DISCUSSION ON PDC BIT WHIRL

The whirl of seven strut-type PDC non-coring bits which were used in Shandong, is a main problem in drilling progress. By means of analysing drilling results, it is pointed out that bit whirl can cause serious vibration of bit and PDC damage, the main causes of bit whirl are unbalanced force of cutters and bit profile. It is also pointed out that efficient processes of solving PDC bit whirl are placing cutters balancedly, reducing the taper of bit face, and improving drilling recomendations.