Anchor Corrosion Study Under Vortex-Induced Vibration Of Stopper In Deep Water Pipeline

Submarine oil and gas transportation pipelines have always been one of the significant transportation methods of offshore oil and gas engineering,and a key hub for deep-sea oil and gas development.However,due to the reason of high pressure and strong corrosion nature of the deep-sea environment,deep-sea pipelines and related equipment inevitably undergowent corrosion and failure.Therefore,the research and development of technologies and equipment for emergency plugging and oil control equipment such as stopper and underwater oil control hoods of deep-water pipelines is necessary.Based on the preliminary research on the direction of emergency plugging and maintenance of deep-water pipelines,this paper aims at the rapid resumption of production of the stopper connecting the jumper,and analyzes the influence of the vortex-induced vibration of the deep sea current on the jumper.The deep-sea current transforms the vortex-induced vibration of the jumper into the torsion effect on the stopper,clarifies the vortex-induced natural vibration frequency and torque of the stopper.Performing a modal analysis of the stopper considering the internal and external pressure and damping,and study its resonance fatigue failure phenomenon under the action of vortex-induced load;Using the electrochemical module and solid mechanics module of COMSOL Multiphysics to couple,analyze the indentation depth and the anodic corrosion current density at the cusp of the block under the designed load,and respectively explore the influence of cusp angle on the indentation depth and limit current density through the controlled variable method.And study the heat transfer problem of hightemperature oil inside the stopper anchoring device,analyze the heat transfer mode between the components of stopper anchoring device,establish a heat transfer model,and analyze the steady-state and transient temperature distribution when anchoring device in the oil transfer process through ANSYS Workbench.The influence of block temperature on its mechanicalelectrochemical corrosion under stress is explored,analyze the corrosion life of the block under vortex-induced load;Develop an experimental plan to verify the indentation depth and shape of the block under the load,the blocks with different temperature distributions,loaded and unloaded,respectively,corrosion weight loss、corrosion current density and corrosion solution PH analysis were studied through heating devices etc;The scanning electron microscope was used to observate the blocks before and after corrosion.According to the observation results,the analysis of the influence of different pitting corrosion on anchoring performance were carried out.The research of the paper can provide suggestions for the optimum devise and the reliability research of block of the stopper in the deep-water pipeline.