Abstract

Field trials for the first all-electric subsea completion system have now been completed off an existing platform in the North Sea. The post-test and equipment evaluation has been conducted. This paper will focus on the planning and execution of the field trails as well as summarize the evaluation results and lessons learned from this program.

Introduction

The development program for an all-electric subsea production system was undertaken with the rationale that it offered significant economic and technical advantages over hydraulic-based systems; particularly for deepwater, long step-out developments. The benefits are generally concentrated in two critical areas, increased reliability and enhanced functionality. Also, health, safety and environmental benefits could be gained from the elimination of hydraulic fluid in the operation and control of subsea systems.

The program to develop the all-electric subsea production system followed a phased and systematic approach that considered several key aspects including technology development, economic justification (using reliability and value assessment tools,) and system testing (involving field trials).

Three distinct phases with specific objectives and deliverables were identified at the inception of the program;

  • Core Technology Development.

  • System Assurance.

  • System Validation.

Figure 1 - Cameron All-Electric Subsea Production Test Tree System (Available in full paper)

Core Technology Development.

The Core Technology Development phase involved the design, development and qualification of the main system elements. These included:

  • Gate valve electric actuators.

  • Electrically actuated production choke (insert retrievable).

Surface controls:

  • Electric power unit.

  • Surface power line modem.

  • Communication controller.

Subsea controls:

  • Power regulator.

  • Subsea power line modem.

  • Electric subsea control module.

Surface-to-subsea elements:

  • Power and signal cable (coaxial).

  • Subsea power connector (wet mateable).

Each system element underwent a series of qualification tests, as a single unit, to prove robustness in design and to provide a useful prediction of component reliability and operational life. The tests included:

  • Life cycle testing (under full load).

  • Performance tests that measure power requirementsand actuation times.

  • Function tests at varying bore pressures (for valves and choke actuators) and power requirements (for controls elements).

  • Shock and vibration tests (actuators and subsea controls elements).

  • Electrical overload and insulation resistance tests.

At the conclusion of the single unit and qualification tests, the system elements were packaged into a subsea test tree system to enable full system integration and qualification testing. (See Figure 1.) An important objective of the system integration test program (and eventually the field trials) was to use the same equipment that had undergone single unit qualification testing, without replacement of parts or refurbishment. This would enable a more comprehensive evaluation of the functional performance and operational life of the main elements integrated into a system. Data from the single unit qualification, system integration and field trail testing would be used in reliability assessments and performance predictions as part of the ongoing system assurance activities.

System Assurance.

The System Assurance phase, initiated after the commencement of Core Technology Development, in

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