  The microstructure of oil sand samples extracted at a depth of 75 m from the
estuarine Middle McMurray formation (Alberta, Canada) has been investigated by
using high resolution 3D X-Ray microtomography ($\mu$CT) and Cryo Scanning
Electron Microscopy (CryoSEM). $\mu$CT images evidenced some dense areas
composed of highly angular grains surrounded by fluids that are separated by
larger pores full of gas. 3D Image analysis provided in dense areas porosity
values compatible with in-situ log data and macroscopic laboratory
determinations, showing that they are representative of intact states. $\mu$CT
hence provided some information on the morphology of the cracks and disturbance
created by gas expansion. The CryoSEM technique, in which the sample is freeze
fractured within the SEM chamber prior to observation, provided pictures in
which the (frozen) bitumen clearly appears between the sand grains. No evidence
of the existence of a thin connate water layer between grains and the bitumen,
frequently mentioned in the literature, has been obtained. Bitumen appears to
strongly adhere to the grains, with some grains completely being coated. The
curved shape of some bitumen menisci suggests a bitumen wet behaviour.
