EVALUATION STUDY FOR THE CONTROL OF THE HEADING OF A TURRET-MOORED FPSO IN BRAZILIAN WATERS

Nowadays, PETROBRAS operates eleven turret-moored F(P)SOs in Campos Basin. The turretmoored system allows the FPSO to align with the resulting environmental condition. However, some of Petrobras F(P)SOs have been experiencing roll motion in excess of fifteen degrees of single amplitude from time to time, caused by a very well characterized swell condition coming from South/Southwest. This roll amplitude exceeds the operational limits and, in that case, a production shutdown can happen. Furthermore, as a result of excessive roll motions, tugboat assistance has been necessary to change the heading of the FPSO when a helicopter needs to land on the platform. Thus, the installation of stern thrusters to control the heading of the FPSO would reduce the roll motion as well as avoid the use of tugboats. This solution seems to reduce costs in addition to improving the operation safety.

Bearing this scenario in mind, a study was developed to evaluate the required power of stern thruster to be installed in the FPSO with sufficient capability to control the vessel heading out of these critical conditions and, consequently, to reduce the roll motion amplitude of the Unit below a specified value, considering Campos Basin environmental conditions.