Experimental Study On Interactions Of Wellbore Corrosion And Scaling During CO₂ Flooding Process In Wusan East Area,Xinjiang Oilfield

In the application of CO₂ flooding in Xinjiang Oilfield,the occurrence of serious corrosion of the oil casing of the production well,and the thinning of the wall thickness of the oil pipe after corrosion,resulting in a decrease in the tensile strength of the oil pipe,and serious accidents such as fracture and perforation of the oil pipe.These problems indicate the need for in-depth study of the fouling and corrosion problems in the CO₂ flooding process.Based on the investigation of the reservoir geology and working conditions in the target block,the tendency of inorganic salt fouling in wellbore under the conditions of injection water and formation water was analyzed.Through indoor experiments,different conditions were simulated and studied.The synergistic effect of fouling and CO₂ corrosion,and the use of scanning electron microscopy?SEM?and electrochemical methods,observed and analyzed the corrosive scaling products of downhole tubing?N80 steel?under the synergistic action of CO₂ and formation water fouling.As well as the corrosion morphology,the microscopic mechanism of fouling and corrosion was analyzed.In the presence of high-pressure CO₂ and formation water,the CO₂ corrosion under the combined CO₂ corrosion and scaling of the N80 pipe was tested by experiments,and the effect of different operating conditions on the CO₂ corrosion under different corrosion conditions was compared.The experimental results show that when the deposition ratio of inorganic salt scale deposition and corrosion rate on the steel surface is about 0.5,the effect of scaling on corrosion is more obvious.When the deposition ability of the local layer is large?the ratio of fouling deposition and corrosion rate is close to 1?,the accumulation of foulants and the increase of scale layer will hinder the contact between the steel substrate and the corrosive medium,and thus hinder the corrosion.The effect of temperature on the corrosion of N80 steel under the combined effects of simple CO₂ corrosion and corrosion scaling is similar,ie,as the temperature rises,the corrosion rate increases,and the corrosion rate around60?.is maximum;pure CO₂ corrosion and its scaling to corrosion The effect increases slowly as the partial pressure of CO₂ rises.This paper analyzes the chemical and microscopic mechanism of corrosion and scaling,establishes a synergetic model for the CO₂ corrosion and scaling of commonly used pipes in oil wells,and reveals the synergistic influence of corrosion and scaling on CO₂ flooding of N80 pipe in Xinjiang Oilfield.Design and CO₂ corrosion and scaling protection provide theoretical guidance.