The Conversion of Spirit of Columbus Semi-submersible into Petrobras 36
Authors: Fachetti Marina B. , Valério Cid G.P. , Loureiro José E. , Jorge Henídio Q. 
Published: October 2008

The conversion of the former Spirit of Columbus semisubmersible into the production unit P-36 for the Phase 1 of Roncador Field faced a set of challenges. The actual platform has the capacity to process 180,000 bopd of oil and to compress 7.2 million m3/d of gas. Allied to the huge process plant capacity, P-36 is installed at 1,360 m of water depth and a total of 90 risers will be connected to the Unit, mainly from 21 subsea production wells and 5 subsea water injection wells.

This paper presents the design and fabrication phases of this conversion performed in England, Canada and Brazil over a 31-month period spanning from 1997 to 1999. Unique aspects of the conversion, such as process facility, hull modifications and mooring system design is discussed. Despite of being one of the biggest semi-submersibles in the world, a set of modifications was required to comply with its new function.

This paper also addresses the management challenges in order to minimize risks, budget and schedule overruns with the strategy to the project development in parallel with the appraisal well phase. Many interfaces with other activities have been successfully managed through a true integrated team approach.

Introduction

The Phase 1 of Roncador Field Development comprises 21 subsea production wells producing 180,000 bopd through flexible lines to a production semi-submersible P-36 located at 1,360 m water depth. After the processing and treatment operation the oil is transferred to the dedicated Floating Storage and Offloading unit (FSO) P-47 for storage and later exportation to shore via shuttle tankers (Fig. 1). The compressed gas is exported, through a new 10-inch gas pipeline, connected to a pipeline manifold (PLAEM), and, from there to an existing fixed platform (PNA-1), through a new 20-inch diameter pipeline. On PNA-1, the gas pipeline is connected to the existing gas to shore pipeline network.

The P-47 is a former VLCC, converted to an FSO. It is equipped with storage and transfer facilities, including cargo pumps and offloading system. Oil and fuel gas from P-36 flow to the P-47 via a turret system. An electric-optical cable for power supply and data exchange is connected through a special swivel for both functions. Dual fuel - gas and Diesel oil - engines are dedicated to three main generators and cargo pumps. There is a small fuel gas plant fed by P-36.

Roncador Field was discovered in October 1996 pointing out as one of PETROBRAS most promising production prospects. And only 5 months later the detail engineering of the semi-submersible had already started. The strategy was a fast track development with parallel investments among appraisal well program, technological development and first phase development bringing a set of challenges that might be surpassed during the project. Paper OTC 12136 (Ref.1) presents an overview of Roncador development program.

Contract History

In January 1997, the Spirit of Columbus semi-submersible was chartered by PETRO-DEEP, on a bareboat basis, to Braspetro Oil Services Company - BRASOIL to be used at Marlim Sul Field.