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Water Management Techbook 2017

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18 | May 2017 | hartenergy.com WATER MANAGEMENT: BEST PRACTICES techniques. Water chemistry is also impacted by the target reservoir's temperature, pressure and naturally occurring elements. To properly choose and size treatment equipment, experts use basic input that includes flow rates, influ- ent water quality and desired effluent water quality. As the first two of these are easily known, best water management practices demand use of only quality assured produced water samples. "What causes less than optimal performance is the water quality data not being identified correctly," Shannon said, referring to operator-taken water sam- ples. "For instance, if crude oil gravity was taken on a sample with diesel in it allowing it to flow better, we need to know that. If the water quality is highly variant due to events in the formation, ongoing field development work or chemical additives–these vari- ations need to be known as well." After analyzing produced water samples, experts design water treatment solutions by establishing the quality window within which a treatment strategy is to perform. Because the quality of produced water changes as wells are produced, the solution must be able to accommodate a wide range of variables that might change over time. For this reason, optimal equipment is selected and then installed based on the quality requirements that evolve over the life of the field. Depending on the operating environment, final water quality targets and budget, water management strategies might consist of a single treatment or of numerous increasingly refined treatments. The for- mer solution, say some experts, is a prescription for less than optimal results and, because of its lack of flexibility, may not be able to deliver desired final water quality as the makeup of the produced water changes over time. In addition, when engineers spec- ify a specific piece of water treating equipment, they may force experts into devising a best single-widget solution that is less effective than a solution that considers use of other options. Integrated water service engineers possess expert knowledge of reservoirs and water treatment technol- ogy. They also understand the regulations that gov- ern the industry and know what water quality must be achieved to accommodate operator plans. While large oil companies have regulatory staffs, because water use regulations vary significantly across rela- tively small geographical distances, most operators rely on water management experts to act as de facto regulatory advisors. "Typically, customers reach out to us when facing challenges with the water they are producing. They basically say, 'we have water that needs to be treated for a particular use,'" Shannon said. "In other words, they are looking for a solution that treats the water from the current quality to the required effluent quality. During this discussion, our process design experts acquire the right information to ensure an optimal solution is modeled." Use of experts is critical to water management best practices because staying abreast of technological improvements to existing equipment might have sig- nificant economic implications for end users. Dunkel advises operators to consider what they do not know about water management and to look to experts to fill the void. "Consulting companies, service companies and other producers are potential sources of new ideas in the rapidly changing water management business for upstream oil and gas," he said. "Companies in differ - ent basins are doing things differently. Be sure not to overlook a method, process or idea that could cut your costs and improve your operations long term." For example, Schlumberger's Shannon pointed out that traditional treatments for waterflood effluent containing polymers is to oxidize the water to destroy remaining polymers and then add polymers back to get the system to requisite viscosity levels before it is pumped back downhole. But, he said, Schlumberger's secondary treatment system can save the extra cost by treating the returned water without removing the polymer. "When the water returns from subsurface, it still contains some valuable polymer," Shannon explained. "The traditional way to treat it is to use chemicals that completely destroy the remaining polymer. The inability to re-use this polymer later in operations can be a costly expense to the customer." In the current oil price environment, trimming operating costs is a compelling driver of best water management practices, particularly in the booming shale plays. According to the Baker Hughes website, the estimated annual cost of water treatment and disposal of surface water in North America is more than $8 billion dollars. This estimate considers the full fracturing water cycle, which includes sourcing, stor - ing, treating, transporting and hydraulic fracturing. Shale, water and trucks In 2014, according to the U.S. Geological Survey, the mining and oil and gas industries accounted for just 1% of all the water used in the U.S. per industry. It would seem a relatively small amount but for the fact that oil and gas exploration and production operations, particularly in shale plays, often take

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