Earthquakes used to be uncommon in Middle America. But in the last decade, quakes numbers have skyrocketed in Oklahoma and Kansas. Here's why.
An Oklahoma home damaged in 2011 during an earthquake that was likely spawned by injecting wastewater during fossil fuel extraction. Earthquakes used to be uncommon in Middle America. But in the last decade, quakes numbers have skyrocketed in Oklahoma and Kansas. The major uptick in seismic activity has risen alongside the growth of oil and gas production in the area.
“Our study implies that simply turning off the injection wells will not immediately stop the earthquakes,” said Virginia Polytechnic Institute hydrogeologist Ryan Pollyea, who led the new research.While attending a workshop in Oklahoma last February, Pollyea molded an idea. “It was super cold outside, and I began thinking about how the weather affects wastewater injection operations,” he said.
“It occurred to me that any wastewater stored above ground was probably getting cold,” he said. When it’s cold, a fluid’s density increases and as density rises, fluid pressure builds up. This led Pollyea to the idea that water density might play a role in the seismic activity associated with wastewater
injections. If the wastewater is denser than the fluid already sitting in deep geologic formations, then injecting high-density wastewater into underground wells could create enough pressure to set off quakes. And, as it turns out, the oilfield wastewater in Oklahoma and Kansas is denser than the fluid in the subterranean geologic formations.
Pollyea was curious to know how this difference in density would affect the underground pressure. To find out, he and his team built a model that reproduces the physics of the system.The model revealed that high-density wastewater sinks and displaces the lower density fluids in the deep rock formations, Pollyea and team report