Safe Drilling Technology for Deep CBM Horizontal Wells
For the exploration of deep CBM in Turpan-Hami Basin,in the early stage,the main method was the vertical well test production,the horizontal well drilling technology is still in the exploratory stage.Due to the fact that the block belongs to the high and steep slope area and the development of coal formation,which leads to the problems of easy deviation exceeding the standard in the vertical well section,easy instability of the borehole wall in the coal formation,difficulty in controlling the trajectory of the horizontal well section and poor cementing quality.This paper analyzes the limiting factors of speed increase in the high and steep slope area,introduces the automatic vertical drilling system,and forms the anti-deflection and fast drilling technology,which solved the con-tradiction between anti deviation and fast drilling under high WOB in high-steep slops.The wellbore instability mechanism of the coal seam was analyzed,the immersion experiment was carried out,and the amine-based organic salt drilling fluid system optimized,which can improve the inhibition and sealing consolidation performance of wellbore,and strengthen the wellbore stability of the coal seam.Combined with the prediction data of the three pressure profile of deep coal seam,the wellbore structure and trajectory control were optimized,and the combina-tion of anti-stuck PDC bit and BHA was designed,along with the amine-based organic salt drilling fluid with strong inhibition and strong plugging,the safe extension of the horizontal section of the coal seam was achieved.By strengthening the drilling parameters,cleaning tool for cuttings and personalized BHA for wiper trip are sued to improve the wellbore cleaning efficiency.Casing selection,centralizer configuration and cement slurry system are optimized to ensure cementing quality.The series of technologies has laid the foundation for achieving safe and ef-ficient drilling of deep coalbed methane horizontal wells in Turpan Hami Basin.
Turpan Hami Basindeep CBMhigh-steep structureanti deviation and fast drillingwellbore stabilitysafe drilling
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