Floating Hose Behavior During Different Scenarios of an Offloading Operation

Considering the deep water oil exploitation in remote fields far away from the coast, the use of shuttle tankers connected to FPSOs (Floating, Production, Storage and Offloading) for offloading and oil transporting shows to be a preferred alternative compared to constructing oil pipelines considering technic and economic matters, even if offshore offloading operation is still considered one of the riskiest operations in the offshore environment. From the concerns about hazards of an offloading operation, one is related to hose failure during oil transferring and the consequences on the environment. Different aspects of FPSO and shuttle tanker influence floating hose behavior during offloading operation as environmental condition, ships loading conditions, ships distance, heading, FPSO offloading station position and number of hose sections. The different aspects may be combined in several scenarios, in which integrity of floating hoses in terms of tension and bending strength shall be guaranteed. In the present paper, global numerical analyses of offloading operation considering a spread moored FPSO and a typical dynamic positioning shuttle tanker (DPST) moored in tandem are carried out. The analyses are based on a coupled numerical model of FPSO, DPST and floating hose [2]. Covering a wide combination of the scenarios considering the aspects listed above, full time domain simulation is used to estimate hose sections force and moments during the operation. Numerical model results are validated for a couple of scenarios against field data. With focus on floating hose integrity, the main objective is to define minimum requirements for a safe offloading operation, as environmental criteria, maximum and minimum distances between FPSO and DPST, limit operating sectors and minimum number of hose sections. The results can be used as reference to offloading procedures and manuals of owners and operators in combination with recommendations of international organizations.