Study On Tidal Effect Mechanism Of Buried Pipeline Pipe-Soil Potential(PSP)

The geomagnetic induced current(GIC)and earth surface potential(ESP)in conductive earth induced by the low-frequency geomagnetic disturbances directly influence pipe-soil potential(PSP)on buried pipelines.The flow mechanism of geomagnetic disturbance in the ground induced electric field and ground pipeline system is obtained,and the mathematical model for prediction and calculation is further established,which is an important prerequisite for the accurate evaluation of the GIC PSP level in oil and gas pipelines and the prediction and prevention of space weather disasters.At present,the influence of complex geological changes has not been taken into account in the study of pipeline induced PSP.The existed pipeline model has defects.In this paper,the modeling and numerical calculation of pipe-ground potential of pipeline in the complex geological structure along the east coast of China were conducted.The following is the main research content and results:In order to study the effect of coastal and fault zone complex effect on pipeline PSP of Rizhao station along the east coast of China,3D model of the land and sea and 3D seashore model at 45-degree angle and 3D coast-fault model were firstly established to explore the distribution of geo-electric field under different geological conditions in coastal areas.Then the 3D conductivity model of the east China region where the east China line of petro-china is located is constructed based on the sounding data.Based on the idea of Fourier transform and inverse transform,the fem of pipeline is proposed,which can directly apply the magnetic field data of geomagnetic station as boundary conditions to calculate the real-time PSP spatial and temporal distribution of pipeline during magnetic disturbance.This method is not only operable,but also suitable for the calculation of pipeline PSP under complex geological conditions.A tidal coast model is established to study the tidal effect of PSP in buried pipelines in coastal areas.It is pointed out that the essence of tidal effect is dynamic coastal effect.Taking the magnetic disturbance during August 10,2017 as an example,this paper compares the calculated and measured PSP values of the Ridong pipeline and draws a conclusion that the calculated PSP of the pipeline has tidal characteristics,verifies the accuracy of the tidal coast model,reveals the mechanism of the tidal effect on the coastal pipeline,and provides a theoretical basis for pipeline corrosion protection.