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.
On the basis of the analysis of the jet-modulating mechanism, a novel tool-a hydraulic-pulsed cavitating-jet generator (HPCJG)is designed to further improve the rate of penetration (ROP). The HPCJG combines the advantages of a pulsed jet and a cavitating jet. When the drilling fluid flows through this tool, the fluid will be modulated to the pulsed and cavitating jet by application of the impellers and by entering into the self-resonant chamber. During this process, a pulsed cavitating jet is formed at the outlet of the bit nozzle. Because of jet pulsation, cavitating erosion, and the local negative-pressure effect, the cleaning efficiency of the wellbottom cuttings and the ROP will be improved. Laboratory and oilfield tests have indicated that the pulsed-pressure amplitude and the pressure drop of the generator increase with the increase of the flow rate. However, the frequency of the pressure pulsation is invariable in this process. This generator has been applied to more than 100 wells in eight oil fields throughout China. The results show that the maximum density of the test drilling fluid is 1.93 g/cm 3 , the maximum test-well depth is 6162 m, and the operation time of the generator is more than 230 hours (the maximum operation time recorded was more than 520 hours). Furthermore, the average ROP was increased by approximately 16.7% to 104.4%. In conclusion, the generator has the characteristics of a simple structure, has a long lifetime, is able to adapt well with existing drilling equipment, and can provide a safe and efficient drilling technique for deep wells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.