CUSHING, Okla. (AP) - Earthquake activity has picked up in the region around Cushing since 2009, but energy company officials at the oil storage hub worry more about tornadoes.
The 30-year period from 1978 to 2008 was relatively quiet for earthquakes, said Austin Holland, a research seismologist with the Oklahoma Geological Survey.
“The number of earthquakes that could be felt prior to 2009 was one or two a month and now it is more like dozens a month,” Holland said.
Depending on the location, generally quakes of magnitude 2.5 can be felt.
There also has been a cluster of earthquakes over the past month in central Oklahoma roughly from Oklahoma City to the Kansas state line.
Carl Karner, the senior engineering specialist for Tulsa-based Rose Rock Midstream, is not shaken by the activity.
“None of the quakes have been in Cushing,” he said.
Rose Rock has 7.6 million barrels of storage in Cushing, The Journal Record reported (https://bit.ly/1eNVzQD ).
About 80 million barrels of crude oil is stored in tanks in the area, one of the largest oil storage hubs in the United States and the price point for West Texas Intermediate crude on the New York Mercantile Exchange. WTI is the U.S. benchmark for oil futures trading.
The standards for building oil storage tanks are exacting, Karner said. Storage companies follow federal and state laws, and also adhere to the standards developed by the American Petroleum Institute for the construction and maintenance of their facilities.
“Our tanks are built according to API 650 standards,” Karner said, referring to a three-ring binder containing more than 1,000 pages of drawings and rules. About a tenth of the pages are dedicated to earthquake design.
Magellan Midstream Partners, another Tulsa energy company with storage in Cushing, complies with all laws and regulations administered by the U.S. Department of Transportation, the Environmental Protection Agency and all the regulatory authorities that have jurisdiction over aboveground storage tanks and pipelines, Magellan spokesman Bruce Heine said.
All of the more than a dozen storage companies operating in Cushing meet similar standards and take similar precautions to assess their pipelines and facilities following a quake.
“We shut down assets and perform inspections as needed,” said Larry Springer, senior manager of community partners and investments for Enbridge Inc. Enbridge operates the largest storage facility at Cushing, with 20 million barrels.
With hundreds of thousands of barrels of crude contained in each tank, they must withstand ground movement. The technical term is known as response acceleration, Karner said.
“It is like being in your car when you step on the gas and feel yourself being pushed back into the seat,” Karner said. “As you approach your final speed there is not that sensation - that is what happens in an earthquake.”
The API standards have specific seismic design criteria for this region, Springer said. Tanks are designed to withstand an earthquake 1,000 times stronger than the magnitude 5.6 quake that struck near Prague in November 2011. That quake was the largest in state history.
Withstanding the initial jolt is important, Karner said.
“Those at the epicenter will feel the jolt, then, depending on the distance, there is the rolling,” Holland said.
Storage companies have installed fire and lightning protection on tanks and have an alliance with the Cushing Fire Department in the event of an emergency, Springer said.
“We’ve also been integral in response-planning efforts with our industry peers and counterparts in emergency activities and spill response drills if we were to ever encounter a tornado,” Springer said.
Cushing is more likely to encounter severe wind conditions, Karner said.
“And, you have to look at each of these storage tanks as six-story building,” Karner said.
Oklahoma has entered a new era of quake activity.
“There is clearly a change,” Holland said. “What is causing that change is unclear.”
In recent months, environmental groups have raised concerns that hydraulic fracturing in the oil and natural gas industry has led to increased quake activity.
Holland is not convinced.
“We have been using hydraulic fracturing in Oklahoma for a very long time,” Holland said.
Hydraulic fracturing, or fracking, has been used to stimulate wells and extract oil and natural gas since the late 1940s.
“While some quakes, a small percentage, can be linked to fracking, it cannot explain all these earthquakes,” Holland said.
The real question is why now, Holland said.
“We know the frequency of earthquakes can change over time and we are trying to understand why,” he said.
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Information from: The Journal Record, https://www.journalrecord.com
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