Research Of Seismic Integrity And Repair Measures For Oil Pipeline With Corrosion Defects

With the development and utilization of petroleum resources,many oil fields in China has come to the middle and later periods of development,which means that the corrosion of oil pipeline has become more and more severe.China is an earthquake-prone country and there have been some frequently-happened earthquakes recently,so the influence of earthquake has gradually become one major security risk for the oil pipeline integrity.So it's extremely urgent to carry out the study on the anti-seismic integrity of oil pipeline with corrosion defects.For the oil pipeline with corrosion defects,the replacement of defected pipeline section will take a long time and cost a lot,so it's of great importance to choose one reasonable and effective repairing method in order to keep the normal operation of defected pipeline section.This paper firstly sums up the present research status of anti-seismic research on pipeline with corrosion defects and repairing techniques in China and abroad.Several typical seismic damage examples are listed and the finite element analysis software,ADINA,is simply introduced.In chapter 2,the theoretical analytical model of overhead oil pipeline with corrosion defects and finite element model are built and static load analysis and inherent formation analysis are conducted on the finite element model.The result shows that stress concentration will take place in the section with corrosion defect under the static load.When the external corrosion defect depth exceeds the 40% of the pipeline wall thickness,or when the internal corrosion defect depth exceeds the 50% of the pipeline wall thickness,there will be damage risks on pipeline.In Chapter 3,based on the current most commonly-used three industrial standards and simplified calculating methods,the stress and residual intensity in the corrosion section of overhead oil pipeline are analyzed.The result shows that with the increase of corrosion depth,the maximum hoop stress and maximum axial stress in the corrosion section also increase gradually.With the increase of corrosion depth,the stress increases faster,which means that the risk of pipeline damage is larger.When the corrosion depth exceeds the 50% of pipeline wall thickness,hooping damage is more likely to occur to pipeline in the corrosion section.In chapter 4,the finite element models of pipeline with different corrosion depth,corrosion location,corrosion defect number and different locating sites are built and seismic response analysis are carried out.The analysis shows that the depth of corrosion defects and location of defect make a big difference on the pipeline strength.The external corrosion has larger influence on the pipeline anti-seismic integrity than the internal corrosion defect.When the corrosion defect is close to the mid-span,it will have more obvious influence on the anti-seismic integrity of pipeline.Two neighboring corrosion defects can reduce the stress concentration effect in defected area and pipelines with corrosion defects have better anti-seismic property in?and ?sites.In Chapter 5,the finite element models of pipelines being repaired by B type sleeve repairing method and carbon fiber composite repairing method are built and seismic response analyses are carried out.The analysis shows that the B type sleeve repairing method is not suitable for the repairing of overhead pipeline defect in seismic area,while carbon fiber composite is very suitable for the repairing of pipelines in seismic area or pipelines which need to improve the safety factor of pipeline operation.