At the Front of Subsea Technology|
by Edward Crowley specialist writer on maritime topics
Many projects involving British companies are at the forefront of underwater technology in the fields of survey work, maintenance and inspection, surveillance and remote control.
One current project being done by GEC-Marconi and assisted by subsea consultants Kordale Engineering is the development of autonomous (free swimming) Underwater Vehicle (AUV) . This vehicle is being developed to undertake autonomous oilfield pipe line survey missions, with minimal weather dependence and without the indeed for surface support vessels. A substantial reduction in operating costs would be achieved.
Built and Tested
Important factors influencing the viability of a practical AUV system include:
Energy sources - how is the AUV powered?Robot Manipulator
The ARM (Automated Remote Manipulation) Project aims to produce a new kind of subsea inspection system, capable of doing advanced cleaning and inspection tasks in areas beyond the reach of divers, It will also be able to work at the same operating depths as divers but at lower cost and with greater safety and reliability. In particular, it was a requirement to be able to clean and inspect complicated node welds on subsea structures - these nodes generally consisting of a number of intersecting tubulars and the welds therefore being of a very complex shape.
The robot system provides a full 3D graphical model of the ROV, toolskid, manipulator and workpiece node. It provides full manual, semi-automatic and robotic control of the manipulator (with collision detection).
The complete ARM inspection toolskid has undergone dry and wet factory inspection tests and it is planned for the system to be mounted on a workclass ROV at the end of 1995 for major wet-tank trials. It will then be used to inspect Mobil's Beryl Bravo platform in 1996.
There are many production challenges in deep water oilfield developments. Typically, reservoirs are produced using subsea completions where subsea wells are concentrated in clusters. Flowlines from individual wells are combined in a manifold at the subsea production control centres.
Multiphase pipelines connect the production control centre to the nearest platform which can be some distance away - where separators process the fluids. Sometimes the produced fluid is handled by a floating production system or by a tanker loading terminal.
This innovation from Ocean Technical Systems enables a subsea wellhead to be controlled from the surface using a unique design of tethered buoy, it offers a cost-effective solution for the economic development of marginal oil and gas fields.
The system was developed as a result of studying the needs of the Subsea Production Systems Market and it addresses the steadily growing requirements for the use of subsea well completions, It allows offshore operators and engineering contractors to optimise subsea developments and is particularly appropriate when a new development can be tied back to an existing offshore facility.
Using proven technology already installed by Ocean Technical in over 60 locations worldwide, it is possible to eliminate the conventional seabed umbilical and provide an inherently safe and redeployable system while saving about 50% in capital expenditure.
As an unmanned facility, it requires far less equipment that traditional solutions and offers the great advantage of modular repair. The total installation cost is extremely low and, as a very flexible solution it can be moved and re-used very cost effectively.
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