Effect of Axial Vibration on Sliding Frictional Force between Shale and 45 Steel

Abstract

Activating drill string vibration is an effective means to mitigate the excessive drag encountered during drilling complexstructure wells. However, the Coulomb model cannot describe the sliding friction behavior between drill string and borehole rock with imposed axial vibrations. To solve this problem, a specially designed experimental setup was utilized to investigate the characteristics of axial vibrating-sliding coupling friction. The results indicate that when vibration velocity is greater than sliding velocity, axial vibration can significantly reduce friction force between contact surfaces. Its friction reduction mechanism embodies not only the changes of instantaneous friction force, but also friction coefficient. Meanwhile, a friction coupling model was established based on the Hertz contact theory and Dahl model. The corresponding computational program was developed in Matlab/Simulink environment. The calculation results are in good agreement with the experimental results, verifying the validity of the present method. Furthermore, to overcome the shortcoming of Dahl model, a dynamic friction coefficient model was proposed to evaluate the friction-reducing effect of axial vibration using dimensional analysis method. The model parameters under different lubrication conditions were retrieved through inverse calculation with experimental data. This method provides a new solution for evaluating the friction-reducing effect of hydraulic oscillator and optimizing its placement.

Influence of the Undercut Anchor Head Angle on the Propagation of the Failure Zone of the Rock Medium—Part II

“…As in the case of concrete, it is also difficult to determine unambiguously the value of the friction coefficient in the contact zone between the undercutting head and the rock, because in many cases, before the actual detachment occurs, the rock is crushed, causing a significant change in the friction and contact conditions. The authors of a number of studies on anchoring give a fairly wide range of values for the coefficient of friction of the medium against the steel or carbide from which the mining tool is made [ 23 , 24 , 25 ].…”

A feasible study for the working mechanism and parameter optimization of the agitator

“…From the perspective of antifriction technology, many investigations have been made to solve this problem. [1][2][3][4][5][6] Various tools such as agitator have been developed and designed to resolve contradictions and improve the extended limits of horizontal wells. [7][8][9] Engineering applications have shown that a small number of anti-frictional tools, such as agitator, had a certain effect on drilling engineering.…”

Predicting the medium-temperature thermal stability of impact-strengthened medium-thick plate aluminum alloy using a back propagation artificial neural network

“…Moreover, the process of learning the analytical formula of weight can be well defined. Therefore, the back propagation network realize the nonlinear mapping of arbitrary inputs to outputs as per the real-world working conditions [ [10] , [11] , [12] , [13] , [14] ].…”