The Alberta Energy Regulator says CNRL (TSX:CNQ) reported a break in a well at its Wolf Lake high pressure cyclic steam stimulation project in late October.
The regulator says since then the company discovered elevated levels of hydrocarbons in the aquifer about 50 kilometres south of Bonnyville.
Ryan Bartlett, a spokesman for the regulator, says the well has stopped operating and CNRL can't resume operations until the well meets regulatory requirements.
He says public health and safety are not at risk and the nearest private water wells are 15 kilometres away.
He says CNRL will be required to clean up the aquifer.