Coal Bed Methane by fdh56iuoui

VIEWS: 5 PAGES: 4

									                                                                               SPRING 2007
                                                                               Volume 4, Number 2




                             Most Montanans have heard something

Coal Bed                     about a new energy industry
                             emerging in Montana and the rest of

Methane                      the Northern Great Plains: coal bed
                             methane (CBM). The production of CBM involves

Its Promise
                             extracting natural gas from buried coal deposits. Once
                             a nuisance and mine-safety hazard, CBM has become a

and Problems                 promising energy source for the nation. Today the most
                             active “play” lies in the Powder River Basin, a geologic
                             bowl stretching from Glenrock, Wyoming, to the
                             Yellowstone River, and from Gillette, Wyoming, to the
by James W. Bauder*          foothills of the Bighorn Mountains. After steady growth
                             over the past 15 years, CBM now accounts for about one-
                             twelfth of U.S. natural gas production. Experts estimate
                             that CBM will play an even more significant role in the
                             nation’s energy future. Environmentalists, however,
                             raise red flags because of CBM’s possible harm to the
                             soil, water, agricultural production, and wildlife.
                                  CBM’s formation, location, and volume. Because
                             CBM is found in coal deposits, it occurs naturally in
                             recoverable quantities throughout the world. Almost
                             100 percent natural gas, it also contains trace amounts
                             of carbon dioxide, nitrogen, water vapor, and hydrogen
                             sulfide. The CBM eyed by the extraction industry in
                             Montana, Wyoming, Saskatchewan, and other parts
                             of the Northern Great Plains was formed by micro-
                             organisms during the geologic conversion of organic
                             material to coal. Because of its low level of impurities,
                             it is not necessary to refine the type of CBM found in the
                             Powder River Basin before putting it to commercial use.
                                  Unlike “traditional” natural gas, CBM production is
                             associated with large volumes of water and occurs close
                             to the earth’s surface. It is generally found at depths
                             of less than 1,000 to 2,000 feet in low-rank coals (low
                             carbon content). “Traditional” natural gas is generally
                             found at greater depths and in higher-rank coals. The
  Powder River Basin         CBM of the Powder River Basin, therefore, is relatively
                             reachable by current drilling techniques. Producing
                             wells in the Basin are located at depths between 200 feet
                             and 2,200 feet; 50 percent of CBM-producing wells are
                             found at depths ranging from 400 feet to 800 feet.


