Uncontrolled Lateral Buckling (LB) of subsea High-Pressure, High-Temperature (HPHT) pipelines can cause high plastic deformation, which could lead to premature failure during operation if it is not mitigated. Conventional LB mitigation methodologies can be very expensive to implement and, in some cases, can have unsatisfactory "trigger" reliability for subsea pipelines. The Residual Curvature Method (RCM) is a relatively new and efficient method for LB mitigation and has, to date, been utilized for shallow water pipelines installed by the Reel-lay method. When compared to other lateral buckling mitigation methods, RCM offers advantages, such as:
reduced pipeline installation cost;
low buckle-initiation (trigger) load, and therefore high buckle reliability, which help prevent "rogue" (unplanned) buckles;
lower post-buckle strains and fatigue damage compared to other mitigation methods, which may eliminate the need for expensive, fatigue-driven welding criteria at the planned buckle locations;
However, in the application of RCM for deep water pipelines, there are some design aspects, such as high top-tension, residual bottom-tension, soft soil, high soil lateral resistance, and orientation of in-place RC sections that present technical challenges. This paper presents the benefits as well as the feasibility of using RCM for lateral-buckle mitigation for deep-water HPHT pipelines.
To justify the implementation of the RCM for deep-water pipelines, advanced non-linear finite-element (FE) analysis is used to assess the installation of the pipeline with RC sections and to determine the achievable in-situ RC parameters for a pipeline on the seabed. This paper addresses the technical challenges of performing detailed analyses, including a sensitivity analysis of RC section performance related to lateral soil resistance and in-lace orientation of the RC pipe section, in order to confirm the suitability of RCM for lateral-buckle mitigation in deep-water pipelines in soft Gulf of Mexico clays.