Rystad Energy has published an interesting article claiming that the US has more oil reserves than Saudi Arabia… if you include shale oil.
A new independent estimate of world oil reserves has been released by Rystad Energy, showing that the US now holds more recoverable oil reserves than both Saudi Arabia and Russia. For US, more than 50% of remaining oil reserves is unconventional shale oil. Texas alone holds more than 60 billion barrels of shale oil according to this new data.
I will not quote the entire article for copyright reasons but would invite you to go there and check it out. Their final total, their 2PCX reserves, includes undiscovered fields.