Friction fighters and ‘shock absorbers’: The benefit of Drag Reducing Agents

Long-chain polymers help get more Canadian crude oil to market (System Optimization Series, Part 2 of 3)

In the face of a pipeline capacity crisis, polymers are providing a helpful push.

While Canada grapples with an ongoing shortage of pipeline export capacity, Enbridge is optimizing our network in multiple ways to get Canadian crude oil to market and help Canadians reap the benefits of the country’s natural resources.

A key element of that system optimization is the use of Drag Reducing Agents (DRAs). These chemical additives are injected at strategic points along our pipeline network in very low concentrations—usually a few parts per million.

“Most of our pipelines operate in what’s called a turbulent flow regime, and that’s where DRAs do their best work,” says Stephen Hunt, a manager of capacity management in Enbridge’s Liquids Pipelines unit. “Essentially, they act like a shock absorber—absorbing the eddy currents that spin off the pipeline walls and create inefficient flow.

“As a result, for the same safe pressure profile, you’re now seeing more flow.”

Enbridge has been using DRAs for more than 10 years on our crude oil pipeline network, which is the world’s longest and most complex. These long-chain polymers—plastic molecular structures, essentially, suspended in solution—can now be successfully applied to both light and heavy crude, and at these low concentrations, have a negligible effect on both equipment and the downstream refining process.

“DRAs are most often injected just downstream of pump stations, but we don’t use them at every location—or in the same concentration, for that matter,” says Patrick Yip, a capacity management engineer with Enbridge. “We optimize them, based on the unique characteristics and requirements of each pipeline segment.”

DRAs are not an alternative to vital projects like Enbridge’s Line 3 Replacement Program, a safety-driven capacity restoration initiative. And average annual capacities for Enbridge’s long-haul pipelines have reflected the DRA capacity boost for some time.

Still, when applied to more than a dozen pipelines across Enbridge’s expansive 17,000-mile (27,400 kilometre) network, Hunt estimates that these polymers make a collective difference of about 400,000 barrels per day.

“Drag reducing agent is a feature we actively use to maximize throughput on the Mainline today,” Guy Jarvis, Enbridge’s Executive Vice President and President of Liquids Pipelines, told the 2018 Enbridge Day investor conference in December.

“Our expectation is that further opportunities will be identified to ease bottlenecks and improve throughput through the further use of DRAs.”