Quantitative Risk Assessment of Oil Well Casing Strings under Non-Uniform External Loadings

Abstract

Considering the uncertainty and randomness of casing loadings and geometry sizes, performance parameters in deep wells, a kind of calculation method of probability distribution of casing external loading and collapse strength was established. Based on the Monte-Carlo method, the probability distribution of casing strength was simulated under non-uniform external loading conditions. With strength-load interference theory, the calculation method of casing safety reliability was obtained, which can analyzes reliabilities of different types of casing strings subjected different loadings in the dangerous section, and a regional relationship between casing reliabilities and safety factors is established. Results show that when casing reliabilities collapse strengths are in the range of 0.5-1.0, the related safety factors locate from 1.0 to 1.25. Safe reliability analysis can provide references for casing strength designs in deep and super deep wells.