Canada oilsands steam extraction environmental safety called into question
16 August 2013
On August 13, more than 20 groups called for a public inquiry by Alberta Energy Regulator (AER) into the safety of oilsands extraction techniques after continuing bitumen leaks in northeast Alberta at a project owned by Calgary-based Canadian Natural Resources Ltd. (CNRL).
The damage at CNRL's Primrose East site, located 250 kilometres northeast of Edmonton, has been contained to a 13.7-hectare area and the company has been cleaning up an estimated 20 barrels — nearly 3,200 litres — that continues to seep out every day at declining rates.
CBC quoted Nikki Booth, spokesperson for Alberta Environment and Sustainable Resources Development, as saying: "We do know some animals have died – including waterfowl, beavers, tadpoles and frogs and shrews."
CNRL says faulty old wellbores are to blame for the Primrose East leak, though the AER says it still does not know the cause and the groups claim this is the latest of a number of unexplained surface seepages that have affected oilsands operations.
An investigation by Alberta's energy watchdog into a similar 2009 leak at Primrose said a potential cause could have been "geologic weaknesses in combination stresses induced by high-pressure steam injection."
CNRL has said it is unlikely that damaged caprock was behind that spill but that the heavy rains which caused severe flooding in southern Alberta could be responsible.
To extract bitumen at Primrose, Canadian Natural uses a method called high pressure cyclic steam stimulation, sometimes described as "huff and puff." This involves injecting steam into a reservoir through a well, letting it soak for a while and then drawing the softened bitumen to the surface through the same well.
The extraction method, which companies have used for decades, involves fracturing the rock to let the steam through, but not so much that it allows bitumen to flow to the surface.
A more common technique is steam-assisted gravity drainage, or SAGD, which pumps steam into one well and uses another well below it to bring the bitumen to the surface. Though cyclic steam stimulation has grabbed the most headlines recently, the environmental coalition wants the Alberta Energy Regulator to examine both techniques.
About half of current oilsands production comes from in-situ methods that pump steam deep underground to soften the tarry bitumen and enable it to flow through to the surface. The rest comes from open-pit mining of the oilsands.
The depth of the oilsands deposit is one of the factors that determine which method is used, but the trend has been towards more in-situ extraction methods.
The environmental groups say the fact that neither operators nor regulators know for certain why the seepages are occurring represents an unacceptable risk, and show that neither party has a good understanding of how much pressure the underground formations can tolerate.
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