Oklahoma now produces more small magnitude three earthquakes than California. A new study links four massive injection wells in Oklahoma to a swarm of earthquakes. For once, the wastewater is not related to fracking, the controversial resource extraction technique.
Fracking is a petroleum industry technique where high-pressure fluids are used to fracture the bedrock. Afterwards, the fracking fluid is disposed of by injecting it into wells.
In Oklahoma, the problem is injecting wastewater from other, non-fracking related oil and gas projects. Although it is difficult to directly tie increases in regional seismicity to injection wells, earthquakes in traditionally tectonically-inactive Oklahoma have previously been tied to wastewater injection.
In this latest research, a swarm of earthquakes near Jones, Oklahoma have been tied to the injection of wastewater from a dewatering operation. A slurry of water, oil, and gas is extracted from the formation. The oil and gas is separated out, and the remaining water is injected back into the ground using one of four injection wells. All four wells are owned by New Dominion: Chambers, Sweetheart, Flower Power and Deep Throat. Combined, they bury 4 million barrels of wastewater a month, enough water to flood half the Empire State Building. The change in water distribution is enough to send a pressure wave through the hydraulic system. This change is enough to induce earthquakes surprisingly far away.
Current practice does not always require disclosure or monitoring of injection wells used to dispose of fracking fluids, dewatering wastewater, or any other mostly-water waste liquid produced by the resource industry. Although it is difficult to absolutely attribute seismicity to injection events, this latest research ties the increase of water pressure in the subsurface to reducing pressure and lubricating locked faults. This can be enough to induce seismicity, triggering earthquakes.
With a bit of luck, this study and others like it will help establish regulations on how, where, and how much wastewater can be injected, or maybe even do something truly outrageous, like monitor the wells, require explicit reporting of well data, or limit operations.
Error correction: The article originally stated Oklahoma had more small magnitude 3 earthquakes "each year" than California. In reality, it's only more small magnitude 3 earthquakes so far this year. Thanks to Andrew Alden for the correction!