Following a magnitude 4.3 earthquake that struck Edmond, Oklahoma, on December 29, 2015, the Oklahoma Oil and Gas Division ordered oil and gas (O&G) operators within a 15-mile radius of the epicenter to restrict their underground water injection activities. Edmond is less than 15 miles from Oklahoma City, the state capital.
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Under the directive, the volumes of daily injection within a 10-mile radius of the epicenter must be reduced by specific percentages or the floor of the well must be raised, called plugging back. For operations 10 to 15 miles from the epicenter, operators must monitor reservoir pressure.
The directive is the latest in a series of actions the Division has taken in response to seismic activity that has been linked to O&G injection into the Arbuckle geologic formation, which encompasses most of the state. The Arbuckle is a deep formation capable of absorbing water, which in theory makes it ideal for receiving industrial wastewater. However, the Division points out that there is broad agreement among seismologists that disposal below the Arbuckle poses a potential risk of causing earthquakes, as it puts the well in communication with crystalline “basement” rock.