Buckling behavior of tubulars in oil and gas wells a theoretical and experimental study with emphasis on the torque effect.

摘要

Tubular buckling can occur during drilling, completion and/or production operations. Its understanding is very important and can have great impact on economic success of oil and gas wells. Therefore, in this study an extensive theoretical and some experimental work are conducted to give a comprehensive insight into this phenomenon.;Derivations of equations for lateral and helical buckling of tubulars are reviewed. New equations for helical buckling are developed taking into account the influence of torque. In addition, equations are derived for post-buckling analysis with and without torque consideration. The energy method approach is used in the development of the analytical solutions.;The influence of wellbore inclination, clearance radius and presence of fluids is analyzed. Also the stability of vertical strings is studied with and without consideration of the torque effect.;The ability of the models to predict buckling behavior and pipe configuration is further investigated using experimental tests performed in a horizontal facility that allows tests with and without application of torque.;The theoretical and experimental results provide a better understanding of the buckling and post-buckling behavior of pipes inside wellbores. The presence of torque, although always causing reduction in the critical loads, is proved to be small for most of the normal field operations.