The cost of managing water has become an increasing and even dominant share of hydraulic fracking operations. In Canada's Montney region formation, for example, drilling and completing a well can require up to 500,000 barrels (21 million gallons) of water. Producers working this unconventional play are constrained by limited access to fresh water sources and distant disposal wells.
One Montney producer recently piloted two treatment lines to effectively develop a "water hub" to serve as a centralized facility, providing a closed-loop water management cycle. This would make the producer well positioned for full field development, allowing it to ramp up multiple rigs with all water management handled by one facility.
Frac flowback/produced water generated by this producer contains high total dissolved solids (TDS) -- approximately 200,000 ppm. The other main criteria for effective treatment, besides TDS and turbidity, include the removal of free oil and grease, removal of iron to an effective level, and the substantial removal of total suspended solids (TSS)/turbidity and sulfate-reducing bacteria.
Samples from Montney well sites were brought to the SUEZ Innovation, Development and Advanced Services Center in Richmond, Virginia, for lab-scale treatability studies to establish process direction and treatment chemistry and to determine the minimum water treatment level necessary for reuse.
From these studies, two highly selective "fit-for-purpose" water treatment lines were developed to recycle flowback/produced water suitable for use in fracking fluid. The pilot-scale components for these lines, installed at one of the producer's well sites, were essentially 1/10-scale versions of a full-scale plant, allowing for the replication of full-scale operations.
The study was executed in late 2016 by SUEZ in North America, with piloting contracted to the company on a turnkey basis. SUEZ provided the pilot units, equipment start-up, daily operations and sample collection.
Treatment processes for one line included primary clarification through a SUEZ Densadeg® clarifier, followed by a SUEZ poseidon® Vertical Oil Water Separator (VOWS) before multimedia filtration (MMF) polishing. Densadeg, a compact, high-rate solids contact clarifier, combines chemically optimized flocculation, internal and external sludge recirculation, and plate settling in two conjoined vessels, exhibiting a considerably small footprint.
The second line included the VOWS unit, followed by a SUEZ poseidon Saturn⢠Dissolved Air Flotation (DAF) pilot unit to remove dispersed and emulsified oil before final multimedia MMF polishing.
The high-rate VOWS process proved a vital component for both lines and played an integral part in the uninterrupted treatment of fluid containing significant oil and grease compounds. Inlet and outlet sampling showed oil and grease removal efficiency averaged above 91 percent, including peak performance above 99 percent for some periods during the trial.
Following oil and grease separation, the water was treated by a pilot-scale SUEZ poseidon Saturn DAF unit to remove dispersed and emulsified oil. The unit consistently achieved a TSS capture rate of 95 percent or better.
Both lines effectively met all treatment requirements established for the trial. The main parameters included:
- TDS: 3,000-200,000 milligrams per liter (mg/l).
- TSS: 400-4,000 mg/l.
- Free oil: 100-2,000 mg/l.
Considering the current objectives, it was determined the VOWS and Saturn DAF processes would form the core process components in any potential treatment scheme, with the Densadeg configuration applied if there is a future need for partial water softening.
The introduction of compact, high-rate water treatment technologies, along with the high-potential incentives provided by unconventional assets such as in the Montney formation, have prompted forward-thinking producers/ developers there to look toward frac flowback/produced water reuse in a big way. It makes sense. The recent Montney pilot study demonstrated to the producer/developer there is an effective strategy for delivering on future production targets while lowering water supply/waste disposal costs and enhancing environmental stewardship.
For more information, email Sreekumar.janardhnan@suez-na.com or visit www.suez-na.com.
