Coal bed methane extraction 67458 219359437 2008-06-14T21:21:34Z Edward 4261 link [[coalbed methane]] '''Coal bed methane extraction''' (CBM extraction) is a method for extracting [[methane]] from a [[coal]] deposit. ==Basic principles== The methane is absorbed into the solid coal matrix (coal macerals) and is released when the coal seam is depressurised. To economically retrieve reserves of methane, [[well drilling|wells are drilled]] into the coal seam, the seam is dewatered, then the methane is extracted from the seam, compressed and piped to market. The goal is to decrease the water pressure by pumping water from the well. The decrease in pressure allows methane to desorb from the coal and flow as a gas up the well to the surface. ==Areas with coal bed methane extraction== This process has resulted in the drilling of tens of thousands of gas wells, and extensive support facilities such as roads, pipelines and compressors. The use of this method is currently expanding in the [[Powder River Basin]] of northeast [[Wyoming]] and southeast [[Montana]]. Seven percent of the [[natural gas]] (methane) currently produced in the [[United States]] comes from CBM extraction. Methane from coalbed reservoirs can be recovered economically, but disposal of water is an environmental concern. Most gas in coal is stored on the internal surfaces of organic matter. Because of its large internal surface area, coal stores 6 to 7 times more gas than the equivalent rock volume of a conventional gas reservoir. Gas content generally increases with coal rank, with depth of burial of the coalbed, and with reservoir pressure. Fractures, or cleats, that permeate coalbeds are usually filled with water; the deeper the coalbed, the less water is present, but the more saline it becomes. In order for gas to be released from the coal, its partial pressure must be reduced, and this is accomplished by removing water from the coalbed. Large amounts of water, sometimes saline, are produced from [[coalbed methane]] wells, especially in the early stages of production. While economic quantities of methane can be produced, water disposal options that are environmentally acceptable and yet economically feasible, are a concern. Water may be discharged on the surface if it is relatively fresh, but often it is injected into rock at a depth where the quality of the injected water is less than that of the host rock. Another alternative, not yet attempted, is to evaporate the water and collect the potentially saleable solid residues; this scheme might be feasible in regions having high evaporation rates. http://energy.usgs.gov/factsheets/Coalbed/coalmeth.html ==External links== * [http://www.nytimes.com/2002/08/04/opinion/04SUN1.html?todaysheadlines Powder River Showdown, ''New York Times'' editorial, August 4, 2002 (regarding proposed project)] * [http://waterquality.montana.edu/docs/methane/cbmfaq.shtml#how_much_methane_gas_is_estimated_will_be_extracted_from_the_powder_river_basin http://waterquality.montana.edu/docs/methane/cbmfaq.shtml#how_much_methane_gas_is_estimated_will_be_extracted_from_the_powder_river_basin] * [http://www.cbmclearinghouse.info/research.html http://www.cbmclearinghouse.info/research.html] * http://wy.water.usgs.gov/projects/qw/data2005/index.htm * [http://deq.state.wy.us/wqd/WYPDES_Permitting/WYPDES_cbm/cbm.asp http://deq.state.wy.us/wqd/WYPDES_Permitting/WYPDES_cbm/cbm.asp] http://www.mines.edu/Research/PTTC/newsletters/volume%207/v7n2p7.html ==See also== [[Fred Meissner]], world renowned geoscientist, Professor of Geological Engineering at the Colorado School of Mines, Scientist at Shell Laboratories, and Author [[Category:Chemical engineering]]