Playbooks Supplements

Water Management Techbook 2018

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50 | April 2018 | WATER MANAGEMENT: CASE STUDIES P roduced water, a byproduct of oil and gas wells, has grown in importance as discussion has moved from waste product to valuable resource. As shale activity increases, so does water demand for completions and produced water dis- posal capacity from producing wells. A natural solution is to consolidate a produced water man- agement program into a water supply program for completion activities. This has pushed produced water management from disposal in injection wells to recycle/reuse programs. Induced seismicity has accelerated the recycle/reuse movement in some areas. Other factors moving produced water from disposal to reuse vary from area to area but include water scarcity/drought, disposal capacity and the cost of recycling. Over the last few years, the industry has seen produced water treatment costs for reuse increase from $0.40/bbl to $0.65/bbl and decrease to less than $0.30/bbl. This reduced cost is primarily a result of improved fracture chemistry and a better understanding of what needs to be treated. The idea of "just enough" treatment has narrowed the focus to bacteria, iron, sulfides and some solids control. This narrowed focus has significantly reduced the need for total dissolved solids control and eliminated pit treatments for a much lower cost aeration approach. Aeration has been used for water quality manage- ment as early as the late 1800s and is a part of most all municipal treatment plants across the country, but it is a relatively new concept for produced water. Produced water aeration allows oxygen from the air to provide oxidation of iron and sulfides, while oxygenating the water to mitigate anaerobic bacteria. This system addresses many of the items on the nar- rowed list of constituents needed to address as part of a produced water reuse program. Aeration is also a fraction of the cost of conventional pit treatments. So why is aeration just getting noticed? As produced water reuse has grown, the need to aggregate and store produced water has grown. Storage has evolved from multiple fracture tanks to larger aboveground storage tanks to large in-ground pits. This evolution has increased the storage time for produced water, which allows bacteria to grow and H 2 S to generate and make reuse more difficult. This concern was addressed initially with chemi- cal pit treatments but has evolved into an aeration solution. Aeration takes longer to work as oxygen is a slower acting oxidizer, so the longer storage time made aeration a more viable solution and much more cost-effective than chemical treatments. Floating versus submersible As companies accept aeration as a cost-effective solution, then comes the choice of what type of aeration. To simplify, consider aeration systems as two categories: floating and submersible. Floating systems are easy to deploy when water is already present, but they typically only aerate the top few feet of water leaving a significant amount of water with inadequate quality. Some floating systems add As practices move from disposal to reuse and recycle, aeration could provide a cost-effective solution. Produced Water Management: The Role of Aeration By Mark Patton Hydrozonix

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