Study of PDC drill bit crown shape for design optimization: angle of blade inclination aspect
Keywords:rock cutting, PDC cutter, rock reaction force, geometric parameters, torque.
The article studies PDC-type bit operation, in particular, the redistribution of loads on drill bit blades is simulated, depending on “cutter-rock” contact areas, which is determined by a drill bit design. This work aims at PDC bit design optimization, namely to study the effect of the blade angle to the horizontal axis on the torque generated by the bit. The study is based on the Voitanovich and Kuru’s model of Voitanovich and Kuru’s and has its core at determining the balance of forces acting on a single cutter.
The scientific novelty of the work is that two areas of contact are considered for each cutter – the on the front and side surfaces. Also, it is hypothesized that the force of the reaction of the pore is directed towards the placement of heterogeneities of the rock. This approach makes it possible to consider the fluctuations of the bits due to the instability of the cutting forces, which in turn are caused by the instability of the properties of the fractured rocks (first of all, their structural heterogeneity).
The spatial shape of the PDC cutter crown was studied, characterized primarily by the shape of its upper part, which in turn is characterized by the angle of inclination of the cutting part of the cutter. Contact areas for each cutter, the volume of the destroyed rock depending on the location of the cutter, as well as the loading for a single cutter, the torque for the whole blade and the bit were simulated in the work. The angles of inclination of the blade to the horizontal axis at which the minimum / maximum torques are observed are determined.
Changing the inclination of the cutting part causes the redistribution of the destroyed rock volumes. This section dealt with worn-out chisels, and the load was distributed in proportion to the volume of the destroyed rock. It was found that increasing the angle of the blade causes an increase in the total torque for the bit. A method is proposed that allows optimization of the PDC bit design. An increase in the total twisting angle and the total deflection is observed for the cutters, which are most separated from the borehole face.
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