An earth-boring tool may include a blade having a face surface, a cutting edge, and a rotationally leading surface. The earth-boring tool may additionally include at least one fluid port extending through the blade, and a fluid port manifold having an opening at a first end and a plurality of openings along a length providing fluid communication between the at least one fluid port and a primary fluid passage of the earth-boring tool. An additional earth-boring tool may include a fluid port manifold located in the tool body and a plurality of fluid port sleeves, each fluid port sleeve of the plurality of fluid port sleeves extending into a corresponding opening of a plurality of openings along the length of the fluid port manifold.

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.

The invention discloses a drill bit design method based on rock crushing principle with local variable strength, including: drill bit is divided into local crushing feature regions; strength mode factors of the local crushing feature regions are calculated; a difference among strength mode factors of the local crushing feature regions is obtained to obtain a vector sum of horizontal cutting forces of the drill bit tooth corresponding to the same group of cutting tooth on the drill bit; treating the difference among the strength mode factors of the local crushing feature region as a target control condition for drill bit design. Based on the rock crushing principle with local variable strength, after dividing the symmetrical cutting tooth into groups, the strength variation factors of the symmetrical position are adjusted and balanced, so that the rock crushing strength of different local crushing feature regions can be changed in a targeted manner.

The invention discloses a drill bit design method based on rock crushing principle with local variable strength, including: drill bit is divided into local crushing feature regions; strength mode factors of the local crushing feature regions are calculated; a difference among strength mode factors of the local crushing feature regions is obtained to obtain a vector sum of horizontal cutting forces of the drill bit tooth corresponding to the same group of cutting tooth on the drill bit; treating the difference among the strength mode factors of the local crushing feature region as a target control condition for drill bit design. Based on the rock crushing principle with local variable strength, after dividing the symmetrical cutting tooth into groups, the strength variation factors of the symmetrical position are adjusted and balanced, so that the rock crushing strength of different local crushing feature regions can be changed in a targeted manner.

An isolated lubrication system for a drill bit is disclosed. The system comprises a body having a cutting arm with a journal and a rotary cutter mounted on the journal. The system also comprises a reservoir in a body to contain a fluid lubricant that isolated from communication outside the body. The system also comprises multiple conduits in communication with the reservoir and with respect to each other. The multiple conduits facilitate lubrication between the journal and the rotary cutter, including the bearings, by means of a gravitational force and/or a centrifugal force acting of the fluid lubricant. Further, the system comprises a sealing system. The sealing system includes a sealing cap provided to the reservoir, a seal provided between the journal and the rotary cutter, and a stepped passageway provided in a clearance between the rotary cutter and a cutting arm of the body.

An isolated lubrication system for a drill bit is disclosed. The system comprises a body having a cutting arm with a journal and a rotary cutter mounted on the journal. The system also comprises a reservoir in a body to contain a fluid lubricant that isolated from communication outside the body. The system also comprises multiple conduits in communication with the reservoir and with respect to each other. The multiple conduits facilitate lubrication between the journal and the rotary cutter, including the bearings, by means of a gravitational force and/or a centrifugal force acting of the fluid lubricant. Further, the system comprises a sealing system. The sealing system includes a sealing cap provided to the reservoir, a seal provided between the journal and the rotary cutter, and a stepped passageway provided in a clearance between the rotary cutter and a cutting arm of the body.

A hybrid drill bit includes both fixed cutting elements and an adjustable cutting structure thereon. An adjustment mechanism is provided to allow an axial position of cutting elements at a leading end of the adjustable cutting structure to be adjusted with respect to an axial position of the fixed cutting elements. The adjustable cutting structure may include counter rotational cutting members mounted obliquely with respect to a bit body rotational axis, and the adjustment mechanism may dynamically support the adjustable cutting structure such that the axial position of the cutting elements may be adjusted as the drill bit is in operation within a wellbore. The axial position may be adjusted by altering a weight applied to the drill bit within the wellbore.

A hybrid drill bit includes both fixed cutting elements and an adjustable cutting structure thereon. An adjustment mechanism is provided to allow an axial position of cutting elements at a leading end of the adjustable cutting structure to be adjusted with respect to an axial position of the fixed cutting elements. The adjustable cutting structure may include counter rotational cutting members mounted obliquely with respect to a bit body rotational axis, and the adjustment mechanism may dynamically support the adjustable cutting structure such that the axial position of the cutting elements may be adjusted as the drill bit is in operation within a wellbore. The axial position may be adjusted by altering a weight applied to the drill bit within the wellbore.

A fixed cutting structure-composite cone drill bit includes a drill bit body, a fixed cutting structure, and at least one cone. The cone and the fixed cutting structure are disposed on the drill bit body. The cone is rotatably connected to the drill bit body by means of a bearing structure. The distance from the outermost tooth or back cone of the at least one cone to the front side surface of the fixed cutting structure La≤πR/3, and the distance from the outermost tooth or back cone of the at least one cone to the rear side surface of the fixed cutting structure Lb≤πR/3. In the composite drill bit, the distance from the cone to the front/rear side surface of the fixed cutting structure is short, the gap between the cone and the fixed cutting structure is small, transition between cutting structure is smooth.

A fixed cutting structure-composite cone drill bit includes a drill bit body, a fixed cutting structure, and at least one cone. The cone and the fixed cutting structure are disposed on the drill bit body. The cone is rotatably connected to the drill bit body by means of a bearing structure. The distance from the outermost tooth or back cone of the at least one cone to the front side surface of the fixed cutting structure La≤πR/3, and the distance from the outermost tooth or back cone of the at least one cone to the rear side surface of the fixed cutting structure Lb≤πR/3. In the composite drill bit, the distance from the cone to the front/rear side surface of the fixed cutting structure is short, the gap between the cone and the fixed cutting structure is small, transition between cutting structure is smooth.