MODEL OF ROCK DRILLING PROCESS IN TERMS OF ROLLER CONE BIT REMAINING LIFE

Abstract

The issue of the absence of any formalized methods showing nonlinear dependence of the drilling rate on the drilling rod assembly speed has been revealed. The peculiarities, influencing the greatest number of cycles prior to the destruction of bit legs, have been defined. The results of an investigation into the process of impact load harmonics formation and superposition, as well as into the interrelation of drilling process parameters in different loading conditions, with due regard for an adaptive element smoothing the impact load harmonics when passing through rock of different drillability indices, have been adduced. It has been determined that an adaptive element is required for ensuring timely system response to the exposed object properties change, as well as for maintaining the optimum ratio of model parameters in the course of its operation. The approach to determining the roller cone bit speed, at which the bit teeth contact time will be sufficient for energy transfer, resulting in the required rock volume cutting, has been defined. The conditions for rock cutting maximum efficiency have been found. The effective way of reducing temporary and cyclic loads on specific bearing rolling elements and teeth has been determined. The procedure for calculating the optimum roller cone bit speed, maximum permissible feeding force and tricone bit life in the course of drilling rock masses of different stress-strain properties has been developed.