This paper proposes a random field model to characterize the corrosion depth on the external surface of buried steel oil and gas pipelines. The model addresses the intermingling of corroded and corrosion-free areas on the pipe surface, similar to the spatial intermittency of rainfall accumulation within a geographic area, by using a latent homogeneous Gaussian random field and a spatial position-dependent threshold associated with the latent Gaussian field. High-resolution corrosion measurement data obtained from corroded pipe segments removed from in-service pipelines are used to estimate parameters of the proposed model, including the probability of corrosion at a given point, marginal distribution of the nonzero corrosion depth and correlation structure of the latent Gaussian field. The results indicate that the nonzero corrosion depth follows a shifted lognormal distribution. The isotropic γ-exponential correlation function is adequate to characterize the correlation structure of the latent Gaussian field with the correlation length varying from 17 to 50 mm and γ from 0.69 to 0.82. A comparison of simulated and measured corrosion fields suggests that the proposed model is able to capture the characteristics of naturally-occurring corrosion field on the pipe surface. The proposed model provides a useful tool for developing fitness-for-service assessment methodologies for corroded pipelines.

本文提出了一个随机场模型来表征埋在地下的石油和天然气管道外表面上的腐蚀深度。该模型通过使用潜在的均质高斯随机场和与潜在高斯相关的空间位置相关阈值，解决了管道表面上腐蚀和无腐蚀区域的混合问题，类似于地理区域内降雨累积的空间间歇性场地。从从使用中的管道中取出的腐蚀的管段获得的高分辨率腐蚀测量数据用于估计所建议模型的参数，包括给定点的腐蚀概率，非零腐蚀深度的边际分布以及潜势的相关结构高斯场。结果表明，非零腐蚀深度遵循对数正态分布偏移。各向同性γ指数相关函数足以表征潜伏高斯场的相关结构，相关长度在17至50 mm之间变化，而γ在0.69至0.82之间变化。对模拟腐蚀场和测量腐蚀场的比较表明，所提出的模型能够捕获管道表面自然腐蚀场的特征。提出的模型为开发腐蚀管道的适应性评估方法提供了有用的工具。