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Expert discusses state’s quakes

Larry Grillot, the dean of the Mewbourne College of Earth and Energy at the University of Oklahoma, said on Friday that research shows that oil and gas drilling in parts of the state have a relationship with an increase in large earthquakes.

Grillot spoke to Bartlesville’s Daybreak Rotary Club, saying that Oklahoma has always had a bit more seismic activity than other surrounding states because of geologic features, but the rise in larger earthquakes in recent years is a cause for concern and additional study.

“We’ve always been active (seismically), but not to the extent that we are active today,” Grillot said. “In the years 1882 to 2008, we had one of those (4.0 or greater earthquakes) about once every 10 years. From 2009 to 2013, we had about three. In 2014, as of October 2014 we had 24 (4.0 or greater). You can see that there has been quite the significant increase in felt earthquakes… Over half since 1980 happened this past year.”

According to Grillot, most of the recent earthquakes in Oklahoma have occurred in the highest areas of oil and gas activity — specifically in areas where high pressure water disposal wells are located.

“You do see a general, regional correlation that where there has been an increase in oil and gas activity and water disposal wells there has also been an increase in earthquakes,” Grillot said. “There is also a natural element to this. There is a geographical relationship with oil and natural gas activities, but there is some natural element to this too.”

In related news, State official links earthquakes to disposal of waste.

According to Grillot, there are several fault lines that run throughout the state and the Nemaha Ridge, which runs south from Nebraska to roughly just north of Oklahoma City. However, the state’s recent rise in hydraulic fracturing, horizontal drilling and water injection wells are also, generally, within the same areas of these geologic features.

“There is a general relationship — and probably a causal relationship to some degree — to where the earthquakes are happening and the disposal, but it isn’t a direct relationship,” Grillot said. “Most of the earthquakes are happening in a time relationship and a location relationship in areas that are consistent with where we have had an increase in water disposal and oil and gas activity.”

But understanding the direct impact of that oil and gas drilling activity is a bit more challenging. According to Grillot, most water injection wells insert wastewater in the upper layers, usually 7,000 to 8,000 feet below the surface. Grillot said the earthquakes are happening at two to three times that depth.

Grillot said that OU researchers and geophysicists with the Oklahoma Geological Society are working with oil and gas industry leaders and the Oklahoma Corporation Commission to better understand the possible cause and effect of drilling activity and earthquakes.

“We are working with (the) industry to start to understand the faults,” Grillot said. “We are working with the Corporation Commission to know where the areas (are) that might be the most risk.”

According to Grillot, the Corporation Commission now has a monitoring system where they look at earthquake activity in regard to the different applications of water disposal wells and they look at that when considering approval of new sites.

 

This article was written by Nathan Thompson from Bartlesville Examiner-Enterprise, Okla. and was legally licensed through the NewsCred publisher network.

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