The Response of Pipelines in High Pressure, High Temperature Offshore Environment.
A Thesis Submitted to the School of Postgraduate Studies, University of Lagos.
This thesis explores the application of Euler-Bernoulli beam theory to derive the equations of motion of fluid conveying pipelines subjected to high pressure, high temperature offshore conditions. The vibration responses show that the higher the density of the transported fluid, the lower the critical velocity at which resonance will take place, hence heavier fluid should be pumped at lower velocity than lighter ones whereas heavier surrounding fluid (as in the case of salty and muddy swamp) behaves as a damper. In addition, the higher the inlet temperature, the higher the period of oscillation but the lower the critical velocity required to initiate resonance. The study also provides theoretical bases for the popular practice of burying of pipeline as a means of controlling buckling and further justifies the same means for the control of pipe walking where the geology permits it. Deformations such as pipeline buckling and pipe walking are found to be enhanced by increase in inlet temperature which is a function of the well condition. Furthermore, the study is shows that the hitherto central role attributed to transient response may not be the main driver for pipe walking since the magnitude of steady state is higher and may after all be responsible. Also, the results of the order of the contributing factors indicate that oscillatory strain, pressure, temperature, tension and friction among others play a significant role in the phenomenon of walking.