Some of the quakes were severe enough to ''experience a few seconds of shaking'' on the ground in seven areas of the province on top of the large Montney shale gas basin.
The events, many of which occurred in clusters or swarms, showed that the regulation of the industry still lags behind the pace of drilling activity in the region.
''Induced seismicity related to wastewater disposal and hydraulic fracturing within the Montney (a 29,850 square-kilometre underground siltstone formation) indicates a more uniform application of regulations is appropriate,'' concluded a December report by the BC Oil and Gas Commission.
The 32-page report states that 38 tremors were caused by the injection of wastewater produced by fracking operations and another 193 events were directly attributed to the hydraulic fracturing of hundreds of horizontal wells in the region.
Hydraulic fracturing is a technology that pumps slurries of water, sand and chemicals at high pressure to crack shale rock as deep as 2,500 metres. Industry models can't always predict how the rock will crack or where the cracks will travel.
The Commission says that none of the recorded events resulted in well damage and that ''ground motions recorded to date are below the damage threshold.'' Yet many of the tremors shook the ground under well sites near Fort St. John and Dawson Creek.
The report appears to contradict its own finding, however, by noting that ''several instances of casing deformation have occurred with the horizontal portion of shale gas wellbores.''
More swarms abroad
Other scientific reports and studies released this month have implicated hydraulic fracturing or the injection of fracking wastes with earthquake swarms in Ohio and Texas.
Since 2008, the U.S. Geological Survey has reported nearly 100 tremors near Irving, Texas, another landscape as highly fractured as northern B.C.
Before oil and gas development, ''a swarm of earthquakes like this would be fairly uncommon,'' John Bellini, a geophysicist at the USGS, told the Guardian this week. ''In the last few years we have seen several swarms of earthquakes in various parts of Texas.''
A new study published by the Bulletin of the Seismological Society of America also links hydraulic fracturing with earthquake swarms outside of Youngstown, Ohio.
That state has now established buffer zones around high-risk areas, while other states such as Colorado have set up a traffic light system for industry-caused earthquakes. A tremor of 4.5 magnitude serves as a red light to further fracking.
Horizontal or slanted wells have a long history of becoming problematic gas leakers due to their complexity and poor cement seals.
Injection of waste fluids a culprit
The BC Oil and Gas Commission report found that the injection of waste fluids (more than five million cubic metres of contaminated waste water a year) into 104 disposal wells in B.C. triggered small earthquakes ranging from 1.2 to 2.9 magnitude, while the highly pressurized frack operations triggered earthquakes ranging from one to 4.4 magnitude.
Any company that now triggers a 4.0 magnitude earthquake in B.C. must immediately shut down its operations. In addition, all felt events on the ground must be reported to the regulator.
The mechanism responsible for the earthquakes was the same whether industry injected short bursts of frack fluids under high pressure or large volumes of waste water over long periods of time: both practices reactivated subterranean faults or fractures, setting off swarms of tremors.
According to the report, more than 450 wells are drilled into the Montney formation every year and each wellbore requires up to 14 different hydraulic fractures.
Each fracking stage uses between 700 and 3,500 cubic metres of water. About half of that water ends up in a waste stream that industry then injects into the ground, triggering more tremors. On average, the province's fracking industry uses three times more water than its peers in Texas or Pennsylvania.*
In 2012, that amounted to more than seven billion litres of water drawn from hundreds of streams, rivers, lakes, dams, municipal waterworks and aquifers.
According to a presentation by Allan Chapman, a hydrologist with the Oil and Gas Commission, the industry will need 14 million cubic meters of water a year for the hydraulic fracturing of 900 wells. About 60 per cent of that water is expected to come from rivers and streams. Another 10 per cent will come from shallow fresh water aquifers. Only 10 per cent of the water consumed by industry is expected to come from deep saline aquifers.
To date, the province's fracking industry has tried to reduce frack volumes or injection pumping rates, but ''the success of these mitigation procedures is difficult to ascertain given the many hydraulic fracture operational parameters at play and the anecdotal nature of the results,'' states the report.
The commission adds that it must increase scrutiny for wastewater disposal wells so that pre-existing faults are identified before the industry sets off swarms of earthquakes.
Since 2005, the number of wastewater injection wells has increased from 89 to 104 in northern B.C. to accommodate all the contaminated water produced by fracking. Disposal volumes increased 60 per cent over the same period. Studies have shown that injection wells tend to leak more than producing wells.
Research on the effects and relationships between industry made earthquakes and hydraulic fracturing and water disposal is ongoing at the University of British Columbia and Geoscience BC.
*Duplicate word removed Jan. 10 at 3 p.m.
Original Article
Source: thetyee.ca/
Author: Andrew Nikiforuk
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