Riser weight increases with water depth. Supporting the risers, tensioning them to control their response, or optimising the platform motions in order to be "riser-friendly" is often one of the most challenging aspects of converting an old floater for use as a deepwater production or drilling platform. A new build platform will address these issues as part of its design for a particular application, but it will soon have payload and water depth limitations when used generically for multiple applications. A solution is proposed, with a focus on the important issues of well access and riser design, which will remove the payload and water depth constraints from the platform, be it a new design or a conversion. Utilising direct access subsea tress and free standing single line offset risers (SLOR), a semi-submersible equipped with production and drilling facilities not only challenges a dry tree platform solution, such as TLP and spar, it offers many additional safety and operational advantages. The benefit of this SLOR production system is best realised in the very deep water depths, when the design of top tensioned dry tree risers and their impact on the platform become even more imposing and costly. This paper compares the merits of the SLOR production system against the more familiar dry tree production systems, and points to ways of implementing this solution in the emerging offshore regions.
Deepwater oil and gas fields are currently developed using wet (subsea) trees or dry (surface) trees, or a combination of both. Once the reservoir characteristics have been determined, the evaluation of development options for a new field is usually focussed around the type of floating production vessel required to develop the field, whilst the well and riser systems are often ignored until the development scenario has been selected.
