A process for forming a deaerated oil sand slurry is provided comprising: providing a first vessel having an overhead space and a bottom space; delivering oil sand and a low vapor pressure hydrocarbon liquid into the overhead space and mixing the oil sand and hydrocarbon liquid to release air trapped in the oil sand and form the deaerated slurry; optionally adding an inert gas stream to the overhead space to displace the air released from the oil sand; and collecting the deaerated slurry in the bottom space to form a slurry layer to prevent gas exchange between the first vessel and downstream extraction equipment.