-
Date submitted2021-03-05
-
Date accepted2021-10-18
-
Date published2021-12-16
Physical and mathematical model of rock destruction by a milling machine cutter
As a result of the analysis of the work on rock destruction by cutters of milling of machines, it was found that the existing developments do not allow us to proceed to the derivation of calculation d dependencies for determining fracture resistance, or can be used only in preliminary calculations of the known by design parameters of milling machines. To eliminate these disadvantages, a combined physical and mathematical model of the process of interaction of a single milling cutter with a spherical tip with the rock has been developed. Consideration of the physical picture of the action of forces and stresses acting from the cutter with spherical tips on the separating rock element in the limiting condition allowed to describe analytically the components of total resistance, which are the mathematical part of the physical and mathematical model of rock destruction by cutters. Analytical dependences for determining the tangential and normal components of fracture resistance of rocks of medium hardness have been obtained. The adequacy of the physical and mathematical model to the physical process of destruction of rocks of different hardness by cutters on a universal stand was tested both in the field and in the laboratory conditions. Technical evaluation of the results of experimental studies confirms the reliability of the developed physical and mathematical model.
-
Date submitted2020-06-09
-
Date accepted2020-11-02
-
Date published2020-11-24
Method of drilling process control and experimental studies of resistance forces during bits drilling with PDC cutters
A rational, theoretically proved and empirically verified control system is a condition for optimal management of the drilling process in compliance with the criteria for minimizing the cost of time and material resources. A new generation of rock-cutting tools using PDC cutters (polycrystalline diamante cutters), which are extremely ef fective when drilling wells for various purposes in medium-hard rocks, dictates the need to develop methods and criteria for optimal control of the drilling process using this tool. The paper presents an analysis of the force interaction between rock-cutting elements, face rock, and drilling mud sa turated with slam, highlights the influencing factors and provides dependencies for determining the parameters of rock failure. Empirical verification of the theoretical propositions was carried out based on the data analysis from experimental bit drilling of marble with PDC cutters with a diameter of 76.2 mm, processed using the method of full factor experiment to obtain mathematical models of factors and their graphical interpretation. The method of controlling the drilling process based on the optimal ratio of the tool rotation frequency, axial weight and deepening per one turnover is considered, which allows determining the rock failure mode at the well bottom by indirect signs and choose the optimal values of the drilling mode parameters that correspond to the most optimal conditions in terms of achieving the maximum mechanical drilling speed in conjunction with the rational mode of rock-cutting tool operation. A scheme is presented that contains possible variants of the bit run mode and ways to recognize them by the ratio of the deepening per turnover and the rotation frequency of the rock-cutting tool.
-
Date submitted2019-11-04
-
Date accepted2020-01-12
-
Date published2020-10-08
PDC cutter pressure on plastic-brittle rock in the process of its destruction
- Authors:
- Oleg B. Trushkin
- Hamzja I. Akchurin
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.