Oklahoma’s efforts to limit powerful earthquakes receives national recognition

OKLAHOMA CITY - A new study concludes that steps taken by the Oklahoma Corporation Commission's (OCC) Induced Seismicity Department (OCC-ISD) to limit where and how much oil and gas wastewater is injected underground are reducing the number of strong earthquakes residents experience.

A report published by the Seismic Record of a study conducted by Robert Skoumal of the USGS and colleagues concluded that:

"Reducing injection rates into the lower Arbuckle through the combination of volume reductions and well plug backs was likely an effective strategy for reducing induced earthquake hazards in Oklahoma and Kansas."

The Arbuckle is Oklahoma's deepest sedimentary formation.

According to data acquired by the study's researchers from the OCC, the Kansas Geological Survey and the U.S. Environmental Protection Agency, oil and gas wastewater disposal rates into the Arbuckle dramatically increased in 2012 and peaked in March 2015 with about 16 million cubic meters of fluid injected into the formation monthly.

Since then, the OCC-ISD issued 33 directives to mitigate the potential for wastewater disposal‐induced seismicity. The directives covered thousands of square miles of Oklahoma and ranged from reduction of volumes for some disposal wells to the shut-down of others. All the directives were aimed at reducing injection volumes into the Arbuckle across Oklahoma, while others aimed to address individual earthquake sequences where operators were directed to shut wells in.

Oklahoma regulators also began rigorously scrutinizing all subsequently filed applications for any oil and gas disposal wells proposing to inject into the Arbuckle.

Before June 2016, researchers estimate those wells had injected about 340 million cubic meters of fluid into the Arbuckle's basement since 1995.

Regulators in Oklahoma and Kansas also directed operators of permitted injection wells to reduce the depths of their wells so that they no longer injected fluids into basement rock underlying the Arbuckle formation.

"Our earthquake forecasts suggest that the plug back requirements for lower Arbuckle wells reduced earthquake rates by a factor of about four," researchers wrote in the study's conclusion adding, "We find that the combination of well plug backs and injection volume decreases can be an effective strategy for reducing induced seismicity rates."

OCC-ISD Manager Charles Lord says the work continues to bring Oklahoma back to what would be considered a normal seismicity rate for the state.

"What's been accomplished so far is the result of a remarkable cooperative effort that includes the Oklahoma Geological Survey, the OCC, Oklahoma's oil and gas producers and others," Lord said.

The report, published in the Seismic Record, can be viewed here.