Quantifying the effect of residual stresses on pipe burst in carbon steel tubulars in sour service through phase-field modeling

The operational integrity of oil country tubular goods (OCTG)-grade alloys, specifically those used for production casing in sour service applications, is significantly influenced by sulfide stress cracking (SSC) due to hydrogen sulfide (H 2 S)-rich environments. Accurate prediction of burst pressure, therefore, becomes more challenging for ensuring safe operation and for advancing fitness-for-service (FFS) assessment methodologies. A key factor often neglected in conventional evaluations is the presence of residual stresses introduced during manufacturing and fabrication. This study numerically investigates the influence of residual stresses on the burst performance of API 5CT C110, a high-strength, low-alloy carbon steel commonly used in deep sour condensate wells within the petroleum industry. We employ a coupled deformation-diffusion-fracture phase-field framework, specifically calibrated to model pipe burst behavior under sour environment conditions, including internal pressure and exposure to H 2 S-containing aqueous test solutions. To represent manufacturing-induced stresses, residual stress fields, quantified in representative pipe segments, are incorporated into the finite element model using a thermo-mechanical equivalent loading approach. The resulting initial stress field is then mapped onto the pipe burst simulations to account for pre-existing stress distributions realistically. The findings reveal how residual stresses alter the crack driving force and, ultimately, influence crack initiation/growth, leading to pipe burst failure.