Subsea Pipeline Lateral Buckling Susceptibility Analysis

2. Group of Hydrology and Water Resources, Faculty of Engineering, Agostinho Neto University, Angola

 Abstract: The research presents a detailed in-service lateral buckling analysis on the water injection (WI9) line of Angola Block 15/06 Agogo 2 Oil field located Development Project. The analysis was performed following the methodology given by the Flowline Global Buckling Design Premises. The study aims at the assessment of susceptibility to lateral buckling, calculation through detailed FE analysis (if necessary), the bending levels reached in the post-buckling configuration, design of corrective measures ensuring the safety of pipelines and the fulfillment of the pipe strength criteria, verification of stability of the curves for in-service conditions and assessment of the fatigue at buckle apex due to operating cycles. A detailed in-service lateral buckling analysis of the water injection Agogo phase 2 was performed through plenty stages namely, calculation of the axial force along the route using pressure and temperature profile and project specific pipe-soil interaction friction, assessment of lateral buckling susceptibility due to in-place loads under both hydrotest and operating conditions, examination of the rogue buckle at the peak compressive effective force location KP6, analysis of Friction combination BE/HE cases, performance of lateral buckling FE analyses by means of 1 mitigation device at KP6, and thus analyzing the Rogue buckle before and after sleeper, analyzing the buckle arrestor of 12 m between KP = 2194 m and KP = 2206 m to assess the impact on its FE models used for lateral buckling analysis, calculation of the bending moment levels originated in the post-buckling configuration with FE detailed analyses using ABAQUS 6.14 software, verification of the pipeline integrity depending on whether the flowline is in “Buckling” condition, then seabed is considered as even or moderately uneven seabed without trawling interference, only a displacement controlled check, based on the best estimate axial pipe-soil resistance and the high estimate lateral pipe-soil resistance. Therefore, the condition load effect factor of 𝛾𝑐 of 1.0 shall be used. The pipeline integrity check for local buckling is satisfied if DCC is satisfied.