Do we know how much oil is available?

Earlier this year I raised the issue as to whether we are getting close to peak oil production. The current issue of The Atlantic raises the question as to whether Saudi Arabia's biggest oil field, Ghawar, has passed its prime. Because of the secrecy with which Saudi Arabia functions, one cannot really know what reality is. However, oil production is down by 1,000,000 barrels a day in the past couple of years, years in which the price of oil has been rising. This decline has occurred despite the Saudis bringing new wells into production. Does the fact that the number of oil rigs in Saudi Arabia has quadrupled since 2001 tell us that they're looking for oil in more places?