A hybrid bit for use in a wellbore includes: a body having a shank for connection to a drilling motor or drill pipe and a plurality of legs attached to the shank; and a plurality of cutting structures. The cutting structures include a roller cone mounted to a first one of the legs and a fixed mill mounted to a second one of the legs and including a pad dressed with a cermet material.

A hybrid bit for use in a wellbore includes: a body having a shank for connection to a drilling motor or drill pipe and a plurality of legs attached to the shank; and a plurality of cutting structures. The cutting structures include a roller cone mounted to a first one of the legs and a fixed mill mounted to a second one of the legs and including a pad dressed with a cermet material.

A hybrid drill bit includes a bit body having a plurality of fixed cutters disposed thereon and at least one rolling-cutter pocket. The hybrid drill bit further includes a rolling cutter rotatably positioned within the rolling-cutter pocket on the bit body. The rolling cutter includes a roller body with an axial bore and a plurality of teeth arranged around the roller body to engage a subterranean formation. Additionally, the hybrid drill bit includes a rolling cutter retention mechanism including a pin received within the axial bore of the rolling cutter, the pin engaging the bit body to rotatably couple the rolling cutter within the rolling-cutter pocket in the bit body.

A hybrid drill bit includes a bit body having a plurality of fixed cutters disposed thereon and at least one rolling-cutter pocket. The hybrid drill bit further includes a rolling cutter rotatably positioned within the rolling-cutter pocket on the bit body. The rolling cutter includes a roller body with an axial bore and a plurality of teeth arranged around the roller body to engage a subterranean formation. Additionally, the hybrid drill bit includes a rolling cutter retention mechanism including a pin received within the axial bore of the rolling cutter, the pin engaging the bit body to rotatably couple the rolling cutter within the rolling-cutter pocket in the bit body.

Design parameters for PDC drill bit are correlated to instances of backward whirl, where backward whirl is detected along a lateral axis in the frequency domain during downhole drilling. Two regimes of backward whirl are described and detected cutting-induced backward whirl and friction-induced backward whirl where each regime has different characteristic frequencies, detection methods, and mitigation guidelines. Design parameters are quantified by gauge fullness, drilling efficiency (DE), and whirl index (WI). Design guidelines to mitigate backward whirl are generated by correlating design parameter quantifiers and instances of backward whirl, including both cutting-induced backward whirl and friction-induced backward whirl. Potential drill bit designs are then validated against the generated guidelines in order to mitigate backward whirl in future drilling runs.

Design parameters for PDC drill bit are correlated to instances of backward whirl, where backward whirl is detected along a lateral axis in the frequency domain during downhole drilling. Two regimes of backward whirl are described and detected cutting-induced backward whirl and friction-induced backward whirl where each regime has different characteristic frequencies, detection methods, and mitigation guidelines. Design parameters are quantified by gauge fullness, drilling efficiency (DE), and whirl index (WI). Design guidelines to mitigate backward whirl are generated by correlating design parameter quantifiers and instances of backward whirl, including both cutting-induced backward whirl and friction-induced backward whirl. Potential drill bit designs are then validated against the generated guidelines in order to mitigate backward whirl in future drilling runs.

An earth-boring tool includes a body, a plurality of fixed blades, a first plurality of cutting elements secured to the plurality of fixed blades, a plurality of removable blade assemblies removably coupled to the body, and a second plurality of cutting elements secured to the plurality of removable blade assemblies, each cutting element of the second plurality of cutting elements exhibiting an aggressiveness that is less than an aggressiveness of each cutting element of the first plurality of cutting elements. A method of forming an earth-boring tool includes forming a body and a plurality of fixed blades extending from the body, securing a first plurality of cutting elements to the plurality of fixed blades, removably coupling at least one removable blade assembly to the body, and securing a second plurality of cutting elements to the at least one removable blade assembly.

A hybrid bit with roller cones having inserts is disclosed, includes a bit body, blades and roller cones. All the fixed cutting elements at the inner cone section, nose section and shoulder section of blades herein constitutes two sets of corresponding fixed cutting elements respectively, forming two profile envelopes of fixed cutting elements at least in the interval at the nose section and shoulder section, the two profile envelopes of fixed cutting elements are spaced at high and low intervals at the nose section and shoulder section, forming two stages of cutting by fixed cutting elements; and the cutting position of the cone insert mainly corresponds to the nose section and shoulder section of blades, the outermost cutting profile envelope of cone inserts formed by all or part of cutting elements on cones herein is higher than the outermost cutting profile envelope of fixed cutting elements, forming the third stage of cutting. The invention can effectively develop rate of penetration in hard and plastic formation, maintain and prolong the service life of the hybrid bit, and broaden the formation suitability of the hybrid bit.

A hybrid bit with roller cones having inserts is disclosed, includes a bit body, blades and roller cones. All the fixed cutting elements at the inner cone section, nose section and shoulder section of blades herein constitutes two sets of corresponding fixed cutting elements respectively, forming two profile envelopes of fixed cutting elements at least in the interval at the nose section and shoulder section, the two profile envelopes of fixed cutting elements are spaced at high and low intervals at the nose section and shoulder section, forming two stages of cutting by fixed cutting elements; and the cutting position of the cone insert mainly corresponds to the nose section and shoulder section of blades, the outermost cutting profile envelope of cone inserts formed by all or part of cutting elements on cones herein is higher than the outermost cutting profile envelope of fixed cutting elements, forming the third stage of cutting. The invention can effectively develop rate of penetration in hard and plastic formation, maintain and prolong the service life of the hybrid bit, and broaden the formation suitability of the hybrid bit.

A drill bit is provided that includes a bit body having one or more blades extending therefrom, a plurality of cutters secured to the one or more blades, and a rolling element assembly positioned within a cavity defined on the bit body. The rolling element assembly includes a rolling element rotatable within the cavity about a rotational axis, and a compliant retainer extendable within a retainer slot defined in the cavity to secure the rolling element within the cavity. The compliant retainer and the cavity cooperatively encircle more than 180° but less than 360° of a circumference of the rolling element while leaving a full axial width of the rolling element exposed. The compliant retainer is compressible responsive to forces from the rolling element to absorb vibrations and/or automatically adjust depth of cut.