While various wastewater recycling technologies have the same ultimate goal -- to give drillers a cost-effective means of reusing flowback and produced water -- there is no clear consensus on how to achieve it. Some companies use chemicals; others use electrical pulses. Some see removal of solids as mandatory, while others see it as costly and unnecessary.
Electro Water Separation
OriginOil uses a system called Electro Water Separation (EWS). EWS combines electrocoagulation (which involves using electrical pulses to prompt organic material in water to coagulate, or clump together) and electroflotation (which makes clumped material float to the surface, where it can simply be raked off the top).
The process leaves a solution that is not potable, but can be sent to disposal wells or used as the first stage in a water-recycling program. “We get it to about 99 percent clean,” said company Chief Executive Riggs Eckelberry. “We license our technology with companies that use it to get most of the stuff out, and then they do a final stage using nanofiltration and reverse osmosis,” he said. These processes can remove additional materials, such as minerals that contribute to water hardness. A company called Pace has integrated OriginOil’s process with a nanofiltration process.
Ecosphere uses a patented oxidation process called Ozonix to remove bacteria from flowback water, according to Ecosphere Energy Services Chief Executive Robbie Cathey. The process primarily uses ozone as an oxidizer to destroy or deactivate contaminants such as bacteria and heavy metals. “Oxidation disinfects the water, but doesn’t remove anything from it,” said Cathey.
Ecosphere also uses acoustic and ultrasonic cavitation to make bubbles that increase the surface area on which the ozone can operate, making it more effective. “That’s truly important [because] it allows us to treat water effectively at lower cost and because we don’t have to produce as much ozone, and it decreases the energy necessary to treat to water,” Cathey said.
Electrocoagulation is the final stage of the process. “We are releasing energy into the water that does a few things. The most important thing it does is precipitate certain scale-causing compounds out in a suspended form,” he said, adding that “scale” is the same material that builds up in a shower head and restricts water flow.
“We treat water to the point that it can be reused effectively in the hydraulic fracturing process at a price point that is very competitive,” Cathey said. “If you’re removing suspended solids (and we do that with certain customers), it becomes much more expensive, and you have a waste stream that you then have to dispose of,” he said. “It’s a logistics problem, a cost problem and an environmental problem.”
And Ecosphere does not use chemicals at any stage. “You’re not having to transport, store or handle chemicals, which has been a drawback to the hydraulic fracturing process,” Cathey said.
Integrated Treatment System
Ecologix Chief Executive Eli Gruber might contend that Ecosphere’s process risks compromising well productivity. Ecologix’s Integrated Treatment System uses chemicals to both remove suspended solids and disinfect the produced or flowback water.
“The key to generating reusable-quality frack water treatment is the removal of suspended solids,” Gruber told Breaking Energy. “And the only way to precipitate the full spectrum of suspended solids out of the water is through chemical means,” he said. “There’s just no other way.”
Suspended solids, which could include soil, metals and hydrocarbons, come in various sizes. “Those that are large can be removed with some superficial or physical means, but those remove only 15 percent to 20 percent,” Gruber said. “The vast majority of the suspended solids are colloidal suspended solids, which are less than 1 micron in size.”
The aggregate surface area of these smaller suspended particles can be orders of magnitude larger than that of a single large particle, and the greater surface area of the suspended solids introduces greater obstruction to the fracturing fluid’s ease of movement through the well, Gruber said. Hydraulic fracturing involves using that fluid to create fissures, or cracks, that allow oil and gas to escape into a well bore.
“If these suspended solids remain in the water, they will basically paste these cracks with a gummy layer that will cause these cracks to close,” Gruber said. More energy will then be required to push the fluid and proppant (which props the cracks open) into the well. Chemicals are required to neutralize suspended solids’ natural negative charge that prevents them from clumping together, he said.
“The ramification of not doing it correctly is that the well owner is going to pay dearly in terms of the lower productivity of the well,” he said.
Salt or Fresh Water?
Although they differ on the matters of both chemical use and suspended solids removal, Cathey and Gruber agree that removing salt from the water is not only unnecessary, it also may be detrimental to well productivity.
“In many cases, it’s actually beneficial to have salt in your frack fluids,” said Cathey. “If you have clay in the formation, then salt acts as a clay stabilizer, so you get better performance out of the well by having salt in your fracturing fluid.”
Gruber explained that in shale formations with significant clay content, injecting freshwater into wells could reduce well efficiency. “Clay tends to swell when you create osmotic imbalance; the natural state of groundwater is very salty,” adding, “If you introduce fresh water into this environment, the clay will swell, and it closes the fractures."
“Both because of that and because some of these companies pump water that is not fully treated, they actually cause themselves damage, anywhere from 2 percent to 40 percent of the productivity of the well,” Gruber said. Well productivity can be improved if injected water has salt levels similar to those in the formation, and “by using brine water, we would use less surface fresh water, or less aquifer water,” he said.
Can They Compete?
Gruber, Cathey and Eckelberry all stressed that their technologies can compete on a cost basis with trucking-produced or flowback water to injection wells or treatment plants. For more on costs, see part three of the series, Wastewater Recycling, Part III: Costs and Challenges.