Management and Effects of Coalbed Methane Produced Water in the Western United States (2010) / Chapter Skim
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7 Conclusions and Recommendations
7 Conclusions and Recommendations
Pages 181-188
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From page 181... ...
The energy value of this resource can often be achieved by pumping water from water-saturated coal seams to reduce the pressure in the seam, allowing methane to desorb and flow to the surface. Thus, CBM production requires management of two important resources -- natural gas and CBM "produced water." Management of CBM produced water is a challenge for regulatory agencies, CBM operators, water treatment companies, policy makers, natural resource agencies, some landowners, and the public because produced water from CBM extraction represents a waste to some and is considered a beneficial byproduct of CBM activity by others.
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From page 182... ...
In examining the known and potential effects of CBM produced water discharges on the environment, the committee focused its efforts on the Powder River Basin, with its relatively shallow coalbeds and less saline produced water and management of CBM produced water primarily through disposal in surface impoundments and surface water. CBM PRODUCED WATER HYDROGEOLOGY: THE IMPORTANCE OF ESTABLISHING HYDRAULIC CONNECTIVITY The degree of hydraulic connectivity between water-bearing coalbeds targeted for methane production and shallow alluvial or water table aquifers that support human activities and natural habitats is an important factor in determining the consequences of water withdrawal during CBM extraction.
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From page 183... ...
The scientifically established age of CBM produced water, and therefore its "renewability," should be considered in the development and implementation of CBM produced water management regulations. CBM PRODUCED WATER EFFECTS ON SURFACE WATER AND GROUNDWATER RESOURCES AND THE ENVIRONMENT The potential effects on the environment of pumping and eventual disposal or use of CBM produced water relate to water quantity, through potential water drawdown or volume addition, and changes in water quality.
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From page 184... ...
Surface Water Quantity and Quality Current surface water discharge permitting requires consideration of the quantity and quality of water in that receiving stream or river and the quantity and quality of discharged produced water. Measurements of the effects of CBM produced water discharges on the receiving stream or river quantity and quality are made periodically and can be used to regulate the discharge quantity and quality, if needed, to comply with permitted levels.
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From page 185... ...
Other physical effects to ephemeral or perennial streams and rivers, such as bank scouring, increased bottom sedimentation, or channel erosion, and to landscapes due to regulated, controlled, and managed, or unregulated and/or unmanaged CBM produced water discharges have been registered on private lands in the Powder River and Raton basins. Regulatory authorities have required operators to control and discontinue practices that have been shown to contribute to these physical effects.
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From page 186... ...
Agricultural Applications Use of some CBM produced waters for site-specific irrigation appears practical given appropriate conditions including availability of produced water and use of various combinations of selective application to nondispersive soils, treatment, dilution or blending of CBM produced water with other water sources; amendment of produced water and soils to be irrigated; and appropriate timing of irrigation practices. However, in the event that CBM produced water is discharged to perennial or ephemeral streams and rivers for the purpose of supplementing irrigation water supplies, careful consideration needs to be given to potential effects on instream water qualities.
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From page 187... ...
Identifiable beneficial opportunities for use of CBM water include irrigation, rangeland habitat improvement, livestock watering, alluvial aquifer recharge, aquifer storage, wildlife habitat enhancement, reclamation of well pads, industry applications, and potentially municipal use or consumption. CBM produced water volumes change over time and eventually decrease to near zero as development of CBM fields mature, making sustainability or long-term dependability of this water supply an issue in consideration of these beneficial use opportunities.
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From page 188... ...
Even in cases such as the Powder River Basin where CBM produced water contains relatively low dissolved solids concentrations, the full range of beneficial use options is not exercised, partly due to economics and partly due to the restrictions of existing water law. CLOSING REMARKS Each beneficial use aligns with a set of criteria and acceptable or appropriate criteria for one beneficial use of CBM produced water may be in direct conflict with the criteria for another beneficial use.
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