ABSTRACT

The development of optimal solutions to satisfy the riser requirements for new platforms has considerable financial implications during platform construction and platform operational life.

Techniques recently developed by OGL offer substantial cost, safety and technical benefits over traditional riser solutions and draws on practical experience gained from over ten years development and installation of retrofit riser systems.

INTRODUCTION

Platform risers are key components of all offshore production facilities having major economic and safety significance. The riser provides access from the sea bed to the platform facilities for:-

  • Product import

  • Export pipelines

  • Platform utilities (control and power lines)

  • Subsea satellite developments, (produced oil and gas, test lines, water injection and control umbilicals).

A riser is usually a pipe which connects between a subsea pipeline and the platform topside and can be made from rigid or flexible pipe in the size range from 2″ DIA to 36″ DIA depending on requirements.

The riser design accommodates substantial environmental loading, particularly in the splash zone. To accommodate the environmental load risers of smaller diameters require additional structural support which is provided by :-

  • Additional clamps to span between main jacket members

  • Located inside a carrier pipe called a caisson which acts as a structural member to provide protection

Risers are of key importance to platform safety as their failure can compromise the complete production facility. For this reason many safety considerations are incorporated into riser designs.

These include:

  • Accidental Vessel Impact Protection

  • Increased Requirements For Corrosion Protection

  • Structural Strengthening

  • Subsea Safety Valves

  • Passive Fire Protection

Riser design is covered by numerous industry specifications and government legislation, included in which, are recent recommendations by the UK Department Of Energy which requires risers to be protected from accidental vessel impact damage. A major requirement on all new production facilities is to accommodate current, future expected and future speculative risers.

Traditional methods for accommodating future riser requirements on production platforms have been:-

  • do nothing, and completely retrofit at a later

  • date if required

  • fit best guess risers requirements during construction

  • fit ‘J’ and/or ‘I’ tubes during construction allows later risers to be installed

  • fit appurtenances onto the jacket structure to assist riser installation

All these methods have economic and technical disadvantages. OGL have delivered new techniques based on retrofitting riser systems onto existing jackets which have considerable technical and economic advantages over traditional methods.

The paper will review the traditional techniques for providing future riser access, both technically and economically. These techniques will be compared with the recent developments in platform riser technology which have recently been deployed on several new jackets.

HISTORICAL

There is no industry standard methodology for the accommodation of risers onto jackets. Each operator and jacket designer have developed methods based on ideas which were developed over 20 years ago. Future riser requirements are often given very little consideration during the initial jacket design leading to risers and future riser requirements being fitted as an afterthought, where the jacket configuration allo

This content is only available via PDF.
You can access this article if you purchase or spend a download.