With the drought in the western U.S. making water—already a scarce resource in much of the country—even more scarce, oil and gas operators must find alternative sources of water for production activities. Treatment of flowback and produced water has emerged as a practical choice for many, lessening the reliability on buying freshwater from local farmers and cutting down on costs.

In addition, with growing regulatory pressure against using disposal wells and evaporation ponds to dispose of produced and flowback water, operators are searching for alternative disposal methods. Water treatment offers disposal alternatives by enabling purification of flowback and produced water for beneficial reuse in oil and gas production or even for agricultural irrigation or use with livestock.

OriginClear’s Electro Water Separation (EWS) system seeks to address both the growing need for alternative water sources and purification for agricultural use as a disposal method. The company recently partnered with Vaquero Energy to test the EWS system for “the treatment of produced water for steam injection and to provide irrigation water for California’s drought-stricken Central Valley,” according to OriginClear’s website. The pilot test took place in Bakersfield, Calif., and included testing of OriginClear’s P250 model, capable of treating 250 bbl/d of water, and the company’s P3000 model, capable of treating up to 3,000 bbl/d of water.

“Operators, particularly in California, are moving toward alternative ways of handling the produced water, and Vaquero was one of those examples,” said Bill Charneski, senior vice president of OriginClear. “They are realizing that at some point in time they are going to lose the freshwater supply that they have from the local farmers, and they’re going to need an alternative source of water.”

In Bakersfield and surrounding areas of California operators rely on steam generation to coax very heavy oil from the ground, using freshwater as the base. Produced water treatment can provide both an environmentally friendly and budget-conscious alternative to sourcing this scarce resource.

An operator in Kansas faced with high trucking costs to transport produced water to the nearest disposal wells—located more than 322 km (200 miles) away—is examining treating produced water for use with livestock on the cattle farms nearby the wells. “Regionally, [water procurement and disposal issues] vary tremendously across the U.S. because of the local economics and the local availability of disposal, the environmental impacts and the regulatory issues that vary from state to state,” Charneski said. “It’s a real mix.”

How the system works
Raw produced water is fed into the EWS system, which combines three technologies in one piece of equipment. “The EWS process is a continuous chemicalfree very low-energy first-stage process for removing hydrocarbons, suspended solids and reducing biological activity,” Charneski said.

In the first stage, water flows through electrocoagulation reactor tubes that break the water-oil emulsion. “This causes the very tiny droplets of the 1-μ to 20-μ oil and suspended solids to conglomerate to larger particles so they will be able to be separated by gravity in the next step,” he explained.

In the second stage, water flows into a flotation chamber, where electroflotation technology generates a cloud of bubbles that attach themselves to the conglomerated oil and suspended solids. The oil and suspended solids then float to the surface, where a rake system pushes the floating solids and oil over a weir to eventually come out on the top. The water, on the other hand, comes out on the bottom of the tank.

In the third stage, the water flows through electrooxidation tubes, where oxidizing agents kill bacteria and precipitate heavy metals that are present.

Each EWS system can treat about 1,000 bbl/d of water, including the systems OriginClear recently tested in Colorado, Texas and California. “We are designing a 5,000 bbl/d [system], and 10,000 bbl/d is certainly within the range of what we can do,” Charneski added.

Unique benefits
Typical operating expense for the system amounts to about 14 cents per barrel, based on 15 cents/kWh and including 3 cents to 4 cents per barrel in energy costs, 4 cents per barrel for the consumable price and 4 cents per barrel for the maintenance cost. “Fourteen cents per barrel is very low if you compare it to other kinds of technologies,” Charneski said. “It even compares to just using straight filters, which do a minimal amount of good compared to what we do.”

In addition to cleaning produced and flowback water, the EWS process can minimize the waste stream created by treatment. During the electroflotation stage of the process, the “sludge” mix of solids and oil that is raked off the top and out of the tank can be pumped back into the primary oil-water separator knockout tank.

“We’ve taken the emulsified oil and turned it into concentrated oil that will float,” Charneski explained. “If it goes back into the knockout tank, the oil will float to the surface. The solids that we’ve also made larger—coalescing those tiny particles into larger particles—will fall to the bottom, so there will be a better recovery of the oil by processing the produced water through our process and putting it right back into the knockout tank.”

The oil will float to the surface, enabling a higher oil recovery rate, and the solids will sink to the bottom of the tank.

Cleaned up results
So how clean is the water that passes through the system?

Overall, the EWS process removes total petroleum hydrocarbon product to a level of about 3 parts per million (ppm) to 5 ppm or less and total suspended solids to a level of about 3 ppm. The process, however, does not remove dissolved ions like boron, divalent ions that cause scaling like calcium and magnesium and monovalent ions like sodium and chloride.

“What it does is remove the hydrocarbons and suspended solids such that downstream processes can then be used to remove the divalent ions, monovalent ions or dissolved ions,” Charneski said. Additional downstream processes like nanofiltration, reverse osmosis and ion exchange resins can then be used to remove the remaining ions.

The EWS enables these secondary processes to work efficiently. “If you don’t use our process before that, the downstream
processes get plugged up with the oil and suspended solids and do not operate efficiently,” he continued.

The EWS system can be a standalone process depending on the final intended use of the water. “If they’re just trying to remove the hydrocarbons and suspended solids and they’re going to reuse the water for waterflooding or something similar, then EWS can be a standalone process,” he added. “If they want to be able to use the water for steam generation, for instance, they’re going to have to use the downstream process to remove the calcium and magnesium that will cause scaling in the pipes.”

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