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Solutions Arsenal For Oilfield Water Management

  October/November 2016

Solutions Arsenal for Oilfield Water Management
By: Brad Biagini, Senior Process Engineer, Water Technologies,
Veolia

Amidst growing public concern and tightening regulation of water resources, exploration and production operators are seeking customized treatment solutions able to improve both environmental and bottom line performance. An array of water treatment technologies is available to meet widely varied oilfield conditions and needs.

Deluge of challenges
How clean is clean? When it comes to removing impurities from oilfield water, the answer may be in the eye of the beholder. It can also depend on the intentions of cost-conscious exploration and production companies looking for new ways to optimize use of available water resources.

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Issues surrounding the management of oilfield water used in upstream oil and gas operations are attracting increasing attention. Disposal by pumping into subsurface zones of fracturing flow-back and produced water is facing increasing regulatory restrictions as awareness grows regarding freshwater scarcity and the potential environmental impacts from oilfield operations. Hauling produced water to disposal wells also can be expensive, and this practice comes with liabilities for truck accidents as well as emissions from truck traffic. Recycling of produced water for reuse has increased but volumes may exceed what can be recycled.

Treatment may be complicated by the specific constituents present in the water due to geological formation and/or exploration method, whether steam flooding, water flooding, slick water fracking, gel fracking or other approaches.

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All of this is generating demand for cost-effective, flexible treatment and disposal options to minimize total water lifecycle costs in the oilfield. To meet it, a range of different technology solutions are available to treat specific constituents to the level needed for the planned use of the treated effluent. Under such conditions, the right expertise — needed to determine the best approach and develop a customized solution — is as important as the right equipment.

Reuse response: ROSS™ technology
A solution for produced water reuse proving popular with oilfield operators in the Midwest and Western states is Veolia Water Technologies’ ROSS™ technology. Ideal for treatment of flow-back and produced water for reuse in exploration and production operations, ROSS™ combines Veolia’s Multiflo™ technology and CeraMem® membranes to produce water suitable for reuse.

Feed water is first treated using the Multiflo™ high-rate chemical softening technology to remove scale formers. This process utilizes a proprietary draft tube mixing technology, Turbomix®, to assist in the formation and separation of crystalline solids. The softened water and crystalline solids are then processed through the CeraMem® ceramic membrane ultrafiltration technology. Operated in cross-flow mode, the membranes remove free oil, suspended solids and bacteria to very low concentrations in a single step.

The solids from the CeraMem® ultrafiltration are continuously recycled to the crystallization tank of the Multiflo™ unit, providing seed for crystal growth. The treated water from the CeraMem® process is neutralized and reused in the shale oil operations as frac water, reducing fresh water demand.

Surface discharge or reuse: OPUS® II technology
In situations where produced water volumes exceed what can be reused, Veolia’s OPUS® II technology produces water clean enough for either reuse or discharge in either shale oil or conventional oil applications. This is the second generation of Veolia’s OPUS® technology, first introduced in 2007 at Chevron’s plant in the San Ardo Field in Monterey County, California.

OPUS® II, already operating at a treatment plant in California goes one step further than ROSS™, providing high quality water suitable for reuse in steam boilers, irrigation or surface water discharge (low boron levels). The compact produced water treatment technology utilizes a ROSS™ system for pretreatment prior to ion exchange and reverse osmosis. The filtrate from the ROSS™ system is further treated with ion exchange softening utilizing Weak Acid Cation (WAC) resin in sodium form for further removal of hardness and metals to lower concentrations, without pH correction.

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The pretreated water is then pressurized through reverse osmosis, operated at an elevated pH in single or double pass mode, to reduce total dissolved solids (TDS), boron and organics. The treated water exceeds state and federal requirements for quality.

Zero Liquid Waste/Zero Liquid Discharge systems
In Eastern states where TDS levels in produced water are very high, such as the Marcellus and Utica shale gas plays in Pennsylvania and Ohio, a thermal process such as an HPD® evaporator or crystallizer is needed. Veolia’s CoLD® (crystallization at low temperature and deep vacuum) process utilizes thermal evaporation and crystallization technology, removing sodium and calcium chlorides as well as the heavy metals found in produced water. Offered as part of a Zero Liquid Waste (ZLW) solution that includes other proprietary technologies in a centralized treatment system approach, CoLD technology is highly efficient and economical for treating produced water containing high levels of TDS.

In Canadian oil sands operations, thermal processes are required to manage the highly soluble brine and reduce system fouling. A typical treatment train would consist of de-oiling pretreatment and HPD® evaporation and crystallization technology to recover high volumes of water for reuse.

Tailored solutions for every situation
As the oilfield industry continues to transition to a more sustainable approach to usage of water resources, determining strategies for cost-effectively managing produced waters will be increasingly important. Whatever the situation with respect to constituents to be treated and the intended use after treatment, experience has shown that one size does not fit all. Determining the best technology requires the analysis of each variable and the expertise and support of a water technology provider working in close partnership with the customer to devise a sustainable solution.

When that solution is combined with an operations contract, performance is guaranteed for the life of the contract, eliminating the risk and environmental liabilities that are typically associated with produced water management. A sustainable solution with guaranteed performance reaps benefits not only for the oilfield producer but also for the surrounding communities.

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Key benefits of ROSS™ Technology:
• Reduce fresh water demand, disposal costs, truck traffic and emissions
• Effectively remove scale formers (hardness, silica, iron, barium, strontium)
• Effectively remove particulates (oil, solids, bacteria)
• Create an absolute barrier to particulates, minimizing downstream carryover
• Achieve high system recovery rates (>98%), minimizing liquid waste generated
• Reduce costs with packaged, modular, shop fabricated technology
• Reuse and recycle produced water from shale oil production

OPUS® II benefits:
• High water recovery rate
• Low waste volume
• Effective control of scaling and fouling
• High salt rejection
• Continuous clean-in-place
• Produces effluents suitable for surface discharge or reuse

Zero Liquid Waste Solutions:
• Ideal for both flow-back and produced water
• Efficient removal sodium and calcium chlorides as well as the heavy metals in the effluent generated in shale gas production
• Only waste produced is a solid salt cake that passes TCLP testing, suitable for landfill disposal
• Eliminates the need for chemical softening pretreatment
• Recovers greater than 95% of the wastewater for reuse

CoLD® Process Benefits:
• Achieves complete desalination of high TDS produced waters
• Lowest OPEX as compared to conventional methods
• Eliminates the need for calcium removal pretreatment, minimizing sludge production
• Produces clean water and stable solids for disposal or reuse
• Simple, robust process with high reliability and availability