Low-Kilowatt Submersible Cable Lowers Electrification Costs for South China Sea Offshore Platform
Authors: van Zanten Wout , van Khadabad Aravind , Shepler Randall A. 
Published: October 2008

Intelligent completion technologies are becoming a popular tool in the oil companies' quest for increased oil recovery. These new technologies place greater demand for electrical power and data transmission from unmanned platforms. A balance between extension of offshore platform life, increased oil recovery, and increased lifecycle costs must be obtained. This paper provides technical concerns, solutions, economic comparisons, and installation considerations through a case history on the application of a unique low-kilowatt submersible power cable for the electrification of offshore unmanned platforms.

Introduction

An Oil and Gas Production Company based in Brunei would like to build a portfolio of opportunities for applying intelligent completion technologies to existing and future wells. Together, with the relevant business cases, identify some key wells for testing and learning from the technology. Intelligent completion technology facilities the integration of state of the art concepts in well engineering, downhole measurement, inflow performance / control and production system optimization. Intelligent completion technology strategies are applicable to different areas and are outlined as:Operating Philosophy: Minimum manning / zero intervention of routine operations.Production Philosophy: Optimum utilization process for gas lift optimization using downhole temperature and pressure measurement.Well Completion Philosophy: Inflow control and multilateral wells.Well Optimization: More horizontal wells with reduced wellhead jacket structural requirement, sequence optimization and dual lateral designs etc.

Effective cost delivery of electrical power to small, lightweight, isolated and unmanned platforms has become important with the introduction of intelligent completion technology facilities. Table A, shows the existing platform's power and capacity, existing loading and the proposed additional intelligent completion technology facilities load. Traditional methods of providing power to offshore platforms centered around the use of solar power, small generators or traditional high-kilowatt sub-sea power cables.

Solar Power Distribution System (SPDS)

Brunei's climate makes solar power an obvious candidate for electrical supply. Platform Peragam's SPDS is rated at 400W, Iron Duke is 2200W and all other locations are 100W. Every 10W of power requires 1 m2 of space for installation of solar panel and batteries. Previous studies showed that SPDS is cost effective for power rating of up to 100W, beyond this, it becomes very expensive due to the requirement of larger space for solar panel and larger battery bank size. This option is considered here since most of the power requirement is marginally higher than the economicalrating of 100 W. Currently, both industrial and certified types are available in the market. The operational experience is poor as summarized below:Limited capacity for future load growth.Hindrance with rigging activities.Batteries disposal problems.Limited available deck space for installation of larger power system.Lower availabilityHigh OPEX.

SOLAR Design:

In general a Solar Battery System and Battery capacity are designed for the site ambient temperature and maximum number of consecutive no-sun days (insolation). For Brunei the batteries autonomy is 3 days based on a daily 20% battery depth of discharge (DoDFactor). The capacity of the battery at the end of the autonomy time shall not drop below 20% state of charge level.