Research On Measurement Technique For Catenary Mooring System And Analysis For Measurement Result

With the growing of energy demands, the development of marine resources becomes more and more important. And the major structure in the exploitation of offshore oil&gas is floating platform. Floating platform normally needs a station-keeping system to limit its location to certain area. Due to structural, reliable features and lower cost, catenary mooring system has been widely used in most of floating platform.Considering preliminary design process of catenary system, the main parameters of environmental parameters, added mass, damping, mooring stiffness, maximum offset, maximum tension, and Response Amplitude Operator of floating unit (RAO) should be considered. In the detailed design process, strength of mooring and fatigue feature of mooring system need to be verified. Restore force of mooring lines is the important index for the design of mooring system and performance analysis. Till now, model text and numerical simulation still can’t satisfy the requirement of mooring design, especially in deep water.In the present paper, based on the analysis of catenary equation considering elastic deformation and the movement of floating vessel, a method of measuring restore force of mooring line is present. By the location, information of six degrees of freedom and inclinations of mooring line, we can get boundary conditions of catenary equation, and calculate the restore force. Relying on the monitoring project in semi-submersible platform in LH11-1oilfield in the South China Sea, the present algorithm is implement and establishment. According to the analysis of measured data, we confirmed that accuracy of the method is satisfied in engineering. Through analyzing the relationship between parameters, the factors affected measurement accuracy had been analyzed. By the statistics and power density spectrum analysis of monitoring data, the wave frequency effect can be observed obviously in the calculation of restore force of mooring system, especially in harsh environments. In general, the prototype measurement method of the catenary mooring system exhibits a good advantage for the design evaluation of mooring system and becomes a reference other mooring system design.