DEVELOPMENT OF A MONO-COLUMN TYPE UNIT FOR HARSH ENVIRONMENT

The Gulf of Mexico offshore floaters scenario is very peculiar when compared to the rest of the world. According to September 2004 data, there are preference for of SPARs and TLPs (13 of 17 TLPs are in GoM), rather than Semi submersibles and FPSOs (There are more than 50 FPSOs in the world, and none in Gulf). The inexistence of FPSOs, which are the most “popular” concept worldwide, is due to an old prohibition of MMS and Cost Guard. Nowadays, the use of the concept is allowed, although still needing special approval. Considering the harsh environment, PETROBRAS came up a special type of FPSO, with cylindrical hull and very low motions, called MPSO – Mono-column floater, Production, Storage and Offloading Unit.

During the last 2 years, PETROBRAS and University of Sao Paulo have been developing a design of a monocolumn unit for oil & gas production in offshore Brazil, the MONOBR concept. The result was a safe unit, due to the high reserve of stability and low motions, especially vertical motion, allowing the use of steel catenary risers (SCR) without fatigue and extreme loads problems. Due to this success, it was started a conceptual design of new unit with the same characteristics of stability and motions, but with oil storage capacity, becoming a FPSO with good sea keeping behavior even in the harsh environmental condition.

This paper will present the concept of this new innovative type of the platform that present a lower vertical motions that can be operating with SCR and reasonable storage capacity (near 800,000 barrels) to operate in the harsh environmental condition. In order to obtain development of the complete concept from sea bottom to process plant, several aspect from subsea systems, hull design, plant design, mooring system, risers system and building process were taken into account. The main challenge was to integrate all the systems concurrently due the high level of interfaces between the disciplines.