The Future of Electric Controls: Trees and Subsea Processing

Published: 03/05/2014

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Schlumberger Oilfield Services

Since 2008, the world’s first all-electric production control system is operating in the Dutch sector of the North Sea. Valuable feedback is constantly being received and lessons learnt are being implemented for future generations of all-electric technology. A new generation has been developed for the operation of subsea production systems, in particular Christmas trees and manifolds. But with subsea processing systems becoming more and more accepted by the industry, all-electric technology could be a key enabler for further enhancement of subsea processing applications. For instance, with the subsea factory emerging on the horizon, a key requirement for complex systems is that control valves be operated in a continuous operation mode, either manually or in a closed loop (PID). For surface applications this generally poses no problem because various technical means are at the industry’s disposal, ranging from pneumatic and hydraulic to electric actuation control. For subsea this is different, with longer step-outs and deep water depths having a hydrostatic pressure constraint (limiting the pressure vessel size, and thus the freedom to allow for slower reaction times). These severe conditions require special equipment capable of handling the increased process control challenges. Controlling valves faster becomes increasingly important, and in general demands electric control characteristics. The majority of applications so far have used hydraulic actuators, although there are systems currently in build that will use electric actuation control.

This paper will focus on explaining electrical technology and its history and identifying its advantages, especially when used for long offsets, zero-discharge requirements, and complicated process controls. The paper will also provide a vision of the control technology for the future, drawing from proven electrohydraulic and electric control systems of today and considering current technology developments.

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