Local buckling of deepwater oil-gas pipeline under high hydrostatic pressure

The special studies were focused on the defective thick-walled steel pipe, and the model test and numerical simulation of the pipe structures were respectively conducted under external high hydrostatic pressure. The uniform external pressure was applied on the pipe specimen by squeezing water into the pressure cylinder, and the peak pressure was measured when the local buckling occurred. The numerical simulation on buckling and post-buckling behaviors of experimental steel pipe under hydrostatic pressure was conducted based on the software ABAQUS. The collapse pressure and deformation shape of the steel pipe after buckling accorded well with the test results. The effects of different material property, ratio of diameter to thickness and initial ellipticity on the buckling of pipe were analyzed by using the established method of numerical simulation. Results show that the larger the material hardening coefficient is, the greater the collapse pressure of pipe becomes; as the initial ellipticity increases, the collapse pressure of pipe remarkably decreases; as to the collapse pressure of deepwater and ultra-deepwater oil-gas pipeline, the formula from the current specifications is somewhat conservative, and takes no into account the effect of material hardening coefficient.