Hydraulic Pulsed Cavitating Jet-Assisted Drilling

How to improve drilling rate in deep wells has been a hot subject. Based on modulating pulse jet and cavitating jet, a new drilling tool is designed which couples advantages of both pulse jet and cavitating jet. When drilling fluid flows through the tool during the drilling process, fluid is modulated to pulse and cavitate. Thus, pulse cavitating jet is formed at the outlet of the bit nozzle. Because of jet pulsation, cavitating erosion and local negative pressure affect bottomhole rock. Cleaning and breaking is enhanced and penetration speed is improved. Oil field tests in five wells show good applicability of the tool to bit types, formation, drilling densities, flow rates, and dynamic hydraulic drilling motors, etc. As a result, penetration rates are improved ranging from 10.1 to 31.5%; the maximum working time is about 235.5 hr in downhole. Pulse and cavitating jet coupling will afford an effective means to improve drilling rate for deep wells.