It’s all about access to the resources. That was the common talking point for the heads of Repsol, Shell and BP during the opening session of the World Petroleum Congress in Madrid. Repsol CEO Antonio Brufau, Shell chief executive Jeroen van der Veer and BP chief executive Tony Hayward talked about what they see as the key drivers for today’s higher oil prices. All agreed that speculators are not the key factor in today’s higher prices. Instead, the main problems are access to the oil and gas reserves that are held by the national oil companies. Given greater access to reserves, all of the chiefs believed that substantial amounts of new oil could be delivered. “It’s about fundamentals,” said Hayward. “Demand is outstripping new supply.”

The other key issue is the psychology of the market. With oil buyers believing that future supplies will be limited, they are willing to continue bidding up the price. Van der Veer said the high prices are like an “anticipation of things that may happen in the future.”

While some critics will undoubtedly dismiss the comments of the three executives as self-serving, the emerging theme of the Petroleum Congress is one of limited supplies. By lunch time of the first day, several speakers at the various sessions were coming back to the same issues: limited access to large reserves, the high costs of materials, and the dire shortage of highly skilled workers – all of which are preventing substantial increases in supply and helping force prices higher.

In a session called “Chasing the Third Trillion,” that focused on the difficulties of delivering the next trillion barrels of oil needed by the world economy, Robert Skinner, a senior vice president at StatoilHydro, pointed out that in 1982, there were 34 universities in the U.S. who were awarding bachelor’s degrees in petroleum engineering. That year, those schools graduated 1,280 students in that field. By 2006, there were just 19 universities awarding petroleum engineering degrees and the total number of graduates was less than 300.

The best summary of the manpower crunch was likely delivered by Shell’s van der Veer, who, while discussing the increasing complexity of oil exploration and production, said that the “easy oil” has largely been found. That means that the energy companies are having to dramatically increase their investments in highly technical offshore fields. “That means “we need more brains per barrel” said van der Veer, “and that takes time.”