PDC cutter pressure on plastic-brittle rock in the process of its destruction

Abstract

Presently, there are no methods for calculating the parameters of the drilling practices with rock-cutting tools equipped with polycrystalline diamond composite (PDC cutters). To create such a method requires the studying their work. The article presents the results of bench studies of the PDC cutters in the process of a rock sample breakdown when reproducing the actual layout of the cutters on the working surface of the bit.
 An important parameter of PDC cutters operation, which is necessary for the bit load analysis, is the pressure of the cutters on the rock during its breakdown. The total pressure of a cutter on the rock can be broken into two mutually perpendicular components: the forcing pressure and the cutting pressure.
 It is proposed to evaluate the PDC cutters loading at breakage of rocks of different hardness using relative values of forcing and cutting pressures, which are calculated relative to the yield strength of the rock by the die.
 It is established that the variability of the average relative pressures of forcing and cutting is significantly influenced by drifting per bit turnover and the radius of the cutter on the bit. The dependences of the maximum relative pressures of PDC cutters at the plastic-brittle rock breakdown on the drifting per bit turnover and the radius of the cutter location on the bit are obtained. It has been established that when drifting up to 0.4 mm per turn, the main mechanism of breakdown is cutting, and with the increase of the breakdown depth, the process of forcing becomes decisive.

Performance dynamics of pdc cutters used in breaking ductile brittle rock

“…The disintegration of the diamond layer and carbide substrate of PDC cutters are largely determined by their fatigue. The practice of using drill bits (Trushkin & Akchurin, 2020) shows that, the farther is the cutter from the drill bit centre, the higher is the probability of its breakdown. One of the reasons for this is a much higher number of loading cycles per revolution of the drill bit.…”

“…The results of experimentally investigating the level and kind of changes in the component loads on PDC cutters and also their dynamic-response coefficients and MSD at the failure of medium-hard ductile brittle rock can be used in updating and developing cutter endurance test methods and the procedure of cutter longevity examination tests at different drill bit radii (Trushkin & Akchurin, 2020).…”

“…The cutters were 13.5 mm in diameter and had a sharp edge or a 0.3х45 о bevel. A special test facility (Trushkin, 2014) was used to drill the rock slabs with three PDC cutters (Trushkin, 2018;Trushkin & Akchurin, 2020)…”

“…However, these works pay almost no attention to the dynamic component of cutter loads. The source material for the article is the result of the testbed drilling of rock slabs using three PDC cutters (Trushkin, 2014(Trushkin, , 2018Trushkin & Akchurin, 2020).…”

Numerical Simulation of Nonlinear Processes in the “Thruster—Downhole Motor—Bit” System While Extended Reach Well Drilling

“…The PDC bit, which has direct contact with the bottom of the well, reacts most strongly to changes in the WOB. Since this type of bit has a cutting-shearing principle of operation, with an increase in WOB, the cutting elements begin to penetrate deeper into the rocks, and the process of "cutting the rock" is more difficult; as a result, an increase in the reactive moment on the bit is observed [37]. The reactive moment on the bit is transferred to the downhole motor shaft and makes it The WOB created by the hydraulic thrusting device consists of two components: hydrostatic P HS and hydrodynamic P HD and is calculated by:…”