HOUSTON, July 18 — A coup this week in the West African island nation of São Tomé and Príncipe is reverberating in the corporate suites of the energy industry here, oil company executives said today. Officials from several companies said they were anxiously monitoring events on the potentially oil-rich archipelago, a former Portuguese colony on the Equator in the Gulf of Guinea.

Exxon Mobil of Irving, Tex., the world's largest oil company, and Chrome Energy, a small Houston-based oil and gas company controlled by Nigerian investors, have secured options for oil exploration in the waters off São Tomé, an area just south of oil-rich Nigeria that geologists estimate could hold up to six billion barrels of reserves.

ChevronTexaco, Royal Dutch/Shell and TotalFinaElf are among the other big oil companies that have shown interest in bidding for licenses to explore other areas in auctions scheduled for October. This interest has sent expectations soaring in São Tomé and Príncipe, ae two-island country of 1,000 square miles and 160,000 people where the main export crop is cocoa and the average annual income is $280.

"Oil has created dreams of grandeur for a tiny place that has been on the margins of global affairs for many years," said Gerhard Seibert, an authority on São Tomé at the Institute of Tropical Scientific Investigation in Lisbon. "The army and the political and business elites sense something coming and want a part of it."

…Still, most cabinet members, including the oil minister, Rafael Branco, were being held captive today, adding to uncertainty over the effect the coup may have on oil exploration. The coup has already affected São Tomé's fragile economy: The World Bank said this week that it would suspend all aid to the nation as long as the coup leaders remained in power.

…No oil is expected to be extracted from São Tomé until 2007 or 2008, but the country has nonetheless become a international flash point, leading experts on West Africa to speculate it was only a matter of time before jostling for power ahead of the oil rush would evolve into political instability. Revenue from licensing agreements alone could reach $200 million in the next two years, an amount about four times the size of the national budget.

&hellip"The age of oil is upon São Tomé, so some level of friction is to be expected," he said.