Water? What flavor would you like?

In general, the best hydraulic fracturing treatment for shale gas plays is the slickwater frac. However, the shortage of frac water has become a serious problem. Fortunately, sand and water comprise 99.9% of fluid used in slickwater fracs, and only 0.1% of fluid consists of chemicals, most of which are used to improve lubricity. The bad news is water is in short supply in several areas.

Fracture treatment companies have been scrambling to acquire water rights with mixed success. They also have initiated water conservation practices. Primarily, these consist of determining how to use produced saltwater as a viable frac fluid as opposed to disposing of it. Additionally, companies are working on ways to recondition frac flowback fluid for reuse on subsequent treatments.

Water treatment is a mature science. For many years, technology has existed to transform the foulest water into crystal-clear potable water. For example, a simple distillation process mimics the hydrological cycle to yield pure water. So what is the problem?

Not all water is for drinking
Several industrial processes use water. It is an abundant resource, easy to handle and transport, and is an almost universal solvent. Only a few processes require 100% pure water. However, many processes require water of a known and specific degree of purity to deliver predictable and consistent results.
So it is with hydraulic fracturing.

Modular NOMAD evaporator treatment units are field-proven and scalable to meet virtually any demand. (Photos courtesy Fountain Quail Water Management)

Operators cannot use produced water or frac flowback water and pump it directly into the next well because water can pick up various impurities as it percolates through rock formations. The most common compound affecting produced water is salt. Produced water comes from thousands of feet beneath the freshwater table and is loosely classified as brine.

Customized treatment is available
Originating in Western Canada and tested in shale plays throughout the US is a treatment process expected to deliver water to operators in any “flavor.” In other words, the treatment can be designed to detect and remove dissolved minerals from produced water or recovered flowback water to be reused for subsequent treatments. Until now, water treatment processes either were inadequate or overly stringent. The result was that some did not perform as needed and others were deemed too expensive. A third issue was volume. Many processes worked perfectly but were unable to deliver the required volume of treated water at a reasonable rate to satisfy demand.

The process, offered by Fountain Quail Water Management (FQWM), a wholly owned subsidiary of Aqua-Pure Ventures Inc., has been designed to address the concerns of both the oil and gas industry and the public. The process features:
• Modular construction – treatment units are designed to be transported by flatbed semitrailer units strategically spotted to meet variable demand. Semipermanent facilities can be upscaled by adding modules;
• High capacity – each evaporator module can treat 2,500 b/d of produced water or frac flowback fluid. Mobile onsite pretreatment modules can process more than 10,000 b/d;
• Regulation compliance – units exceed requirements of the communities or states in which they are licensed. For example, in Pennsylvania, units exceed the recently-passed 500 ppm total dissolved solids (TDS) and 250 ppm chlorides requirement for disposal quality;
• Energy conservation – once the evaporation process is initiated, 97% of the energy demand is recycled and used to sustain the process;
• Customization – operators can choose from at least five “flavors” of output water. Solutions range from the basic onsite removal of total suspended solids to complete removal of TDS with evaporators; and
• 100% turnaround – water haulers can deliver produced water or frac flowback water and immediately refill their tankers with treated water for the return trip to the well site.

The new facility with Eureka Resources in Williamsport, Pa., is strategically located in the center of Marcellus shale activity.

Practical solutions offered
Due to its transportability, the patented modular evaporator technology is called NOMAD. It was developed for use in treating oil or gas field fluids. Like all processes, it has a variable recovery rate, so depending on the input fluid and the output quality requirements, a certain percentage of recovery is possible. The volume varies. For example, Barnett shale wastewater recovery factor averages 80% to 85%, Marcellus shale achieves 75% to 80% recovery, and the Fayetteville currently is targeted at 95%.

FQWM has treated more than 500 million gal of Barnett shale wastewater. Its latest treatment facility currently is capable of 5,000 b/d throughput but is permitted to 7,500 b/d. It uses a mechanical vapor recompression (MVR) evaporation technique that requires little makeup energy to sustain because latent heat is recovered as the steam condenses into pure distilled water in the process. Energy is used continually to boil more brine into steam.

MVR evaporation is an energy-efficient process that produces pure distilled water from wastewater containing dissolved solids. With MVR, pure water is boiled from wastewater and subsequently condensed as distilled water. The dissolved solids remain in solution and are removed from the system as concentrated blowdown.

Treatment quality can be varied on demand. Although the process is capable of producing pure distilled water, few customers require it. Accordingly, users can ask that the volumetric concentration of certain elements be reduced to predetermined threshold levels in output water. Elements like iron, strontium, and barium can contribute to scale either in well tubulars or in the formation itself. FQWM can lower concentrations of elements to acceptable levels using the necessary level of treatment. This offers gas producers the ability to reuse brine on site with limited treatment or frac with freshwater, depending on preference. Cost varies with the level of treatment required.

The MVR process was developed by petroleum industry veterans to serve industry needs. (Image courtesy of Aqua-Pure Ltd.)

Accessibility is important
Because of their modular design, NOMAD evaporator units or mobile pretreatment modules can be staged to handle demand. A single unit can be dispatched to a well site, or multiple units can be deployed temporarily to serve a center of high fracturing activity such as a multiwell pad or several closely spaced well sites. Semipermanent sites are most efficient in areas of sustained activity.

Minerals, chemicals, and waste recovered from the treatment process are disposed of in permitted waste treatment facilities according to local, state, and federal regulations. Anything that is capable of being recycled is. A flexible process is required because every load of produced water or frac flowback water is different, and each operator has different requirements regarding the preferred composition of its recycled water.

As shale gas development grows worldwide, practical solutions for water recycling are expected to experience increasing demand. Again, technology delivers the answers.