ABB Offshore Systems has set in motion the 30@3000 research and development program, through which it aims to extend its subsea capability to the design, supply, installation, and maintenance of complete subsea production systems in ultra-deepwater. The number "30" refers to the 30-ton upper limit the company has set for any lift from a supply vessel onto a drilling rig, and "3000" for the water depth in meters for which the systems will be developed.
"Currently, we have the technology for total systems in up to 650 meters water depth," said Program Manager Patrice Aguilera. "By mid-2000, we aim to complete the conceptual phase for the R&D program. We then will move on to engineering, and then to prototype building and testing. For these phases, we will be looking for external funding. The current plan is to start prototype testing in late 2001."
The company is not short of ideas as to what a total system for 3,000 meters water depth might constitute, but has been careful to cull ideas from potential customers. "We've done a survey of major oil companies in areas such as the Gulf of Mexico, Brazil, and Norway, to find out what they see as the main issues and what their preferred solutions are," says Aguilera. "We want to make sure we develop something the market wants."
New program
The 30@3000 program breaks down into nine sub-projects covering template and cluster, installation, tie-in and module replacement, well systems, production control system, subsea processing; production risers, composites, and field applications.
A four-slot template and a six-well manifold cluster will both be developed. The template will come in two versions, installable by the drilling rig or by a conventional lift vessel.
The self-imposed 30-ton limit is to ensure that, where required, all items of equipment can be handled by the drilling rig without having to call on extra assistance. However, ABB intends to remain flexible on this point. "If clients accept items heavier than 30 tons, that's fine," says Aguilera. "But we want to make sure that we can deliver 30 tons when necessary."
The use of composite materials is one avenue by which the weight of equipment can be reduced, and ABB already has experience in this field, delivering, for example, subsea protection structures made of composites.
Installation in 3,000 meter water depth involves a series of problems not met in shallower water depths, where guidelines can be used. For example, a reliable way has to be found of landing a 300-ton blowout preventer (BOP) guidelineless on a wellhead on a template with perhaps only 400 mm clearance from a subsea tree already installed on an adjacent slot. An analysis has been carried out of the motion behavior of a BOP at depths of 1,500-3,000 meters.
Another problem is the lack of visibility when, for example, the ROV's thrusters disturb the soil and there is no current to carry away the clouds of mud.
The whole issue of making ROV operations and the associated tooling efficient at 3,000 meters is a big challenge, and ABB intends to interface with ROV suppliers who are also working on these problems, says Aguilera. Another set of challenges arises with intervention issues:
- Changing out the retrievable inserts in equipment like chokes, multiphase meters, and control modules is necessary when failures occur. Further development of the ROV-deployed Remote Component Replacement (RCR) tool developed by ABB will include making it possible to remove a faulty insert and install a replacement in a single trip.
- Flow assurance constitutes another problem area. Various solutions to combat problems such as hydrate and wax formation already exist, such as the chemical injection of methanol, heated lines, insulation and regular pigging, and these are all likely to find application depending on the particular circumstances of a field development.
- Where insulation is concerned, the thickness of the insulation material is reduced as the water depth and pressure increases, and its effectiveness correspondingly reduced. No proper insulation is yet available for 3,000 meters, Aguilera says. Novel solutions such as syntactic foam, which has been qualified down to around 1,000 meters, will be investigated.
- Mechanical design of the manifold must ensure that potential water traps are avoided.
Cluster manifold supplied by ABB for installation in 540 meters water depth on Marathon's Arnold Field in the Gulf of Mexico.
One possible solution for the hydrate problem is the use of subsea processing to remove water from the wellstream on the seabed. While ABB is preparing for the installation of its first subsea processing and injection system - Subsis - on the Troll Field, work is in hand to prepare the system for operations in 3,000 meters water depth. A series of ABB companies - including ABB Offshore Systems, ABB Vetco Gray, and ABB Corporate Research, will contribute to the program.
ABB's deepwater deliveries
ABB already has a growing list of references for deepwater projects. These include:
- Front-end engineering design for Elf's Dalia Field development in 1,255 meters water depth off Angola, its most recent assignment
- Three subsea manifolds for installation in 1,000 meters water depth on Petrobras' Marlim Field in Brazil
- Tree installed in 1,709 meters water depth on Marlim in 1997 - at the time the deepest production tree in the world
- A 12-slot manifold, horizontal subsea trees, control system, and ROV-based intervention services using its Icarus and Remote Component Replacement (RCR) system, for Chevron's Kuito Field in 450 meters water depth off Angola
- EPCI contract for three guidelineless horizontal trees, jumpers, a cluster manifold, pipelines, and tie-ins for Marathon's 540 meters water depth Arnold Field in the Gulf of Mexico
- Horizontal tree to PennzOil for a 450 meters water depth field in the US Gulf of Mexico, currently being supplied.
