The Experimental Research On Drillstring Buckling Characteristics In Wavy Horizontal Section

A drillstring in axial compression will eventually lead to lateral deflection.It will at first go into so-called sinusoidal buckling while it goes from side to side in a sneaky manner.If the axial compressive load is increased further the drillstring will go into helical buckling where the drillstring locks up in spiraling manner against the sides of the borehole.The onset of buckling will depend on the stiffness and outer diameter of the drillstring components and wellbore diameter.Compared with ordinary directional wells,the drillstring has high friction forrce(tripping in,sliding drilling)and torque(rotating drilling)in horizontal wellbore.The drillstring will deform and buckle if the axial compressive load is too high.The buckling phenomenon will lead to drillstring damage and significant increase of drillstring frictional force.The changes of deviation angle and azimuth angle often exist in actual wellpath.The actual horizontal wellbore becomes the wavy horizontal section,which makes the buckling of drillstring more complex.In this paper,we will summarize the related literatures about the drillstring buckling in horizontal wellbore in China and other countries.We also organized and summarized the research progress and the related theoretical achievements of drillstring buckling characteristics in horizontal wellbore.The existing device to simulate drillstring buckling characteristics is transformed to carry out the simulation experiment of drillstring buckling characteristics in wavy horizontal section.We analyzed the changes of critical buckling load and drillstring friction force after buckling with different wellbore curvatures and the annular clearances.These can provide a basis for the selections of the drillstring size and weight on bit(WOB)in the drilling site.