The Nonlinear Response Research Of The New Type Of ETLP Under The Impact Load

With the rapid development of global offshore oil to the deep sea, theexploitation of Chinese deep sea has been paid more attention. Offshore oil and gasexploitation in China is in transition from shallow to deep sea, the deepwater oil andgas resources development is urgent. As a kind of half compliant semi-rigid platform,compared with other forms of platform, tension leg platform (TLP) which is good forwater depth range, sports performance and stability, has been widely used anddeveloped, it has become one type of the main oil and gas exploitation platform of thedeep sea in the world. For the sea conditions in Chinese deep sea, in various forms ofthe tension leg platform, the Extended Tension Leg Platform (ETLP) takes a dominantposition.This paper introduces the structure characteristics and research status of extendedtension leg platform, and a new type of extended tension leg platform was analyzed.Compared with the traditional extended tension leg platform, this paper introduces aseries of advantages by structure optimization of the new extended tension legplatform. Based on the sea state of the South China Sea and the environmental loadscalculated according to corresponding specifications, this paper works with a depth of1500meters of a new type of extended tension leg platform as the research object，which takes the method of numerical simulation of the platform motion response andtension legs dynamic response analysis, fully considering the combination of wind,wave and flow and the mutual coupling between platform and tension legs. Thecalculation methods of the new platform response in frequency domain and timedomain are introduced separately.The study mainly in the following aspects:1. A new type of ETLP is put forward, compared with the traditional extendedtension leg platform, its extension structure and pontoon become a whole, so that the modules are reduced, the welding joint between extension structure and columns canbe ignored, which enhances the strength and reliability of the structure.2. Based on the three-dimensional potential flow theory, it uses the theoreticalanalysis with numerical calculation to research the dynamic characteristics of TLP infrequency domain. By using DNV software SESAM/WADAM hydrodynamic module,the added mass force and the potential flow of new platform damping force arecalculated, and ETLP’s dynamic response transfer function is gotten. Meanwhile, bycomparing with two kinds of ETLP’s the dynamic response of transfer function, theirrespective hydrodynamic performance and relative merits are obtained.3. By using DNV software SESAM/Deep C domain module, considering thecoupling between the new platform and the tension leg system, the nonlinear dynamicresponse of the new platform is calculated in load combination of wind, wave andflow and the effect of tension leg system, the time domain analyses are carried out.New platform displacement time history, tension leg tension time history and itsextreme value are gotten.4. By simulating breaking waves as impact load, the new platform in loadcombination of wind, wave and flow at the same time, its dynamic response underimpact load is carried out. Then these time domain analyses under impact load liketime domain results of the platform’s displacement and tension legs system’s tensions,the extreme tension, etc are calculated.The results show that the new type of ETLP has good hydrodynamicperformance, at the same time, the time domain results of the platform in the SouthChina Sea state environment under impact load meet the safety requirements. Theresearch design will afford some references for our country to make researchindependently in the optimized selection and structure innovation of TLP forms indeep water of South China Sea.