Probabilistic Approach for Lateral Buckling Analysis in Virtual Anchor Spacing (VAS) Models of Rigid Flowlines Subjected to High Pressures and High Temperatures (HP/HT)

Resumo

This study deals with the main topics related to the phenomenon of thermomechanical buckling of rigid flowlines laid on the seabed. It focuses on the latest versions of DNV-ST-F101 [1] and DNV-RP-F110 [2]. Additionally, the study presents a probabilistic approach for lateral buckling analyses in Virtual Anchor Spacing (VAS) of rigid flowlines exposed on the seabed, subjected to High Pressures and High Temperatures (HP/HT) in deep-water environments. The methodology includes determining the probability curves of the parameters with the greatest influence on the analysis: Pipe-Soil Interaction (PSI), friction between the pipe and sleeper (buckling mitigator), and geometric imperfections (lateral out-of-straightness). This is followed by a Design of Experiment (DoE) analysis to create a matrix composed of a representative set of load cases to be simulated using the Finite Element Method (FEM). These simulations are performed using Abaqus to obtain the probability distributions of the effective Critical Buckling Force (CBF) and Post-Buckling Force (PBF). The tolerable VAS is determined through FEM analyses applied to a dedicated load case matrix to identify the most critical failure criteria. The results are post-processed to generate response surfaces and failure probabilities for each of these criteria using the Monte Carlo Method. Finally, a case study is performed to illustrate the probabilistic approach, which requires more simulation time than a deterministic method but offers more detailed probability ranges for lateral buckling responses, potentially reducing a project's overall cost. It can be used to assess the reliability of lateral buckling responses during the detailed design phase of subsea pipelines susceptible to lateral buckling.