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.