Study by four universities: Oil field operations caused California earthquakes by David R. Baker, February 4, 2016, San Francisco Chronicle
For the first time, scientists have reported that the underground disposal of wastewater from oil drilling has probably triggered earthquakes in California, a problem already rattling nerves in Oklahoma and other states. [And Frac’d Alberta and BC]
Researchers on Thursday tied a September 2005 swarm of moderate earthquakes in Kern County to three wastewater disposal wells nearby. The wells opened between 2001 and 2005, rapidly increasing the amount of wastewater stored underground near the White Wolf fault.
The research paper, published by the American Geophysical Union, could not prove with absolute certainty that the wastewater injections caused the quakes. Earthquake swarms, such as the one that hit San Ramon last fall, are hardly unusual in California. But the authors calculated only a 3 percent chance that the Kern County swarm was mere coincidence.
The study also does not offer any indication of how common such human-induced quakes may be in California. “However, considering the numerous active faults in California, the seismogenic consequences of even a few induced cases can be devastating,” the authors note.
America’s recent oil production boom created a strange side effect – earthquakes shaking places that rarely felt them before. In 2015, for example, Oklahoma experienced 907 quakes larger than magnitude 3. Prior to 2008, the state averaged just two similarly sized quakes per year.
Scientists fixed the blame on injection wells, once considered the most environmentally responsible way for oil companies to deal with their wastewater. [Really ? Or the least conspicuous and cheapest?]
… As injection wells pump large volumes of water back underground – often into different rock formations than it came from – they can change the pressure within the rocks, making faults more likely to slip.
The emergence of hydraulic fracturing, which uses high pressure water to crack underground rocks, has produced even more oil-field water that needs disposal.
Wastewater injection wells can pose other problems. As detailed in a Chronicle investigation last year, California regulators for years let oil companies inject their wastewater into relatively high-quality aquifers that were supposed to be protected by law.
… Scientists had previously tied quakes to underground injections of water into California’s geothermal energy fields, but not to injections of oil-field waste water.
“You do have these swarms popping up unexpectedly in random places,” said the research paper’s lead author, Thomas Goebel, with UC Santa Cruz. “So we tried to be as rigorous as possible.”
The quakes included in the new study, which struck near the Central Valley’s southern edge, weren’t large, with the most powerful registering magnitude 4.7. But injection wells have been linked elsewhere to quakes as large as magnitude 5.6, Goebel said.
“These are quakes that can be felt and can cause damage,” said Shaye Wolf, climate science director for the Center for Biological Diversity environmental group. Her organization in 2014 issued a study that counted 350 injection wells in California within 5 miles of an active fault.
“There probably have been other earthquakes induced by wastewater injection that haven’t been documented, just because no one looked,” Wolf said. [Emphasis added]
FIRST RESEARCH LINKS CALIFORNIA QUAKES TO OIL OPERATIONS by Ellen Knickmeyer, February 4, 2016, Associated Press
SAN FRANCISCO (AP) — A 2005 spate of quakes in California’s Central Valley almost certainly was triggered by oilfield injection underground, a study published Thursday said in the first such link in California between oil and gas operations and earthquakes.
Researchers at the University of California at Santa Cruz, the University of Southern California and two French universities published their findings Thursday in a publication of the American Geophysical Union. The research links a local surge in injection by oil companies of wastewater underground, peaking in 2005, with an unusual jump in seismic activity in and around the Tejon Oilfield in southern Kern County.
…
In Kern County, the shaking topped out on Sept. 22, 2005, with three quakes, the biggest magnitude 4.6, researchers said.
Researchers calculated the odds of that happening naturally, independently of the oilfield operations, at just 3 percent, Goebel said. However, the oilfield operation “may change the pressure on … faults, and cause some local earthquakes” in California, he said.
Researchers are now studying other areas of the state to see if California’s high background level of shakiness is obscuring other seismic activity possibly linked to oilfield activity. California is the country’s No. 3 oil-producing state.
The Center for Biological Diversity environmental group, using state figures, estimates that the amount of oilfield wastewater injected underground in California climbed from 350 million barrels in 1999 to 900 million barrels in 2014.
… California on Dec. 10 commissioned Lawrence Berkeley National Laboratory to study the overall potential for oilfield-induced quakes in the state, said Don Drysdale, spokesman for the state Division of Oil, Gas and Geothermal Resources, the main oil regulatory agency. Rules that went into effect last year for some intensive forms of oil production require monitoring for seismic activity.
“In California, of course, we have a lot of natural seismicity here, so it’s much more difficult” to establish that an earthquake was caused by oilfield activity than it is in places like Oklahoma, which used to be quiet, said Art McGarr, a seismologist at the U.S. Geological Survey’s Earthquake Science Center in Menlo Park, California.
“Nonetheless, I think they made at least a fairly convincing case that these earthquakes were related to fluid injection” by oilfield operators, said McGarr. He called the researchers’ analysis “quite careful.” [Emphasis added]