Pulse-cavitation vibrating drilling prototype development and evaluation

Abstract

The drilling rate decreases with an increase in depth due to high pressure at the bottom hole. Accordingly, there is a need for an improved rock penetration mechanism to increase the drilling speed in deep drilling conditions. Historically, vibration assisted drilling has shown the ability to improve the penetration rate. Therefore, current research aims to develop a vibrating tool to be used for experimental investigation in the laboratory and in the field. -- Considering existing vibration and pressure pulsation tools, a pulse-cavitation vibrating prototype was proposed. The vibrating tool, suggested for drilling penetration improvement, was proposed to be installed behind the bit as a drill collar sub. It should operate in deep drilling conditions and produce two major effects: high amplitude and high frequency pressure pulsations and vibrations. -- Prototype feasibility was tested using computational fluid dynamics (CFD) analysis. The tool was simulated to examine cavitation initiation and observe pressure pulsation patterns over a pressure range available in the laboratory facilities, and at pressures similar to deep drilling conditions. In addition, the density and viscosity of different drilling fluids on the performance of the prototype were analyzed. The prototype pulse-cavitation tool was manufactured and tested in laboratory facilities. A series of experiments was performed to obtain a significant tool operation experience. Measurements of pressure pulsations along with vibration accelerations were obtained during these experiments. Data yielded agreement of these parameters, therefore, it was concluded that cavitation produced the high frequency pressure pulsations, which caused vibration accelerations on the prototype. -- Initial CFD and experimental results show promise for the pulse cavitation tool use in creating high frequency pressure pulses and vibrations. The prototype can now be used for further performance and vibration assisted drilling investigations. The experience gained in the experimental operation provides a background for future prototype improvement and development.