Tuesday, November 14, 2006 - 10:00 AM
149-3

Coalbed Natural Gas Production in the Powder River Basin: Encroachment and Research at the University of Wyoming Sheridan Research and Extension Center.

Justin Moss, Sheridan Res. & Ext. Ctr, Univ WY, 663 Wyarno Road, 663 Wyarno Road, Sheridan, WY 82801, United States of America

Coalbed natural gas (CBNG) has become a relatively new source of natural gas production in many parts of the United States and currently accounts for approximately 10% of United States natural gas production.  A large volume of CBNG production is occurring in the Powder River Basin which is located in southeastern Montana and northeastern Wyoming.  Coalbed natural gas extraction requires the removal of large volumes of water located in coal seams.  Water is removed from the coal seams which reduces hydrostatic pressure and allows for the recovery of CBNG.  When this naturally occurring groundwater is removed, it is referred to as “produced water”.  One of the major issues concerning CBNG production in the United States is disposal and/or use of the CBNG produced water.  Generally, the produced water is characterized as having elevated levels of sodium, calcium, magnesium, iron, bicarbonate, alkalinity, electrical conductivity, and sodium adsorption ratio, but these levels may vary throughout the season and/or by location.  Coalbed natural gas produced water may be surface discharged, discharged into holding ponds, re-injected into shallow aquifers, utilized for livestock and wildlife watering, or utilized for irrigation purposes.  The CBNG produced water may also be treated before disposal utilizing ion exchange and/or reverse osmosis.  Oil and gas companies in Wyoming and Montana have made agreements with local landowners to utilize CBNG produced water for irrigation purposes.  Marathon Oil Company currently has two CBNG wells on the property of the University of Wyoming (UW) Sheridan Research and Extension Center (SREC).  In addition, Marathon Oil Company owns the land directly adjacent to the UW SREC that contains two large CBNG produced water infiltration reservoirs.  Surface use agreements between landowners and oil and gas companies, CBNG produced water quantity and quality, and CBNG produced water uses will be discussed.