There are "original oil in place" reserves. They become reserves when you find them.
There are "economically recoverable" reserves. They become reserves when the prices and technology arrive.
Alberta has more total hydrocarbon reserves than Saudi Arabia. Oil shale and tar sand.
Inland America was once an open sea. Oil seems to occur at the edges of seas and oceans. That's one speculation, that sealife fell to the bottom and was compressed by sediment where it gradually turned to bitumen and oil and then emerged along the shoreline. That would account for oil deposits from Indiana to Texas/Louisiana and the tar sands from Colorado to Alberta.
"Alberta has more total hydrocarbon reserves than Saudi Arabia. Oil shale and tar sand."
I agree but the tar sands will be capacity limited for some time. An interesting company to follow in this regard is OPTI Canada Inc. They have raised significant capital to put to work in the tar sand play. It's worth watching.