A PARADIGM SHIFT FOR SHALE: THE ENVIRONMENTAL, FINANCIAL, AND LITIGATIVE IMPETUS FOR PRODUCED WATER RECYCLING


The new heart of the American energy landscape, the Permian and Delaware Basins, is an exciting place to be right now. Production wells are expanding rapidly across western Texas and eastern New Mexico, which has brought forth the promise of economical prosperity for the region and greater energy security for our nation. However, with this growing opportunity also comes an immense set of responsibilities, particularly with respect to environmental stewardship and the implementation of sustainable practices.


A lot has been made about the seemingly thirsty process of production well stimulation, hydraulic fracturing, whereby large amounts of water are utilized to extract sequestered hydrocarbons from relatively impermeable subsurface strata. In the case of production wells in the arid Permian region, where lateral fractures have increased in length from 5,700 to 6,800 lateral feet on average, the median amount of water used to stimulate each lateral has increased to 12 million gallons (Backstrom, 2018). Water use has increased by more that 400% in the past few years, which is attributable to the favorable subsurface geology and the fact that there are multiple petroliferous strata in west Texas that are ‘stacked’ underground and can be stimulated sequentially.


Further to this point, unconventional wells in the Permian region generate approximately 3 times more wastewater (produced water) than oil (Scanlon et al., 2017). When considering the water requirements for well stimulation, in conjunction with the fact that more than 2 million barrels of oil are being produced each day in the Permian (Khan et al., 2016), it is easy to see that the effective management of fresh and produced water streams is paramount to the oil and gas industry.


What is the most sustainable way to manage these waters? Are there treatment technologies out there that can recycle produced oilfi eld waste so that we don’t have to use so much fresh water, and does this strategy makes sense on the balance sheet? Are there any legal liabilities? To address these questions, we discuss the mutually inclusive environmental, fi nancial, and litigative impetus for produced water recycling in an effort to illustrate that this paradigm shift in the shale energy sector makes sense on multiple fronts.


Environmental


What if we could treat the produced waste to the point that it could be reused for the stimulation of subsequent production wells? This would not only reduce the reliance on fresh water resources, but it will also reduce the occurrence of induced seismicity, which has been linked to the subsurface disposal of produced water (Hornbach et


al., 2016). Unfortunately, waste streams from shale energy extraction can be incredibly complex matrices. They are comprised of multiple organic, inorganic, and biological constituents, which can preclude their direct reuse for practically any application.


The presence of certain volatile organic compounds and metal ions can affect downhole polymer chemistry, whereas various species of sulfate-reducing and iron-oxidizing bacteria can cause the souring of produced hydrocarbons, as well as compromise production infrastructure. Collectively, these contaminants have traditionally rendered the repurposing of these waste fl uids a signifi cant challenge, which, in turn, has made the subsurface disposal of oilfi eld waste a more functional and convenient option. Nonetheless, our research team has recently partnered up with several industry colleagues to evaluate a wide range of water treatment technologies (i.e., ozonation, particulate fi ltration, UV exposure, and the use of variable carbon medias), to ultimately assess the feasibility of oilfi eld waste recycling under fi eld conditions.


Screening hundreds of samples for over 2,500 variables, we observed raw waste samples that exhibited total organic carbon levels as high as 1,500 mg/L, be treated to a clean state (<10 mg/L) resembling unperturbed brackish groundwater (Figure 1, left to right). Collectively, our experiments revealed that multiple treatment technologies were required in order to remove pertinent organic, inorganic, and biological contaminants below their respective reuse thresholds (Hildenbrand et al., 2018).


The next challenge for the environmental stewardship of produced water recycling will be to secure additional desalination technologies, which can convert any treated brine into a viable source for agricultural discharge and/or other benefi cial uses. This is particularly germane to the Permian Basin region where the increased number of production wells and amplifi ed scrutiny surrounding injection well permitting has created a perfect storm whereby quantum amounts of waste need to be


Figure 1: The multistep treatment of produced water using complementary separation technologies (Challenger Water Solutions) (Hildenbrand et al., 2018).


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