Oklahoma geology group links quakes to oil waste wells

OKLAHOMA CITY – The Oklahoma Geological Survey said Tuesday it is “very likely” that most of the state’s recent earthquakes were triggered by the subsurface injection of wastewater from oil and natural gas drilling operations.

Geologists have been studying the cause of hundreds of earthquakes that have shaken the homes and the nerves of residents in central and north-central Oklahoma, where the pace of oil and gas drilling has accelerated in recent years.

A statement released by state geologist Richard D. Andrews and state seismologist Austen Holland said the rate of earthquakes and geographical trends around major oil and gas drilling operations that produce large amounts of wastewater indicate the earthquakes “are very unlikely to represent a naturally occurring process.”

The survey said the “primary suspected source” of the temblors is not hydraulic fracturing, or fracking, which is the practice of injecting fluid under high pressure to create cracks in deep-rock formations so natural gas and oil will flow more freely during drilling. It said the source is more likely the injection into disposal wells of wastewater produced as a byproduct of fracking.

“The OGS considers it very likely that the majority of recent earthquakes, particularly those in central and north-central Oklahoma, are triggered by the injection of produced water in disposal wells,” the statement said.

Earthquake activity in Oklahoma in 2013 was 70 times greater than the rate of earthquakes prior to 2008.

Geologists historically recorded an average of one and a half earthquakes of magnitude 3 or greater each year. The state is now recording an average of two and a half magnitude-3 or greater earthquakes each day, according to geologists.

The statement is the survey’s strongest since it began looking into the source of the state’s earthquake swarm.