Study on Failure Pressure Prediction of Double Corrosion Defects in Oil and Gas Pipelines

Corrosion defects in actual oil and gas pipelines tend to occur in clusters, and the mechanical interaction between adjacent defects alters the local stress field, thereby affecting the overall failure behavior and load-bearing capacity of the pipeline. Existing pipeline integrity assessment codes often adopt simplified treatments (e.g., the defect projection method) for multi-point corrosion, which fail to fully consider the influence of defect spacing and may lead to inaccurate (overly conservative or unsafe) evaluation results. To reveal the interaction mechanism of double-point corrosion, this paper takes X65 pipeline as the research object, establishes finite element models for two typical types of double-point uniform corrosion defects (planar axial and circumferential arrangements), and systematically investigates the effects of defect spacing, depth, and length on the failure pressure. The results show that the axial spacing has a significant influence on the failure pressure, and a critical spacing (60 mm) exists. When the spacing is smaller than the critical value, the failure pressure decreases by up to 18% compared to the single-defect case, and the critical spacing decreases with increasing corrosion depth. In contrast, the influence of circumferential spacing is much weaker and can be neglected. Based on extensive numerical results, empirical fitting formulas for the failure pressure of axially and circumferentially spaced double-point corrosion are provided. The goodness-of-fit (R²) reaches 0.97805 and 0.99964, respectively. This study clarifies the mechanical interaction mechanism of double-point corrosion and can serve as a reference for the residual strength assessment of pipelines containing adjacent corrosion defects.