| The exploration and development of offshore oil and gas resource are urgently requested along with people’s increasing demands on oil resources and gradual exhaustion of land resources. Nowadays, many countries in the world strive to develop offshore drilling and production platform technology to take the advantageous position in upcoming resource competition. To rapidly, safely and economically install platform onto the specified sea area will be a research focus in construction of offshore platform. Lift and float-over are two common methods for offshore installation of platform, and the application scope of traditional lift is limited upon increasing installation charge and weight of topsides as well as platform structure. Therefore, float-over installation is widely used all over the world. Among which, as one of float-over installation methods, twin-barge float-over has become a hotspot for offshore platform installation for it’s being unlimited by size of platform opening and draught as well as being capable for installation of larger topsides.At first, this thesis introduces operation process for float-over installation, and illustrates research and development status on it by scholars, and then detailed defines steps for twin-barge float-over installation. Secondly, this thesis establishes a hydrodynamic model of objective platform on different stages during installation process by using hydrodynamic calculation software of AQWA according to characteristics of weight loading transfer during installation of topsides by means of twin-barge float-over and taking the conceptual model of Cell Spar applicable for the Nanhai Sea area for reference. This thesis takes frequency-domain analysis on hydrodynamic model on different stages by following the three-dimensional potential theory and then gets added mass coefficient, damping coefficient and movement amplitude response operator (RAO) of float-over barge and Spar platform and other hydrodynamic power parameters as well as motion characteristics in regular wave during the process of unloading. Thirdly, based on frequency domain analysis, this thesis establishes time domain calculation model for twin-barge float-over installation. This thesis simulates the movement of float-over barge, topsides and platform in actual ocean environment by two connection methods of rigid and hinge connection by using the AQWA-Drift software. This thesis analyzes the movement characteristics of upper modules of Spar platform in installation of twin-barge float-over by different connection methods on four aspects of contrast of relative motion between barge and platform, contrast of single floating body motion response upon rigid and hinge connection, contrast of stress status of joint touch point and contrast of stress of mooring rope. To take the upper loading of float-over barge’s transferring to main body of platform by 50% as an example, this thesis takes a contrast on different incidence direction upon rigid connection, hinge connection and environmental loading, then it is deemed as to be the most appropriate for float-over installation numerical simulation upon connecting float-over barge and upper module by means of rigid connection on this stage. Finally, according to basis of rigid connection, this thesis conducts motion response forecast to main body of platform in float-over installation models by changing distance between float-over barge and main body of platform, stormy wave flow ocean environmental parameter and other relevant parameters when the environmental loading incidence is 180°, and therefore obtains change rule of its motion, which provides a reference evidence for future research.By using method of numerical simulation analysis, this thesis studies relevant issues of deep sea platform of Cell Spar during the installation of twin-barge float-over, and impact on installation of different connection methods, which supplements installation by methods of twin-barge float-over and has a certain reference value for future numerical calculation of offshore float-over installation. |
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