Strain-based casing design approaches have been used for high-temperature thermal and geothermal well applications by accepting a limited amount of axial plastic strain while maintaining the casing integrity.

However, there are still challenges in burst and collapse design for axially yielded casing strings since there are no analytical equations available in industry standards or recommended practices for calculating the post-yield casing burst and collapse strengths.

There is a technical gap in the rationale for selecting the appropriate design methodologies and the associated design margins in post-yield casing burst and collapse design.

Finite Element Analysis (FEA) was conducted in this study to assist a technical investigation of the casing burst and collapse strengths in high-temperature geothermal wells. The FEA demonstrated the impact of key mechanical properties and the stress path on casing burst and collapse strengths at a few critical conditions through the thermal cycle.

Based on the FEA results, extra design margins associated with the selected burst and collapse design equations were quantitatively evaluated. This study led to critical examinations of the applicability and limitations of the traditional burst and collapse design equations for high-temperature geothermal well applications.

Physical testing is recommended for improving the confidence in casing burst and collapse design for high-temperature geothermal wells. The technical discussions presented in this paper are not only applicable for steel casings but also considered particularly valuable for corrosion resistant alloy (CRA) casings that have been used in geothermal wells, specifically due to the lack of test data and casing design methodologies for these casing candidates.