Remote Field Control and Support Strategy - Umbilicals versus Control Buoys
- P.E. Christiansen (INTEC Engineering) | S.A. McKay (INTEC Engineering) | K. Mullen (INTEC Engineering) | L.R. Upston (INTEC Engineering)
- Document ID
- Society of Petroleum Engineers
- SPE Asia Pacific Oil and Gas Conference and Exhibition, 18-20 October, Perth, Australia
- Publication Date
- Document Type
- Conference Paper
- 2004. Society of Petroleum Engineers
- 4.5 Offshore Facilities and Subsea Systems, 5.3.2 Multiphase Flow, 4.6.2 Liquified Natural Gas (LNG), 4.5.7 Controls and Umbilicals, 2.3.1 Remote Monitoring, 4.3.4 Scale, 4.5.5 Installation Equipment and Techniques, 1.3.2 Subsea Wellheads, 4.5.4 Mooring Systems, 4.6 Natural Gas, 4.2 Pipelines, Flowlines and Risers, 3 Production and Well Operations, 4.1.5 Processing Equipment, 6.3.6 Chemical Storage and Use, 4.3.1 Hydrates, 4.2.4 Risers, 2 Well Completion, 4.2.3 Materials and Corrosion, 3.2.2 Downhole intervention and remediation (including wireline and coiled tubing)
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This paper addresses the latest developments in remote field control strategy and focuses on long distance umbilical control versus the use of a control buoy located over the field. The paper provides an insight into both the technology and also the commercial key drivers for the selection of control strategy.
The historical development of umbilicals and control buoys is summarised. The relevant technologies are described, covering aspects such as buoy design, telecommunication options, onboard power, fluid storage and injection capabilities, operational issues including access and maintenance, and opportunities for workover activities. The discussion is supported by case examples drawn from a number of fields around Australia.
In the Asia Pacific region there are many known remote oil and gas fields in environmentally hostile areas or at deep-water locations. Such fields can typically only be made economical to develop if low cost subsea solutions can be implemented. At such remote locations where there is no existing platform infrastructure, the support of subsea facilities by umbilical can be difficult and expensive to implement. An alternative such as a control buoy for monitoring, control and injection may provide a better solution.
Development of Umbilical Technology
Since Xmas Trees first went underwater in 1961, the industry has been struggling with reliable and cost effective ways of operating them. There is a requirement for controlling valves on the Xmas Tree and downhole, and also for monitoring key parameters (such as annulus pressure).
The early subsea completions involved single wells in shallow water at short step-out distances, and direct hydraulic control of the tree valves from the surface facility was straightforward, using one hose per valve. Pressure in the well annulus could also be measured at the surface via another hose. The first umbilicals were little more than bundled hydraulic hoses with a "cheap and cheerful" philosophy. Reliability was not a concern as repair and replacement were easily carried out.
As the industry matured, longer step-outs made direct hydraulic control less attractive. Umbilical cost increased with length, and the response time of the valves became longer. This was cause for concern, because it took longer to shut in a Xmas Tree in an emergency, and the stroking time of the valve became so long that significant wear could occur.
Multiple completions resulted in the umbilicals growing significantly in size, because one hose was needed for each valve on each of the Xmas Trees. Also, when the subsea Xmas Trees were manifolded together, the chokes had to be relocated from the platforms to subsea. This presented problems because the opening/closing time for stepping chokes became excessively long, and resulted in an unacceptable delay when opening up Trees for production.
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