Shell, Nexen locate more oil in gulf Norphlet trend

Shell Gulf of Mexico Inc. and Nexen Inc. have demonstrated a contingent recoverable resource of 215 million bbl of oil equivalent in the Jurassic Norphlet formation in the northeast fault block of the Appomattox structure in the deepwater Gulf of Mexico, where they are conducting further exploration and appraisal activity and evaluating development concepts.

Nexen said the range of contingent recoverable resource is 120-370 million boe of light oil. The Appomattox structure is comprised of three large fault blocks on the east side of the Mississippi Canyon planning area. Further appraisal drilling will refine the range, it said.

Nexen has a 20% interest in Appomattox, whose discovery well is on Mississippi Canyon Block 392, and a 25% interest in the Vicksburg discovery about 5 miles east on De Soto Canyon Block 353 and various other blocks in the area; Shell Gulf of Mexico has the remaining interest and is operator.

The companies have also defined but not yet drilled the Gettysburg prospect east of Vicksburg and the Rydberg and Petersburg prospects south of Appomattox and Vicksburg. All are Norphlet prospects. The general area is 150-160 miles south of Mobile, Ala., in the eastern gulf.

Shell said the Appomattox appraisal well in 7,257 ft of water on Mississippi Canyon Block 348 went to 25,851 ft and encountered 150 ft of oil pay. The discovery well encountered 530 ft of oil pay and an appraisal sidetrack cut 380 ft of oil pay (OGJ Online, Mar. 19, 2010).

The Appomattox structure is comprised of three large fault blocks, Nexen noted. The 2010 discovery well is in the south fault block. In 2011, Nexen booked 65 million boe net of probable reserves from the south fault block. The newly discovered resource in the northeast fault block is in addition to these probable reserves.

Shell and Nexen are drilling an appraisal well in the Appomattox south fault block and will continue exploration and appraisal into 2013.

From the current appraisal well, the companies will sidetrack into the northwest fault block to test another major part of the structure. Then they expect to drill an exploratory well on a structure between Appomattox and Vicksburg and a later sidetrack to further appraise the northeast fault block discovery.

The evaluation of development concepts could result in project development sanction in 2014. The current discovered resource has hub potential with production capacity of more than 100,000 boe/d.