This ultra-deepwater drilling vessel moves many conventional surface systems below the waterline.
With a continued focus on drilling and prod ucing in ultra-deepwater, Herman J. Schellstede & Associates has released a new concept that combines the stability of a spar with the low-cost and flexibility of a compliant buoy. Although the new design is dynamically positioned, as opposed to a taut-moored compliant buoy, it locates many of the traditional surface systems below the water line in a spherical vessel. Not only does this lower the vessel's center of gravity, but it protects all of these systems from surface wave and atmospheric conditions.
Overall, the design looks much like a round flask or a fishing cork with a spar running through a center sphere. The spar section extends 580 ft below the surface, and above the waterline, to provide a support platform. The surface platform is used for quarters and supply boat docking, and is equipped with a jacking system that raises and lowers the vessel. The vessel is designed with ultra-deepwater harsh environment drilling in mind.
The idea is to lower the majority of the systems below the surface and out of the splash zone. According to product information, 75-80% of the overall weight of the vessel will be contained in the below waterline sphere. Systems, including riser handling and drill floor equipment, are located near the center of the sphere, below the waterline.
To save on weight, the major components of the sphere itself as well as the tubulars, tanks, superstructure, surface quarters, walls, and decks are constructed of "ultra-light" materials. The lower hull and riser pipe containment body are constructed of steel.
Modec greenlights Moses TLP
Under a contract with El Paso Energy to develop the Prince Field in Ewing Banks area of the Gulf of Mexico, Modec, a company jointly owned by FMC and Mitsui, will build its first Moses tension leg platform (TLP). The contract is for a turnkey installation that includes construction and installation of the hull, tendons, pilings, and production risers in 1,500 ft water depth.
The Moses is designed to perform drilling or workover in up to 6,000 ft water depth. This unit will be designed to support 6,000 short tons of topside facilities and process 50,000 b/d and 80 MMcf/d, as well as support a workover rig. Moses was initially tapped as the solution for Prince last year, but analysis of the subsea development plan for the field resulting in shelving of the project. Now, it appears to be back on track.
System creates wax slurry at wellhead
Halliburton has released more details on its new flow assurance technology that will ultimately be part of a much broader innovative production system. Subsea tiebacks in deepwater fields are hampered by the formation of paraffin waxes and hydrate crystals, which clog flow lines. Cold temperatures at the seafloor, combined with the long distances these flowlines cover, mean some form of remediation is necessary.
Typically, chemical injection and flowline insulation are the two primary choices, along with pigging loops to keep the oil flowing. Brown & Root Energy Services, with help from Westport and KBR, has developed an unusual approach to dealing with wax and hydrates.
Rather than chemically avoiding them, the Cold Pipe/Wax Eater system encourages their formation. Combining a cold pipe coil near the wellhead with an unusual pigging system, Halliburton and BRES are able to quickly chill the production stream, trap the hydrates and wax in a slurry, and transport the mixture intact to the host platform.
The system works as follows: The production stream leaves the wellhead and enters a coil that uses the near freezing temperatures of deep water to quickly chill the flow. Chilling drops the wax out of the stream and forms hydrates very quickly. The trick is to keep these materials from bonding with the pipeline walls. To accomplish this, a specially designed pig, called Wax Eater, constantly travels through the coil.
The Wax Eater is not designed to scrape the walls. Instead the pig will move through the flow keeping the wax and hydrate slurry in tact. As the pig wears out, it can be retrieved at the platform and a replacement element released from a magazine at the wellhead. Once the supply of pigging elements is exhausted, the magazine can be changed out by remotely operated vehicle (ROV).
This program has passed into initial proof of concept using single-phase fluid and a 1-in. test loop, according to Halliburton. Currently, it is being tested on live crude to evaluate the impact of multiphase flow on the system's performance. After proof of concept, the program will move to a flow assurance test facility, where it will be tested in a larger test loop. From there, a pilot test will be performed using a 6-in. or 8-in. pipeline.
Coflexip Stena sets flexible pipe record
The Coflexip Stena Offshore pipelay vessel Sunrise 2000 recently installed a 6-in. insulated flowline in 1,840 meters water depth for Petrobras' Roncador field. This set a new world depth record as the deepest flexible flowline ever installed.
This was the first of two 6-in. flexible flowlines Petrobras has hired Coflexip to install for the development of Roncador. The first line covers almost 9.5 km and connects the RO-9 wellhead, in 1,840 meters water depth, to the P36 platform, in 1,360 meters water depth. This line allows production to begin flowing to P36, which was installed in February. The second flowline is being installed. The 6-in. line was designed, qualified, and manufactured by Brasflex and Flexibras, Brazilian entities of the CSO Group. The Sunrise 2000 underwent an upgrade in 1999, enabling it to lay three lines simultaneously in 2,000 meters water depth.
Oceaneering sets dive support depth record
The Oceaneering remotely operated vehicle (ROV) Hydra Millennium 5 has set a new depth record for drilling support with a dive of 9,350 ft water depth for Petrobras. The ROV set this record on a qualification dive from the R&B Falcon drillship Deepwater Frontier offshore Brazil. The Millennium 5 is cage-deployed 150-hp work class ROV installed initially on the Deepwater Frontier when it was first constructed. The ROV has supported the rig in operations offshore New Zealand and West Africa. The unit is designed to operate in as much as 10,000 ft water depths and was at the record setting depth for a total of 11 hours.
