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Two multinational energy giants, Chevron Corp. (NYSE:CVX) of the United States and Norway's Statoil (NYSE:STO), have begun extracting oil and gas from the large Jack and St. Malo fields in US waters of the Gulf of Mexico.

The two fields are among the largest in the Gulf and are expected to yield 94,000 barrels of oil equivalent and 21 million cubic feet of gas per day for an estimated 30 years, Chevron said in a statement on Dec. 2.

The Jack field's reserves were discovered in 2004 and the St. Malo oil was discovered a year earlier. The fields are situated about 25 miles apart beneath 7,000 feet of water and about 280 miles south of New Orleans, according to Chevon. They were developed simultaneously and feed their fuels to a single, semisubmersible, floating host production unit on the surface of the Gulf.

This host, the largest of its kind in the Gulf, can handle 170,000 barrels of oil and 42 million cubic feet of gas per day, Chevron said, and its capacity can be expanded. Once the crude oil is harvested, it will be moved 137 miles along the Jack/St. Malo Oil Export Pipeline to the Green Canyon 19 Platform, then to refineries on the Gulf Coast.

George Kirkland, Chevron's vice chairman and executive vice president for upstream operations, said the company expects the Jack/St. Malo fields to produce 3.1 million barrels per day by 2017. And Jay Johnson, the company's senior vice president for upstream operations, said the technologies used to develop the fields "can now be transferred to other deepwater projects in our portfolio."

Statoil issued its own statement on the development, saying the two fields represent "an important building block of Statoil's plan to have more than a four-fold increase in offshore production from the U.S. Gulf of Mexico by 2020."

"We are very pleased to see production begin of these high-value barrels at Jack/St. Malo," said Jason Nye, senior vice president, U.S. Offshore, Statoil. "Also, this large, complex project was delivered on-time and on-budget, which is world-class execution."

Chevron owns a 50 percent share in the Jack field, while Statoil's stake is 25 percent, as is that of Maersk Oil of Denmark. As for St. Malo, Chevron owns 51 percent, while Petrobras of Brazil owns 25 percent, Statoil 21.5 percent and 1.25 percent each held by ExxonMobil of the United States and Eni of Italy.

Good news aside, the production of even more crude meant adding to the existing glut of oil on the world market, which has led to a nearly six-month slide in prices by more than 30 percent. As soon as production at Jack/St. Malo was announced, the price of oil dropped even further.

West Texas Intermediate immediately fell by more than $1. And Brent crude, the global benchmark, dropped about the same, 75 cents.

By Andy Tully of Oilprice.com. Oilprice has no position in any stocks mentioned. The Motley Fool recommends Chevron and Statoil (ADR). Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.