| Horizontal well technology,as one of the core technologies for efficient development of unconventional oil and gas resources,has been applied more and more in practice.However,there are still many technical problems in horizontal well drilling,such as difficulty in carrying cuttings,serious pressure support,low penetration rate,long drilling cycle and high drilling cost.Jet Mill Bit(JMB)is a new type of PDC bit invented by China University of Petroleum,Beijing,aiming at providing a new downhole tool for solving these technical problems.This thesis focuses on the hydrodynamic characteristics of JMB in horizontal well.The basic hydrodynamic characteristic equation of JMB is established.And hydraulic characteristic parameters are optimized.Through analysis and calculation,the optimum impact angle of cuttings of JMB in horizontal well is 70 degrees,and the ratio of the optimum suction flow rate to the reverse nozzle flow rate is 0.9.The drilling risk of JMB in horizontal well is predicted and analyzed,and the bit structure is optimized,that is,adding junk slot in the gage protection section of the bit and the layout to bit edge is optimized.The bottom hole flow field of JMB is analyzed by numerical simulation software,and the bottom hole pressure reduction characteristic and the suction capacity of JMB are verified.It is found that increasing the size of junk slot has a negative impact on the pressure reduction characteristic of JMB.Through laboratory experiments on full-scale bit,it is revealed that the bottom hole pressure reduction characteristic of JMB in horizontal well is positively correlated with the inlet pressure of drilling fluid and the propotion of reverse nozzle flow rate. |
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