Fate of Coalbed Natural Gas Produced Water in Disposal Ponds in the Powder River Basin.

Increases in worldwide demand for cheaper cleaner forms of energy have led to a dramatic increase in natural gas production from coal seams in Wyoming’s Powder River Basin (PRB) over the past two decades. The coal bed natural gas (CBNG) extraction process results in the co-production of several million cubic meters of varying quality water per year. Coal Bed Natural Gas co-produced water is generally considered a waste product and is managed by disposal in retention/evaporation ponds. Some of the CBNG co-produced water disposal ponds in the PRB are lined with impermeable clays while most are unlined. The objective of this study was to determine the fate of the co-produced water in the unlined ponds. Constant-head column infiltration studies were conducted in the laboratory using soil and produced water from five sites across the PRB to better understand the effects of water quality and soil type on infiltration and solute transport in CBNG ponds. Data collected from the column studies was used to determine changes in soil hydraulic conductivity over time. In addition, solute transport in the columns was simulated using the Hydrus 1-D model.