超深水钻井隔水管动力分析理论研究与数值模拟

随着钻井作业向深水(500～1 500m)和超深水(1 500m以上)发展,在交变海洋环境载荷波浪力、海流力和浮式钻井平台运动的共同作用下,隔水管的动态响应更加显著.文中探讨了隔水管侧向振动的数学模型、动态特性分析中的结构与环境载荷建模技术及其非线性动力分析方法,研究并对比了不同分析方法在计算效率、计算精度和工程适用性等方面的差异.介绍了时域内应用ABAQUS软件进行超深水钻井隔水管非确定性动力分析的算法与详细流程,算例比较了不同边界条件对深水钻井隔水管动态特性的影响.研究表明,时域非确定性分析最为精确但需要时间最长,且只能采用线性AIRY波浪理论;理论上,海流主要引起隔水管动态响应的时不变部分,但该时不变部分不等同于海流引起的隔水管静态响应,一种简化方法只将海浪与钻井船运动作为动载荷而不考虑海流对动态响应的贡献;钻井船运动和波浪载荷是隔水管动态响应分析主要的动载荷,对于超深水隔水管来说,钻井船运动是首要的动载荷,其慢漂运动对隔水管性能有重要影响,而波浪仅对隔水管局部产生作用.

Theoretical Investigation and Numerical Simulation of Dynamic Analysis for Ultra-deepwater Drilling Risers

With the drilling operations moving into deepwater and ultra-deepwater, risers exhibit more severe dynamic response excited by random waves,ocean current and the floating vessel motion. In this study, mathematical formulation of lateral vibration, modeling techniques of structural and environmental loads in dynamic behavior analysis as well as the methods of nonlinear dynamic analysis for the deepwater drilling risers are investigated. The difference of the methods in calculation efficiency, accuracy and practical application is studied and compared. The algorithm and the detailed flow chart of the nondeterministic dynamic analysis of the risers using ABAQUS in time domain are introduced.An example is presented which illustrates the effect of vessel motion boundary condition on riser dynamic performance.The study shows that time domain nondeterministic analysis is the most accurate but it is time -consuming,and only linear AIRY wave theory can be employed in it. Theoretically,time-independent part of the dynamic response caused by current does not equal the static response caused by it. An applicable dynamic analysis method takes vessel motion and wave as the sources of dynamic analysis,ignoring the contribution of current to dynamic response.Vessel motion and irregular wave are the main dynamic load of the riser dynamic response,however,the most significant portion of the dynamic behavior was caused by motions of the drilling vessel.rather than by wave forces on the riser. Wave forces only act on the local part of the riser in wave zone.Long term drift motion of the vessel has major influence on deepwater riser dynamic performance.