Three years after the Macondo well blowout and resulting drilling moratorium, oil and gas exploration has been slowly but surely returning to the Gulf of Mexico (GOM). On Wednesday Royal Dutch Shell plc reported a successful exploratory well at Vicksburg in the deepwater GOM.

The well is located 75 miles offshore in the De Soto Canyon Block 393 in 7,446 feet of water. It was drilled to a total depth of 26,385 feet and encountered more than 500 feet of net oil pay, the company reported.

In total, Shell said the Vicksburg "A" discovery is estimated to hold potentially recoverable resources of more than 100 million boe, adding to the more than 500 million boe of potentially recoverable resources that have already been discovered and appraised at the nearby Appomattox discovery in Mississippi Canyon blocks blocks 391 and 392 (see Daily GPI, April 29, 2011). Vicksburg "A" is a separate accumulation from both Appomattox and the 2007 Vicksburg "B" discovery.

"The results of the Vicksburg well strengthen our existing deepwater Gulf of Mexico exploration portfolio and should contribute to the nearby Appomattox discovery," said Mark Shuster, executive vice president, Shell Upstream Americas Exploration.

Shell is the operator of Vicksburg "A" with a 75% interest and Nexen Inc., a subsidiary of CNOOC Ltd., holds the remaining 25% stake. The companies are following up the well with a sidetrack well to test the Corinth prospect, a separate fault block from the Vicksburg discovery. Further exploration drilling targeting tie-backs to Appomattox are expected to follow.

Further exploration in the De Soto Canyon faces a few hurdles in the immediate future. Late last month a coalition of conservation groups led by Natural Resources Defense Council inked a settlement agreement with the Interior Department and the oil and natural gas industry that would restrict seismic testing in certain parts of the GOM over the next two and a half years to protect whales and dolphins from high-intensity airguns that are are used to find oil and gas deep underneath the ocean floor (see Daily GPI, June 24).

The airgun restrictions apply to the De Soto Canyon in the Northeast Gulf; Mississippi Canyon in North Central Gulf; an area west of the Florida Keys and Tortugas; and coastal waters shoreward of the 20-meter isobath (waters within 20-meter depth or shallower). De Soto Canyon is considered important for sperm whales and critical to Bryde's whales, the Gulf's only resident population of large baleen whales, also known as the "great whales," which prefer tropical waters.

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