Friday, March 11, 2016

Induced seismicity update: Oklahoma Issues Earthquake Response Plan

On March 7, 2016, the Oklahoma Corporation Commission (OCC) issued a regional earthquake response plan in an effort to limit the impact of wastewater injection wells overlying the Arbuckle formation in seismic regions of central Oklahoma. In addition, the Commission also envisages expanding the size of the area of interest for the purpose of reducing waste volumes. Oil & Gas Conservation Division (OGCD) Director Tim Baker declared that “the central Oklahoma action will cover more than 5,000 square miles and more than 400 Arbuckle disposal wells [which] is similar to the regional response strategy that was instituted in western Oklahoma on February 16.”

The response plan for central Oklahoma will be phased in over 4 stages and provides some limitations as to the daily disposal capacity of injection wells in the area of interest. Among those limitations, operators will have to ensure that daily disposal will not exceed “the lesser of 20,000 bbls per day of two times (x2) the reported daily average” and that the 30 day average daily disposal volume should not be more than 15,000 bbls for each well and not exceed the total allowed daily disposal volume capacity.” Operators are responsible for ensuring compliance with the response plan’s provisions before May 28, 2016.

The Commission also announced that the size of the area of interest will now cover 118 more Arbuckle disposal wells and, to the end of reducing waste volumes, the response plan provides that operators may plug some of their wells into or in communication with the crystalline basement rock, following comprehensive plug back procedures and schedule.

Researchers have found that there is a causal link between increased earthquake activity in Oklahoma and wastewater injection wells. The Commission has taken many different measures since March 25, 2015 to mitigate the risks of induced seismicity. In November 2015, the Commission announced a plan to end operations at two disposal wells located in Cherokee-Carmen with a volume reduction of 41% for some wells considered at risk after a magnitude 4.7 earthquake hit northern Oklahoma. More recently this year, the Commission also observed that the recent seismic events in the Fairview area might have “a very close correlation to the storms that created power outages in such area. It is believed that the power outage may have created a situation where a number of producing wells were shut in, then simultaneously came back on line.”

The Commission noted that from March to July 2015, 224 wells have been forced to be plugged back and 14 others wells have had their waste volumes reduced by half.

Written by Chloe Marie - Research Fellow

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