Chevron said it struck oil at a deepwater well in the U.S. Gulf of Mexico just 12 miles from another discovery announced last week by partners Anadarko Petroleum Corp and ConocoPhillips.

Chevron said on Monday the Walker Ridge Block 98 well in the Coronado prospect encountered more than 400 feet of net pay -- or the thickness of an oil reservoir that can produce hydrocarbons.

San Ramon-based Chevron holds a 40 percent working interest in the prospect and is the operator of the Coronado discovery well. The well is located about 190 miles off the Louisiana coast.

Other owners of Coronado are ConocoPhillips with 35 percent, a unit of Anadarko with 15 percent and Venari Offshore with 10 percent stake.

Last Tuesday, Anadarko announced its discovery of a large amount of oil at the Shenandoah-2 well nearby. Anadarko and Conoco each hold 30 percent of that well, while Cobalt International Energy has 20 percent and Marathon Oil and privately held Venari both hold 10 percent.

"Between the Coronado discovery, the potentially giant Shenandoah discovery, and our recent high bids on remaining open blocks in the Shenandoah/Coronado mini-basin, Venari is firmly positioned for significant growth in a future production hub in the Gulf," Venari Chief Executive Brian Reinsborough said.

While Conoco and Chevron shares were trading lower in Monday morning trading, Anadarko shares were 1 percent higher.

Wells Fargo analyst David Tameron noted that Anadarko had a 15 percent interest in the Yucatan prospect -- also in the Shenandoah mini-basin.