Technical Improvements Incorporated in One Company's Subsea Umbilical and Distribution Systems
Authors: Williams V.T. , Ross C.M. 
Published: October 2008

Over the previous decade a rapid and significant design evolution has occurred in Shell's subsea umbilical and distribution systems. This design evolution is principally the result of key drivers including more stringent flow assurance requirements, increasing water depth, continuous cost improvement and standardization. This paper will address these key drivers and their influence on the design of Shell's subsea umbilicals and distribution system as well as how the umbilical and distribution system has been integrated into Shell's standard subsea system overall. Improvements, advancements and lessons learned since Shell's first deepwater subsea development in the early 1990's will be reviewed. Also addressed are significant technology andimprovement areas.

The creation of a group to specifically focus on the umbilical and subsea distribution system has resulted in a unique team of experts within Shell and its Subsea Alliance partner, FMC, that has demonstrably added value to the subsea system design process. Managing the umbilicals and subsea distribution on a portfolio basis has enabled this group to improved reliability and cost of these deepwater systems.

Introduction

The umbilical is the "lifeline" of the subsea system. Together with the local subsea network of hydraulic and electrical flying leads it provides the electrical power, communications, chemical injection and hydraulic fluid power necessary to control and operate subsea wells. In the last decade a rapid and fascinating design evolution of Shell's umbilicals and subsea distribution systems has occurred. This evolution has been driven by several key factors, namely evolution of the flow assurance requirements, increasing water depth, cost improvement and standardization of subsea equipment. These challenges have been met through the efforts of a dedicated team responsible for the umbilicals and associated subsea distribution network. By focusing on the umbilicals and standard subsea equipment for all ongoing subsea projects, the team has been able to transcend traditional project boundaries and leverage innovations and standardization across the entire portfolio of projects laying the foundation for continuous technical and cost improvement. Several advances in umbilical technology and cost improvements have resulted from this focused effort including the use of large, steel tube umbilicals, the introduction of new materials for steel tube umbilicals, the design and standardization of modular subsea distribution system and the standardization of umbilical design. Of course, along with the achievements and advances come some lessons that will also be discussed.

Evolution of Umbilical Design Requirements

Flow assurance requirements have changed dramatically as we have moved beyond the subsea gas wells developed initially into more difficult oil developments containing paraffin and asphaltenes. Standardization and cost improvement have also been predominant themes in evolution of subsea developments and have had a significant influence on the umbilical system design as have deeper water and flow assurance.

Flow Assurance Requirements.

Flow assurance, as it is used here, refers to the means by which continuous hydrocarbon flow throughout the subsea system from the well tubing to flowlines and ultimately the host is ensured.