|Fig. 1: This image is of a drilling rig in Yemen - a country with water scarcity concerns. You can see products and byproducts of the well stored in open pools. If produced water could be treated and made useful for agriculture or as drinking water, it would be particularly valuable in arid locations such as this. (Source: Wikimedia Commons)|
"Produced water" refers to the naturally occurring water, which comes up alongside oil and gas during production and is composed of varied organic and inorganic compounds. Produced water is the most volumetrically significant byproduct of oil and gas recovery. Legislation limits the discharge of produced water into the environment and requires the water be treated, the standard method for which is gravity-based separation.  Alternatively, produced water can be sent directly down disposal wells.  In all, water management activities can compose up to half the cost of operating a shale well, and consequently produced water management is the subject of substantial study. [1-3]
This interest is compounded by the increase in produced water volume over the last 10 years in the US and developing countries, as well as by interest in recycling produced water. A further increase in volume is anticipated. [2,3] There are a wide variety of available solutions for treating produced water beyond gravity based separation, including chemical treatments, biological treatments, heat or pressure based treatments and physical treatments such as using a filtering membrane or evaporation.  Most treatment methods focus on extracting Notably, produced water is distinct from "flowback", which refers to the reappearance of injected water during hydraulic fracturing. Fractured wells yield both flowback and produced water, which may then be recycled in further fracturing. However, this use only consumes a small portion of an oil field's total produced water.  An alternative is recycling produced water for beneficial uses, such as agriculture or even for drinking water, a particularly attractive prospect for oil fields in the many oil producing countries with water scarcity concerns.  Fig. 1 shows a drilling rig in Yemen, where fresh water is scarce - a problem recycling produced water could assist in solving.
Produced water, though a waste product is an interesting and significant part of oil and gas recovery, which poses both significant future problems and opportunity.
© Brad Hakes. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 E. T. Igunnu and G. Z. Chen, "Produced Water Treatment Technologies," Int. J. Low-Carbon Technol. 9, 157 (2014).
 T. Jacobs, "More Oil, More Water: How Produced Water Will Create Big Cost Problems for Shale Operators," J. Petrol. Technol., 30 Nov 16.
 A. Fakhru'l-Razi et al., "Review of Technologies For Oil and Gas Produced Water Treatment," J. Hazard. Mater. 170, 530 (2009).