Ram-Powell TLP nears installation in gulf

Aker Gulf Marine's twin-boom SLD positions Ram-Powell's wellbay module onto the TLP hull during yard integration. Photo courtesy Shell Deepwater Development Inc. Shell Deepwater Development Inc. (SDDI) is nearing activation and commissioning of the Ram-Powell tension-leg platform.

To be installed in 3,214 ft of water on Viosca Knoll Area Block 956, the TLP is scheduled to depart Aker Gulf Marine's yard at Ingleside, Tex., Apr. 24 for towout to location about 125 miles east-southeast of New Orleans.

TLP will develop Viosca Knoll Area Blocks 867, 868, 911, 912, 913, 955, 956, and 957 acquired in 1984, 1986, 1987, and 1988 sales for bonuses totaling about $16.17 million.

Initial production is expected this August. Gross reserves total 250 million bbl of oil equivalent.

SDDI is a member of Shell Oil Co.'s New Orleans-based exploration and production group. Shell has a 38% project interest. Partners are Amoco Corp. and Exxon Co. U.S.A., 31% each.

Latest-generation TLP

Standardization and cloning are integral design features of the Ram-Powell TLP.

It is the third TLP to be installed in the gulf by Shell after Auger and Mars, installed in 1993 and 1996, respectively.

Although Ram-Powell is similar, it's bigger, and total expected project cost is less. Auger and Mars have a price tag of $1.2 billion each, while Ram-Powell is pegged at $1 billion, excluding leases.

For now, Ram-Powell will hold the TLP water-depth record in the gulf, but that's expected to fall when Shell installs the next TLP, Ursa, in 1999.

Based on Auger and Mars, Shell has been able to sharply cut its costs, increase unit size, and refine and enhance design, fabrication, and construction parameters on Ram-Powell to extract maximum possible efficiencies, according to Lou Wilkerson, SDDI's project manager, and Lisa Johnson, Ram-Powell asset leader for Shell Deepwater Production Inc. Wilkerson said similarities between Ram-Powell and Mars were intentional for maximum transfer of learning: "The Mars design work was winding down just as the Ram-Powell work was starting up."

Added benefits

The project benefited from an overlapping contracting, design, and fabrication/construction schedule.

An alternative contracting-negotiating approach with Mars contractors allowed Ram-Powell fabrication to get under way and incorporate major improvements "without the design being complete," Wilkerson added.

Among refinements, Ram-Powell has top-tensioned drilling riser and export pipeline systems, which cut costs of the TLP's 26-mile, 12-in. oil and 25-mile, 14-in. gas pipelines and adds operating efficiencies. Mars has a steel catenary drilling riser system.

The top-tensioned option was also chosen because of the higher anticipated production rates.

Ram-Powell's BOP stack is on the TLP's lower deck rather than on the seafloor, another cost reduction.

The 17,000-ton hull, built by Belle* SpA, Taranto, Italy, is actually 3 ft taller than Mars', measuring 165 ft high and 661/2 in. in diameter.

Belle* constructed the hulls for Auger and Mars and is also constructing the hull for Ursa.

Unlike previous designs, Ram-Powell will not use a lateral mooring system; Auger incorporated a lateral system consisting of eight lines with a 9,000-ft radius. Ram-Powell will be secured to the seafloor via twelve, 28-in. diameter steel tendons, three per corner.

The foundation involves 12 piles, 84 in. in diameter and 349 ft long. Tendons will be attached by means of tendon receptacles.

McDermott International Inc., Morgan City, La., built wellbay, quarters, process, power, and drilling modules, which were installed by Aker using a 4,000-ton capacity, twin-boom, special lifting device first used for Mars.

Modules were installed onshore to eliminate weather-related risks associated with offshore installation.

Drilling/production plans

The TLP can handle 200 MMcfd of gas, 60,000 b/d of oil and condensate, and 30,000 b/d of produced water from 20 TLP wells and four subsea wells.

After the TLP is installed, it will first complete four predrilled wells before additional wells are completed.

Johnson said 20 wells were batchset drilled and cased to 5,500 ft. Initial production will be from 10 wells, seven producers, and three water injectors. Six producers will be completed as horizontal wells, producing from the J, L, and N sands at 12,300-13,400 ft subsea.

Water will be reinjected for pressure maintenance.

Ram-Powell can employ 51/2-in. tubing vs. Auger's 31/2-in. tubing., enabling higher rates of production. A new drilling riser for a platform rig, Helmerich & Payne's Rig 202, enables the rig package to be removed. Oil and gas will be shipped to platforms on Main Pass Block 289-C and Viosca Knoll Area Block 817, respectively.