FIGURE 1.1 Illustration of the main features at a producing CBM well (not to scale). The black brick-like pattern represents a coal deposit lying between two sandstone units. The blue shading represents water that is present in the coal deposit. Methane gas (white dots and white shading) is adsorbed to the surfaces of the coal along cleats or fractures or is adsorbed to walls in the micropore structure of the coal matrix itself. Confinement of water in the coal by consolidated overlying and underlying sedimentary rock (sandstones in this figure) maintains the water in the coal under pressure, which in turn maintains the methane gas adsorbed to the coal. A submersible pump near the bottom of the well-bore cavity which penetrates the coal deposit pumps water from the coal. Pumping water reduces water pressure enough to allow methane to desorb from the coal surfaces and internal spaces and flow freely up the well bore. Water and methane flow through separate pipes to the surface. SOURCE: Adapted from Rice and Nuccio (2000).
professional football stadiums per day with water. While this volume of irrigation withdrawals contrasts to the approximately 42 billion gallons of CBM produced water generated in five western states in all of 2008 (see Chapter 2), water remains a vital resource and the effective, safe, and economical management of produced water from CBM wells is an important issue of consideration for government authorities, the general public, and industry.
NATIONAL CONTEXT FOR FUTURE CBM DEVELOPMENT AND PRODUCED WATER MANAGEMENT
Natural gas supplied about 24 percent of all domestic energy consumed by the United States’ residential, commercial, industrial, and electrical power generation sectors in 2008 (EIA, 2009a). That same year the nation met about 87 percent of its domestic natural gas