Management and Effects of Coalbed Methane Produced Water in the Western United States (2010) / Chapter Skim
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2 Coalbed Methane Produced Water in Western U.S. Basins: Hydrogeological and Geochemical Foundations
2 Coalbed Methane Produced Water in Western U.S. Basins: Hydrogeological and Geochemical Foundations
Pages 19-56
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From page 19... ...
These basins capture and contrast the currently known range of CBM produced water quality and quantity and produced water management approaches throughout the western CBM basins. The Uinta, Piceance, and Raton basins of Utah, Colorado, and New Mexico are also briefly discussed (see Figure 2.1)
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From page 20... ...
S . FIGURE 2.1 Map of western CBM basins within the six states that are the subject of this study.
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From page 21... ...
above and below the coal seams -- sometimes A permeable geological material, or a material's "permeability," refers to its ability to transmit fluids and is generally 1 associated with the degree of connectivity between pores in the material. A higher degree of pore connectivity would indicate higher permeability or ability of the material to transmit fluids.
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From page 22... ...
. The age of the water in coalbeds from which CBM is being extracted thus can become an important factor in determining how produced water is managed.
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From page 23... ...
In contrast to conventional oil and gas fields where produced water is sometimes reinjected into the producing formation to enhance oil and gas recovery, CBM produced water is not returned to the coal seams from which it was extracted because doing so would hinder additional methane recovery. Thus, other options are considered with respect to storage, disposal, or use of the CBM produced water.
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From page 24... ...
When natural gas prices are above a certain level, CBM operators will generally increase production to generate more income and profit. The total volume of CBM produced water generated by a CBM operator will thus vary as a result.
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From page 25... ...
For example, CBM produced water from the Powder River Basin is sometimes described as "relatively fresh," whereas CBM produced water from the San Juan Basin may be described as having "relatively high salinity." The section on "Geochemi TDS (total dissolved solids) is an expression for the combined concentration of all inorganic and organic substances 3 contained in a liquid which are present in a molecular, ionized or micro-granular suspended form, and which will pass through a sieve opening of 2 micrometers (Water Systems Council, 2007)
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From page 26... ...
Powder river Basin The Powder River Basin of Wyoming and Montana covers approximately 25,800 square miles (see Figure 2.4)
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From page 27... ...
Although oil and gas production began bitmap in the Powder River Basin in the 1920s, the first CBM well was not drilled there until the late 1980s (in the Wyoming portion of the basin)
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From page 28... ...
can also constitute important aquifers. The Wyodak and Wyodak Rider coal zone of the Fort Union Formation is the most hydrologically continuous unit in the Powder River Basin and, together with its related coalbeds (the Anderson, Canyon, Big George, and Smith coals; Figure 2.4b)
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From page 29... ...
. As a result of some combination of these natural circumstances, relatively fresh connate water and/or higher relative permeability, produced water from the Powder River Basin coalbeds is generally less saline than waters produced from other western CBM basins.
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From page 30... ...
Although oil and gas production began in the San Juan Basin in the 1920s, CBM development did not flourish until the mid-1980s. By the end of 2008, more than 7,000 CBM wells were active, extracting methane from coal deposits primarily within the Fruitland Formation at depths up to 4,000 feet below the surface.
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From page 31... ...
, CBM producers in the San Juan Basin put a large majority of produced water from the coalbeds into temporary storage in above-ground storage tanks for later reinjection into formations below the coal. raton Basin The Raton Basin of Colorado and New Mexico covers approximately 3,100 square miles (see Figure 2.5a)
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From page 32... ...
The coalbeds in the Mesaverde Group consist of coal interbedded with sandstone and a combination of shale and siltstone. As with the Piceance Basin, water quality associated with the Uinta Basin CBM can be very saline, and salinity of produced water may be as much as that of seawater.
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From page 33... ...
(b) Generalized figure 2.7b.eps west-east geological cross section across the Piceance Basin of Colorado.
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From page 34... ...
S . Variations in CBM Produced Water Volumes The Powder River and San Juan basins have seen the most CBM development, followed by the Raton Basin, as illustrated by the number of wells operating in each basin (Table 2.1)
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From page 35... ...
3.00E+ 07 2.00E+ 07 1.00E+ 07 0.0 0E+00 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 (c) San Juan Basin, Colorado figure 2.8b.eps 5.00E+ 08 bbl or MCF Water Production (bbl)
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From page 36... ...
A graph of production from the San Juan Basin shows a steady increase in gas production since the mid-1990s, while water production from the basin peaked in 1993 and has since followed a steady decline. In an example from the Piceance Basin, which has the lowest CBM production levels of any of the western CBM basins, two spikes in water production are apparent (Figure 2.8d)
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From page 37... ...
of CBM water in the San Juan Basin is on the order of thousands to tens of millions of years (e.g., Phillips et al., 1986, 1989; Snyder et al., 2003; Riese et al., 2005; see Box 2.2)
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From page 38... ...
