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Case Study: Subsea System Provides Fieldwide Production Monitoring and Control
Oilexco employs advanced subsea monitoring and control system to maximize production flexibility and simplify control interface
Challenge
Identify and implement an innovative and reliable system for complete monitoring and control of the Brenda field, UKCS Blocks 15/25b and 15/25c, North Sea.
Solution
Used a subC-pod subsea monitoring and control system to provide fully redundant control for the field-wide production tree and choke valves, Framo multiphase pump, multiport selector valve, and multiphase metering system, as well as to allow monitoring of real-time data at the surface.
Results
A cost-effective, “future-proofed” solution that enhances production by providing redundant full-field control, increased monitoring functionality, and improved overall reliability.
Integrated subsea manifold required for full-field solution
Consisting of four horizontal wells, Oilexco’s Brenda field is located approximately 220 km northeast of Aberdeen in the UK sector of the North Sea and ties into the Balmoral production platform. To maximize production from the field, an artificial lift combination of multiphase pump and gas lift techniques was selected and designed into a single production manifold by Framo.
An additional well from the Nicol field, located approximately 10 km away, will also be tied in. Because Oilexco is only one of the owners of the Nicol field, any solution implemented will have to allow individual testing of each well’s production.
This was Oilexco’s first major development in the North Sea, and the company was seeking a reliable solution for advanced artificial lift to boost production, as well as a cost-effective method to tie in the additional well from Nicol.
The subC-pod system solution
Based on demonstrated successes in previous deployments, Oilexco decided on a complete field production solution from the Schlumberger and Framo partnership, consisting of the Framo multiphase pump, multiport selector manifold, and multiphase metering system, and the Schlumberger subC-pod subsea monitoring and control system.
The solution is meeting Oilexco’s needs by enabling efficient management of up to six Brenda wells and two remote fields, including the gas lift required to maximize their production. The multiport selector manifold allows each well to be production tested individually, including the Nicol well, so that well production and artificial lift performance can be determined.
The design of the subC-pod system simplified installation and reduced the complexity of interfacing, along with the number of contractors needed. Because Schlumberger and Framo work as partners to provide a complete field solution, Oilexco has a single supplier for the complete subsea production system.
The specifics of the solution
The flexible subC-pod system provides transparent communications and external control for all subsea devices. It consists of a single topside data hub situated on the Balmoral platform, which provides the link to a network of subsea data hubs that monitor and control all the production equipment in the field, including the multiphase pump, multiport selector manifold, multiphase flowmeter, sand detector, production sensors, production tree valves, and gas-lift chokes.
In the Brenda field, six subC-pod modules were mounted in three subsea control modules on the manifold to provide fully redundant monitoring and control. Multiplexed controls reduced the number of control and monitoring lines combined in the single 8.5-km umbilical.
Each subsea hub is itself a complex and fully configurable system. Valve control is provided by 40 external solenoid drivers, while production sensors are routed through the 30 individually addressable isolated analog inputs. The subC-pod system also provides a number of device-independent, transparent communication links and switchable 24-VDC power supplies that can be used for external sensors, such as flowmeters and sand detectors. Individual I/Os, in turn, are directly addressable by any subsea or surface control system on the network.
Whenever a new sensor is connected to a subsea hub, it is automatically added to the subsea communication network, allowing immediate production monitoring of additional real-time data. For Oilexco, this plug-and-play functionality means that any future expansion can proceed very cost effectively.
Data transmission from the subsea data hubs to the topside data hub is provided in real time by the subC-pod high-speed (100-MB/s) fiber-optic communications system. The use of redundant, fiber-optic communication lines eliminates the effect of electromagnetic interference from the multiphase pump high-voltage power lines in the umbilical. Additionally, the production data gathered on the host facility are delivered onshore via satellite to a Framo-hosted database in Norway so that Oilexco engineers and their partners can view their data in real time over the Internet from any location in the world.
The subC-pod system’s open architecture provides transparent communications, independent of protocol, from seabed to surface for multiple sensors. And because identical subsea hubs can be configured to provide different functions on the manifold, Oilexco has complete freedom in the selection of control equipment and sensors, eliminating the need for high-cost, project-specific solutions.
This configuration flexibility also allows modules to be interchanged, reduces the expense of keeping spares, and enables complete redundancy, thereby improving overall reliability and availability of the field control system.
The benefits—immediate and long-term
Beyond the immediate benefits of gaining full-field control and monitoring from a single system, Oilexco will realize long-term operational savings. The ability to add new sensors and tie production easily into the manifold effectively “future proofs” the Brenda field subsea system.
Since the initial installation, Oilexco has placed two additional orders for complete subsea production manifold systems incorporating the Schlumberger subC-pod control and monitoring solution.
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