In the formation of the well under the influence of an axial load and speed core drilling shell is curved, with its lower bottomhole part consists of elements of different stiffness: a set of core and drill pipe. To determine the length of the half-wave in this part of the technological tools used energy method, according to which the whole work of external forces on the length of said potential energy goes into twisted drill. The solution of the corresponding equation is possible to obtain a formula for determining the length of the half-wave of the bottom-hole shell. The resulting relationship is different from the well-known formula B. I. Vozdvizhenskogo, MG Vasilyeva that it additionally takes into account the ratio of the core set, and half-wave ratio of moments of inertia and the core set of drill pipes and the mass ratio of coring and drilling labor per unit length. To reduce the curvature of the wells is recommended to install in the «crests» half-waves of the bottomhole shell ribs.

Keywords

Bending, core drill, ribs, half-wave length, half-wave crests.