A new concept Spar FPSO (Floating Production Storage and Offloading) is proposed for South China Sea deepwater oil field development integrating the advantages of the deep-draft Spar concept whose excellent stability and global performance enables dry-tree drilling and production, and the conventional ship-shaped FPSO for oil storage and offloading.
This paper presents a study of the tandem offloading system for the new concept Spar FPSO. The paper will first give an overview of various offloading configurations and their characteristics for deepwater development; then a tandem offloading system similar to conventional ship-shaped FPSO is recommended for further investigation considering operational experience, safety and economical benefits. As the offloading operations are generally weather-limited, offloading environmental conditions for the study are selected based on API, ABS and South China Sea offshore operation practices. For a case study, hydrodynamic performance of the Spar FPSO in tandem offloading configuration with a shuttle tanker in 1500m water depth was investigated numerically and experimentally. Numerical simulations were conducted by means of fully coupled nonlinear time-domain analysis. The distance between the shuttle tanker and the Spar FPSO is optimized based on the relative motions of the two floaters and the hawser tension requirement of the shuttle tanker. Experimental results from model test are presented and compared with analytical time-domain simulation results. It is shown that the results of numerical simulations are consistent with the model test. The tandem offloading system demonstrates robust performance and cost-effectiveness for the proposed Spar FPSO concept.