Effects Of Drillstring End Constraints On Sinusoidal Buckling Loads

In recent years, the deep wells, horizontal wells, big high-deviated wells and large displacement play more and more important roles in in oil and gas exploration. Controlling of wellbore trajectory, drilling fatigue, drilling cost have been a sharp problems, It is required to understand the detailed buckling behavior of them in order to optimize the design of drilling assembles and to reduce the cost. Therefore, the inevitably actual working conditions of the borehole, control and precisionthere is the drill string bucklingan development direction.First , the research contents are determined based on the current status of the drillstring buckling in wellbores. Then, based on the actual working conditions of the drillstring in wellbore and to ensure the consistency of the minimum of an energy functional with its corresponding equilibrium equation eigenvalue, the boundary conditions are given. For a length of drillstring under circular string constraint, using the differential quadrature (DQ) element method FORTRAN programs were written for sinusoidal buckling analyses of drillstrings in inclined wellbores, and various numerical examplç–¤?ere given. The effects of oblique constraint conditions of ends ,angles of wellbores and drillstring length on the buckling loads are investigated, and the rationality of the proposed model and mothod is confirmed by being compared with the theoretical solution and experimental results in literature. , Some results for engineering reference are given.