Study On The Influence Of Corrosion On Buckling Bearing Capacity Of Deep-sea Pipelines

As the world’s largest energy consumer,China’s energy problem is increasingly prominent.At present,China is vigorously developing deep-sea oil and gas exploitation.However,due to the characteristics of service environment,corrosion damage is one of the most common damages of deep-sea conveying system^[1].Therefore,it is of great significance to analyze and study the performance of pipeline structures containing corrosion damage.This paper analyzes the buckling capacity of deep-sea pipeline from the following three parts.In the first part,the finite element model is established to analyze the influence of2-D ring buckling pressure under internal random pitting and external pressure.Due to the influence of multi-phase flow erosion and corrosion in the pipeline^[2][3][4],the pipeline is easy to generate internal groove corrosion and point corrosion at the six o’clock direction.Aiming at the influence of internal random pitting on the buckling pressure of deep-sea pipeline,the user-defined Python program is embedded into Abaqus finite element numerical simulation software for research.The results show that ovality（△）,diameter thickness ratio（D/t）and the corrosion ratio（α）are the main factors affecting the buckling pressure reduction coefficient of two-dimensional ring.Based on the analysis results,an empirical formula for buckling pressure reduction of two-dimensional ring with internal random pitting under external pressure with the above three parameters is established.Second part for the erosion of a deepwater oil and gas pipeline in the damage of90°bend buckling problem,establishes a simplified model more accord with the actual damage,the buckling erosion type distribution,and proposed a classification according to different buckling form including scouring corrosion damage of 90°bend buckling pressure of explicit expression.The analysis shows that the radial maximum corrosion depth will limit the influence of axial range and circumferential width,and the radial maximum corrosion depth and scour corrosion axial range will affect the buckling type of the elbow model,and three buckling modes appear.The research shows that three different buckling modes are caused by different damage parameters.Based on numerical simulation and sensitivity analysis results,combined with multi-parameter nonlinear regression analysis,the empirical formula between dimensionless buckling pressure（P_c/P_y）and the five parameters of ovality（△）,diametric/thickness ratio（D/t）,bending/diameter ratio（λ）,dimensionless corrosion depth（ED_m/t）and corrosion ratio（β）is established.The results can be used to evaluate the buckling strength of submarine oil and gas pipeline under erosion and corrosion.In the third part,a finite element model is established to solve the buckling problem of 90°bend containing erosion and corrosion damage in deep-sea oil and gas pipelines under complex loading conditions.In this paper,the buckling of the bending pipe with bending deformation and bending moment under the actual working condition is studied,and the influencing factors are summarized.On the basis of the research in the second part,the bend subjected to the combined action of complex bending pressure is analyzed.The bend makes the buckling pressure of the bend affected,and the maximum corrosion depth and corrosion ratio of erosion corrosion also make the bend more prone to buckling.The results can be used to evaluate the buckling strength of the bent pipe with erosion and corrosion damage under the combined action of bending and compression.