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Devon’s Dunvegan natural gas field offers a textbook case of ingenuity, desire and a little luck converging to solve a potential environmental issue.
The field, located close to the hamlet of Dunvegan in northwest Alberta, is the site of 250 existing wells. Each well required roughly 80,000 gallons (300 cubic meters) of fresh water to stimulate recovery. However, a new play within the field would require a tenfold increase in water per well -- roughly the same amount used each month by the nearby town of Fairview. While that usage was approved by regulators, Devon’s project team struggled with the environmental effect.
“That water would be lost forever. The cumulative impact of stimulating potentially more than 100 wells didn’t sit well with us,” said Bryan Helfenbaum, an engineer who is Devon Canada’s leader of the Peace River Arch exploitation department.
The new wells needed a gelled fracturing fluid. Historically, this had been done using fresh water and chemicals, which produce a substance with the consistency of hair gel. The project team experimented with a slick water “frac” like those performed in the Barnett Shale and elsewhere. However, it didn’t work.
The team sought a solution for months, but none appeared. A week before the first scheduled frac was to begin, the team learned of a product that was being tested at BJ Services lab in Calgary. The chemical additive would allow produced water to be used in place of potable water to form gelled frac fluid. If successful, this additive would eliminate the need for nearly 800,000 gallons (3 million liters) of fresh water per well.
Two kilometers from the frac site is a Devon-owned natural gas plant that produces huge volumes of salt water that normally is injected downhole for disposal. The project team created a tank farm onsite, where the produced water was stockpiled into 55 tanks, each holding about 400 barrels. (See photo above.) The process took nearly a week.
This experiment presented a huge opportunity, but also significant risk. The frac site operational cost was $500,000 a day. Although lab tests had proven successful, “there was the potential for a huge cost issue if the experiment didn’t work,” Helfenbaum said.
This act of environmental stewardship did work, however. And, not only was it cost-neutral, the process also offered additional benefits that didn’t become apparent until later.
For instance, the proximity of the salt water supply reduced heavy truck traffic through the town of Fairview, which means fewer greenhouse gas emissions, less road wear and decreased disturbance for local residents. Also, because salt water is heavier than fresh water, pumping it into the ground required less horsepower, which also reduced emissions and costs.
This project holds great reward potential as its positive impact compounds over the years.
“We were thinking long term about being a good neighbor and trying to do the right thing,” Helfenbaum said. “With the success at Dunvegan, we have tried to use produced water everywhere we can rather than fresh water.”