Numerical Simulation Of Floatover Installation For Offshore Platform

With the increasing development of people’s demand for oil and gas resources, theexploitation of offshore oil and gas resources is increased, so more and more offshoreplatform is widely used in the offshore oil and gas exploration and production, but most ofthe offshore platforms can’t be exploited or produced before the installation is completed.Until now, there are two methods to install the offshore platform on the sea, the traditionallifting and the rising floatover method, among them, the floatover method is a seaborneinstall method for large modules, which is safe, economic and reliable at present.First of all, this paper introduces the main program, the key technology and equipmentabout the installation of offshore platforms using floatover method, summarizes theresearches on the technology to use floatover method to install offshore platform at homeand abroad, then there is the general understanding of the domestic and foreign researchpresent situation. Meanwhile, the research of floatover technology is very little, especiallyfor the research of impact force in floatover procedure, and there is almost no oneresearches the rigid impact between the floatover barge and the legs of the jacket platform,so this paper launched a series of studies about this problem.Secondly, based on the floatover installation of one jacket platform, this paperestablished the numerical floatover model using the ANSYS-AQWA software. Based onthree-dimensional potential theories, this paper does the calculation and analysis of thehydrodynamic parameters for floatover barge in frequency domain, including the addedmass and damping, first-order wave force (torque) transfer function, second-order waveforces (torque) transfer function and so on, and studies the influence to these parameterswhen the water depth changed.Again, the paper makes the time domain coupled analysis foe the floatover model, thekey points motion of barge and topside are studied under the different wave height, wave direction angle and spectral peak period when barge is in place, the results show that thekey points motion can’t meet the demand of the barge is in place, meanwhile, the mooringtension also studied, the mooring tension can’t meet the API specification demand when thewave is1.25m beam sea,1.50m quartering sea and beam sea. Therefore, the author hascarried out the optimization of mooring system, finally found a more suitable mooringsystem arrangement plan, make the key points motion and mooring tension can satisfy therequirements of barge in place and the API specification.Finally, after the optimization of mooring system, this paper mainly studies the rigidand flexible impact force between the ship’s rail of the barge and jacket legs when the bargein place, and the vertical impact force between the upper part and jacket pile tip when ittransfers the load of the topside by0%. The problem of simulating the impact force of theship’s rail in AQWA software is solved, especially for the rigid impact force problem, andthis is the main innovation point in this paper. And then researches the simulation of LegMating Unit and the vertical impact force. Through the research of the impact force ofship’s rail and the vertical impact force, the scope of safety conditions for the installationand construction offshore is got, that the wave height is below1.25m, the spectral period isbelow7s, and the wind and current the smaller the better, make an effort to avoid the1.5mheight when the wave direction is90°.The study of the paper solves the key important issue of simulating the impact force inthe procedure of floatover, enriches the research content of the floatover technology in thedomestic, and at the same time has the important reference value guiding significance forthe practical engineering installation.