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Researchers in the Walker Department of Mechanical Engineering at The University of Texas at Austin have developed a new method to cleanup wastewater produced in United States shale oilfields.

Producing oil-gas via hydraulic fracking is very water-intensive. The water needed to fracture an average well can fill four Olympic-sized swimming pools. Supplying all this water has been a longstanding issue for the industry. A bigger challenge is the disposal of wastewater coming out of wells when they begin producing. Typically, wells produce more water than oil -- you end up with more water than you injected into rocks to break them apart. Compounding the challenges are the high level of salts and chemicals in this water, which can make the water look more like toxic soup. Current wastewater solutions involve long-distance trucking to water disposal sites or ground reinjection; however, this practice has been linked to earthquakes.

Now, Associate Professor Vaibhav Bahadur (VB) and PhD student Aritra Kar in the Walker Department of Mechanical Engineering have devised a new technique to cleanup and reuse this wastewater. Reverse-osmosis (RO)-based filtration can clean up the water produced in multiple oilfields in the US. The key factor, which can enable widespread adoption of this technology, is the use of the currently flared excess natural gas, which can instead be used to power the RO unit. Many oilfields that need freshwater and have wastewater issues also have plenty of excess gas that is either flared or vented. This environmentally disastrous practice is globally frowned upon, but nevertheless continues almost unabated, as there is no use for this gas.

“The key for industry to realize is that you can solve two critical issues here,” says Bahadur. “You can use waste gas to clean up wastewater -- this will reduce your water costs and also benefit the environment.”

Detailed findings, modeling, economic analysis and case studies for this technology are reported in an article in Energy. In particular, the analysis shows that this technology will work very well for the Eagle Ford Shale in Texas, which extends from south of San Antonio all the way into Mexico. A cubic meter of gas can end up producing 200 up to gallons of freshwater in some fields. The article outlines other uses of waste gas for water treatment in other large US oilfields such as the Permian basin and Barnett in Texas, and the Bakken oilfield in North Dakota.

Bahadur is convinced that this technology has global use. “Oil-gas production is inextricably linked to water issues and excess gas generation, whether you are located in the US or in the Middle East or Africa. While the oil sector is in a downslide right now, all estimates indicate that it will continue to contribute to future energy supply at very meaningful levels. It is high time that we made oil-production greener, and this technology is a step in that direction.”

Schematic of a natural gas-powered RO system for wastewater treatment

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