* Oil leak of 100,000 bpd "next to impossible"
* Leak won't deplete the Macondo oil prospect
WASHINGTON, May 4 (Reuters) - Nobody knows the rate that oil is leaking out of BP's Macondo well nearly a mile under the waters of the Gulf of Mexico, but one U.S. official's estimate of 100,000 barrels per day is nearly impossible, industry and environmental sources said on Tuesday.
The leak may become the worst U.S. oil spill in history, but petroleum experts said the rate was almost certainly much less than the doomsday figure raised at the weekend by U.S. Interior Secretary Ken Salazar. [ID:nN02158331]
After examining the size of the oil slick on top of the water, BPestimated that the leak rate from the Macondo well was 5,000 bpd, up sharply from is initial estimated rate of about 1,000 bpd.
The Coast Guard, which has used remote underwater cameras to help estimate the volume of the leaks, also says it is about 5,000 bpd. While a much slower rate than some had feared, at that rate the leak could eclipse the Exxon Valdez disaster by around mid-June.
"To have such a high production of 100,000 barrels, that is physically next to impossible," said a petroleum engineer at a U.S. university, who asked not to be identified.
Even in top producer Saudi Arabia, individual wells typically produce only 20,000 to 30,000 barrels per day. BP's 250,000 bpd capacity Thunder Horse deepwater Gulf of Mexico project, which drew first oil in June 2008, required around three dozen production and injection wells, according to company data.
Additionally, at a depth of some 5,000 feet (1,525 meters), the weight of the water partly staunches the flow, the petroleum engineer said.
SkyTruth, an environmental group that has looked at satellite pictures of the sheen from April 28, estimates the leaks are closer to 20,000 bpd. Two Texas-based petroleum geologists, who did not want to be identified, said that rate or a bit less was much more likely than the 100,000 bpd flow.
Beyond discounting the possibilities of the highest estimates, it is difficult to determine the rate without knowing things like the reservoir pressure, the total depth of the well and the find's geology.
"We don't have any physical way to measure this," said Bob Fryar, senior vice president of Angola for BP. "We're clearly not metering the flow. We don't have flowing pressures at the well."
Answers could come as soon as a week or two after BP lowers a 98-ton iron box it has built to channel oil from the leaking pipe on the sea floor to the surface. In theory, the funnel would capture 85 percent of the oil rising from the floor. This type of fix, however, has never been attempted at such depth.
The two-week old disaster that left 11 dead after the rig exploded threatens fishing and tourism along the Gulf Coast and threatens to put the brakes on the U.S. climate bill, which aimed to boost offshore oil drilling. (Reporting by Timothy Gardner, additional reporting by Kristen Hays in Houston; Editing by David Gregorio and Marguerita Choy)
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