maximum production rates. These fairways generally correlate to where coal beds are individually and compositely thick. The most prolific wells in the thickest coal units record maximum production rates as great as 615 mcf/day.
The median as-received gas content for coals in southeastern Kansas is 139 scf/ton, with maximum gas content of approaching 400 scf/ton. Gas content in eastcentral and northeastern Kansas coal beds generally runs half that of southeastern Kansas, indicating economics of coal-bed natural gas production are harsher northward. Coals increase in depth westward at a rate of approximately 20 feet per mile. Their gas content commensurately increases by 10 to 20 scf/ton for each 100 feet of burial. Thin (<4 foot) black shale beds interbedded with the coal units may have commercial potential, for their as-received gas content can be great as 65 scf/ton, but 20 scf/ton is the median of all shale samples assayed.