Sep. 3--A major new oil discovery by BP in the Gulf of Mexico underscores the potential of a highly touted deep-water area where other oil companies also scored big in recent years, but the task of producing the crude has just begun.

The London-based oil company announced Wednesday that its Tiber prospect, in Keathley Canyon about 250 miles southeast of Houston, may contain more than 3 billion barrels of oil.

That would make it among the biggest discoveries ever in the Gulf of Mexico and the latest big find in an ancient rock bed called the Lower Tertiary trend, which runs miles below the seafloor in an outer rim of the U.S. Gulf between Texas and Louisiana.

But experts said it could be a decade or more before BP begins pumping oil from the field, given the technical hurdles and huge costs involved with operating in the harsh environment.

"I would say 2020 would be a good target," said Matt Pickard, analyst with Quest Offshore Resources, a Sugar Land company that studies deep-water oil discoveries.

The same may be true for other high-profile Lower Tertiary discoveries in recent years, including Chevron Corp.'s Jack field. Three years ago at Jack, an industry-first well test confirmed that the trend contains a vast quantity of oil and that it can be brought to the surface.

Last month, San Ramon, Calif.-based Chevron began a contract to use a new high-tech drilling vessel owned by Switzerland-based Transocean for additional exploration in Jack and other fields.

BP will need to drill additional wells to determine the size of Tiber and how to develop it, company officials said.

But on Wednesday, the company focused more on touting the "giant" oil discovery, as well the 35,055-foot depth of the Tiber well, one of the deepest ever.

'A matter of cost'

In recent years, improved drilling and production technology has enabled oil and gas companies to unlock resources in dense formations or remote locations once considered out of reach.

Yet the Lower Tertiary trend has posed new challenges because of the high temperatures and pressures downhole, extreme well depths and low oil viscosity, said Adam Anderson, vice president of marketing at Houston oil field services giant Baker Hughes, which is working with oil companies on solutions to the problems presented by the Lower Tertiary.

"Certainly, we could develop these fields; it's just a matter of cost," Anderson said, pegging current outlays at $250 million per well to produce a scant 5,000 barrels of oil per day.