                       Montana’s Agenda: Issues Shaping Our State                               
         The contiguous United States is estimated to          equals 1,000 cubic feet), 1 Tcf of CBM would supply
    contain 700 trillion cubic feet (Tcf) of CBM. And          the natural gas needs of approximately 400,000
    because most coal beds are so methane rich, a cubic        households for 20 years. Actual gas production,
    foot of coal can contain six or seven times the volume     however, varies according to location. After several
    of gas that is contained in traditional natural gas        months of dewatering, the average production per
    reservoirs. Small areas of land, therefore, can be a       well in the Powder River Basin reaches 160 Mcf of
    “source rock” for substantially more natural gas than      CBM per day and 6 to 12 gallons of water per minute.
    traditional reserves contain.                              Conservative estimates put the amount of CBM
         Extracting CBM from coal. Extracting CBM              available per well at 400,000 Mcf.
    from shallow coal seams is relatively easy, from               The water management controversy. No aspect
    an engineering perspective. Methane adheres to             of CBM recovery in Montana’s Powder River Basin has
    the surface of coal where the coal is fractured and        received more attention than managing the water
    broken. These open spaces between coal particles           produced. The controversy: Is the water pumped
    fill with water that is under pressure. This water         from the coal seams harmful and can and should the
    pressure prevents the methane from escaping into           water be treated to minimize the potential harm?
    the air or surrounding soil. When the water pressure       Experts estimate that .25 million acre feet of water
    is reduced, the methane detaches from the coal             will be produced annually for the first 7 to 10 years
    and forms recognizable bubbles of gas. Pumping             of development, enough water to fill Canyon Ferry
    water from methane-rich coal seams stimulates              on the Missouri or a swimming pool the size of a
    this detachment process. It also opens channels            football field 50 miles deep. With 7,000 to 10,000
    in the coal fractures, which provide an avenue for         wells projected for Montana, pumping could spread
    the methane to flow to a recovery well. Because            an additional 100,000 acre feet of water a year over
    methane is lighter than air, it rises in the well to the   the Yellowstone River watershed.
    surface through a different pipe than the one which            One can also view water production from the
    is pumping water out of the coal seam.                     perspective of a single CBM well. Once a well has
         The Powder River Basin and Montana’s CBM              been completed, aggressive water pumping begins
    potential. Although the presence of CBM in coal            in order to free the gas from the coal. The volume of
    seams has been known for centuries, only during the        water produced varies, depending on the technology
    past two decades has much attention been given to          used, the number of wells nearby, and the desired
    its commercial potential. Between 1997 and 2007,           rate of gas recovery. Actual water production ranges
    the number of producing CBM wells in the Powder            from as little as 1 or 2 gallons per minute to as
    River Basin increased from 360 to more than 22,000.        much as 100 gallons per minute. Typically, a CBM
    More than 95 percent of that development occurred          well initially produces 15 to 20 gallons of water per
    in Wyoming. CBM development in Montana has been            minute, eventually decreasing to 4 to 5 gallons per
    limited by the requirements of environmental impact        minute.
    statements and other permits, litigation pertaining to         Gas production from a CBM well, like water
    management of the water produced, and insufficient         production, goes through several stages. During
    industry infrastructure to support commercialization.      the “dewatering” phase, the ratio of water to gas
         The U.S. Geological Survey estimated in 2001 that     produced is high, that is, much more water than
    the amount of recoverable CBM in the Powder River          gas. With continued production, the volume of
    Basin ranges from 8.24 Tcf to 22.42 Tcf. A recent          water decreases and the volume of gas increases.
    environmental impact statement projected 2.5 Tcf           Stability is reached when methane production peaks
    of recoverable CBM in the Montana portion of the           and water production holds steady. In time the well
    Basin. The Montana Bureau of Mines and Geology             enters a stage of decline when the amount of gas
    and the U.S. Department of Energy arrived separately       subsides so much that continued pumping becomes
    at an estimate of .8 to 1 Tcf of recoverable gas in the    unprofitable.
    same area. Considering that the average Northern               A CBM well’s total volume of gas production
    Great Plains household’s natural gas usage in the          is as unknowable as its total volume of water
    winter is somewhere between 80 to 120 Mcf (1 Mcf           production. The life of a CBM well depends on the




