A new calculation model for casing collapse resistance strength considering manufacturing imperfections

The influence of manufacture technology and manufacturing imperfections on casing collapse resistance strength is not included in API 5C3 standard, so the actual casing collapse resistance strength cannot be predicted accurately by API 5C3 standard. API/ISO working group revised the current API 5C3 standard and proposed the new collapse resistance strength model with manufacturing imperfections, which upgrades the casing strength calculation accuracy significantly. The study on the ISO collapse resistance new model disclosed that it could not be used to predict the collapse resistance strength for all casing thickness. On the base of ISO collapse resistance new model, a new formula for predicting the casing collapse resistance strength was presented. Numerical and experimental comparisons show that the predictive values calculated by the new formula were proper and reliable, and the calculation accuracy is higher than that of API 5C3 standard and ISO new model. It supplied a new reference in casing designs.