By March 29, 2016 0 Comments Read More →

Fracking, not water disposal, behind earthquakes: study

Study estimates 0.3 per cent of fracking wells create problems

fracking

A group of Canadian researchers have determined that hydraulic fracking of oil and gas wells is behind earthquakes in Alberta and British Columbia.  Nexen photo.

EDMONTON _ New research suggests that hydraulic fracking of oil and gas wells is behind human-caused earthquakes in western Canada.

The study, published Tuesday by a group of top Canadian researchers, concluded that it isn’t injecting wastewater underground that’s causing problems in Alberta and British Columbia, a major step in understanding seismic events in those provinces that have already changed regulations and caused public concern.

“It’s critical that we get to a complete scientific understanding of the issue,” said David Eaton, a University of Calgary geophysicist and a co-author of the study.

Fracking involves pumping high-pressure fluids underground to create tiny cracks in rock and release natural gas or oil held inside. Scientists have previously concluded that oilpatch activity can cause earthquakes by making it easier for faults in underground rock to slip, but they didn’t know whether the Canadian quakes were caused by fracking or by the injection of wastewater back underground.

Public interest in the issue has been high, especially after an event in January shook pictures on the walls of homes in Fox Creek, Alta., a community in the centre of the Duvernay oil and gas field. Measuring between 4.2 and 4.8 on the Richter scale, that quake was the largest of hundreds of similar shakers around the community since 2013.

Eaton and his colleagues began with a database of more than 12,000 fracked and disposal wells drilled between 1985 and 2015. They cross-referenced that with another database of all seismic events over that time.

A complex statistical analysis pinned the blame convincingly on fracking and not disposal, Eaton said.

“There are more earthquakes in western Canada that are more related to hydraulic fracturing than wastewater injection by a factor of about two.”

Eaton said that’s the reverse of the situation in the United States, where wastewater disposal is considered to be behind most human-caused seismicity.

That doesn’t mean that a lot of wells cause earthquakes. Eaton calculates that about .3 per cent of fracked wells create problems.

But there are enough wells drilled for even that tiny fraction to be a concern.

“Even at .3 per cent, because of the very large number of hydraulically fractured wells, it still represents an issue that is of high priority to address scientifically,” said Eaton.

Alberta’s energy regulator has already changed its regulations for the industry as a result of the Fox Creek earthquakes. Eaton said regulators in British Columbia are also considering changes.

“The regulators have been quite responsive,” he said.

Eaton said his findings raise questions about how well the geology of heavily fracked oilfields in Alberta and British Columbia is understood.

“The occurrences in Canada have come as a surprise, in some cases, to industry, because there was a belief that all the potential faults had been identified,” he said. “One of the things we’re actively researching is to find new and better ways to identify these features.

“We’re looking for the signature of critically stressed faults in new and different ways.”

Eaton said scientists are aware of the pressure they face getting this issue right.

“There’s a mixture of science and the whole social-political aspect of this,” he said.

By Bob Weber of The Canadian Press

Posted in: News

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