Experts weigh in on strategic considerations when deciding how to rejuvenate production from a tired well.
They are called re-fracs, re-entries, re-completions and other variations on re-peat terms. Whatever the name, the purpose is the same—to re-enter an existing and declining well to access more rock and pump new life out of it—and it is becoming a much more common practice for operators.
‘Pump and pray’
There are two main types of refracs: bullhead and cemented liner. The first is less directed and therefore less costly. The second is used mainly in older wells with more untouched rock.
Garrett Fowler, COO of modeling company ResFrac, said that a bullhead refrac does not direct frac fluid.
“You’re just kind of hoping that it goes into the right place. We’ve seen great results, but it’s certainly less consistent. Sometimes we call them ‘pump and pray,’” he told E&P.
By contrast, a cemented liner refrac involves installing a new liner inside the existing casing, which covers all the previous fracs.
“Then you frac it as if it were a new well,” Fowler said.
After setting new plugs and perforating, stimulation is pumped into targeted sections of the well, usually many more than were fracked the first time, generating “a much higher likelihood of initiating new fracs” than with a bullhead. The new fracs become the point of re-entry; however, it is important to note that cemented liner refracs cost substantially more than bullhead refracs, and inventory can be limited by the size of the original casing.
Most good targets for the latter procedure are in early frac plays such as the Barnett, Bakken and Eagle Ford, where there is more unfractured rock. Permian fracking developed later, so that play has more fracs per foot, leaving less virgin rock to target with a refrac, Fowler said.
Companies are considering refracs for several reasons, according to Fowler.
“One motivation for refracs would be creating fractures where there were not fractures previously,” he said. Another reason could be to protect an existing well when stimulating an adjacent well.
By fracturing the depleted well before fracturing an infill well, “a stress barrier or boundary around that existing well is created, which helps to mitigate, or at least limit, the severity of the interaction between the infill and the existing well,” he said. Without that barrier, the child well could rob productivity from the parent.
Additionally, he said this “protective refrac” also can add to the fracture area in the existing well, which is likely older and might have fewer original frac zones, which leaves some rock untapped.
