The P-25 platform is located at 575 m water depth in Campos Basin, offshore Brazil. In the time of its conversion (1996), its process plant was designed to use cold water streaming from the Antartic continent to cool its equipment, accessories and compressing gas plant for exportation.
The uptake riser installed in 1997 is 330 m long, 24″ OD pipe, hanging from the pontoon and the cold water flowing through it enters a sea chest located next to the support.
This fully rigid riser was recently asked to be replaced. This paper presents the stages of the reanalysis of this compliant structure under conditions of low cost, so that the platform continues to suck cold water. Because of the presence of the uptake riser, the platform does not have a cooling plant that would else request area and weight, two important items in an arrangement, besides the high cost involved.
Within the scope of the analyses, the replacement of the material (originally steel) with offloading hoses is tried out, in search for weight savings and lower cost. These hoses were reinforced with steel cables and their behavior was checked. Some tests were performed to verify the mechanical strength of this material and vibrations by VIV that occur in this structure.
Monitoring systems were designed to check all forces and displacements during the referred installation.
These actions will consolidate the technology for Petrobras leading to another riser system option for production in ultra deep waters.