Oklahoma Earthquakes Decreased 58 Percent in 2017

The number of “felt” Oklahoma earthquakes — those registering magnitude-2.8 or greater on the Richter scale — fell 58 percent in 2017 from 2016 levels, according to an Energy In Depth review of United States Geological Survey data.

The monthly average number of M-2.8 and greater earthquakes in 2017 was also down 82 percent from the June 2015 peak, and felt earthquakes were down 71 percent from levels seen in Oklahoma’s most seismically active year of 2015.

Notably, these declines occurred at the same time that average weekly rig counts increased 70 percent higher than they were a year ago. State oil production is also projected to increase 5 percent from 2016 levels, based on the latest available data through October.

In other words — Sooner State earthquakes dramatically decreased in 2017 even as shale development increased significantly. This trend further dispels the common misconception that fracking is the cause of Oklahoma’s earthquakes, an inaccurate narrative that has been reinforced by a seemingly endless stream of headlines.

In sharp contrast to the all-too-common media narrative, the United States Geological Survey (USGS) has made it crystal clear that the fracking process is not responsible for Oklahoma’s increased seismicity and that the separate process of wastewater disposal from day-to-day production is likely the cause.

In fact, the very first sentence of the USGS’s list of myths and misconceptions regarding induced seismicity states:

Fracking is NOT causing most of the induced earthquakes,” further clarifying that, “Wastewater disposal is the primary cause of the recent increase in earthquakes in the central United States.”

Not only is wastewater disposal a completely separate process from fracking, the vast majority of wastewater being injected into disposal wells is not related to fracking, either.

A recent study by Stanford geophysicist Mark Zoback found that more than 95 percent of wastewater injected into disposal wells located in Oklahoma’s most seismically active areas is produced water, which is co-produced with oil and gas whether a well has been hydraulically fractured or not. As Dr. Zoback has explained:

“Basically, it is not hydraulic fracturing and it’s not hydraulic fracturing flowback water. It’s produced water.”

Produced water — also known as brine, saltwater or formation water — is typically ancient ocean water. It is not used fracking fluid, sometimes called flowback.

In the areas of Oklahoma recently plagued by seismic activity, wells typically co-produce a large amount of saltwater, sometimes 10 to 15 barrels for every barrel of oil produced, according to Oklahoma Geological Survey (OGS) director Jeremy Boak. Back when oil prices were well above $100, such wells suddenly became far more economical, leading to an increase in drilling in these regions and, subsequently, a significant increase in produced water from day-to-day production that needed to be disposed of in Class II injection wells.

Wastewater disposal has decreased significantly in the state since 2015 for a couple reasons. Not coincidentally, seismic activity has decreased in Oklahoma since 2015 as well.

Since 2015, Oklahoma regulators have implemented measures that have either shut in or reduced volumes of injection in roughly 700 disposal wells. Though these more than a dozen directives — which included increased monitoring, well plugging, and volume reductions for hundreds of injection sites near seismic events — have resulted in a “significant economic impact,” they have been largely supported by industry and have proven effective.

As a result, wastewater injection volumes dropped 40 percent from 2014 levels in 2016. The Tulsa World also recently reported that saltwater disposal volumes into the Arbuckle formation — suspected by scientists to be the geological layer where seismic activity is being triggered — dropped 21 percent through the first 11 months of 2017 from the same time frame in 2016.

Another factor contributing to a decrease in wastewater disposal is the fact that the focus on development in the state has shifted from the Mississippi Lime formation — which has an abnormally high brine-to-hydrocarbon ratio — to the SCOOP and STACK formations, which produce far less co-produced wastewater.

SCOOP and STACK development really started to take off midway through 2017, contributing to an 11 percent increase in monthly oil production in September compared to the same month last year. At the same time, earthquake activity declined 76 percent.

E&E News recently reported that the decrease in earthquake activity in Oklahoma can be “attributed to actions by state regulators and a slowdown in the industry.”

But drilling activity has actually been on a steady increase in the Sooner State for more than a year now, with higher rig counts than when seismic activity peaked in 2015.

The fact that earthquakes have declined by more than 50 percent at the same time drilling activity has ramped up underscores the fact that wastewater disposal — not fracking — is the true issue, and mitigation efforts to address that issue are proving effective.

As Boak recently said, “There are important issues to be addressed with respect to seismicity in Oklahoma, but hydraulic fracturing is not the critical one…

 

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  1. […] registering M-2.8 or greater — decreased 58 percent in 2017 from 2016 levels, according to an EID review of United States Geological Survey (USGS) data. The monthly average number of M-2.8 and greater […]

  2. […] registering M-2.8 or greater — decreased 58 percent in 2017 from 2016 levels, according to an EID review of United States Geological Survey (USGS) data. The monthly average number of M-2.8 and greater […]

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