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Mensa Subsea Development
Mensa is located in approximately 5,300 feet of water, 140 miles southeast of New Orleans and encompasses Mississippi Canyon Blocks 686, 687, 730 and 731. Shell acquired Mississippi Canyon Blocks 730 and 731 in OCS Lease Sale 98 in May 1985. In June 1993, Shell traded with Pennzoil, Amoco and Arco for Mississippi Canyon Blocks 686 and 687. Mensa is 100% Shell owned.
Exploration and Discovery
The discovery well was drilled in 1987 by Transocean’s drillship, Discoverer Seven Seas. One delineation well was drilled. The target reserves are in the Upper Miocene "I" sand, at a depth of approximately 15,500 feet. The average net thickness is approximately 100 feet.
Development
Mensa initially consisted of three wells connected via individual 6-inch jumpers to a subsea manifold five miles away, which is then tied back to a shallow water platform at West Delta 143 via a 63-mile 12-inch flowline.
This 68-mile tieback formerly held the record for the the longest in the world. The previous tieback record was 30 miles for the Troll Oseberg Gas Injection project in the Norwegian sector of the North Sea.
Shell then developed and began production from Mensa's fourth well in 2003. Transocean's Marianas drilled Mensa 4, which features a larger completion from the previous three wells, but draws from the same sands.
January 1997 | Electrical distribution structure |
|---|---|
| March 1997 | Subsea manifold/template |
| February/March 1997 | All hydraulic and electrical umbilicals and the three infield 6-inch flowlines |
| May 1997 | 12-inch flowline from the manifold to West Delta 143 |
| July 1997 | First tree |
| Fall 1998 | Tree installation continued as the final well was drilled and completed. Jumpers were installed following each tree installation. |
Production
Production of Mensa's initial three-well system began in July 1997. Mensa 4 began production in March 2003.