Evaluation of hydraulic power of drilling string with a cavitation hydrovibrator

Abstract

Purpose. To develop a method for assessing the drill string hydraulic energy based on mathematical modeling of dynamic processes at the drill string with a hydraulic vibrator rock system, taking into account the nonlinear dependence of system dissipative losses on the drill string vibration amplitudes at drill operating modes. Methodology. Methods are based on experimental and theoretical studies on the drill string dynamic parameters and the evaluation of efficiency of converting stationary fluid flow into pulsating flow. Findings. The results are presented in the form of calculated and experimental dependences of pressure, volumetric flow rate, vibration accelerations and hydraulic vibrational power in the section of the rock cutting tool on the criterion parameter of cavitation . Originality. Taking into account the influence of the string elements vibration amplitude on dissipative losses, made it possible to obtain an acceptable agreement with the drilling experimental data as well as: - to determine the peak to peak (from 43.5 to 9.8 kW) and average (from 9.8 to 2.35 kW) values of hydraulic oscillatory power at the cavitation parameter range = 0.120.475; - to evaluate the efficiency of converting the drilling fluid stationary flow power at the inlet to the hydraulic vibrator into the oscillatory power (for the oscillation period) on the rock cutting tool. Within the investigated range of the drilling operation parameter, the maximum calculated value of the efficiency was approximately 76% with the value of the cavitation parameter t equal to 0.16, and the minimum efficiency value was 19% at = 0.475. Practical value. Practical value of the results obtained is that the improved mathematical model of the drill-rock dynamic system allows establishing a rational mode of cavitation hydraulic vibrator operation at the drill string design stage to implement acceptable levels of hydraulic power on the drill bit.