Predicting sulfide stress cracking in a sour environment: A phase-field finite element study

Sulfide stress cracking (SSC) is a leading cause of failure in sour service environments, where the presence of wet hydrogen sulfide (H₂S) causes hydrogen embrittlement and significantly influences the performance and lifespan of casing and tubing pipes. This work presents a numerical investigation on predicting the onset and growth of SSC in a sour environment using a coupled deformation–diffusion phase-field finite element framework, which incorporates the role of sub-surface hydrogen concentration due to H₂S exposure and mechanical loading effects on the crack growth response. The numerical results agree with the experimental data from the notched slow strain rate testing performed on high-strength low alloy steel (HSLA) in a sour environment at room temperature. Recently, the oil and gas industry has been heading towards unconventional gas well applications that expose crucial parts of a well construction, such as production casings, to high internal pressures and a sour environment. To simulate such conditions, a numerical study is conducted that examines the onset and growth of SSC in pre-notched pressurized pipes subjected to H₂S exposure. The geometry and boundary conditions used for the pre-notched pipes adhere to the API 579 standard for fitness for a service assessment of equipment containing identified flaws or damage. The findings of this comprehensive numerical investigation provide valuable insights into the effectiveness of a coupled phase-field approach for SSC and demonstrate its potential as an engineering tool for structural integrity assessments that consider environmental effects.