Geologists are increasingly looking at waste water disposal wells as the cause of earthquakes linked to oil drilling.
A report from the National Academy of Sciences says injection wells are the likely cause of earthquakes linked to oil production, including in Oklahoma. The state is on track for as many as 400 quakes this year, 20 times what was normal before a big jump in oil production five years ago.
Geologist Donald Clarke lectured on the report Wednesday at the University of Tulsa. He said to think of pumping fracking waste water back into the ground like filling up an empty glass.
"When that glass fills up, it overflows," Clarke said. "So when you get the maximum pressure on this, the pore pressure, it's got to go somewhere. Something gives. It either comes up or it cracks, and that's when you get the little earthquakes."
More than 800 billion gallons of fracking waste water were pumped into more than 30,000 wells in 2012. Clarke said just eight quakes have been felt where injection wells were the likely cause.
"If we clean up those few, it's problem-free. Do you have no problems with 30,000 automobiles produced by Detroit?" Clarke said. "You can't get 30,000 without problems."
Clarke added the long-term effects are unknown. He would prefer states require geologic assessments before pumping begins and collect data through the active life of a well.