Vytvytskyi I. Selection of non-steerable bottom hole assemblies for rotary well drilling

The thesis is devoted to the problem of improvement of the centering technology of casing strings in directional wells in order to increase the level of reliability of their casing. The model of contact interaction of a casing string with key seat of different forms is developed, which allows for estimating forces of resistance of the column advance; the influence of various factors on the size of the gap between the casing and the well wall is determined. The analytical dependences between the clamping force and the mutual approximation of the string and the well wall, which characterize the radial rigidity of the centralizers, as well as the expressions for determining the maximum stresses, by which its strength is evaluated, are obtained. For calculating the elastically rigid characteristics of centralizers models of equipping of a casing with centralizers of different types and their fastening schemes have for the first time been created. The problem of rational centering of the casing string with the condition of providing the minimum allowable gap between the column and the well wall is formulated. The calculations of distance between elastically rigid centralizers for different variants of well designs and sizes of permissible gap, which confirm the received regularities, are carried out.