Results of coalbed-methane drilling, Mylan Park, Monongalia County, West Virginia
The Department of Energy National Energy Technology Laboratory funded drilling of a borehole (39.64378°N., 80.04376°W.) to evaluate the potential for coalbed-methane and carbon-dioxide sequestration at Mylan Park, a public park in Monongalia County, W. Va. The total depth of the borehole was 2,525 feet (ft) and contained 1,483.41 ft of Pennsylvanian coal-bearing strata, 739.67 ft of Mississippian strata, and 301.93 ft of Devonian strata. The drill site was located directly over abandoned mines in the Pittsburgh and Sewickley coal beds. Coal cores from remaining Pittsburgh and Sewickley coal-bed-mine pillars were cut and retrieved for desorption from both mines. In addition, coals were cored and desorbed from the Redstone, Pittsburgh roof coal interval, Little Pittsburgh, Elk Lick, Brush Creek, Upper Kittanning, Middle Kittanning, Clarion, Upper Mercer, Lower Mercer, and Quakertown coal beds and coal zones. All coals are Pennsylvanian in age and are high-volatile A bituminous in rank. A total of 34.75 ft of coal was desorbed over a maximum period of 662 days, although most of the coal was desorbed for about 275 days. Measured raw-total-gas contents ranged from 0.43 standard cubic feet per ton (SCF/ton, an industry abbreviation) for the mined Sewickley coal bed to 130.98 SCF/ton for the Upper Kittanning coal bed. Volumes of residual gas were not measured; therefore, the gas volumes reported here should be regarded as minimum volumes. The amount of oxygen in the gas samples collected from the desorption canisters ranged from 2.55 to 20.13 percent. Methane contents ranged from 0 percent for one single canister from the Pittsburgh (WV–02–B3–4) and Little Pittsburgh (WV–02–CB3–2) coal beds to almost 81 percent for two canisters from the Clarion coal zone (WV–02–B3–16 and WV–02–B3–17), which suggests that all of the gas samples were contaminated to some degree by air. Therefore, all gas compositions reported have been normalized to remove the air. With a single exception (the Quakertown coal zone), the coals from the Mylan Park study area are thermogenic in origin with the isotopic composition of carbon (carbon 13, 13 C) in methane (expressed as δ 13 C in units of parts per thousand (per mil) relative to the Vienna Peedee belemnite (VPDB) standard) ranging from -32.39 to -50.66 per mil and ratios of methane to hydrocarbons of higher molecular weight ranging from 10 to 53. The Quakertown coal zone has a C 1 /C 2+ ratio of 913, suggesting that it contains some microbial gas. High-pressure carbon-dioxide adsorption isotherms were measured on composite coal samples of the Upper Kittanning coal bed and the Middle Kittanning and Clarion coal zones. Assuming that the reservoir pressure in the Mylan Park coals is equivalent to the normal hydrostatic pressure, the estimated maximum carbon-dioxide adsorption pressures range from a low of about 300 pounds per square inch (lb/in 2 ) in coals from the Clarion coal zone to 500 lb/in 2 for coals from the Upper Kittanning coal bed. The estimated maximum methane adsorption isotherms show that the coals from the Upper Kittanning coal bed and the Middle Kittanning coal zone are undersaturated in methane, but coals from the Clarion coal zone are close to saturation.