In North America’s most active shale fields, the drilling and hydraulic fracturing of new wells is directly placing older adjacent wells at risk of suffering a premature decline in oil and gas production.
The underlying issue has been coined as a “frac hit.” And though they have long been a known side effect of hydraulic fracturing, frac hits have never mattered or occurred as much as they have recently, according to several shale experts who say the main culprit is infill drilling.
“It is a very common occurrence—almost to the point where it is a routinely expected part of the operations,” said Bob Barree, an industry consultant and president of Colorado-based petroleum engineering firm Barree & Associates.
He added that frac hits are also an expensive problem that involve costly downtime to prepare for, remediation efforts after the fact, and lost productivity in the older wells on a pad site.
A frac hit is typically described as an interwell communication event where an offset well, often termed a parent well in this setting, is affected by the pumping of a hydraulic fracturing treatment in a new well, called the child well. As the name suggests, frac hits can be a violent affair as they are known to be strong enough to damage production tubing, casing, and even wellheads.
Claudio Virues, a senior reservoir engineer with CNOOC Nexen, said frac hits have become a top concern in the shale business because they can affect several wells on a pad, along with those on nearby pads too. Based on his experiences in Canada and in south Texas, the question is no longer if a frac hit will happen, but how bad will it be.
He is alluding to the fact that some wells impacted by frac hits never fully recover and, in the worst cases, permanently stop producing after taking frac hits. The frequency of these outcomes are unknown as there are no publicly available statistics. In a small minority of cases, and in select formation types, frac hits have been known to increase production in the impacted well, but this is unusual.