Integrated Riser and Mooring Design for the P-43 and P-48 FPSOs
Authors: Seymour B. , Zhang H. , Wibner C. 
Published: October 2008

This paper presents the approach adopted for the design of the mooring and riser systems as part of the Barracuda and Caratinga field development project in the Campos Basin offshore Brazil. For deepwater field developments, where FPSOs are selected as the host facilities, an integrated approach is required for optimization of the riser and mooring system design. The principal parameters in the optimization process include vessel offsets, overall riser configuration and local pipe design. In the case of the Barracuda and Caratinga field developments, the integrated approach has resulted in a safe and cost-effective design, thereby enabling the use of a catenary configuration for the flexible risers. This paper further addresses the practical constraints typically encountered as part of the riser and mooring system design within the context of large-scale fast track deepwater field development projects.

Introduction

In July 2000, Halliburton was awarded a contract to proceed with the development of the Barracuda & Caratinga fields by the Barracuda and Caratinga Leasing Corporation (BCLC). The nature and scope was on a full engineering, procurement, installation and construction (EPIC) basis. This included work related to the drilling and completion of 54 wells, fabrication and installation of 133 flexible flowlines, risers and umbilicals, conversion and mooring of two very large crude carriers (VLCCs) into floating, production, storage and offloading vessels (FPSOs) and the commissioning, start-up and operations support for both fields. The project duration, from the time with a clear seabed to the point of handing over two working fully commissioned FPSOs in Barracuda and Caratinga fields, was about 3 years, representing a fast-track delivery schedule.

The overall project specification and major deliverables is presented in Table 1. This scope of supply represents one of the largest of its kind ever awarded to a single contractor. The conversion schedule for the FPSOs was one of the most important factors to be considered in the riser and mooring system design. Several key schedule related issues to be considered during the design process include:Vessel dry-docking schedule;Vessel reinforcement interface loads;Mooring line chain size;Fairlead loads and fabrication lead time;Polyester rope prototype testing, production;Riser Design LoadsRiser manufacturing scheduleRiser pipe prototype qualification testing schedules;Riser ancillary equipment (endfitting, bend stiffener and abrasion protection and flowline anchor) schedules;Overall riser and mooring installation/pre-installation schedule. Based on the above, the project milestones are defined and these become the backbone to the process. Therefore as the design progresses along the schedule timeline, certain decisions are made for equipment design parameters. Once these are set, no further optimization can take place. As the imeline progresses the available options decrease. In short the degree of optimization of any piece of equipment is directly related to how far down the timeline the design parameters are required.