To investigate the configurations and force characteristics of deepwater S-lay pipeline during abandonment and recovery (A/R) operation, the stiffened catenary theory was applied to establish the static equilibrium governing differential equation of a pipe element, combined with the mechanical analysis of cable and the movement of pipelay vessel, then numerical solution method was derived for the configuration of pipeline and cable during two stages of A/R operation, and the corresponding program was developed to carry out the numerical simulation on the abandonment process of offshore pipeline in 2 000 m water depth. The results show that in the first stage, the pipelay vessel has to move ahead so that the tension of A/R winch keeps invariable, along with the configuration of pipeline becoming flat gradually, the tension of the pipe increases whereas the bending moment decreases. In the second stage, the pipelay vessel maintains motionless, and the tension of A/R winch need decrease step by step; the configuration of offshore pipeline becomes increasingly steep along with the pipeline continuously being lowered, thus the tension of the pipe decreases whereas the bending moment increases rapidly. The results are compared with the ones obtained by the OFFPIPE software, and close agreement further demonstrates the effectiveness and practicality of this calculating program, which can offer the theoretical basis for the laying design of deepwater pipeline in the practical engineering．
GONG Shun-feng, XU Pu, ZHONG Wen-jun, HE Ning, YAN Hui. Analysis on abandonment and recovery of offshore pipeline for deepwater S-lay Operation. J4, 2013, 47(11): 1904-1910.
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