Abstract: To understand the mooring energy during positioning, the configuration and tension of three types of mooring lines were derived using catenary formula. The gravitational and elastic potential energy distributions of a single mooring line with the lower end fixed were calculated for different upper end positions. The horizontal force calculated from potential energy was compared with that of calculation directly, and the results show good agreement, and satisfy the law of conservation of energy and also prove the correctness of the results of potential energy. For a deep-water platform moored by nine composite mooring lines, the potential energy distributions of the mooring system were analyzed, and the offset-lateral force relations were compared in different directions. They are found to meet each other very well, which indicates a balanced performance of the mooring system. The potential energy distributions and the offsetlateral force relations in different wave directions were calculated for the damaged case. From the results, it can be found that the potential energy distribution can reflect the performance of the mooring system in all directions effectively, which has important practical value in ocean engineering.

Key words: gravitational potential energy, elastic potential energy, energy distribution, catenary mooring line, taut mooring