Riser Systems for Deep and Ultra-Deepwaters
Authors: Sertã Otávio B. , Longo Carlos E.V. , Roveri Francisco Edward 
Published: October 2008

The development of deeper water fields by Petrobras has required continuous improvements with respect to their riser systems. The recent efforts for SCR development were not an isolated action. Besides this program, that involved the installation of a prototype at P-18 (Marlim Field), the studies for SCR utilization in an FPSO unit at the Barracuda/Caratinga Field, and the installation of two more SCRs in another SS unit (P-36, Roncador Field) using the hybrid installation method (i.e. reel + J-lay), other actions are being conducted, such as: search for new designs for flexible riser structures and configurations, the Hybrid Riser System with Subsurface Buoy Concept, and the riser system for the Floating Production and Workover Unit (FPWU). More recently, Petrobras has been considering Conceptual Studies for Alternative Riser Systems, which will comprise the evaluation of concepts, different from the ones previously mentioned, for Albacora Leste Field.

Albacora Leste is the next relevant deep water field to be developed and operated by Petrobras. It is the first scenario considered for riser studies and development under PROCAP 3000, the new version of the Petrobras Deep Water R&D Program. The traditional flexible riser concept, the SCR, the Hybrid Riser System with Subsurface Buoy, and some Alternative Riser System (mainly riser tower type solution) concepts are being evaluated for this field. The learning from these studies will give the basis for the future deeper fields that Petrobras will be challenged to develop.

This paper will bring the Petrobras experience on riser systems and views on future possibilities for deep and ultradeep water fields.

Introduction

Since the beginning of the exploitation of Campos Basin offshore fields, Petrobras has been facing new challenges to produce in deeper and deeper waters. The option for the use of Floating Production Systems (FPSs), in the majority of the cases, had a strong impact on the kind of risers employed.

The historical evolution of the riser systems of Campos Basin is described in this paper. Some good reasons for the emphasis given to flexibles are explained, and the main steps related to the technological advances of this technology is documented. Other technical options for riser systems, either actually used, or just investigated, are presented. Alternative Riser Systems, presently considered for the Albacora Leste Field development, are focused. Finally, some thoughts about possibilities for the future, that may be included in the PROCAP 3000, are added.

It is important to mention that, although Petrobras has no deep water system based in dry completion (TLP, Spar, etc.) in operation, such option is always considered in a comparison basis with the wet completion (subsea) system, which has always been selected. Thus, to be able to properly evaluate the dry completion systems, Petrobras has performed several conceptual studies, that included the riser systems in a quite detailed level. Nevertheless, risers for dry completion systems are out of the scope of this paper.