Produced-water recycling and Energy Reduction for Central Oklahoma

Water Reuse Focus for Central Oklahoma

Enhanced oil and gas recovery (fracturing) techniques and water go hand in hand. Current pressures including limited fresh water sources, transportation, fracturing volume requirements, and disposal costs and restrictions are driving the development of new water management strategies. Recycling and managed biologic treatment of surface water is proving to be a cost-effective, more environmentally sound solution for produced water.

The facility provides surface water management for the surrounding area and has a nominal treatment capacity of 30,000bbl/d. The key elements for treatment include pre-treatment for oil recovery and solids separation, biological treatment for management of dissolved constituents, and storage for fracturing activities. The use of biological treatment is broadly applied in a wide range of wastewater treatment applications; however, its use is just emerging in the oilfield. With proper process design and aeration equipment selection, a robust, cost effective solution is now available and is being demonstrated at this and other oil and gas facilities.

Sourcing suitable water for initial injection and high operating cost to store and chemically treat produced water are two reasons why the industry is seeking more economical and environmentally sound solutions for produced water management. Greater reuse of produced water conserves limited fresh water resources, reduces handling and hauling costs, and drastically reduces the volume of water injected underground for disposal.
The application of biologic treatment requires a broad understanding of the operational objectives for the facility. Unlike conventional wastewater treatment plant design which focuses solely on future design capacity and regulatory effluent standards, produced water treatment is akin to a manufacturing function that needs to respond to the operational requirements of the business. This includes but is not limited to mitigating the health and safety issues of stored water, ensuring downstream chemical treatment effectiveness, and providing biological treatment and operational performance under highly variable flow and pit operating water level conditions. Further, the energy required to support the biological process is significant. From a mass perspective, the removal of one pound of organic material requires the supply of one pound of oxygen. Mitigating the operating cost of the biological process is key to the cost effectiveness of this solution.

Unfortunately, high salinity and dissolved solids concentrations in produced water severely challenge traditional aeration techniques. Mechanical surface aeration consumes a lot of energy, suffers shortened equipment life through fouling and corrosion, and requires awkward and hazardous on-water maintenance. Their configuration also limits the ability to drawdown the pit and restricts the use of the stored water for fracturing needs. Subsurface diffused aeration provides improved pit use but also suffers shortened equipment life and losses in operating efficiency.

EDI, with its extensive expertise in biological treatment and aeration including over 7000 installations worldwide, engineered and delivered a turnkey solution that specifically addresses the unique challenges presented by produced water treatment.

EDI’s solution incorporated:

Floor-mounted configuration for full pit drawdown capacity
Floating configuration for cost effective flow-through capacity
Customized modular construction for faster installation and re-deployment
Variable output blowers for operational flexibility, and hands-off operation
Chemically-compatible, flexible membrane fine-pore diffusers for high operating efficiency and long service life.
Temperature and corrosion-resistant materials of construction to withstand elevated operating temperatures and high salt concentrations.
Front to back maintenance service program for high uptime performance

EDI also provided a customized front-to-back maintenance service package to assure the aeration system is always in top operating condition.

System commissioning was completed in July 2017 and is expected to begin treating produced water immediately. Results will be compiled over time to document the performance of the system; however, similar operating facilities in the region have already demonstrated the treatment and cost metrics for the facility. EDI’s advanced design provides a reduction in energy use by more than 50% compared to alternate aeration techniques, and the installed solution reduces the capital and O&M costs for the aeration equipment to a few cents per barrel of water treated. The anticipated project term for this facility is quite long; however, even for the usual 2 – 5 year project life, a significant payback and short return on investment are big wins for the customer.