An Economical Process to Treat Produced Water From Coal Bed Methane Deposits in the Powder River Basin

摘要

Coal bed methane (CBM) is one of the most important and fastest-growing energy sources in the United States. One of the factors discouraging development of this resource is the large amount of water ("produced water") associated with CBM. Reverse osmosis (RO) has successfully treated this saline water but at a relatively high cost. A new technology, the Hydro process, has been developed and tested at the bench scale with several produced waters. The Hydro process uses weak acid cation (WAC) ion exchange to remove total dissolved solids (IDS), which are primarily sodium bicarbonate, and includes a small RO unit to recover most of the WAC regeneration waste. The process delivers treated water with a TDS concentration below 800 ppm and a sodium absorption ratio (SAR) less than 6, at a typical operating cost of $0.30 per 1000 gallons discharged ($0.013 per barrel). It can also generate treated water with lower TDS and SAR values at a slightly higher operating cost. A typical recovery rate of the process is 96 percent, meaning that 96 percent of the water could be discharged and only 4 percent would require further treatment, such as deep well disposal.