Causes Analysis on Pullout of a Round Thread Casing Connection in an Oil Well

Pullout might happen to round thread casing connections for reasons of design and process of products,properties of material,make-up torque or make-up position and field operation problems.In recent years,Chinese casing properties had got a high improvement.But the numbers of casing connections pullout accident were not declined obviously.These led to great economy loss and safety hazard.Research on a round thread casing connection pullout case was carried out by combining relative theoretical analysis with test.Macroscopic analysis and material’s physical and chemical properties test were done to the casings and couplings.Thread inspection and full-scale tensile simulation test were done to casing samples that was the same lot with the pullout casing.Comprehensive analysis was carried out on these results at last.The results show that pullout failure was ascribed to two main causes.One was make-up location could not reach standard location at field end,and the other was incorrect holding position on coupling in the course of make-up.