Reserves increase because a.) we find more than we're using and b.) technological improvements steadily increase the amount of recoverable oil in a given reservoir.
Technology is an important part of this equation. I can recall two times in the past when the cry was "We're running out of oil". Then, somebody invented the pumpjack. The next time, somebody introduced injection.
Now, we've got sophisticated directional drilling technology. There will be more...
Agreed