Development of spiral PDC ream bits for long borehole at high position of roof

Owing to the problems，such as short service life,large lead-in resistance and low drilling efficiency in the construction process of a conventional PDC ream bit in a high-level long drilling hole on the top plate,a ø220/120 mm spiral PDC ream bit has been developed in this paper,based on the research of bit guide structure,crown curve,cogging arrangement and the blade structure.In addition,a field test was also carried out in the south area of Guqiao Mine,Huainan Mining Group.Test results show that in medium sandstone and carbonaceous mudstone stratas,the single hole footage of this drill bit is 498 meters.Compared with the ordinary hole dilating drills in the field,its drilling efficiency is increased by 20% and the service life is increased by more than 60%.What’s more,the whole drilling process is stable,the drilling speed is fast,and the anti-deviation effect is relatively obvious,which greatly improves the construction efficiency of the high-level long drilling on the top plate and saves the drilling cost at the same time.