Man-made earthquakesEarthquakes in Oklahoma linked to oil, gas drilling
A new study finds that the recent spike in triggered earthquakes in Oklahoma is primarily due to the injection of wastewater produced during oil production. Geophysicists have identified the triggering mechanism responsible for the recent spike of earthquakes in parts of Oklahoma — a crucial first step in eventually stopping them. The study shows that the state’s rising number of earthquakes coincided with dramatic increases in the disposal of salty wastewater into the Arbuckle formation, a 7,000-foot-deep, sedimentary formation under Oklahoma.
A new Stanford study finds that the recent spike in triggered earthquakes in Oklahoma is primarily due to the injection of wastewater produced during oil production.
Stanford geophysicists have identified the triggering mechanism responsible for the recent spike of earthquakes in parts of Oklahoma — a crucial first step in eventually stopping them. In a new study published in the 19 June issue of the journal Science Advances, Professor Mark Zoback and Ph.D. student Rall Walsh show that the state’s rising number of earthquakes coincided with dramatic increases in the disposal of salty wastewater into the Arbuckle formation, a 7,000-foot-deep, sedimentary formation under Oklahoma.
A Stanford release reports that in addition, the pair showed that the primary source of the quake-triggering wastewater is not so-called “flow back water” generated after hydraulic fracturing operations. Rather, the culprit is “produced water” — brackish water that naturally coexists with oil and gas within the Earth.
Companies separate produced water from extracted oil and gas and typically reinject it into deeper disposal wells.
“What we’ve learned in this study is that the fluid injection responsible for most of the recent quakes in Oklahoma is due to production and subsequent injection of massive amounts of wastewater, and is unrelated to hydraulic fracturing,” said Zoback, the Benjamin M. Page Professor in the School of Earth, Energy & Environmental Sciences.
The Stanford study results were a major contributing factor in the recent decision by the Oklahoma Geological Survey (OGS) to issue a statement that said it was “very likely” that most of the state’s recent earthquakes are due to the injection of produced water into disposal wells that extend down to, or even beyond, the Arbuckle formation.
“The Stanford scientists’ findings were carefully considered before we issued the statement, and contributed to the scientific credibility of the statement,” said OGS state seismologist Austin Holland, who was not involved in the study.
“We’ve been waiting for exactly this type of study,” said Michael Teague, Oklahoma’s Secretary of Energy & Environment. “These findings help us understand the case better so that we can evaluate options that we can take to go forward in finding ways to reduce the quakes.”
