A unit of Shell Oil Co. is poised to shatter the world water depth production record (29293 bytes) with a subsea field development project in 5,400 ft of water in the Gulf of Mexico.
Several records for subsea technology will fall as well when production begins in 1997 from Shell Offshore Inc.'s Mensa field. It lies under parts of Mississippi Canyon Blocks 686, 687, 7,30, and 731, about 140 miles southeast of New Orleans.
Mensa's water depth will exceed by more than 2 000 ft the current deepwater record for oil and/or gas production.
Petroleo Brasileiro SA in late April 1994 began producing oil and gas from its 4 Marlim well in 3,370 ft of water off Brazil in the Campos basin (OGJ, May 9, 1994, p. 18). Shell holds the present water depth record for production in the Gulf of Mexico with its Auger project in 2,860 ft of water on Mississippi Canyon Block 426.
Shell expects Mensa to flow about 300 MMcfd of gas, a rate that would boost by 25% the company's current gulf gas production of 1.2 bcfd.
Minerals Management Service data show the biggest active gas well in the gulf produced slightly more than 79 MMcfd in 1993. That flow came from Jurassic Norphlet pay at 21,600 ft in the Mobile federal planning area off Alabama.
Mensa production is to come from as many as four development wells flowing through a 12 in., 68 mile subsea pipeline to a shallow water platform on West Delta Block 143. The 68 mile connection will more than double the world's current longest tieback, a 30 mile link to the Norwegian North Sea gas grid from the Troll Oseberg gas injection project.
Shell Offshore, New Orleans, holds a 100% interest in Mensa field. The company is a unit of Shell Oil Co.'s Shell Exploration & Production Co.
MENSA OVERVIEW
Shell estimates Mensa's recoverable reserves at 720 bcf of gas. On an oil equivalent basis, the field ranks as the 72nd largest discovered in the gulf, MMS said.
The company decided to develop the field based on logs run in a discovery and a delineation well and other subsurface data. Shell's confidence in its geophysical and well data apparently more than offset the benefits that would have accrued from technically challenging flow tests in 5,400 ft of water.
Shell is wrapping up design of Mensa's subsea system. The company estimates total development cost of the field at $230-290 million, depending on the number of wells included in the final development plan.
FMC Corp.'s wellhead equipment unit, Houston, is to manufacture Mensa's subsea equipment. Kvaerner FSSL, Sugar Land, Tex., will manufacture the production control system.
Shell expects to decide by third quarter 1995 whether to develop Mensa with four vertical wells or two horizontal ones. If it selected the horizontal option and still achieves gas flows of 300 MMcfd, Mensa's two wells would nearly double the flow of the gulf's current leaders.
Development drilling is to occur in 1996.
Mensa gas will flow to the same platform as production from Shell's Mars tension leg platform (TLP). The Mars TLP, in 2,933 ft of water on Mississippi Canyon Block 807, is to go on stream in 1996.
Mensa will use a clustered subsea production system with wells tied back to a central manifold. Shell used a similar clustered subsea production system to develop Popeye field in 2,100 ft of water on Green Canyon Block 116.
Shell Project chart (27340 bytes)
SHELL IN DEEP WATER
News of Mensa project solidifies Shell Offshore as the leading deepwater oil and gas developer in the Gulf of Mexico.
The operating unit owns nearly 33% of all gulf acreage leased in more than 1,500 ft of water. In 1987, it claimed the world water depth drilling record with a wildcat in 7,520 ft of water on Mississippi Canyon Block 657 in the gulf.
Shell's Mars field in 1996 will surpass the production water depth record set in 1993 by Auger. Shell's Ram-Powell development in 3,218 ft of water on Viosca Knoll Block 956 in 1997 will better the water depth at Mars. In addition, Shell is studying plans to develop about a dozen other deepwater prospects in the gulf before the end of the century, industry sources say.
Shell is targeting Mensa reserves in about 100 ft of upper Miocene I sand at 15,500 ft below the seabed. Shell found the field in 1987 with a wildcat drilled on Mississippi Canyon 731 by Sonat's Discoverer Seven Seas drillship. The field was delineated in 1988 with a well on Mississippi Canyon 730. The company plugged and abandoned both wells.
Shell acquired Blocks 730 and 731 at MMS Sale 98 in May 1985 with combined bonus offers of $12.6 million. The company in a 1993 trade with units of Chevron, Amoco, and ARCO acquired Blocks 686 and 687 at a cost of $2.3 million.
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