Adrian C Hedden | Carlsbad Current Argus | November 4, 2019

Extracting oil and gas via hydraulic fracturing – or fracking – uses and generates millions of gallons of water unfit for human consumption.

The Chevron Corporation estimated that for every barrel of oil it produces – about 42 gallons – up to seven to eight barrels of produced or waste water is generated.

Much of that water is brought up from underground with the oil and natural gas as it is extracted, and some of it flow-back fluid created when water and chemical are pumped down-hole to break up oil-rich shale rocks and return to the surface.

In the past, the waters generated or contaminated by oil and gas operations was disposed of via injection wells that return the water thousands of feet underground.

The industry largely believed fracking operations required fresh, pristine water.

But recently, companies like Chevron found they could reuse produced water in the process and cut down on the impact to freshwater supplies – especially in the arid Permian Basin of southeast New Mexico and West Texas.

Abdul Sule, Chevron’s Permian water operations supervisor said some research even showed well production increased with the use of produced water, because returning water back into the shale it came from has less of an impact on altering the chemistry of the formation.

“What we’ve seen over time is that the water that is being produced from a certain formation, if you’re treating it, you have the ability to re-inject it for completions activity right back into the formation," Sule said.

“That’s where it came from.”

Before produced water can be re-injected to fracture shale rocks, Chevron takes it through a treatment process, often onsite, to remove contaminants such as iron and bacteria while chlorine could be injected to prevent bacteria from forming.

Sule said that although the produced water’s chemistry is similar to the geological zone it will be re-injected into, even brief exposure on the surface can cause bacteria to grow.

The company uses a process call selective chemical extraction through Denver-based Gradiant Energy Services, a third-party water treatment company servicing the oil and gas industry.

The company was developed by a group of students at the Massachusetts Institute of Technology (MIT), starting out with an evaporation process that would see a portion the produced water evaporated to cut down on disposal injection.

Gradiant later evolved to include water recycling and disinfectant services, such as those provided to Chevron.

Dianne Nguyen, technical support engineer at Gradiant said the process starts with pumping hot water into a storage tank and separating the water from any remaining oil.

The oil is skimmed off and sent to market for additional revenue, while the water is sent to another tank for a chemical treatment.

Other solids are also pulled out of the water, and trucked away to a landfill.

In the mixing tank, a proprietary combination of chemicals is used to remove heavy metals and other contaminants, followed by a disinfectant – usually chlorine – and another process to lower the water’s PH level.

The resulting treated water is pumped into retention ponds known as recycled water containment structures (RWCS).

At Chevron’s Salado facility in southern Lea County, Sule said the RWCSs can hold up to 350,000 barrels of water, or 14.7 million gallons, while up to 30,000 barrels can be treated per day.

That facility has two ponds, with others others in Hayhurst, New Mexico and Texas along with Chevron’s Delaware Ranch in Culberson County, Texas, Sule said.

Salado was the first water treatment facility the company built in the Permian in 2017.

Chevron also uses “recycle on the fly” facilities during time if production ramps up, treating water to a lower standard but at a faster rate at up to 100,000 barrels per day.

Some of the water sent to the ponds it lost due to evaporation, meaning workers must keep a close eye on the levels coming in and pumping out.

“We’ve got to keep track of exactly how much water goes in to the pond, and how much goes out,” said Joshua Parks, water production specialist. “It gets kind of tricky. The going in is never the same as the going out because of evaporation and everything.”