Hydraulic fracturing, or fracking, the rock-cracking method to release trapped oil and natural gas, always takes place thousands of meters below Earth’s surface — or so many people assume.
But a new study, published July 21 in Environmental Science & Technology, reveals that 16 percent of about 44,000 U.S. wells were fracked at less than about 1,609 meters. The researchers found 532 wells, or 1.3 percent of those studied, that were fracked about 300 meters or less from the surface — within the depth range of drinking water wells. Some oil and gas wells were fractured as little as 30 meters belowground. This raises concern that toxic chemicals used during the drilling could seep into shallow drinking water sources.
The data do not include all U.S wells and may underestimate the incidence of shallow fracking, the authors say.
Average depth of U.S. fracking wells studied
Fraction of wells studied that were fracked at less than 1,609 meters (a mile) deep