弯曲特性对非粘合挠性管深水安装的影响

摘要

非粘合挠性管是深水和超深水海洋工程开发的重要水下设备之一。有效地将挠性管安装到深水对于大部分水下设备安装承包商来说是一个重要课题。在最近多个深水安装项目中，发现挠性管安装姿态与安装模拟结果相比未能保持一致。主要的原因是挠性管制造商所提供的挠性管名义弯曲刚度无法准确地定义挠性管在安装过程中的受力特性。制造商所提供的弯曲刚度通常比较小，从而过于保守地描述了弯曲曲率。这对于挠性管的设计是可以接受的，但是过于保守估计的挠性管的弯曲曲率对于其安装模拟并非是合理的。与挠性管安装姿态相关联的参数是最小弯曲半径及安装角度。论文阐述了弯曲特性的定义对挠性管安装模拟准确性的影响。选用滞回曲线及其它弯曲刚度常数来定义挠性管的弯曲属性，并对挠性管安装进行了静态及动态安装模拟。与实测的挠性管安装姿态进行了比对，表明采用滞回曲线能较准确地模拟实际的挠性管安装姿态。因此，采用滞回曲线作为挠性管安装属性进行安装模拟是一种较有效及准确的方法。%Unbonded flexible pipe (Flexible) is one of the key subsea equipment for deepwater and ultra deepwater developments. The efficient solution to offshore installation of the Flexibles in deepwater is of significant concern to subsea installation contractors. In several recent subsea installation activities performed in deepwater, the offshore Flexible installation configuration did not match well as planned according to installation analysis. The main reason was found that the initial nominal bend stiffness provided by Flexible manufacturer is not able to well represent the bending behavior of Flexible during its installation service. This bending stiffness is usually very small and produces conservative over-estimates of the pipe bending curvature, which is acceptable for a Flexible riser design. However, the over-estimates of Flexible bending curvature might not be a conservative solution to Flexible offshore installation. It is because Flexible installation configuration is required to be well controlled to protect the pipe from over-bending and over-rotation. Flexible minimum bend radius and tie-in angle are the governing criteria during its offshore installation. This paper presented the impact of bending properties on predicting the configuration of deepwater Flexible during its installation. Hysteresis curve and other selected constant bend stiffness values were applied to defining Flexible bending properties in simulating Flexible 2nd end installation under both static and dynamic conditions. The recorded offshore observation of Flexible I nstallation configuration has been numerically reproduced well by employing Flexible hysteresis bend behavior. Hysteresis curve is found to be more applicable and precise in numerically predicting the Flexible configuration during offshore installation.