When we report on induced seismicity, or man-made earthquakes in Oklahoma, we generally point out that these are quakes believed to be caused by injecting oilfield waste water underground, and not by hydraulic fracturing. But a new study shows there may be some exceptions to this.
In the last five years, there have been a few series of low-magnitude quakes that were nowhere near any wastewater injection wells. At the same time, there was evidence these weren't naturally occurring earthquakes.
In January 2011, there were more than a hundred minor quakes in Garvin County. Then-state geologist Austin Holland wrote a paper, concluding the swarm was triggered by a nearby hydraulic fracturing operation.
In May and June of this year, there were a handful of mild quakes around Blanchard. And then just last month, another few quakes out in Canadian County. All of these are outside the Corporation Commission's 15,000 square mile area of interest, in areas where wastewater disposal is minimal.
In a statement Tuesday, Oklahoma Geological Survey director Jeremy Boak said, "Scientists with [OGS] have reached the conclusion that wastewater disposal was probably not the cause" of these recent quakes west and south of the metro.
"Hydraulic fracturing in wells in the SCOOP and STACK play nearby may have been the cause," he wrote.
Drilling in the SCOOP and STACK is beginning to take off, so, while wastewater disposal is not a big concern with these formations, the Corporation Commission is working on guidelines that they believe will minimize earthquakes there.
Meanwhile, new actions for the big area of interest are expected to be announced before Christmas.