Earthquake hazard linked with deep well injection in Alberta
Deep well disposal of oilfield waste over time leads to increased earthquake risk
Rural Albertans have been saying for years they can feel tremors under their feet near oil and gas activity, especially around areas of hydraulic fracturing — also known as fracking.
While the movements are small, and don't cause damage, they have been cause for concern.
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The U.S Geological Survey has said in the past there is a connection between oil and gas production and seismic activity. While the science in Alberta isn't settled, researchers say there is a growing correlation.
The Alberta Energy Regulator (AER) says they are also keeping a close watch on the pressure in deep well disposals.
"The papers in the science community do reference hydraulic fracturing as a possible cause [of earthquakes]," AER spokesman Bob Willard told CBC News.
"But I think most scientists would suggest that deep well disposal and storage would be far more likely as an industrial activity that might cause one."
Willard says Alberta has more than 3,000 disposal wells, which are injected with everything from waste water to toxic fracking fluids over long periods of time, but that number is expected to grow as the industry expands.
"What happens is over that long period of time the stresses can increase in and around that well bore, and if the rate of injection is too fast or if there is a geological feature, such as a fault or fracture in that area, that can be pressured up and that can actually cause some movement," said Andrew Beaton, the director of the Alberta Geological Survey (AGS).
The province says it's important to remember the disposal wells are regulated and new monitoring is making it easier to identify problems.
The disposal wells are divided into different classes with the most toxic oilfield waste falling under Class 1. Willard says there are 354 Class 1 wells that have "integrity tests" every five years. The company that owns the disposal well also has to check the pressure daily.
"Class 1 wells are subject to more strenuous requirements on well completion, operations [and] monitoring practices than a Class 2 well," said Willard.
The disposal wells are often encased in cement and remediation plans must be in place in the case of a leak.
Willard said many of the disposal wells are concentrated in areas of oil and gas activity to reduce the trucking implications of moving toxic material long distances. The area extending from northwest of Calgary along the foothills to Grande Prairie is where the majority of horizontal drilling happens, including fracking, and where most of the disposal well waste is generated.
Beaton said there are natural earthquakes that happen in Alberta frequently at low magnitude, but the AGS is trying to sort out what’s being caused by the oil and gas industry and the risks involved.
Notification system set up
"We are starting to look at these occurrences a little more in-depth, that always helps you see more and more, but in general most of the activity is very, very low and most people won’t feel it,” he said.
There are currently 24 seismic monitors in the province, which are also tied into other networks like those belonging to Environment Canada, University of Calgary and University of Alberta.
"We have a notification system set up so that if our network actually records some high-magnitude events we're notified instantly," Beaton said, adding that information would then be shared among the province's regulatory agencies.
One area that seems to be a hotbed for seismic activity in the province is Rocky Mountain House.
“It’s a known area of higher than typical in Alberta seismic activity, and it looks like it is in part due to industrial activity," said Beaton. "But some preliminary geological investigations are also showing there are geological features in the area, so it could be a combination of some natural and some industry-induced events.”
Alberta has experienced 819 earthquakes between 1918 and 2009. In comparison, Saskatchewan recorded 13 in the same time and B.C. had more than 1,200 earthquakes recorded in 2007 alone.
AGS, which is part of AER under the science and evaluation branch, plans to release more information on the data it is currently collecting in the coming months.