超大型FPSO原油质量分布模拟与水弹性响应研究

FPSO在近海油气田开发中得到了越来越广泛的应用.大多数在渤海海域服役的FPSO工作在浅水海域.主尺度大与水深吃水小,直接导致FPSO水动力特性与深水条件下船舶的水动力特性有较大区别,因此采用水弹性理论研究超大型FPSO在浅水中的运动与波浪诱导载荷响应具有重要意义.浅水超大型FPSO满载时原油重量将近占载重量的80%,因此如何正确模拟原油重量分布对干结构的固有频率、广义质量和振型的计算非常重要.本文建立了基于三维水弹性理论的数值模型,开发了有限水深复合格林函数的数值计算程序模块,对一艘300K DWT FPSO在特定水深海况下的运动与波浪载荷响应进行了研究;同时采用三种方法模拟了原油质量分布.计算结果表明,不同的原油质量分布模拟方法对水弹性计算分析影响很大.

A Study on Oil-Mass Distribution Simulation and Hydroelastic Response of Very Large FPSO

FPSO is becoming the dominant facilities for offshore oil and gas industry in recent years. Most FPSOs in the offshore Bohai Bay sea area in China are operating in shallow water. The large dimension and small ratio of water depth to draught of the FPSO make the hydrodynamic characteristics quite different from those of other FPSOs operated in deep water, so it is very significant to study the motion and wave-induced load responses of very large FPSO in shallow water based on three-dimensional hydroelastic theory. Since the fuel weight of very large FPSO in shallow water accounts for nearly 80 percent of total displacement, it is very important how to correctly simulate the fuel mass distribution for calculating natural frequency, generalized mass and modes. In this paper, the hydroelastic model has been established, the finite water depth composite Green function is employed to develop a program for the computation of the hydrodynamic coefficients of the FPSO in shallow water, and the motion and wave-induced load responses of a 300K DWT FPSO in a given water depth have been numerically calculated. In the course of numerical calculation, three methods are applied in order to simulate the fuel mass distribution. The calculation results show that the these methods result in rather different effect on hydroelastic analysis.