In this paper,the state-of-the-art and adaptability to formation of PDC bit were presented,the form mechanism of PDC bit whirling motion was analyzed,and the methods of prevention bit whirling motion were introduced.According to the requirement of bit steady drilling,the optimization design of prevention bit whirling motion was done.Through field application,the results showed that the anti-whirl PDC bit could shorten drilling cycle,improve drilling speed,prolong operating life,and the borehole inclination was controlled well.

Drilling in complicated formation can easily result in collapse,shortening diameter and high abrasiveness,which causes low average mechanical drilling velocity,difficult drilling and difficulty in meeting the demand of high-efficiency drilling regarding the common drill bit.Therefore,the study of a kind of new PDC bit used in complicated formation is put forward according to regional feature.The advanced means are used to carry out the individuated design in terms of teeth-distribution way,crown head shape,hydraulic structure and force balance of the PDC bit.The goal of increasing mechanical drilling velocity,reducing running and pulling times,preventing drilling accident,shortening drilling period and saving drilling cost can be reached by using the new bit in the complicated formation.The field application shows that the bit significantly increases drilling velocity,shortens drilling period and saves drilling cost with obvious economic benefit.