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ABOUT A HALF-WAVE LENGTH OF THE BOTTOM-HOLE CORE DRILL COMPOSED OF STRUCTURAL ELEMENTS OF DIFFERENT STIFFNESS

Boranbay Ratov

Abstract

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. The researches allowed to formulate a number of conclusions. 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 half-wave length decreases with increasing axial load C and decreasing diameter of drilling (decrease in stiffness of the core set. 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. To drill a certain size decreasing the intensity of half wavelengths with increasing number of revolutions n of the column is much higher than with increasing axial load C. The resulting relationship is different from the well-known formula B. I. Vozdvizhenskogo, M.G. 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. The formula for the first half-wave length from the bottom hole of the drill core, composed of the elements of different stiffness allows to determine location of the centralizers, increasing stiffness of the bottom-hole tool and contributes less twisred wells. To reduce the curvature of the wells is recommended to install in the "crests" half-waves of the bottomhole shell

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DOI resolver: doi.org/10.5593/sgem2017/12/s02.005

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