The Editor's Perspective: Earthquakes differ in strength; the difference matters
Cracking rock in the subsurface causes earthquakes. There’s no escaping it.
Because hydraulic fracturing of oil and gas wells cracks subsurface rocks, it causes earthquakes.
Yet earthquakes vary greatly in strength. To opponents of hydraulic fracturing, though, one earthquake is much like any other.
Cuadrilla, a privately held UK operator, grapples with this absence of crucial distinction with two gas wells drilled into Carboniferous Bowland shale in Yorkshire.
Yet again, it has halted completion of the second well under the UK Oil and Gas Authority’s cautious “traffic light system.”
In that scheme, the operator monitors seismicity during injection of frac fluids and must proceed cautiously if local magnitude exceeds 0, possibly lowering rates. If seismicity reaches 0.5 it must suspend injection for at least 18 hr, reduce pressure, and monitor seismicity and ground motion for further events before work can resume.
Cuadrilla recorded an event of local magnitude 1.55 on Aug. 21 and paused as required. It only recently had resumed work at its Preston New Roads location after a suspension last December triggered by a magnitude 1.5 recording.
Describing the latest event in a news release, Cuadrilla said, “Most local people will not have felt it due to its small size. The equivalent ground motion would be similar to a large bag of shopping dropping to the floor.”
Opponents were appalled.
“We deplore Cuadrilla’s attempts to downplay and trivialize these quakes,” complained a spokesperson for Frack Free Lancashire to the Independent newspaper.
“It’s obvious that fracing can’t be done without triggering earthquakes,” said another Cuadrilla antagonist, insisting the completion method “just isn’t part of the future if the government is serious about avoiding climate breakdown.”
Thwarting oil and gas development to address climate change is, of course, the core motivation. Fracing’s just an excuse.
Still, the antagonist is right that no one can frac wells without inducing earthquakes.
It’s just that some earthquakes topple buildings, while others, like those from fracing, barely can be felt. The difference matters.
(From the subscription area of www.ogj.com, posted Aug. 30, 2019. To comment, join the Commentary channel at www.ogj.com/oilandgascommunity.)
Bob Tippee | Editor
Bob Tippee, Editor of Oil & Gas Journal, has written the weekly magazine's editorials since 1981. Since 1996, he also has written a weekly online feature called "Editor's Perspective," which appears first on OGJ Online and later in the print magazine. A member of the OGJ staff since 1977, Tippee has been chief editor since January 1999. He holds a degree in journalism from the University of Tulsa.