Bent screw drills and MWD directional correction technology with in ultra-deep section of Well Tashen-1

The fifth spudding of Well Tashen-1 is drilled from 6800 m to 8408 m when completed.The formation mainly consists of dolomite and features in complex lithology,which makes it difficult to control well deviation.All conventional deviation control technologies to drill vertically have been applied for many times,but they do not work at all.Later,bent screw drills and MWD(measurement while drilling) technology for deviation measuring and straightening are applied.The difficulties in using tools to drill ultra-deep well sections are solved,based on controlling the drilling pressure,the screw rod camber,and the tool surface,controlling well deviation through directional and compound drilling,adjusting untwist angle correctly,using MWD and dynamic drilling tool resistant to high temperature and high pressure,drilling down in segmentation and reducing temperature in circulation.Well deviation is controlled effectively,as well as drilling tasks are fulfilled with high quality and high efficiency.Application results show that the anti-deviation with MWD and bent screw drills features in high efficiency,safety,simplicity and practicality.It is not only practical in dealing with difficult well deviation control,but can also be applied to conventional drilling to improve the efficiency and control deviation.