Analysis of casing collapse pressure based on energy balance method

Key words:  casing  energy balance  fullscale experiments  collapse pressure  initial ovality

Abstract:

The mechanics model was built up to calculate the collapse pressure of casing according to the force state and deformation behaviors of casing subjected to external pressure, based on energy balance method. The deformations of casing were divided into elastic and plastic deformations. The collapse pressure calculating equations of casing were deduced by the mechanics model. The influences of initial ovality, yield stress and diameterthickness ratio on collapse pressure of casing were discussed. The collapse pressures of six V140 casings were tested and calculated by fullscale experiments and available method respectively to verify the calculating results. And also, the finite models (FM) were set up to simulate the casing subjected to external pressure. The comprehensive results indicate that the mechanics model agrees well with the experiment testing data, ISO/TR104002007(E)code and FM results. The mechanics model is satisfied with the engineering demands. The elastic and plastic collapse pressures of casing decrease with the initial ovality and diameterthickness ratio increasing. The collapse pressures of casing increase with the yield stress increasing.