Analysis of Burst and Collapse Strength for Tubular with Wearing Defects

Abstract

Taking account of the influence of friction between the outer wall of buckling tubular and the inner wall of casing under vibrating loads, the burst and collapse strengths of worn tubular would be reduced greatly compared to the unworn tubular. If the reduction of burst and collapse strength weren’t taken into consideration, there may be potential risk in well completion. The models of worn tubular strings were established based on finite element method, and thus the relationships between strength of burst and collapse and the degree of wear were analyzed. The results of FEM were verified by the equations in API 5C3. The results show that the strengths of burst and collapse will be reduced with the increase of wear degree, and the burst strength will be reduced more sharply. When the tubular strings are worn by 30%, the strengths of burst and collapse will be reduced by almost 50%. While the strengths of burst and collapse will be reduced by almost 60%, when the tubular strings are worn by 50%. So, to avoid the accident caused by the worn tubular, the work case should be controlled strictly correspondingly.