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 The changes include new protocols for inspecting the health of
crude tanks, potentially halting operations after temblors, and
monitoring quake alerts.
The revisions, fully implemented in 2015 and first detailed to
Reuters this past week, appear to mark the most significant
acknowledgement by a major energy company that its seismic
procedures were recently updated.
They also come as some researchers say tougher standards for energy
infrastructure such as pipelines and tanks could be needed to handle
an uptick in quakes since 2009 in Oklahoma.
Scientists have tied a sharp increase in the intensity and frequency
of quakes in Oklahoma to the disposal of saltwater, a normal
byproduct of oil and gas extraction work, into deep wells. Oil
fields have boomed in Oklahoma over the past decade thanks to
advances in hydraulic fracturing and horizontal drilling.
 A 4.7 magnitude quake struck in Oklahoma on Thursday, the strongest
temblor there since 2011. About a month earlier, a 4.5 magnitude
quake hit near Cushing. Regulators responded by calling for nearby
disposal wells to shut or curb intakes.
Phillips, a refiner, has 167,000 barrels per day of pipeline
capacity and 700,000 barrels of storage tanks at Cushing, home to
about 57 million barrels of crude and a nexus for U.S. supply,
according to a 2015 investor presentation.
Though its new protocols apply to all its U.S. infrastructure, when
asked specifically about potential Cushing risks, Phillips said its
"seismic response protocol was developed as part of our enhanced
geohazard program, which addresses geotechnical, hydrotechnical and
seismic hazards."
To be sure, most oil companies test the integrity of tanks on an
on-going basis and many told Reuters their tanks are built to the
latest construction standards and building codes.
But some scientists are questioning whether standards should be
tightened.
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Geologists led by D.E. McNamara of the USGS said in a September
academic paper that including human-caused quakes in the National
Seismic Hazard Model, a reference for engineers, "would result in
serious implications for design standards."
Currently, man-made quakes are also not accounted for in tank
standards published by the American Petroleum Institute (API), an
industry group, and design loads from the American Society of Civil
Engineers.
Strong quakes in regions outside Oklahoma have split steel as
rolling ground motion puts the weight from the liquids on one side
of the tank, known as "elephant footing," said Thomas Heaton, a
professor at California Institute of Technology.
Engineers told Reuters most tanks in Cushing rank in Seismic Use
Group 1, the weakest classification in API standards. TransCanada
Corp said its seven Cushing tanks are in SUG 1.
The largest quake in Oklahoma was 5.6, a level with potential to
damage tanks. Tanks normally have containment berms to catch leaking
oil.
"Anything more than a 5.0 you have to worry about a little more,"
according to Muralee Muraleetharan, a civil engineering professor at
the University of Oklahoma.
(Reporting By Liz Hampton; Editing by Terry Wade and Christian
Plumb)
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