Recycling produced water and fracture flow back water for hydraulic fracturing can contribute significantly to water supplies for unconventional gas field development. Waste water may also be cleaned to supplement fresh water supplies for drilling and cementing surface pipe, surface construction, and other field development needs.
The Pinedale Anticline field in western Wyoming is an example where recycling water has contributed significantly to supplies for field development. Early in the field development the need to conserve available water supplies and the limitations on waste disposal injection capacity demonstrated the need to recycle water.
The Anticline Disposal Process was designed and constructed to meet the field development needs in two phases. The first phase utilized anaerobic and aerobic biologic treatment followed by clarification and filtration to clean fracture flow back and produced water. The process successfully cleaned and recycled 22,000,000 barrels of "frac water" in the first four years of operation. The second phase was designed to process surplus water to supplement fresh water supplies and also to meet discharge standards for a local river. This requires removing constituents such as methanol, dissolved aromatic compounds, excess dissolved solids, and boron. The process utilizes a membrane bioreactor, reverse osmosis, and ion-exchange process treatment steps. Organic constituents are removed to below detection limits. Inorganic salts are reduced from over 8,000 mg/l in the feed to below 100 mg/l in the product water. Boron is reduced from 15 to 30 mg/l in the feed to less than 0.75 mg/l, the drinking water standard, in the product water. Over 200,000 barrels of processed water has been used locally in the first year of operation with over 1,000,000 surplus barrels discharged to the river.
The results demonstrate feasibility to construct water processing plants to clean fracture flow back water for re-use in well completions and to reclaim water to supplement fresh water supplies. Design considerations, process steps, and lessons learned for consideration in application to other areas will be presented.