Shell proves Deimos deepwater discovery in Mars basin

Shell Exploration & Production Co. (Sepco) has confirmed the presence of hydrocarbons in its Deimos prospect on Mississippi Canyon Block 806, off Louisiana-Mississippi.

By OGJ editors

HOUSTON, Oct. 9 -- Shell Exploration & Production Co. (Sepco) has confirmed the presence of hydrocarbons in its Deimos prospect on Mississippi Canyon Block 806, off Louisiana-Mississippi.

Deimos, in 3,000 ft of water, is adjacent to the huge Mars discovery, which has been producing from Shell's Mars tension leg platform since 1996. Shell said additional drilling would be required to delineate the actual field potential.

"Oil was present in excess of 535 vertical net ft of sands, which included both exploratory sections and known producing field pays," said David Loughman, Sepco's vice-president, exploration and development. "We are currently evaluating appraisal drilling options." Sepco, as operator, has a 72% interest in the prospect, and BP PLC has 28%.

Transocean's Deepwater Nautilus spudded the Deimos well in June, reaching total depth in September.

Cutting edge offshore technology has continued to push the limit of offshore exploration into increasingly deeper waters of the Gulf of Mexico beginning in the late 1970s and early 1980s (OGJ May 6, 2002, p. 52).

Shell's Cognac field on Mississippi Canyon Block 194 set a record in 1979 for a deepwater fixed platform at 1,014 ft. Peak gas production was 130 MMcfd. Then 10 later, Shell's Bullwinkle platform in Green Canyon 65 was set in 1,330 ft of water, pushing the water depth limits for fixed structures.

In the early 1990s Shell's Auger field in Garden Banks 426, which had a peak capacity of 300 MMcfd, established an important deepwater hub at 3,000 ft of water.

The second half of the 1990s has been marked by acceleration in new field discoveries, records for deepwater exploration and development, and most significantly, the discovery of such giant size fields as Mars. A single Shell Ursa field well in Mississippi Canyon Block 854, for example, produced 30,000 b/d of oil and lease condensate, and a single well in Shell's 1 tcf Mensa field produced 100 MMcfd. That field will be developed with only 3 subsea wells.

Shell and partners BP and ChevronTexaco Corp. also announced in mid-September the deepwater discovery of Great White Prospect, a greenfield prospect on Alaminos Canyon Block 857 on the newly prospective Perdido Foldbelt about 250 miles south of Houston in the western Gulf of Mexico.

Also operated by Sepco, that well, drilled to 19,907 ft. TD, is located in about 8,000 ft of water.

Great White is also ChevronTexaco's second discovery in Alaminos Canyon, following its recent significant Tahiti discovery in Green Canyon Block 640, about 190 miles southwest of New Orleans, that had a total net pay of 400 ft. Tahiti is in 4,017 ft of water (OGJ Online, Apr. 3, 2002).

"(The Deimos) discovery reinforces the validity of our current exploration strategy," said Sepco CEO and Pres. Raoul Restucci. "(The strategy) includes both a vigorous greenfield component as well as a nearfield program, of which the Deimos discovery is an excellent example. We continue to be pleased with the richness in the Mars basin. We have confirmed about 2 billion bbl so far in the basin, with developments and discoveries such as Mars, Ursa, Crosby, Europa, King, Princess, and Deimos. This gives us strong encouragement regarding other similar prospects in our inventory," he said

Crosby was the first field in the southern portion of Mars basin to come on stream. Ursa, Mars, King, and Princess, are all in the northern part of the basin (OGJ Online, Jan. 18, 2002).

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