Coalbed Methane Produced Water In The Western Us

• Economics of storage and disposal versus options for treatment and beneficial use; and

• Concern on the part of the CBM operator over liability associated with produced water management, including water use, discharge, and transfer.

Commercially available water treatment techniques can be employed individually or in combination to attain the water quality to support any beneficial use, but at variable costs (Veil, 2009; see Chapter 6).1 Disposal and storage options include direct discharge to surface water bodies (depending on produced water quality and quantity and relevant regulations), deep- or shallow-well reinjection and/or storage in surface impoundments, evaporation, and land application. Table 4.1 summarizes the strategies used to manage produced water in the western CBM-producing basins.

Two broadly contrasting approaches to produced water management are highlighted in this chapter: (1) the Powder River Basin, where substantial water volumes and relatively low salinity have yielded a variety of options for eventual use of treated or untreated CBM produced water, and (2) the San Juan Basin, where low water volumes and relatively high CBM produced water salinity have made deep-well injection of untreated produced water a standard practice (see Table 2.1; Table 2.2).

The volume of water produced annually from Powder River Basin CBM wells is substantially greater than that of any other western basin (see Chapter 2 and Table 2.1). The large number of wells with high water production from relatively shallow depths has thus focused much of the attention regarding management of CBM produced water and its impacts on this basin, particularly the Wyoming portion of the basin where most CBM production currently occurs (Box 4.1). However, as outlined in Chapter 3, within each of the CBM producing basins where water is being brought to the land surface, volume is not the only factor taken into consideration in the context of produced water management. State natural resource and regulatory agency statutes and administrative rules, in addition to U.S. Environmental Protection Agency (EPA) permitting requirements for disposal or beneficial use application, dictate or regulate which disposal and management strategies may be employed by the operators and water management contractors.

Existing infrastructure, transportation costs associated with shipment of water, and the present-day value of water all influence the extent to which either treated or untreated CBM produced water is perceived or used as a resource. Because the vast majority of CBM produced water is managed by disposal and storage, very little is currently treated for beneficial use. A large majority of the treatment is completed as a requirement for permitted disposal by discharge to surface water.

1T. Olson and D. Beagle, Exterran Water Management Services, personal communication, August 4, 2009.

TABLE 4.1 Summary of Primary CBM Produced Water Management Strategies in Western Basins

Basin

Primary Water Management Method Reference

99.9% reinjected

97% reinjected, 3% evaporated

64% surface impoundments, 20% direct discharge to streams, 13% for surface or subsurface irrigation, 3% reinjected

61-65% direct discharge to streams, 4-5% industrial dust control, 26-30% for surface and subsurface irrigation, 5% surface impoundments

San Juan

Uinta

Powder River

(Wyoming)

Tongue River drainage— of the Powder River

(Montana)

Raton (Colorado)

Raton (New Mexico)

Piceance Nearly 100% reinjected; remainder in (Colorado) evaporation ponds

70% direct discharge to streams, 2% surface impoundments, 28% reinjected

Nearly 100% reinjected

Bryner (2002) Bryner (2002)

D. Fischer, Presentation to the committee, Denver, CO, March 30, 2009.

Calculated from information provided by A. Bobst, Montana Bureau of Mines and Geology, Personal communication, December 21, 2009; T. Reid, Montana Department of Environmental Quality, Personal communication, December 30, 2009; and J. Zupancic, BeneTerra, Inc., Personal communication, December 28, 2009.

Bryner (2002)

M. Fesmire, Presentation to the committee, June 2, 2009; data for 2008

S.S. Papadopulos & Associates, Inc. (2007); data through 2006

NOTE: North Dakota is not listed in this table because the state does not currently have any CBM production. All permitted discharges to ephemeral and perennial drainages in the Montana portion of the Powder River Basin are located in the Tongue River drainage. The Northern Cheyenne tribe has expressed considerable concern about potential impacts of CBM development and produced water management on water resources of the Tongue River drainage (see also Appendix F). Data for water management in this region were pooled from several different sources collected by the committee, each with different levels of detail. Some percentages are thus presented as ranges to reflect the appropriate level of uncertainty.

Table 4.2 provides a summary of the most typically used water management methods, treatment requirements and challenges, and possible ancillary benefits. The management methods have been separated very generally into two categories: storage and disposal options and beneficial use options. Note that these categories are not mutually exclusive in that storage and disposal options do have a range of potential ancillary benefits and uses. The remainder of the chapter discusses these methods in detail.

COALBED METHANE PRODUCED WATER IN THE WESTERN U.S.

BOX 4.1

CBM Produced Water Management in the Powder River Basin

CBM producers in the Wyoming portion of the Powder River Basin store the majority of produced water (about 64 percent) in surface impoundments to allow it to evaporate, to be sprayed into the air to enhance evaporation, or to infiltrate into the shallow subsurface or shallow alluvial aquifers (see figure below; Table 4.1). Twenty percent of the CBM produced water is discharged directly to surface water, either after treatment or without treatment if treatment is not required. Although the CBM produced water in the Powder River Basin generally has the lowest total dissolved solids (TDS) concentrations of all the produced water from the western CBM basins, only 1 3 percent is put to beneficial use, primarily as managed surface irrigation or subsurface drip irrigation. Use of produced water for subsurface drip irrigation requires an underground injection control (UIC) permit (see Chapter 3), inasmuch as the amount of water applied per unit of land is intentionally controlled to promote drainage below the crop root zone and into shallow alluvial aquifers. Only 3 percent of all Wyoming Powder River Basin CBM produced water is disposed of by deep-well reinjection, which also requires a UIC permit. In the Wyoming portion of the basin, 26 million barrels (3,350 acre-feet) of CBM produced water were reinjected in 2008; over the period from 2000 to 2008, 235 million barrels (30,300 acre-feet) were reinjected. In contrast, in 2008 alone in the Wyoming portion of the basin, nearly 77,000 acre-feet of CBM produced water were discharged into surface impoundments, while approximately 15,400 acre feet were directly applied to identifiable beneficial use for irrigation (including managed surface irrigation and subsurface drip irrigation).

In the Montana portion of the Powder River Basin, the two principal water management methods are permitted discharge and managed surface irrigation. The majority of produced water (61 to 65 percent) from CBM operations is discharged to surface water bodies, as treated discharge (see figure below); a 2010 Montana judicial ruling now prohibits the discharge of any untreated CBM produced water to any state waters. Managed surface irrigation comprises 26 to 30 percent of the discharge, of which 7 percent is apportioned to UIC subsurface drip irrigation. Impoundments are used for only 5 percent of the CBM produced water in Montana, and recently the Montana Supreme Court has declared the use of impoundments for disposal of CBM produced water to be unconstitutional. Industrial use of the water for dust control constitutes the final 4 to 5 percent of the produced water management.

The reason for the differences between the two states regarding the selection of management options for CBM produced water is that Montana currently has only two permitted CBM operations. One of these operations produces more than 95 percent of all produced CBM water in Montana and has a preexisting permit for the discharge of about 61 percent of all its produced water into the Tongue River.

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