Subsea All Electric
Authors: Aadland Alf-Kristian , Petersen Kjetil 
Published: July 2010

Is the oil and gas offshore industry ready for all electric subsea fields?

A lot of work has been done on the development side for closing the gap between traditional subsea production equipment operated by hydraulic control systems to systems that are all electric operated. Is the gap closed? Is the supplier industry ready?

Oceaneering owned Ifokus Engineering has developed and qualified the subsea actuators for the Ormen Lange Subsea Compression Pilot (OLSCP). The challenge was to develop compact all electric actuators with &gt;25 years subsea lifetime, quick response, high accuracy, full redundancy, Remotely Operated Vehicle (ROV) interchangeability, full failsafe and that met Safety Integrety Level (SIL) requirements. These actuators were defined in the early phase of the OLSCP as a critical component that had to be developed for installing a fully operational all electric operated subsea gas compression installation.

The challenging development faced numerous technical issues that have been solved. Extensive testing for qualifying the components and complete assemblies was undertaken. No standards cover this type of equipment directly, so the process of establishing procedures and test criteria has been difficult.

The presentation will describe the electric linear and rotating actuators developed for the OLSCP and present experience from the extensive testing and the project execution. It will highlight the lack of standards covering this type of equipment, and aid in defining future design and test criteria.

Introduction

History

For many years there has been a drive to convert hydraulic subsea applications to electric. Factors holding back a wider acceptance of subsea electrification previously were caused by the mixed experience with subsea electric distribution systems and subsea electronics. Typical failures could be caused by subsea cables, connectors, terminations and electronic components. These failures caused downtime and created a need for re-cabling of subsea installations and frequent changeout of components since designs have trended toward keeping the electrical components to a minimum instead of a maximum level.

In the 90's, initiatives were taken to run power and communication on inductive couplers in the subsea distribution systems. These couplers had weak points and were only utilized for a short time period. After a number of failures, the systems were changed to conventional coupler concepts.

Different qualification programs for cables and connectors have been performed with the goal of establishing connector programs with low failure rates and as more robust solutions. The quality achievements through qualification programs have clearly decreased the failure rates and increased the acceptance of standard subsea connectors and cables.

With today's available technology and the extended need for electrical connection points on subsea structures, it is Ifokus' perception that the increased flexibility offered by inductive coupler technology will again be utilized on low power and control applications subsea. This is due to the advantages of no galvanic connections between supply and consumer.