INTRODUCTION

The recent reduction in oil prices throughout the world has led to an increase in the number of offshore oil and gas fields attracting marginal status. The reduction has led many operators to reconsider the conventional offshore development scenario involving above-water production facilities and associated export pipelines. This revaluation has led to a significant increase in the number of subsea satellite developments, together with the accompanying transport and service lines tied back to existing production facilities.

This approach often allows for maximum utilization of existing investments by the addition of further throughput achieved by a new, relatively low-cost satellite development Currently, the lack of available subsea process facilities-demands that wellhead flowlines be manifolded and extended back to the "parent" facility Typically, this may result in a number of flowlines between the satellite development and existing facility to provide services such as oil and gas production, well test, gas lift, and chemical and water injection

Some examples of development schemes of this type currently in production or being constructed are as follows

  • Texaco-Highlander Field tied back to Tartan (North Sea, UK Sector),

  • Occidental-Scapa Field tied back to Claymore "A" (North Sea, UK Sector),

  • Statoil Tommeliten Field tied back to Edda (North Sea, Nonvegan Sector),

  • Mobil Ness and BBSWI tied back to Beryl "B" (North Sea, UK Sector)

In contrast with conventional above-water developments, this new generation of offshore oil and gas fields may involve the installation of a significant number of small-diameter, relatively short-length pipelines

This feature requires that the use of the conventional high-cost third-generation lay-barge, developed for deepwater installation of larger-diameter pipelines be re-evaluated Consequently, detailed consideration should also be given to alternative methods of pipeline installation Moreover, as the provision of pipelines forms a large proportion of the capital cost of a satellite development, it is necessary for the pipeline designer to evaluate carefully all available installation methods early m the design process, in order to identify the most cost-effective solution

This chapter presents a brief review of the requirements for pipelines for this application of satellite developments, and the suitability of various pipeline design and installation methods

GENERAL DESIGN CONSIDERATIONS

Design requirements for traditional offshore pipelines are well documented and are not addressed here However, where multiple small-diameter pipelines are envisaged for satellite developments, special consideration of the following areas may be required during pipeline design.

  • material selection,

  • thermal insulation,

  • installation - pipeline corridor requirements, tie-ins,

  • deepwater installation and tie-in

Internal corrosion may result from high hydrogen sulphide or carbon dioxide levels in the produced reservoir fluid However state-of-the-art technology relating to subsea process equipment is not yet sufficiently developed to influence internal corrosion in satellite field export pipelines Consequently, selection of more-exotic materials, such as duplex stainless steel or carbon steel clad with stainless steel, may prove to be more attractive than the use of an anticorrosion chemical-injection system.

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