Fracking has made North Dakota oil fields much more productive, and a process known as refracking is also having an effect.
It's a method of reusing old wells and increasing output.
The technique was used during the downturn as a cheaper alternative to digging new wells.
It became less common when oil prices went up.
"Technology is not slowing down, and so the companies are going to continue to find ways in order to produce additional oil and gas from those wells. Refracking or recompleting those wells is just one of the techniques," said Pipeline Authority Director Justin Kringstad.
Kringstad says the process is a gamble for companies. It could double output or have little effect.