Latest earthquake response targets 400 disposal wells over 5,000 square miles in central Oklahoma

Posted: Saturday, March 5, 2016

By COREY JONES World Staff Writer

State regulators announced Friday that their latest widespread earthquake abatement measures will encompass in excess of 5,000 square miles in central Oklahoma and include more than 400 wastewater disposal wells.

In a news release, the Oklahoma Corporation Commission revealed the plan will include dozens of communities, including Edmond, Luther, Pawnee, Perry and Stillwater. Full details of the plan are expected to be released Monday.

The Corporation Commission said the plan will be similar to a plan implemented in mid-February calling for a 40 percent disposal volume cutback across a 5,200-square-mile area that for the first time involved proactive moves to include areas that aren't seismicity hotbeds. That plan affects 245 disposal wells, and another 38 in that area owned by SandRidge Energy Inc. were folded into that plan for a total of 283 wells.

The Tulsa World first reported Thursday that state regulators were drawing up another large-scale mitigation effort in central Oklahoma that also would likely target areas not yet affected by prior volume reductions.

A 5.1-magnitude quake — the third strongest in Oklahoma history — struck Feb. 13 near Fairview in northwestern Oklahoma. Three days later state regulators rolled out their largest regional volume reduction to that point.

The preliminary figures revealed so far in the new plan indicate it will be even larger than the Feb. 16 action.

Wastewater produced in oil and gas activities is blamed in the seismic rise of man-made quakes that have been plaguing the state for several years now. Experts point to disposal wells pumping that wastewater into the state's deepest geologic formation — the Arbuckle — as the most pressing concern.

The Corporation Commission's measures taken to reduce disposal volumes apply just to those wells injecting wastewater into the Arbuckle. There are about 4,200 disposal wells in Oklahoma, with about 1,000 disposing into the Arbuckle.

The Tulsa World in mid-January reported on a recent Oklahoma Geological Survey study that detailed an 81 percent jump from 2009 to 2014 in wastewater volumes injected underground. The rise coincides with the state's leap in seismicity. Even more strikingly, wastewater injected into the Arbuckle ballooned 141 percent in the same period.

Prior to February, the only regional-scale measures pushed by the Corporation Commission targeted well depths rather than disposal volumes. Wells deemed to be injecting below the Arbuckle were to plug back their depths and cut volumes in half in the meantime.

Those measures were enacted in March and July 2015, covering a total of 558 wells. As of mid-February, 224 wells had reduced their depths and 14 wells had reduced volumes by half, records show.

http://www.tulsaworld.com/earthquakes/latest-earthquake-response-targets-disposal-wells-over-square-miles-in/article_b8c9be78-eb3f-5c2e-b68e-6d00f4ade48f.html