| Deep formation of Xujiaweizi District is the priority of natural gas exploration anddevelopment in Daqing Oilfield. To enchance the natural gas exploration and development ofXujiaweizi District, it is necessary to increase penetration rate, reduce downhole accident rate,shorten drilling cycle to speed up the exploration step of Xujiaweizi District. Therefore it isextremely urgent to resolve the problems of low penetration rate, high drill stem failure, highdownhole accidents rate and hard inclination control, etc.Firstly, this thesis analyses the rock mechanics and drillability characteristics of rock under highpressure and high temperature condition, optimizes rock bits and PDC bits, thus gets the bitsseries for drilling deep wells. Secondly, this thesis researches the theory and applicationcondition for compound drilling and air drilling technology, thus provides important methods toincrease the penetration rate of the formation under Quan’er segment. Thirdly, the thresholdWOB can be determined by analysing the mechanical characteristics for downhole drill string.Field experiments have been done for PDMs and new types of STBs to control well inclination.Based on the mechanical characteristics analysis for downhole string, improvements have beendone for double-acting shock absorber. Indoor test and field application have been carried outfor high weight pipe-freeing agent, which provides one effective way to resolve pipe stickingproblem. And this thesis researches one new type of STB which can be milled.Based on the above research, this thesis get a set of matching technology for increase drillingefficiency of ultra-deep wells, including bit optimization, compound drilling, wellbore qualitycontrol and downhole accident prevention. These methods and technologies had been carriedout and improved for22deep wells and5ultra-deep wells, therefore enchances the matchingtechnology and raises the drilling performance of ultra-deep wells. |
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