The amount of bitumen released to surface from four locations at Canadian Natural Resources Ltd.’s Primrose South and East thermal projects totaled 6,670 bbl as of Aug. 2, Alberta Energy Regulator (AER) reported (OGJ Online, July 18, 2013).
AER last month ordered CNRL to restrict steam injection in the cyclic steam stimulation project areas about 55 km north of Bonnyville in the Cold Lake region of Alberta.
It said the releases had affected 20.7 hectares of land.
“We do not currently have the evidence or data to support any conclusions as to the cause of the incident and look forward to reviewing CNRL’s information supporting their conclusions on the root cause of the releases,” AER Chief Executive Officer Jim Ellis said in a press statement.
On July 31, CNRL said the rate of release had declined to below 20 b/d of bitumen emulsion. Clean-up had cut the area of focus to 13.5 hectares, it said.
“Canadian Natural believes the cause of the bitumen emulsion seepage is mechanical failures of wellbores in the vicinity of the impacted locations,” the company said.
It said it has begun production in some Primrose areas where steaming would have continued if the releases hadn’t occurred.
“The company is of the view that reserves recovered from the Primrose area over its life cycle will be substantially unchanged,” it said.