A recent report by State Geologist Ronald Surdam and seven co-authors has recommended a moratorium on coal-bed methane (CBM) development in the western reaches of the Powder River Basin.

   The recommended moratorium is due to two findings in the report “An evaluation of coal-bed methane production trends in Wyoming’s Powder River Basin.” The report found that:
• The ratio of water produced per thousand cubic feet (MCF) of gas rises a hundred-fold as CBM development moves from east to west across the basin.
• The salinity and sodium absorption ratio (SAR) rises dramatically in the western reaches of the basin.

  

   Surdam’s report further states that implementing these changes would be a positive step in developing a strategy to minimize both produced water and animosity toward future CBM development.

   Only 500 copies of the report have been printed and is not available online.

  

   The report documented the past 10 years of CBM production history in the PRB, then predicted future gas and water production out to 2020.

   The report contrasted east and west production in the basin, noting that the eastern Upper, Middle and Little Powder River and Tongue River drainages produce an average of three barrels of water per thousand cubic feet of gas. Yet in the western drainages of Clear Creek and Crazy Woman Creek in the basin, the report predicts that energy companies would have to pump out 300 barrels of CBM water to tap one thousand cubic feet of gas.

  

   Research for the study also showed that salinity rises dramatically as CBM development moves from east to west across the Powder River Basin.

   For the above reasons, the report states: “This report strongly supports a moratorium on all CBM activity in the Clear Creek and Crazy Woman Creek drainages,” says the report in its final recommendations. “Historically, these areas have very little commercial gas, yet have produced immense quantities of water. Predicted production trends based on projected CBM wells indicate that these areas will contribute only 0.15 percent of gas produced in the future, yet will account for 20 percent of future produced water. A moratorium on future CBM activity in these two drainages would save 3.3 billion barrels of water (130 billion gallons).”
  

   Keith Clarey, a Geological Survey geohydrologist who contributed to the report, said the geology of the Powder River Basin is the root cause of the water problem.

  

   “The coal beds that are so near the surface near Gillette, dive down to a thousand-to-1,500 feet below the surface as you head west,” said Clarey. With the coal beds so deep, there’s a corresponding amount of water that has accumulated over the eons in and over the coal beds, he said – as many as 800 feet of water in the deepest reaches of Powder River Basin coal.

   The challenge facing the energy companies, said Clarey, involves complex calculations considering the current and projected market price for natural gas; energy costs in pumping out enough water to release the trapped gas in the coal seams; and the costs of transporting or treating the released CBM waters.

  

   Clarey said energy companies face an additional risk of not removing too much water, which might lead to a collapse of rock structures in on themselves, thereby cutting off the many fractures and pores that allow the gas to be tapped.
Clarey said Surdam was unavailable, as he was traveling out of state.
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