Purpose. A methodology development for calculating the bottom hole assemblies (BHA) with two rock cutting tools for drilling the wells of large-diameter with an ability to manage the trajectory. Methods. A mathematical model has been developed for calculating the assemblies for drilling wells of large-diameter using two rock cutting toolsa bit and a reamer. The main technical and geological factors have been modelled, which influence the assembly elements (stress-strain state of the BHA, deflecting forces arising due to the rock influence). An algorithm for determining the distribution of axial load between the bit and the reamer has been developed. It has been modelled the formation of the reamer eсcentrical displacement relative to the pilot wellbore and the change in the intensity of the wellbore curvature in the process of deepening. Further on, a practical calculation according to the developed methodology is given. Findings. It has determined that an increase in the resource coefficient of cutting structure (that is, an increase in the total number of teeth on a bit, or a decrease in teeth on a reamer) leads to a decrease in the load on the bit. With an increase in the coefficient of destruction areas, the load on the bit decreases. It has been revealed that when drilling with assemblies, a significant influence on the stress-strain state of the BHA and on the change in deflecting forces, has an eccentricity on the reamer, while the intensity of the well curvature changes. It has been proven that the same assembly allows the well to be drilled with different curvature intensities, which can be adjusted by placing a restrictor under the reamer. Originality. A new comprehensive approach is proposed to the calculation of assemblies with two rock cutting tools, which is different in that it allows to perform an iterative cyclic calculation with constant refinement of the main parameters and the creation of a data set for constructing a well trajectory. Practical implications. The developed methodology for calculating the bottom hole assemblies with two rock cutting tools makes it possible to determine a rational design of the BHA for drilling a well in a specified direction by changing the design parameters of the drill collar (DC), supporting-centering elements (SCE), a bit, a reamer and an eccentricity restrictor.

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On the basis of the theoretical analysis and practical studies of hole drilling of large diameter, a method for designing the BHA with two rock cutting tools is proposed, taking into account the geological and technical factors that have an impact on the formation of the trajectory. The calculation of BHA with two rock cutting tools and a different number of supporting and centralizing components for different geological conditions of drilling is carried out and the analysis of their work in the process of drilling is conducted. The graphic dependences of the deviation intensity variation and the inclination angle with the sinking of borehole of the large diameter for the BHA that can be used for the drilling of vertical and directional wells.