|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper OTC 17106, "Benefits of All-Electric Subsea Production-Control Systems," by M. Theobald and C. Lindsey-Curran, BP plc, prepared for the 2005 Offshore Technology Conference, Houston, 2-5 May.
Abstract 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. Introduction 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. Umbilical Solutions 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.
Abstract This paper prepared for 2018 OTC Offshore Asia explores the current history of electrically driven functionality for subsea production systems. It is expected that co-existence of hybrid electrohydraulic and all-electric functionality will dominate the market for subsea tree and manifold control short term. Electric choke and manifold valve actuation offer many advantages as proved successfully during the last 16 years, e.g. related to modularity and flexibility, with zero discharge, with high operational speed and high positioning accuracy, along with CAPEX and OPEX benefits. Performance of systems such as Statoil's Asgard Subsea Gas Compressor is a game changer that will make all-electric valve control base case also for future subsea processing plants. Reliability & Availability concerns were the major concerns by many operators for not switching to all-electric technology. The excellent reliability of trickle charged batteries in subsea systems, combined with modern safety electronics eliminate the traditional actuator spring as failsafe mechanism power source. All of this has simplified the equipment, reduced the size, and enables continuous equipment status monitoring. Competitive all-electric systems are expected to be introduced in stages, starting with infill wells. This will eliminate the risk of new technology for the best business cases, being long distance gas fields, water injectors and deep water systems. Subsea all-electric solutions benefit from general technology developments in other industries. Full utilization is however slow in the subsea market, hampered by current rules and regulations, risk aspects and conservative mindsets. All-electric solutions need Champions and a continued successful staged development initiatives to realize their full potential for significantly reducing subsea field development capital and operational cost.
Abstract Objectives There is an increased need for cost effective subsea technology to enable oil companies to have more flexibility in system architecture and also enable access to developments in deeper water and with longer step-outs than before. As the current subsea production systems struggle to meet those challenges, the need for a suitable, flexible and cost efficient technology has emerged. All-Electric systems have this capability. By using the Aker Solutions developed portfolio of products and concepts this paper will show cases of simplified, easy integratable and cost reduced All-Electric solutions that can be installed independent of depth. The paper will also touch upon the advantages of All-Electric systems in terms of reliability compared to traditional electro/hydraulic systems. Methods, Procedures, Process By integrating automotive and telecom competence with subsea expertise, it has been possible to implement a rigorous design-to-cost mind-set in the development of the various All-Electric system building blocks. All-Electric hardware and software will give large benefits in terms of OPEX and be competitive in CAPEX (in addition to enabling improved environmental impact, increased levels of safety and increased functionality). Some of these benefits will be further enhanced when applying subsea and downhole All-Electric technology solutions on a wider scale. Results, Observations, and Conclusions The paper explores the potential benefits an All-Electric system can have both in relation to CAPEX and OPEX. Novel/Additive Information Electric actuation, sensing, integrated power management and control offer the promise of smaller, lighter and more cost effective subsea production systems. They also offer the potential for more precise measurement, control and maintenance monitoring over time compared to their hydraulic counterparts, which enables planned maintenance of equipment, with significant benefits in terms of reduced OPEX.