What’s Causing Mysterious Bitumen Seepages in Alberta? Spills show fragility of so-called in-situ, or steam-assisted, production, say experts by Andrew Nikiforuk, Septemeber 24, 2013, TheTyee.ca
In 2006, Total, a French multinational company, over-pressurized one bitumen formation north of Fort McMurray. The accident allowed the steam to create or find a fracture in the cap rock and then blew to the surface. The resulting explosion created a 300-metre hole in the forest. The Alberta Energy Regulator described the explosion as a “catastrophic event” but didn’t publicly report on the matter for four years.
In 2009, CNRL had a major leak near the present bitumen ruptures, but stopped injecting steam and depressurized the formation as soon as it found bitumen leaking on the forest floor. That event, which contaminated the Bonnyville Aquifer, released 12,000 barrels of bitumen and wasn’t reported to the public until 2013. But CNRL and the Alberta Energy Regulator reacted differently this summer when bitumen mysteriously exploded to the surface at three different well locations, according to one independent geologist who requested anonymity. “For 24 days, the Alberta Energy Regulator allowed CNRL to steam the reservoir while still getting oil to surface over a three week period,” the geologist said. In other words, during that time neither CNRL nor the regulator acted to contain the seepage from fissures as long as 150 metres in the boreal forest by depressurizing the formation.
On June 24, a fourth leak appeared underneath a lake that CNRL has now been ordered to drain and clean up by the Alberta government. The energy regulator didn’t demand that CNRL lower its steam pressures at its Primrose facilities until July. The regulator says it does not know what caused any of the four leaks and is looking “forward to reviewing CNRL’s information supporting their conclusions on the root cause of the releases.” CNRL, one of Canada’s largest oil and gas producers and a significant bitumen player, says that mechanical failures or leaky wellbores are the problem, because they act as holes in the barrier of the cap rock. The company reported 18 leaking wellbore casings in 2013. But geologists and other scientists suspect the company has broken the cap rock by injecting too much steam. “You can fix a wellbore, but you can’t repair a fractured cap rock,” explained the geologist. “You have to reduce pressure which means producing less bitumen. But I suspect wellbore integrity is part of the problem too.” [Emphasis added]