The blowout at an offshore oil well in the Gulf of Mexico is showing the potential of one of Mexico's richest oil fields, officials of the government oil company say. It also threatened to affect the ecology.

The runaway test well has been spewing about 30,000 barrels - 1.26 million gallons - of light crude oil a day and comparable amounts of natural gas in the gulf's worst blowout. The well ran wild last Sunday when a spark from an electric motor ignited leaking fuel escaping under pressure, apparently from a ruptured pipe.

"It goes to show how rich that oil field is," said Miguel Tomassini, a spokesman for Pemex, the government oil monopoly.

The test well is 50 miles offshore in Campeche Bay, one of Mexico's richest oil fields, and about 800 miles south of the Texas Gulf Coast.

Tomassini said two collector boats with a capacity of 5,000 barrels each were scooping up about 15,000 barrels of the spilled oil daily and dumping it in a tanker anchored nearby.

"The other 15,000 barrels is either evaporating because of the intense heat or is being allowed to burn along with natural gas," Tomassini said.

Representatives of the shrimp boat industry, which earns $100 million a year in Campeche Bay, had already complained that oil pollution cut their catch by 20 percent in recent months. One of them said the latest accident posed "a grave risk to the marine ecology of the area."

A Pemex spokesman said the spill is now about 2 1/2 miles long and more than half a mile wide. But pilots flying over the bay yesterday said the slick extended over an area 40 miles wide and 70 miles long.

Cardenas said Red Adair, the Houston expert in fighting runaway wells and well fires, was in Mexico, but he could not immediately confirm that Adair had been hired by Pemex to bring the well under control.

Officials say a "relief" well will have to be drilled to cap the flaming runaway. The relif well would be drilled at an angle to the burning well and would link up with it so that oil and gas are diverted into the new shaft cutting off fuel to the flaming well. They say the operation could take more than three months.