The large number of wells expected to be drilled in ultra-deep Brazilian waters for exploitation of oil and gas fields encouraged PETROBRAS to evaluate the feasibility of upgrading one of its four existing semi-submersibles drilling platforms of the series TH2800, to operate in water depths up to 2500 m with slender drilling risers. Originally designed to operate in up to 360 m water depth, anchored to the seabed by a spread mooring system, the new station keeping of the Unit will be provided by a DP System, including eight azimuthing thrusters, powered and monitored by a new integrated automation and control system. Also, two new cranes with improved lifting capacity will be installed in order to handle the drilling risers joints from the riser racks to the catwalk machine and to position the wet christmas-tree close to the moonpool at cellar deck area. All these new features led to a dramatic increase in hull submerged volume, to account for new hydrostatic equilibrium and stability requirements, which, in turn, pointed for the necessity of new global structural analysis and reinforcements.
The large number of wells expected to be drilled for exploitation of oil and gas fields in ultra deep Brazilian waters, as well as the lack of Units in the market that are capable to operate in this range of water depths, encouraged PETROBRAS to study the feasibility of upgrading one of its four existing semi-submersible drilling platforms of the series TH2800. The main purposes of the upgrading are to install a DP system for station keeping in up to 2500m water depth, at which neither conventional nor taut-leg anchoring systems are adequate, as well as new drilling facilities, in order to operate with a higher performance.