RISER SYSTEMS 

For deepwater application, Risers are transporting various fluids (oil, gas, water, etc.) from the seabed to the surface (production fluids) but also from the surface to the seabed (for water injection, gas lift, service line, etc.). Risers are ‘dynamic’ systems which operate at both high pressures and temperatures often with highly corrosive fluids.

As a result, they are technically complex with very stringent fabrication tolerances and the materials and methods of manufacture and installation have an important economic impact and safety significance of offshore production systems. These issues are of course compounded as depths increase, due to higher loads and lengths involved making riser system selection and optimisation even more complicated.

Although high pipe flexibility is needed to accommodate vessel motions in shallow water, at greater depths stiffer pipe (like SCR) is considered to be of worthy consideration because of the beneficial effect of water depth (> 1000m) on riser system compliancy.

During the last ten years, flexible technology has been significantly improved and new riser concepts proposed to the market (like SIR by Saipem or TCR (tethered catenary risers) by SS7, …) to meet the challenge of ultra-deep waters (>1500m to 3000m) offering significant commercial and technical advantages over previous riser systems.

The aim of this document is to review the current state of the art riser technologies, which are well adapted to deepwater field developments, and to highlight its key engineering topics, limitations, advantages and disadvantages.

This document commences, in Chapter 2, Executive Summary, with a brief overview of the design process for deepwater risers made out of flexible pipes, steel catenary riser and hybrid riser tower.

Chapter 3, deepwater riser design methodology provides information on top and bottom interfaces requirements for the different riser systems (material and configuration), these systems being further described in Chapter 4, Interface requirement.

Technical solutions such as thermal insulation and heating to mitigate hydrate and/or wax formation later in field life are described in Chapter 5, riser system review and Chapter 6, Insulation Techniques.

Chapter 7, Heating techniques and Chapter 8, Vortex induced vibrations discusses deepwater riser vortex induced vibration (VIV) and the buoyancy can vortex induced motion (VIM) problems affecting riser fatigue life, and provides some options often selected for VIV suppression.

As high well productivity is essential in offshore deep waters, Chapter 9, Vortex Induced Motion (VIM) describes one of the most widely used artificial lift method, namely, gas lift.

Chapter 10, Artificial lift requirement is dedicated to the installation methods related to the different types of riser configuration. The monitoring devices used to check the integrity of the risers during the installation and operation phases are depicted in Chapter 11, Installation Techniques.

Applications and limitations on riser material (flexible or steel pipe or hybrid riser systems) are discussed in Chapter 12, Monitoring Devices for risers ; in Chapter 13, Applications & Limitations, advantages and disadvantages of different riser configurations conclude this document.

Tip Click these links below for access to 3D resources: 3D Interactive Model of riser structures ( SHR, HRT) 3D Pictures of Lazy Waves 3D Pictures of Risers

This document is based on the following sources

We wish to thank the manufacturers and subsea contractors for the provision with courtesy of technical information and photographs of their products.