Study On Corrosion Behavior And Protective Measures Of Oil Pipeline In Xinjiang Oilfield

Xinjiang Oilfield Oil and Gas Storage and Transportation Branch Company undertakes the business of transporting and transferring crude oil and natural gas in Xinjiang Oilfield,Recently,there are 101 crude oil and natural gas pipelines with a total mileage of 4044 km.Among them,the buried insulated pipeline is 708 km,accounting for only 29%of the mileage of crude oil pipeline,however,since 2006,124 times of perforation have been made,accounting for up to 84%.The buried insulation pipeline is more prone to corrosion perforation,and the corrosion status is more prominent.Therefore,this research carries out the investigation and study on the corrosion status of buried insulated pipeline,explores the main control factors and corrosion mechanism of the pipeline corrosion caused by Xinjiang Oilfield Company,and tries to carry out targeted anti-corrosion study from the source,and provides safe,economic and effective prevention and control measures to guide the improvement of existing pipelines and the design of new pipelines.The main conclusions are as follows:（1）Due to the blocking effect of insulation layer on cathodic protection current,the main cause of corrosion of buried insulated pipeline is cathodic protection current shielding.At the same time,the minimum cathodic protection potential is too high,the service time of pipeline is too long,the selection of anti-corrosion coating is unreasonable,and the pipeline transportation temperature is high,which also affects the corrosion process and degree of buried insulated pipeline.（2）The external corrosion mechanism of buried insulated pipeline is mainly the macro galvanic cell corrosion formed at the damage point of the anti-corrosive layer and far away from the damage point.Cathodic protection may accelerate the anodization process of the pipeline surface under the aging stripping coating and the promote the formation of oxygen concentration difference battery.The surface closure of the pipeline under the stripping coating may be stronger,the environment will be worse,and the corrosion may be more serious.（3）Compared with zinc alloy anode material,aluminum alloy anode material still has good electrochemical performance at 80℃,that is,lower working potential,higher capacitance and current efficiency,and uniform dissolution,which can be used as embedded sacrificial anode material in buried insulation pipeline;The new sacrificial anode with embedded aluminum alloy can reduce the pipeline potential to-0.95 V_CSEunder the high temperature of more than 60℃,and the polarization potential difference is more than 150m V.（4）In the simulated Hongqian line corrosion environment,after adding 5000 ppm solid corrosion inhibitor,there is no obvious local corrosion on the surface of T/S-52k sample,the corrosion rate and corrosion inhibition efficiency are 0.0748 mm/a and 72.19%,respectively.In the process of construction or maintenance of buried insulated pipeline,the solid corrosion inhibitor is added to the joint patching position,which can effectively protect the pipeline once the anti-corrosive layer enters water.