Hydraulic pulsed cavitating jet drilling is a new combined drilling technology. In this technology the hydraulic pulsed cavitating jet generator is installed upon the bit in the drilling process. Based on modulating pulsed jet and cavitating jet, a new drilling tool is designed which couples advantages of both pulsed jet and cavitating jet. When drilling fluid flows through the tool, fluid is modulated to pulse and cavitation. Thus, pulsed cavitating jet is formed at the outlet of the bit nozzle. Because of jet pulsation, cavitating erosion and local negative pressure effect, bottom cuttings cleaning efficiency is enhanced and the rate of penetration (ROP) is improved. This paper studied the mechanisms of improving the ROP and cuttings cleaning efficiency in hydraulic pulsed cavitating jet drilling. Hydraulic pulsed cavitating jet drilling technology has been applied in 8 oil fields in China, such as Tarim oil field, Xinjiang oil field, etc. The tests in more than 40 wells showed good applicability of the tool to bit types, formations, drilling fluid densities, etc. Hydraulic pulsed cavitating jet can mate with helicoid hydraulic motor and Power V system drilling technology, this technology also can be used in underbalance drilling. The test well depth is 1274 ~ 6162 m. As the result, ROP was improved by 10. 1 to 104. 4 percent and the maximum operation time is about 260 hours in wellbore. Pulsed and cavitating jet coupling can afford an effective approach to improve ROP in deep and ultra-deep well.

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