Abstract
We have proposed approaches to analytical assessment of the moment of inertia related to the curved rotary sections in a drill string. Research into rotation processes of the curvilinear sections in a drill string is associated at present with a particular difficulty, which arose because of the lack of precise expressions to evaluate the moments of inertia for a curved pipe based on the parameters of its deformation. Solution to such problems is important for the analysis of dynamic resistance of drill strings at rotor and rotor-turbine drilling techniques, when studying the stressed-strained state of its elements, refining the energy costs for rotation process of the curved sections in a well, as well as for analysis of critical rotation speeds. We have investigated the moment of inertia for a bent section in the rotating drill string using the models with concentrated and distributed masses. Based on the results, we have established the exact and asymptotic analytical dependences in order to determine inertial characteristics of the curvilinear sections in a drill string, as well as provided recommendations regarding the application of these dependences. A current trend in the development and modernization of drilling equipment is the use of drill pipes made of unconventional materials. Given the scientific and practical interest in the application of these materials, we calculated the moments of inertia for the curved sections of drill strings, which can be equipped with steel, aluminum, titanium, or glass-plastic drill pipes. Analytical estimation of the moment of inertia of curved sections refers to a different scale of the deformed state of a drill string. The formula for the moment of inertia, established for simple models, holds in cases when the curved section of a drill string executes large displacements. For the case of small displacements, it is necessary to apply the analytical result derived when using a model with distributed parameters. The established patterns are essential for analyzing the dynamics of a drill string in deep conditionally vertical, inclined-directional, or horizontal wells with a complex mining-geological profile
Highlights
The commonly adopted world-wide practice that continues to develop at present is the directed drilling of deep oil and gas wells at which the axis of a bore often happens to be a spatial curve
Estimation approaches to the theory of rods have been developed quite well, when studying the processes of rotation of the curved sections of a drill string, there are certain difficulties related to the lack of precise expressions to evaluate the moment of inertia of a bent pipe based on the parameters of its deformation
It can be argued that a change in the moment of inertia for the curved sections in a string depends in the first place on the density of pipes’ material, with which it is equipped
Summary
The commonly adopted world-wide practice that continues to develop at present is the directed drilling of deep oil and gas wells at which the axis of a bore often happens to be a spatial curve In this case, a string of drill pipes is a rather complex spatial system with distributed parameters. To refine the parameters of loading and the stressed-deformed state of a drill string, it is necessary to have a well-defined procedure for determining the moments of inertia of its curved sections. It is a relevant task for the theory of dynamic stability of elastic systems to investigate the inertial properties of a curvilinear string of pipes at rotation. The solution to this problem is necessary in order to properly conduct a dynamic analysis of drill strings at rotor and rotor-turbine drilling techniques
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