S . BOX 2.2 Age of Groundwater Hydrogeologists can test the validity of their conceptual models of groundwater flow systems, including predic tions of where groundwater may recharge and discharge, by determining the approximate age of groundwater since it entered the subsurface as precipitation recharge.
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From page 39... ...
Although comprehensive isotopic studies similar to those in the San Juan Basin have not yet been conducted in the Raton Basin, these results suggest a conceptual model for CBM water in the Raton Basin similar to the San Juan Basin, particularly given the common depositional environments for the coals in the two basins.
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From page 40... ...
Although removal of water from coalbeds during CBM operations may induce some degree of leakage of water over time into the coalbeds from surrounding finer-grained rocks and potentially from other aquifers through deep fracture zones, CBM water at depth does not appear to be a "renewable" resource in the San Juan and Raton basins, based on the suite of data available. Powder River Basin Few studies have been conducted specifically to date the age of groundwater in the Powder River Basin, but existing results indicate that some of the CBM produced water may be thousands of years old.
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From page 41... ...
. Case Study Summary With respect to CBM basins, isotopic and other data in the San Juan Basin demonstrate that much of the produced water may not be a renewable resource because of its great age compared to human lifetimes.
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From page 42... ...
CBM produced waters of the San Juan, Raton, Piceance, and Uinta Basins also have a chloride signature which is not shown in the conceptual diagram of Brinck et al.
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From page 43... ...
. The Powder River Basin contains primarily sodium bicarbonate-type formation water, whereas waters from the Piceance, Uinta, Raton, and San Juan basins contain sodium bicarbonate/chloride-type water.
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From page 44... ...
. Generally, TDS concentration ranges from the hundreds to thousands of milligrams per liter in produced water in the basins where sodium bicarbonate dominates, such as in the Powder River Basin, whereas TDS concentrations can exceed tens of thousands to more than 100,000 mg/L where sodium chloride dominates the chemistry of the CBM water, such as in the San Juan Basin (Table 2.2)
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From page 45... ...
Note also the difference in concentrations in sodium and bicarbonate within the San Juan Basin where concentrations decrease from south (New Mexico) to north (Colorado)
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From page 46... ...
(2006) documented changes in concentrations of trace metals in surface water in the Powder River Basin as such waters moved downgradient, below produced water discharge points.
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From page 47... ...
concentrations of organic compounds in CBM produced waters in the Powder River Basin, with PAH values up to 23 µg/L. The committee was unable to find other data regarding organic substances dissolved in CBM produced waters of the other western basins.
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From page 48... ...
related to the effects of regional CBM withdrawals in the San Juan Basin have also been employed and model results interpreted to suggest stream depletion and drawdown of the potentiometric surface of coal-bearing formations within 20 miles of their outcrop area (e.g., S.S. Papadopulos & Associates, Inc., 2006; Hathaway et al., 2006)
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From page 49... ...
Despite these limitations, groundwater models of basins can predict general travel time of groundwater along flow paths, and these predictions can be tested by age dating the water. Until the gap is filled between the results of groundwater models and the necessary data to test them, care is urged with regard to using model results alone to make regulatory or other determinations regarding produced water management.
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From page 50... ...
In the Powder River Basin of Montana and Wyoming, relatively high CBM produced water volumes with generally low dissolved salt concentration in comparison to other western CBM basins are due to the occurrence of methane-bearing coalbeds with relatively high permeability and water-filled porosity. CBM-produced water volumes are lower in the San Juan and other western CBM basins, where the methane-producing coalbeds typically occur at greater depths than in the Powder River Basin and have correspondingly lower permeabilities.
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From page 51... ...
Although a few isotopic studies have suggested some of the CBM produced water in the Powder River Basin is fossil water, more detailed analyses incorporating water chemistry, isotope study, and geophysical data collection -- such as those done in the San Juan Basin -- would clarify the extent to which fossil water and/or recharge with younger water occurs in the Powder River Basin. Using a full suite of geological, geochemical, hydrological, and geophysical data, and particularly using isotopic analyses to approximate the age of the water, will help determine whether the produced water is a resource that will be depleted by CBM production or replenished over shorter timescales.
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From page 52... ...
2002. Water Quality and Environmental Isotopic Analyses of Ground-Water Samples Col lected from the Wasatch and Fort Union Formations in Areas of Coalbed Methane Development: Implications to Recharge and Ground-Water Flow, Eastern Powder River Basin, Wyoming.
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From page 53... ...
2007. Trace element chemistry of coal bed natural gas produced water in the Powder River Basin, Wyoming.
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From page 54... ...
2007. Organic com pounds in produced waters from coalbed natural gas wells in the Powder River Basin, Wyoming.
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From page 55... ...
Presentation to American Water Resources As sociation Colorado, January 27, Colorado Geological Survey. Available at www.awracolorado.havoclite.com/sites/191/ pics/CBM-Produced Water.pdf (accessed March 4, 2010)
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