Analysis and Testing of Factors Affecting Collapse Performance of Casing

This paper describes testing and analysis which demonstrates that collapse specimens tested in short testers with rigid end seals give artificially high collapse values. It also compares the API collapse formulas with conventional strength of materials collapse criteria which incorporate ovality and finds the two approaches give very similar results. A statistical analysis indicates that ovality, while not nearly as important as yield strength and D/t, is important to collapse. Finally, it shows that pipe with lower ovality exhibits better collapse resistance.