Definition of 'Re-fracking'
Re-fracking is the practice of returning to older shale oil and gas wells that had been fracked in the recent past to capitalize on newer, more effective extraction technology. Re-fracking can be effective on especially tight deposits – where the shale produces low yields – to expand their productivity and extend their life.
Investopedia explains 'Re-fracking'
Wells sunk as little as three years ago and fracked until yields fell too low to be worthwhile are now being re-fracked. One technique is sealing up larger cracks in the well's shale with small plastic balls so that new proppant can find its way into tighter cracks with the help of a higher well pressure. With wells costing many millions of dollars to drill and complete, it makes sense to return to see if new technology can extend their life.
(For more, see: Fracking Can't Happen Without These Companies) and (Why Schlumberger Is A Name You Should Know.)