Environmental Impacts of Coalbed Methane Production in the Powder River Basin, WY
Dr. Jennifer McIntosh, of the UA's Department of Hydrology and Water Resources, presents "Environmental Impacts of Coalbed Methane Production in the Powder River Basin, WY"
Coalbed methane (CBM) comprises a significant portion of natural gas resources worldwide; despite this, there are numerous environmental impacts associated with CBM production. In the Powder River Basin in eastern Wyoming, which is the 2nd largest CBM producer in the United States, there are over 24,500 gas wells to date. In 2007, there was a moratorium on drilling to protect sage grouse, which has since been lifted. Coalbed methane in the Powder River Basin is generated by microorganisms (methanogens) and adsorbed onto coal surfaces. Large volumes of groundwater must be extracted to lower the hydrostatic pressure and release the gas. Over 17,000 gallons of water are pumped from each CBM well per day, causing the water table to drop ~60 m. Stable isotopes of coalbed formation waters are isotopically-depleted relative to modern precipitation, suggesting that these groundwaters were recharged during the Last Glacial period (>18,000 years ago). Most waters produced from CBM wells have low enough salinities to be discharged to surface reservoirs, streams, and evaporation ponds, or used for agricultural irrigation. Application of CBM waters with high Na contents to agricultural fields can decrease soil quality and crop yields, and high discharges of CBM waters to surface streams (especially during natural low flow periods) can impact riparian areas and cause tree die-off. These water quality issues have led to an on-going U.S. Supreme Court battle between the states of Wyoming and Montana.