2   Montana’s Agenda: Issues Shaping Our State
spacing of wells, the subsurface interconnections          Milk River during mid-summer flow. Because salt
between the wells, and the amount of gas available         can harm agricultural soil and irrigated crops, some
in the field. In the Powder River Basin, experts can       farmers and ranchers object strenuously to putting
only speculate about these and other production            CBM water into streams and rivers that are used for
factors. Most CBM producers in the region expect           crop irrigation.
that a well will provide methane for 10 to 12 years,           Another environmental concern relates to aquifer
depending on the site variables just mentioned.            depletion. The water pumped from coal seams
In the Powder River Basin, some CBM wells have             during CBM extraction is part of an aquifer that
produced gas continuously for more than 20 years,          supports the springs and stock watering holes of the
and some wells have been shut down because                 prairie’s agricultural economy. Because coal seams
their low yield does not warrant the expense of            are the most continuous geologic unit in the Powder
pumping and maintenance. To keep a marginal well           River Basin and have aquifer characteristics equal
or field going, scientists in the Powder River Basin       to or better than sandstone, they are frequently
are experimenting with new technology to extract           targeted for water wells. Geologists estimate
through a single well hole                                                          that the time for refilling
methane from multiple seams                                                         these coal seams after CBM
and with the introduction                                                           extraction may exceed 100
of microbes into coal seams                                                         years. In addition, CBM
to stimulate additional                                                             extraction could introduce a
production.                                                                         water chemistry significantly
    The public policy                                                               different from that which has
issues. CBM clearly offers                                                          existed for centuries. This
Montana a major economic                                                            lesson has been learned from
development opportunity.                                                            previous inter-basin water
Witness Wyoming’s present                                                           transfers – for example,
budget surplus of almost a                                                          the Freezeout Lake Wildlife
billion dollars, a less than 2                                                      Area near Fairfield and the
percent unemployment rate,                                                          Bowdoin National Wildlife
and its huge infrastructure                                                         Refuge near Malta.
investment. But CBM                                                                      Other questions raised by
development in Wyoming                                                              concerned citizens deal with
has also brought about                                                              CBM’s impact on wildlife
unwelcome changes and                                                               – particularly sage grouse
                                                Diagram of CBM Well
problems. For example, split                                                        reproduction, antelope herd
mineral estates and the primacy of mineral-rights          migration, predator-prey relationships, and stream
ownership over surface ownership have meant                fisheries. Another issue relates to prairie grasslands,
that residents who own surface lands but not               specifically the transport and relocation of invasive
mineral rights have been obligated to permit CBM           weed species.
exploration and development on their property.                 Opponents to CBM production also cite
    The water quality issue looms even larger than         negative social impacts, some well founded and
land ownership complications. As water is pumped           some speculative: increased traffic, loss of privacy,
from CBM wells, it is stored on the land, discharged       social service overloads, labor force shortages, and
into a stream or channel, or injected into different       increased housing costs, to name a few. The lifestyle
geologic zones, sometimes a different coal seam.           changes that have occurred in Wyoming are yet to be
Sodium bicarbonate – baking soda to most of us - is        experienced in the Montana portion of the Powder
the universal component of CBM water in the Powder         River Basin.
River Basin. The actual amount of salt in CBM water            Montana’s challenge. A few certainties and
is less than one-quarter of that in ocean water and        many unknowns surround the state’s coal bed
about one-half of that found in the Powder River and       methane choices. Energy prices, including what we




                                                 Montana’s Agenda: Issues Shaping Our State                          
                                                                                                                     
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           pay for natural gas, will continue to increase, and
           science will continue to learn about the efficiencies
           and consequences of CBM development. In the
           interim, however, many uncertainties will plague us.
           It is often said that the states are the laboratories of
                                                                       Montana’s Agenda is published by
           the nation, and in this sense we may be able to learn
                                                                       The University of Montana, Missoula, MT,
           from Wyoming’s experience. With that state pushing          59812 and is edited by James Lopach,
           ahead full bore with CBM development, Montana’s             professor of Political Science; Carol Van
           best course of action might be looking toward our           Valkenburg, professor of Journalism;
           neighbor to learn as many lessons as we can. The            Jean Luckowski, professor of Education;
           short- and long-term future of coal bed methane             James P. Foley, University Executive
                                                                       Vice President; Larry Swanson, director,
           development in Montana, therefore, should be                and Bob Brown, senior fellow, O’Connor
           determined by prudent restraint, science, politics, the     Center for the Rocky Mountain West.
           courts, and time.
                                                                       Send ideas for future issues to james.
           *James W. Bauder, a graduate of Utah State University, is   lopach@umontana.edu.
           Professor of soil and water quality in the Department of
           Land Resources and Environmental Sciences, Montana State
           University-Bozeman. For more information on CBM, see
           http://waterquality.montana.edu/docs/methane.shtml.




4          Montana’s Agenda: Issues Shaping Our State

								
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