Theoretical identification of forces resisting longitudinal movement of drillstrings in curved wells

The equations of balance of external and internal forces acting on a drillstring in a curved well are set up based on the formulations of direct and inverse problems in the mechanics of flexible curvilinear rods. The lowering, lifting, and rotation of a drillstring are studied. A method is proposed to calculate the internal longitudinal force, the forces of interaction between the drillstring and the well wall, and the forces of friction. An example is considered. It is shown that even small geometrical imperfections of the well path have a significant effect on the balance of external and internal forces __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 11, pp. 80–89, November 2007.