From Early Production Systems to the Development of Ultra Deepwater Fields - Experience and Critical Issues of Floating Production Units
Authors: Mastrangelo Carlos F. , Barusco Pedro J. , Formigli José M. , Dias Ronaldo 
Published: October 2008

This paper describes a real "Journey" starting in 1977 with the first production well in Enchova Field, at a water depth of 110m. It covers twenty-five years, since the concept of a Mobile Offshore Drilling Unit was first used to produce an oilfield in advance of a definitive production system, evolving to a complex and fit-for-purpose Platform, able to handle all requirements of fields located in Ultra-Deep waters of around 2000m.

This Journey follows, step-by-step, the technology challenges to be overcome with a sequence of field experiences as well as lessons learned at each step.

The article details milestones and very innovative systems, like the first Semi-Submersible based System, with an oil production capacity of 10,000 bpd, as well as flaring of all associated gas exporting the crude to a spread-moored FSO through a floating hose. This Floating Production System combined simultaneous production and drilling capabilities.

A further step was one of the first FPSOs around the world. Designed in 1977, with oil produced for the first time in 1979, it used an innovative concept that comprised atmospheric wellhead cellars (WHC) and a multiplexed subsea control system. The FPSO was installed using a tower-yoke system able to keep the Unit on station as well as to gather all fluids from the subsea system and export treated oil to a vessel moored at another tower system.

With the increasing water depth, new challenges arose. They have driven PETROBRAS to innovative concepts like taut-leg mooring, vertical connection method for flowlines into subsea hardware and new flexible line developments. Since there were, at that time, no similar situations around the world, PETROBRAS had, along these twenty-five years, to take the lead and, many times, Campos Basin was used as a real fullscale lab, applying concepts that were yet to be field-proven. The operational experience throughout these years was fundamental for the new coming projects and a summary of their respective performance is also presented at this paper. Today Campos Basin has on stream 13 fixed platforms and 21 floating product systems. Four new production units will be installed until 2004 at water depths as deep as 1,250m and oil production capacities of up to 180,000bpd each. We shall compare and address key points of these new units and, in addition, show the success of Dynamically Positioned Floating System, producing wells down to 1,800m water depths.

Introduction and Background.

It was in 1974 that oil flowed out or the first time in Campos Basin, through an open well test of the wildcat RJS-9. This very first oilfield was named Enchova and, thus, the exploitation of Campos Basin started 25 years ago. Today, this field is still on stream and together with many others around it, contribute with more than 80% of Brazil's oil production and about 45% of the Brazilian natural gas output.

Campos Basin is located on the north coast of the Rio de Janeiro State and comprises an area of around 115,000 km2.