MEMBRANE DISTILLATION OF CONCENTRATED PRODUCED WATER BRINES FROM OKLAHOMA, TEXAS AND COLORADO

Oil and gas production by hydraulic fracturing and horizontal drilling is a water-intensive industrial process. Multi-stage fracturing of a single horizontal well can use several million gallons of water that is typically supplied by ground water wells and surface water sources. Such sources of fresh water become scarce and costly during times of drought. The costs and logistics of disposing of produced waters are also rising because deep-well disposal by underground injection induces seismicity and over-pressurizes the injection formations. When properly treated, produced water generated from oil and gas production can be used instead of fresh water for many beneficial applications, including hydraulic fracturing, but treatment is difficult because the water is often highly saline and contains undesirable contaminants, including naturally occurring radioactive materials (NORM). Membrane distillation (MD) is a promising technology for the recovery of minerals and water from produced water since it can process highly saline brines that can’t be economically processed using other membrane separation technologies such as reverse osmosis and nanofiltration. Here direct contact membrane distillation (DCMD) was used to process produced water brines taken from the water phase of the three-phase separator attached to long-lateral horizontal wells producing from the First Wilcox, Woodford Shale, Mississippi and Hunton formations in Oklahoma; the Permian Basin in Texas; and the Thorton formation in Colorado. Polytetrafluoroethylene (PTFE) and Polypropylene (PP) membrane materials were evaluated during the DCMD of the four Oklahoma brines and a PTFE membrane was used to process the Colorado and Texas brines. The produced water brines processed by DCMD contained between 20,800 mg/L and 154,000 mg/L total dissolved solids (TDS) and yielded water recoveries ranging from 86% to 60% at fluxes greater than 8 LMH. The distillate from all of the brines contained less than 200 mg/L TDS and essentially all of the NORM present in the feed brines remained in the concentrated feed water stream. The results show that DCMD with a PTFE membrane recovered high yields at low energy cost of essentially pure water and crystalline solids from produced water taken from six productive formations in Oklahoma, Texas and Colorado.