30th July 2015
Fracking Industry Has Changed Earthquake Patterns in Northeast BC
Impact on groundwater and migrating gases mostly unknown, critics say.
A special report.
By Andrew Nikiforuk, 21 Jul 2015, TheTyee.ca
New research and presentations by both provincial and federal scientists show that the shale gas industry, which the B.C. government hopes will eventually supply proposed liquefied natural gas terminals with fracked gas, has caused more than a thousand earthquakes in northeast B.C. since 2006 and changed the region's seismicity.
The earthquakes, ranging in magnitude from 1.0 to 4.3, include six events higher than 4.0 and more than 20 events that shook buildings and moved furniture in places like Fort St. John. Several events caused casing damage to horizontal wells. Moreover, industry-caused tremors remain an ongoing geological revolution for the region.
Earthquakes with a magnitude of about 2.0 or less are called microquakes and can't be felt at the surface. Events above 3.0 can be felt on the ground, and tremors just larger than 4.0 can cause minor damage. A great earthquake, capable of extensive damage, typically measures a magnitude of 8.0.
Scientists originally thought that hydraulic fracturing wouldn't trigger anything more than microquakes. But now that the technology has set off magnitude 4.4 quakes in Alberta, scientists are grappling to determine what kind of hazard industrial tremors might pose to pipelines, dams and other infrastructure.
At Upper Halfway, a community northeast of Fort St. John, residents have described the tremors as a series of crashes and bangs comparable to someone driving "a truck into the side of the house."
The shale gas industry involves the injection of highly pressurized fluids into wells to crack open difficult oil and gas deposits. The injections create a network of cracks that can also connect to fault zones. The reactivation of these faults can then trigger an earthquake, scientists say.
Due to limited monitoring, industry and government lack a full understanding of how the wave of quakes is changing the flow of groundwater in the region or the migration of gases such as methane, radon and carbon dioxide into the atmosphere throughout northeast B.C.
Earthquakes triggered by the shale gas industry in B.C. have not injured anybody or damaged public property to date. But industry-made tremors in the U.S. Midwest have caused damage in Oklahoma and created new insurance liabilities.
The United States Geological Survey concedes that "the most probable risks in areas of increased seismicity include life-threatening injuries caused by falling objects and economic loss from damage to structures with low capacity to absorb moderate earthquake shaking... there is no question that increased hazard accompanies higher levels of earthquake activity."
A recent presentation by Dan Walker, senior petroleum geologist for the BC Oil and Gas Commission, identified public safety, property damage, well bore integrity (the shaking can cause wells to leak methane) and aquifer contamination as genuine hazards from industry quakes.
But the BC Oil and Gas Commission would not grant the Tyee an interview with Walker to discuss his presentation in detail.
Walker gave another presentation on lessons learned from the industry-triggered earthquakes in B.C. at a 2015 Montreal meeting of the American Geophysical Union.
At that meeting, he said that controlling earthquakes caused by wastewater disposal wells was easier than managing tremors set off from fluid injection from hydraulic fracturing. There are more than 100 wastewater injection sites in northern B.C.
At disposal wells, the Commission can reduce rates of fluid injection or find alternative disposal zones with no faults nearby, Walker wrote in an abstract of his talk.
But hydraulic fracturing blasts fluids at much higher pressure into the ground and "responding immediately to hydraulic fracture induced events is limited to avoiding known active faults, altering hydraulic fracture parameters or suspending operations."
In addition to the need for comprehensive seismic monitoring and event reporting, Walker said one of the key lessons learned to date was that "Areas considered to be high risk for inducted seismicity should be considered for exclusion from development."
In a series of emails to The Tyee, the Commission said this lesson was not part of its policy and that the agency, which is funded by industry, would "respond to events as they occur and take measures to protect the public and environment."
...continued in PART TWO