Falling oil prices have caused a sharp reduction in oil drilling in southern Kansas, and state geologists believe a decline in the number and intensity of earthquakes in the region might be directly related.
In the past year there have been 67 earthquakes emanating from Harper and Sumner Counties with a magnitude of at least 3.0, including one measured at 4.9 in November, the U.S. Geological Survey said.
But since April – a month after state regulators ordered a reduction in the amount of saltwater pumped into injection wells in the two counties – there have been only 15, including none in July, The Wichita Eagle reported.
A panel of state geologists and regulators gave an update Monday at the Kansas Independent Oil & Gas Association’s annual meeting.
Geologists don’t yet know how much of the decline in earthquakes is caused by a slowdown in the use of disposal wells for the wastewater created as a byproduct of oil and gas drilling.
Rex Buchanan, interim head of the Kansas Geological Survey, said it’s too early to start issuing rules on how drillers must operate.
In March, the Kansas Corporation Commission ordered a reduction in saltwater pumped down 20 injection wells in five areas of Harper and Sumner counties that have seen heavy seismic activity.
Kansas oil and gas drillers have been using hydraulic fracturing, a drilling method also known as fracking, for more than 60 years across the state with relatively little activity. That’s why the oil and gas industries were skeptical when people started connecting the two.
The injection wells are drilled down to the Arbuckle formation, a porous layer of sedimentary rock that sits many thousands of feet down just above the “basement” layers of much-harder igneous and metamorphic rock. The saltwater for decades has been easily absorbed into the Arbuckle.
But that was at much lower volumes than what the region has experienced since large-scale horizontal drilling and multi-stage fracking of the Mississippian Lime started in 2010 and produced huge quantities of subsurface water, said Lynn Watney, a geologist with the Kansas Geological Survey.
In 2014 oil and gas drillers pumped 10 million gallons of water into the Arbuckle in Harper County, he said.
Buchanan said it’s important to keep studying the problem because the price of oil will go back up, as will drilling in southern Kansas.
“What you don’t want is to be back in the same spot five years from now,” he said.