Technological advances in hydraulic fracturing and horizontal drilling have unlocked a vast reserve of new domestic energy. While many credit hydraulic fracturing with job creation, economic growth, and energy independence, the process also has brought water issues to the forefront and has stirred global debate.

Hydraulic fracturing can typically devour more than 100,000 bbl of water per well. As many parts of the US struggle with drought, operators are balancing bottom lines with limited freshwater supplies, negative public perception, increased regulation, limited disposal capacity, and increased disposal cost.

HydroDrive flexible pipe is deployed at a location in the Eagle Ford shale. (Images courtesy of Swire Oilfield Services)

Water has become an increasingly crucial commodity, and operators are now looking at ways to manage water from initial freshwater transfer to the fully produced well with a goal of working toward efficient and sustainable solutions.

To meet this new demand, Swire Oilfield Services created HydroLutions – a complete water management system that includes several sustainable systems to transfer, blend, treat, and recycle all water needed during completion and production.

Rethinking water transfers

For decades, aluminum pipe and agricultural pumps have been used to move water across land. These aluminum pipes leak and can dump nonpotable water across fields, potentially polluting the soil and groundwater.

Leaking pipes cost operators millions of dollars every year, especially in areas like the Permian basin where water sources are scarce. Besides the potential for pollution, leaks mean more water must be trucked or pumped to the job site, which increases the environmental impact. Landowners and workers, used to flooded fields and muddy boots, are looking for more sustainable ways to move water.

With this in mind, a water transfer system called Hydro-Drive was created. It features high-volume pumps; discharge manifolds; a specially designed retrieval and deployment system; and a leak-free, flexible pipe.

Instead of aluminum pipe that can only be laid out at 90° angles, this new technology curves over land and does not leak like traditional aluminum pipes. It is safer and faster to deploy and requires fewer workers to lay it down and pick it up.

The hose-like pipe is made of extruded through-the-weave, single-wall thermal plastic urethane and has been used by the military for years to transfer fuel and water. A reduction of friction within the pipe helps produce a 140-bbl/min flow rate, which has been virtually unheard of until now.

Apache Corp. and other operators are now using this technology in the Permian basin and have been pleased with the results.

Innovations in blending

During multistage hydraulic fracturing, the well is treated from the bottom up, and blending liquids are needed before the actual hydraulic fracturing occurs as well as after the final zone has been treated and the plugs need to be removed from the well.

Chemicals such as polymers to carry the cuttings, coiled tubing (CT) friction reducers, and lubricants are vital to the process. Lubricants and CT corrosion inhibitors also can be used during the CT drill out.

The HydroLutions system was used by Apache Corp. for an operation in the Permian basin.

Responsibly handling flowback

Operators are working to meet stricter requirements set forth by landowners and legislators. Making matters more muddled is that there is not a general specification for the final treated water. Different operators have different requirements because fracturing fluids depend on geology, operating environments, fracturing design, and results required.

Service companies must be able to provide customizable solutions to meet numerous needs, and operators need to understand how many different technologies and processes treat flowback. There is not one that offers a complete solution; the type of technology used depends on the chemistry and the treated water requirements.

During a hydraulic fracturing job, 15% to 30% of the fracture fluid returns to the surface as flowback, which is typically deposited in disposal wells. However, this fluid can be recycled and reused for future hydraulic fracturing jobs.

Coagulation and flocculation process

The most versatile and cost-effective treatment process is the chemical coagulation and flocculation process where flowback fluid is chemically pretreated to precipitate the unwanted constituents and then separated by physical means. This process typically involves four stages: oil separation, coagulation and flocculation, settling tanks, and sludge handling.

During the oil separation phase, flowback fluids contain water that can be recovered. There are numerous types of technology that can separate oil from water, including hydrocyclones, which spin the mixture and use acceleration to separate oil from water. The water is then forced outside of the unit where it is then removed.

The next stage is the coagulation and flocculation process, which is primarily based on the particles’ electrical charges. Most particles dissolved in water have a negative charge and tend to repel each other. In the coagulation stage, these electrical charges are neutralized so that particles are capable of sticking together.

For chemicals that have no charge, such as boron, there are coagulants such as a double-layered hydroxide compound that can be used to selectively precipitate the boron. Due to Van der Waal’s force, which is the tendency of particles to attract to each other weakly if they have no charge, the particles drift toward each other and join together into a group.

In water treatment systems, adjustments are often necessary to maximize the coagulation process. These adjustments are a reaction to changes in the raw water entering the system. Coagulation will be affected by changes in the water’s pH, alkalinity, temperature, time, velocity, and zeta potential.

Flocculation is the gentle mixing stage where the particle size of the flocculate increases and joins together before settling out of the water. Once the flocculate has reached its optimum size and strength, the water is ready for the sedimentation process.

Following coagulation and flocculation, water containing flocculates normally passes to a settlement and clarification phase where solids are settled by gravity. As the solids settle downward, the liquid flows upward and over a weir. Settled solids collect on the floor to form what is known as a sludge blanket.

The final process is to recover as much water as possible and to reduce disposal cost of solid wastes. Sludge dewatering includes centrifuges, vacuum filters, belt filters, and filter presses. The best dewatering solution for a facility is a function of many variables such as the sludge quantity and characteristics, the sludge disposal methodology, available space to house the equipment, and the dewatering time period.

The future of water management

Restrictions and new legislation will certainly have an impact on the future of hydraulic fracturing, and these issues will continue to propel the industry to seek new ways to conserve and recycle water.

The industry must continue to explore solutions that treat and manage the entire life cycle of water. As new technologies that offer sustainable solutions are developed, costs will come down. Lower costs coupled with the continued greening of the oil fields will make it even easier for the industry to adopt sustainable water management systems.

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