DP crane barges operate in close proximity to FPSO (Floating Production Storage and Offloading) during lifting operations. This operation is critical since small variations of the relative position may result in collision between the bodies or large motion of the lifting load. The hydrodynamic interactions between the units are an important effect that must be considered in the analysis of those operations. The interactions are an intricate problem that cannot be modeled analytically in an appropriate way. Hence, experimental and numerical tools are applied for the definition of the environmental conditions for a safe operation or the optimal relative positioning between the vessels.
A research project conducted by Petrobras in cooperation with Brazilian universities aims to develop and to validate numerical tools for aiding the design and analysis of the DP lifting operations. They are based on dynamical time-domain simulations of the operation and can be used for predicting several parameters of the operations. The experimental tests that will be used for validating this numerical model, concerning the DP performance when the crane barge is close to a FPSO, are presented in this paper. The tests were conducted in an ocean basin using the model of a moored FPSO and the DP crane barge. The station keeping ability (relative motion) and the performance of the propulsive subsystem of the DP crane barge (power and thrust utilization parameters) are measured. Several relative positions and wave conditions were considered.