Government scientists are focusing on the disposal of wastewater from oil and gas drilling as the possible cause of scores of earthquakes that have shaken the central part of the U.S. since 2000, according to a study.
Researchers think the increased seismic activity may be linked to wastewater injected into the ground by oil and gas drilling operators, William Ellsworth, Earthquake Science Center staff director for the U.S. Geological Survey, said yesterday as he discussed the findings at a conference in San Diego.
“Something unusual is going on, and we think many of these earthquakes can be traced to industrial activity,” Ellsworth said, adding that scientists need more data to confirm their findings. An abstract of the study was published online earlier this month, and the full report will be issued this summer.
U.S. Geological Survey researchers found that for three decades prior to 2000, seismic events in the nation’s midsection averaged 21 a year. They jumped to 50 in 2009, 87 in 2010 and 134 in 2011, according to the study, which was presented at the annual meeting of the Seismological Society of America.
The findings add to pressure on the industry over a drilling process known as hydraulic fracturing — or fracking — that has sparked concerns the method may provoke earthquakes and taint drinking water. The study was discussed the same day that the U.S. Environmental Protection Agency released the first regulations to combat air pollution from gas wells.
No Significant Damage
Hydraulic fracturing has opened vast new shale gas deposits and helped push gas prices to the lowest level in a decade. Gas for May delivery fell to $1.94 per million British thermal units yesterday, the lowest intraday price since January 2002.
Ellsworth’s presentation drew an overflow audience of about 100 seismologists, engineers, government officials and industry representatives, according to meeting organizers. He said that none of what government researchers consider to be man-made earthquakes has caused significant damage and that more long- term studies are needed.
In hydraulic fracturing, water, sand and chemicals are injected into deep shale formations to break apart underground rock and free natural gas trapped deep underground. Much of that water comes back up to the surface and must then be disposed of.
The scientists traced the jump in seismic activity to disposing of that wastewater down wells, rather than to the process of extracting oil or gas, Ellsworth said.
“We find no evidence that there is any association whatever with these earthquakes to fracking,” Ellsworth said. He said that disposal of the water that returns to the surface during this process is the cause of the problem when it is injected deep underground.
There’s “a difference between disposal injection wells and hydraulically fractured wells,” Daniel Whitten, a spokesman for the America’s Natural Gas Alliance, which represents companies such as Chesapeake Energy Corp. (CHK) and Cabot Oil & Gas Corp. (COG), said in an e-mail last week after the release of the abstract. “There are over 140,000 disposal wells in America, with only a handful potentially linked to seismic activity.”
“We are committed to monitoring the issue and working with authorities where there are concerns, but it should be noted that currently there is no scientific data associating hydraulic fracturing with earthquakes that would cause damage,” he said.
In the U.K. yesterday, an independent panel of scientists said fracking operations there should be allowed to resume, as long as “robust” measures are followed to safeguard against future risks.
Cuadrilla Resources Ltd. suspended operations in the northwest of the country last year after causing two minor earthquakes. Operations can continue as long as precautions are taken, according to the report commissioned by the U.K. Department of Energy and Climate Change.
The area studied by the U.S. government researchers included a swath of the country running east-west from Alabama to New Mexico and north-south along the Great Plains, the study said.
“A naturally occurring rate change of this magnitude is unprecedented outside of volcanic settings or in the absence of a main shock, of which there were neither in this region,” Ellsworth and his colleagues wrote in the abstract.