Modular subsea production equipment is nearing the end of a qualification process to provide off the shelf facilities for a major operator.

Shell Technology Ventures has backed qualification of modular subsea processing equipment developed by a UK-based engineering company which was originally used 30 years ago in the Middle East.
Work is now underway on actually using the newly qualified equipment on offshore fields, but details remain confidential at present.

Described as "moonshot" technology, the modularized subsea equipment is intended to provide the means for production from subsea to beach as an enabling technology.

Equipment tests by Det Norske Veritas are nearing conclusion in both the United Kingdom and Sweden in order to qualify the all-electric equipment for use offshore. And soon the supplier hopes to hear where it will be field-tested.

The Alpha Prime technology developed by Alpha Thames provides a range of subsea production systems, from subsea separation to artificial reservoir boosting apparatus without well shut-ins to change equipment configuration and capacity on the seabed.

Heart

At the heart is a Central Processing Unit, the "brain," which provides a modular hydrocarbon production system. This contains all equipment for providing well control and hydrocarbon processing. It incorporates pairs of autonomous system modules with power and control functions. These modules have been designed in collaboration with major process equipment manufacturers, and they incorporate the AlphaThames Keyman connection system which is designed to accommodate most proprietary diver-less pipeline and flowlines connections with remotely operated vehicle (ROV)-operated valves. All connections are wet-mateable, for high voltage electrics, control and chemical fluids and multi-bore wellhead type connectors.

The Keyman and a proprietary FlowCap, together with the CPU, provide all the functions of a conventional subsea manifold.

Overall cost savings of between US $2-$3 per barrel are possible using this system, the manufacturer claims.

Crucial to the appreciation of this technology is its adaptability and changeability during the life of a field, so that it can evolve from an early production system through to handling peak output and beyond.
David Appleford, managing director of Alpha Thames, said an Alpha-CPU could completely automate a field. "A CPU can act as a control center that provides feedback data, especially as it operates autonomously, yet offers the operational flexibility of being re-programmable from the host facility," he said. "The system-modules can incorporate reservoir surveillance and testing and distribute power to neighboring seabed systems if required. They can be configured to include hydraulic power units (HPUs) in order to control conventional electro-hydraulic trees." He suggested that an entire field could be controlled from a laptop. "Maintenance is not the reason you are going to change a module," Appleford explained. "The reason you are going to change [equipment] is that the field demands the changes that are required."

Philosophies

Eliminating the need for equipment maintenance was one of the philosophies behind the design. "The Keyman is absolutely dumb," he said. "It has no actuated parts, no controls, nothing."

He added, "Once you go for a modular method, it opens up a completely new way of doing things."
Sizing of the system modules is infinitely variable, too. "There is no minimum and no maximum for these modules. It does not matter. We can make them any size you like. We can therefore design to suit the throughput. It could be 40,000 b/d per module. In a two-module system it is 80,000 b/d," Appleford said. "It is a question of sizing the module for whatever throughput is required by the industry."

However a notional weight limit of 150 tonnes is imposed on equipment components to ensure they are within the operating limits of most rig and support ship cranes.

Field applications are under consideration in water depths from 918 ft (280 m) to nearly 5,000 ft (1,500 m) and more, although the equipment is designed and rated for almost 10,000 ft (3,000 m). Theoretically, equipment design allows deployment in any water depth, regardless of step out distance from a host facility.

"This is not blue sky - this technology is available. It is not new. Everybody has been waiting for the right way for this to be packaged on the seabed." Appleford added.

Modular subsea component characteristics are:

• Continuous production during module replacement;
• All-electric power and control;
• Processing and boosting subsea;
• Constant speed pumping;
• Real-time monitoring and control;
• Sand handling;
• Integrated local well testing;
• Integrated power distribution; and
• First stage, high pressure, separation on seabed.

Previous insights to modular subsea equipment technology have been provided by a Subsea UK forum held towards the end of 2003 when OTM (Offshore Technology Management) Consulting and Douglas Westwood forecast subsea processing technology expenditure of $1.6 billion over the next decade. Chris Dudgeon, managing director of OTM, said, "Subsea processing is a true 'gamechanger' technology in that by separating or pressure-boosting well fluids on the seabed, it has the potential to massively reduce expenditure on offshore platforms."

He described how subsea processing technology had first been used experimentally offshore Abu Dhabi more than 30 years ago in which founder members of Alpha Thames were involved. But only within the last couple of years have operators begun to collaborate with suppliers on developing subsea processing equipment.

Ian Ball, of Shell Technology Ventures, told the forum of his collaboration with Alpha Thames to further the potential of subsea processing.

Ball said subsea processing ". . . adds global value by enhancing production through reduced wellhead back pressure and enabling ultradeepwater production and longer subsea offsets." He suggested Norway's Ormen Lange field, which is based on exporting hydrocarbons from subsea to land over a distance of 87.5 miles (140 km), might benefit from subsea compression if the technology is available during a second phase of development.

FMC Kongsberg has already won a $145 million contract from Ormen Lange partners - led by development phase operator Norsk Hydro - to supply subsea equipment for the project comprising eight subsea trees, manifolds, production controls plus flowline and umbilical connections. Within the contract, FMC is to provide technical services for field installation and start-up which is scheduled for 2007. There are also options for additional equipment.

Guidelines

Elsewhere work is underway on developing stricter industry design guidelines for subsea equipment under the intelligent well industry standards (IWIS) project.

The aim is to overcome the multitude of interfaces on subsea equipment by standardization.
And the "mission" of the joint industry project is, "To assist the integration of downhole power and communication architectures, subsea control systems and topsides by providing recommended specifications (and standards where appropriate) for power and communication architectures, and other associated hardware requirements."

The premise is that downhole equipment suppliers are required to develop different variants for subsea interfaces from different vendors, resulting in costly and avoidable duplication.

"All of these interfaces must be tested and qualified, and this duplication has a significant cost, which must be borne by the industry," IWIS program members argue. "This need results in logistical limitations and lack of flexibility. Project efficiency is impacted and lead times are increased.

"In addition, performance and reliability are compromised by the need for a multitude of individual project and vendor specific interfacing solutions."

Work is taking place on technical specifications for various physical subsea interfaces, communications, electrical and hydraulic power, tubing hanger penetrations plus testing.

Operators, subsea and downhole equipment suppliers are part of the project which has organized technical discussions between suppliers and operators.

Project members have already worked on a submission to the International Standards Organization (ISO) and American Petroleum Institute (API) to formulize the standard - for inclusion in ISO 13628, "Petroleum and natural gas industries - design and operation of subsea production systems - part 6: Subsea production control systems." Already a useable IWIS specification is available to project members and vendors are developing equipment to meet the new standard while operators are beginning to specify it in new tenders, Gavin Duncan of Kværner Oilfield Products reports.

Further work is planned on tubing hanger feed-through and penetration specifications, aiming to standardize physical preparation for electrical, fiber optic and hydraulic penetrations. Also, work is to focus on workover systems and hydraulic fluid compatibility, and hydraulics operating directional control valves.

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