Prices arc sky-high, with profits to match. But looking further ahead, the industry faces

wrenching change, says an expert of energy.

"The time when we could count on cheap oil and even cheaper natural gas is clearly ending." That was the gloomy forecast delivered in February by Dave O'Reilly, the chairman of Chevron Texaco, to hundreds of oilmen gathered for a conference in Houston. The following month, Venezuela's President Hugo Chavez gleefully echoed the sentiment: "The world should forget about cheap oil."

The surge in oil prices, from $10 a barrel in 1998 to above $50 in early 2005, has prompted talk of a new era of sustained higher prices. But whenever a "new era" in oil is hailed, scepticism is in order. After all, this is essentially a cyclical business in which prices habitually yo-yo. Even so, an unusually loud chorus is now joining Messrs O'Reilly and Chavez, pointing to intriguing evidence of a new "price floor" of $30 or perhaps even $40. Confusingly, though, there are also signs that high oil prices may be caused by a speculative bubble that could burst quite suddenly. To see which camp is right, two questions need answering: why did the oil price soar？ And what could keep it high？

To make matters more complicated, there is in fact no such thing as a single "oil price": rather, there are dozens of varieties of crude trading at different prices. When newspapers write about oil prices, they usually mean one of two reference crudes: Brent from the North Sea, or West Texas Intermediate (WTI). But when ministers from the Organisation of the Petroleum Exporting Countries (OPEC) discuss prices, they usually refer to a basket of heavier cartel crudes, which trade at a discount to WTI and Brent. All oil prices mentioned in this survey are per barrel of WTI.

The recent volatility in prices is only one of several challenges facing the oil industry. Although at first sight Big Oil seems to be in rude health, posting record profits, this survey will argue that the western oil majors will have their work cut out to cope with the rise of resource nationalism, which threatens to choke off access to new oil reserves. This is essential to replace their existing reserves, which are rapidly declining. They will also have to respond to efforts by governments to deal with oil's serious environmental and geopolitical side-effects. Together, these challenges could yet wipe out the oil majors.

Dave O'Reilly and Hugo Chavez believe that

A．prices of oil and natural gas are very high.

B．prices of oil and natural gas will not go down.

C．oil and natural gas will keep sustained high prices.

D．the world has forgotten about cheap oil.