Drill bit design for mitigation of stick slip
View Patent ↗A method of designing an earth-boring rotary drill bit includes designing a bit body and cutting elements of the drill bit such that features of the drill bit other than cutting elements engage and rub against a subterranean formation being drilled by the drill bit at depths-of-cut beyond, but close to, an intended median depth-of-cut, and such that the amount of rubbing area between such features and the formation increases at a relatively rapid rate as the depth-of-cut increases beyond the intended median depth-of-cut. Such methods may be employed to mitigate the occurrence of the “stick-slip” phenomenon during drilling. A method of fabricating a drill bit includes configuring a bit body and cutting elements in accordance with such a design. Earth-boring drill bits include a bit body and cutting elements so configured.
1. An earth-boring rotary drill bit, comprising:
a bit body including a plurality of blades; and
cutting elements mounted to the blades of the bit body;
wherein the cutting elements and the blades of the bit body are configured such that an expected average rubbing area between a surface of the blades of the bit body and a subterranean formation to be drilled by the drill bit over at least one drilling interval increases to a value over zero at a depth-of-cut that is about one hundred and fifty percent (150%) or less of an intended median depth-of-cut for the drill bit over the at least one drilling interval, and such that the expected average rubbing area increases with increasing depth-of-cut at an average rate of at least three square inches per inch per revolution of the drill bit (3.0 in. 2 /(in./rev.)) as the depth-of-cut increases from the intended median depth-of-cut for the drill bit to about two hundred percent (200%) of the intended median depth-of-cut for the drill bit.
2. The earth-boring rotary drill bit of claim 1 , wherein the cutting elements and the blades of the bit body are configured such that an expected average rubbing area between the surface of the blades of the bit body and a subterranean formation to be drilled by the drill bit is at least substantially zero at depths-of-cut equal to and below the intended median depth-of-cut.
3. The earth-boring rotary drill bit of claim 1 , wherein the cutting elements and the blades of the bit body are configured such that the expected average rubbing area increases to a value over zero at a depth-of-cut that is about one hundred and thirty percent (130%) or less of the intended median depth-of-cut.
4. The earth-boring rotary drill bit of claim 1 , wherein the cutting elements and the blades of the bit body are configured such that the expected average rubbing area increases to a value over zero at a depth-of-cut that is about one hundred and twenty percent (120%) or less of the intended median depth-of-cut.
5. The earth-boring rotary drill bit of claim 1 , wherein the cutting elements and the blades of the bit body are configured such that the expected average rubbing area increases with increasing depth-of-cut at an average rate of at least four and one-half square inches per inch per revolution of the drill bit (4.5 in. 2 /(in./rev.)) as the depth-of-cut increases from the intended median depth-of-cut for the drill bit to about two hundred percent (200%) of the intended median depth-of-cut for the drill bit.
6. The earth-boring rotary drill bit of claim 1 , wherein the bit body further includes depth-of-cut control features.
7. The earth-boring rotary drill bit of claim 6 , wherein the bit body is configured such that the expected average rubbing area between the surface of the blades of the bit body and a subterranean formation to be drilled by the drill bit further comprises a rubbing area of one or more of surfaces of the depth-of-cut control features.
8. The earth-boring rotary drill bit of claim 1 , wherein the bit body is configured such that the expected average rubbing area between the surface of the blades of the bit body and a subterranean formation to be drilled by the drill bit extends over one or more surfaces of the plurality of blades of the bit body.