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

Hamzja Akchurin,Oleg Trushkin

doi:10.31897/pmi.2020.4.7

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.

Highlights

When drilling oil and gas wells, rock-cutting tools of cutting and chipping action equipped with polycrystalline diamond composite cutters (PDC cutters) are widely used [6, 9, 10]
In the process of drilling, there is a load on the bit that is distributed unevenly between individual cutters, depending on the design of the bit and the mechanical properties of the rock, so the development of such a technique can be based on analytical studies of the cutters work at rock breakdown or on experimental studies, both field and bench
In the works of K.I.Borisov, V.V.Neskoromnykh, V.L.Rubtsov [2,3,4,5, 8], a description of the results of the study of cutter performance in the process of rock breakdown is given on the basis of experimental study of single cutter performance, with the cutter itself being stationary and the rock sample rotating, which does not fully correspond to the real dynamics of the cutters work in the bottom

Summary

Introduction

When drilling oil and gas wells, rock-cutting tools of cutting and chipping action equipped with polycrystalline diamond composite cutters (PDC cutters) are widely used [6, 9, 10]. The efficiency of rock breakdown with PDC bits and the efficiency of the entire drilling process depends on both the design of the bits and parameters of drilling practices. In the process of drilling, there is a load on the bit that is distributed unevenly between individual cutters, depending on the design of the bit and the mechanical properties of the rock, so the development of such a technique can be based on analytical studies of the cutters work at rock breakdown or on experimental studies, both field and bench. In the works of K.I.Borisov, V.V.Neskoromnykh, V.L.Rubtsov [2,3,4,5, 8], a description of the results of the study of cutter performance in the process of rock breakdown is given on the basis of experimental study of single cutter performance, with the cutter itself being stationary and the rock sample rotating, which does not fully correspond to the real dynamics of the cutters work in the bottom. The main drawback of these works is that the interaction of a single cutter with the rock is studied, whereas in reality, the performance of each cutter is influenced by the profile of the bottom, which is formed by cutters that affect neighboring areas

Methods

Discussion

Conclusion