How would we know if Saudi oil reserves were beginning to dwindle?

Saudi Arabia is fairly secretive, concerning its oil reserve capacity. What sort of clues might we see that would indicate that Saudi oil has crossed peak supply? Would they begin to lower output production, despite the inevitable rising global demand ?How would we know if Saudi oil reserves were beginning to dwindle?
first and foremost, you would stop hearing about gigantic deals being signed with oil companies, then you would hear that investments in the gas sector are surging comparatively. Also you would see a privatyization of the oil sector hence cashout operation. and also as an indicator, oil price within the country would start going up, hence here again taxes on oil products to compensate for loss of income.


I wouldn't think that this will happen in this generation and officially the next country that will run out of oil is Norway.