Influence Of Geomagnetic Disturbance On Cathodic Protection System Of Oil And Gas Pipelines

Under the geomagnetic storms,the pipe soil potential(PSP)generated in buried metal oil and gas pipelines may cause the cathodic protection of pipelines to exceed the safe and stable operation range,thus affecting the effect of cathodic protection.The corrosion may even lead to pipeline leakage,endangering the safe operation of the pipeline.In this thesis,considering the leakage of pipeline insulation coating,the pipeline PSP calculation model is improved.The cathodic protection potential distribution of pipelines with different anode systems under geomagnetic storms is studied by combining the cathodic protection model of pipeline with the improved pipeline PSP calculation model,which provides a reference for the protection of pipeline safety.The specific research contents are as follows:1)The principle of cathodic protection of pipeline is analyzed,and the governing equations of potential distribution under the cathodic protection are deduced.Combined with the actual parameters,the calculation model of pipeline-cathode protection boundary element is established by using the COMSOL multiphysics software.The potential distributions on buried oil and gas pipelines using distributed anodes,deep well anodes and flexible anodes as cathodic protection are calculated separately,which shows that the flexible anode has the best protection effect,and the deep well anode and distributed anode protection effect is slightly inferior.2)The influence of the leakage point of the insulating coating on the leakage conductance and transmission resistance of the pipeline is analyzed.The equivalent concentrated parameter model of the pipeline PSP calculation considering the leak point is constructed.The model is verified by using ANSYS and is combined with the distributed parameter model to simulate the influence of the leakage point on the PSP distribution when the pipeline is invaded by geomagnetic storms.The results show that the larger the radius of the leak point,the greater the influence on the PSP distribution of the pipeline;the closer the leak point is to the two ends of the pipeline,the greater the influence on the PSP distribution of the pipeline.3)The potential distribution of the pipeline under the influence of magnetic storm for the cathodic protection of different anode systems is calculated.Taking the Shaanxi-Beijing pipeline No.1 as an example,based on the geomagnetic data of Beijing geomagnetic station and the structural data of the earth's conductivity,the potential of Shanyinshangxiaohe Station during the geomagnetic storm is calculated.The results show that the flexible anode with the best protection effect under general conditions is inferior to the distributed anode and deep well anode when the pipelines is invaded by the geomagnetic storms.As a result,using the flexible anode may lead to the peeling of the pipeline insulation coating.