The conventional practice of retrieving the whole length of deepwater drilling riser during imminent typhoon is tedious, time-consuming, and has huge risk of untimely evacuation of personnel and facilities for safety. A proposed operational solution is one which has the drilling riser disconnectable near surface while the longer section is left tensioned by buoyancy can (BC) in freestanding mode. This prompts the need to investigate the survivability of drilling riser when disconnected in freestanding mode and reuse for continued drilling operation after typhoon. In this paper, a mathematical model is presented to analyze the mechanical behavior of drilling riser freestanding mode (DRFM). Finite-difference method with derived end-point formula to reduce imaginary nodes was used to obtain the solution. BC upthrust ratio required to support the DRFM weight and maintain its response while keeping stress and lower-flex joint angle within allowable limits has been figured out to determine survivability threshold for DRFM in extreme sea current condition. BC effect shows potential region for DRFM failure. Accuracy of the threshold condition was verified with numerical simulation in Abaqus. Threshold conditions for various BC positions were established. Influence of current loadings and riser thicknesses on the threshold condition have also been investigated.

在即将来临的台风期间取回深水钻探立管的整个长度的常规做法是乏味，费时的，并且存在不安全地疏散人员和设施以确保安全的巨大风险。提出的一种操作解决方案是使钻探立管可在近地面断开，而较长的部分则以独立式浮力罐（BC）保持张紧状态。这促使需要研究以独立模式断开时钻探立管的生存能力，并在台风过后继续用于钻井作业。本文提出了一个数学模型来分析钻井立管自立模式（DRFM）的力学行为。用导出端点公式来简化虚节点的有限差分法来求解。已经计算出支撑DRFM重量并保持其响应同时将应力和下屈关节角度保持在允许范围内所需的BC上推比，以确定在极端海流条件下DRFM的生存能力阈值。BC效应显示出DRFM失效的潜在区域。在Abaqus中通过数值模拟验证了阈值条件的准确性。建立了各种BC位置的阈值条件。还研究了电流负载和立管厚度对阈值条件的影响。在Abaqus中通过数值模拟验证了阈值条件的准确性。建立了各种BC位置的阈值条件。还研究了电流负载和立管厚度对阈值条件的影响。在Abaqus中通过数值模拟验证了阈值条件的准确性。建立了各种BC位置的阈值条件。还研究了电流负载和立管厚度对阈值条件的影响。