A study published two weeks ago reveals a connection between wastewater injections — a common technique used in oil production in the U.S. — and earthquakes.
According to co-author and UC Berkeley professor of earth and planetary sciences Michael Manga, when oil is extracted from the earth, much more water is removed than actual oil. Manga said since the water is often too contaminated to return to the ground water, oil production companies utilize wastewater injection to create a disposal well for the oil.
“As long as we produce gas and oil, we have to inject water back under the surface, and we have to think of ways to do that without causing earthquakes,” Manga said. “(Our study) is a reminder that geology matters.”
The study examined the relationship between four disposal wells in eastern Texas and earthquakes — such as a 4.8 magnitude quake in 2012. Manga and his team found that the deep disposal wells caused earthquakes, rather than the shallow ones.
When oil companies created these specific disposal wells in eastern Texas, according to co-author and Stanford professor William Ellsworth, they either inserted them above or below a certain geological layer. Therefore, Ellsworth said, if a well was below the layer, liquid was trapped and could not move throughout the earth.
Fluid pressure would then increase when wastewater was injected into these deep wells, Ellsworth said. He added that if a disposal well is located close to a fault, this increase in fluid pressure could move the fault slightly apart and cause an earthquake.
Although the shallow disposal wells did not cause any earthquakes, Ellsworth said, injections into them caused the earth’s surface to rise. For the deep wells, no upliftings occurred because the water could not move at all, according to Ellsworth.
Co-author and University of Colorado professor Kristy Tiampo said they used a scientific model to locate where the water went after it was injected. The location of the water and the lack of change in surface height helped the team relate earthquakes to the deeper wells.
Wastewater injection is causing earthquakes in other states too, Manga said. He added that Oklahoma has had more earthquakes from injecting fluids than Texas.
“Oklahoma and Texas should not normally have a lot of earthquakes,” Manga said. “Oklahoma has now more earthquakes than California, although it isn’t located at a plate boundary.”
Instead of using a few deep wells to dispose of wastewater, oil companies could distribute the water between several shallow wells and avoid faults, according to campus professor of geoengineering James Rector, who is not affiliated with the study. Rector added that even if oil companies completely stop using deep disposal wells tomorrow, earthquakes could still occur as a result of previous actions.
“This advances our quest to better understanding the forces causing earthquakes — both natural and human-induced,” Ellsworth said.