The present invention relates to a combined crushing super-variable-diameter drill bit for natural gas hydrate exploitation, including a joint, an outer cylinder connected to the joint by thread, a nozzle I mounted in the outer cylinder, a mechanical locking mechanism, a blade telescoping mechanism, an end cap connected to the outer cylinder by thread, a seal ring IV mounted to the end cap, and a nozzle II mounted in the end cap by threaded connection. The present invention achieves integrated operation of conventional drilling and draw-back expanding, which can effectively solve the problems that the existing hydrate drill bit cannot drill a large borehole, cannot mechanically lock an extending position of the blade to stabilize the size of the borehole, and a single crushing method is inefficient.

The present invention relates to a combined crushing super-variable-diameter drill bit for natural gas hydrate exploitation, including a joint, an outer cylinder connected to the joint by thread, a nozzle I mounted in the outer cylinder, a mechanical locking mechanism, a blade telescoping mechanism, an end cap connected to the outer cylinder by thread, a seal ring IV mounted to the end cap, and a nozzle II mounted in the end cap by threaded connection. The present invention achieves integrated operation of conventional drilling and draw-back expanding, which can effectively solve the problems that the existing hydrate drill bit cannot drill a large borehole, cannot mechanically lock an extending position of the blade to stabilize the size of the borehole, and a single crushing method is inefficient.

A seal assembly for downhole use that includes a sealing ring, and a backup ring set generally coaxial with and adjacent to the sealing ring. A height of the backup ring exceeds a diameter of the sealing ring; and is disposed on a low pressure side of the seal assembly to prevent the sealing ring from extruding into the low pressure side. The backup ring is made of a core and a coating on the core. Material properties of the coating are generally unaffected when exposed to downhole conditions, and the coating prevents diffusion of fluid or gas molecules into the low pressure side.

A seal assembly for downhole use that includes a sealing ring, and a backup ring set generally coaxial with and adjacent to the sealing ring. A height of the backup ring exceeds a diameter of the sealing ring; and is disposed on a low pressure side of the seal assembly to prevent the sealing ring from extruding into the low pressure side. The backup ring is made of a core and a coating on the core. Material properties of the coating are generally unaffected when exposed to downhole conditions, and the coating prevents diffusion of fluid or gas molecules into the low pressure side.

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 seal structure includes a ring-shaped seal member. The seal member is disposed in a seal groove. The case includes a low-pressure lateral face in a cross section of the seal structure, the cross section being taken along an imaginary plane in parallel with a shaft axial direction of the shaft and passing through a center line of the shaft. The seal member includes a first protruding portion. The first protruding portion protrudes from a main portion having a bottom face in contact with the low-pressure lateral face, and has a shape such that the first protruding portion extends toward the shaft as the first protruding portion extends toward the low-pressure side. The first protruding portion includes a tip. The first protruding portion includes a contact region in contact with the shaft. The tip is closer to the low-pressure side than the contact region is.

A seal structure includes a ring-shaped seal member. The seal member is disposed in a seal groove. The case includes a low-pressure lateral face in a cross section of the seal structure, the cross section being taken along an imaginary plane in parallel with a shaft axial direction of the shaft and passing through a center line of the shaft. The seal member includes a first protruding portion. The first protruding portion protrudes from a main portion having a bottom face in contact with the low-pressure lateral face, and has a shape such that the first protruding portion extends toward the shaft as the first protruding portion extends toward the low-pressure side. The first protruding portion includes a tip. The first protruding portion includes a contact region in contact with the shaft. The tip is closer to the low-pressure side than the contact region is.

A spiral magnetic fluid composite sealing structure of a roller bit comprising a cone leg and a roller, wherein the roller and the cone leg are in rotatable connection in a fitting manner through a roller inner hole and a cone leg shaft journal, a sealing groove is formed in an opening end of the roller inner hole, and a spiral magnetic fluid sealing assembly is arranged in the sealing groove. Through the arrangement of the spiral magnetic fluid sealing assembly, a spiral sand discharging effect is realized, compared with a passive sealing mode, the sealing performance is greatly improved by active sand discharging mode, and the service life of sealing is significantly prolonged; a slurry sealing effect of magnetic fluid seals is realized, resulting the sealing gap is tightly sealed under the magnetic action; in addition, the automatic compensation function of magnetic fluid can also be realized.

A spiral magnetic fluid composite sealing structure of a roller bit comprising a cone leg and a roller, wherein the roller and the cone leg are in rotatable connection in a fitting manner through a roller inner hole and a cone leg shaft journal, a sealing groove is formed in an opening end of the roller inner hole, and a spiral magnetic fluid sealing assembly is arranged in the sealing groove. Through the arrangement of the spiral magnetic fluid sealing assembly, a spiral sand discharging effect is realized, compared with a passive sealing mode, the sealing performance is greatly improved by active sand discharging mode, and the service life of sealing is significantly prolonged; a slurry sealing effect of magnetic fluid seals is realized, resulting the sealing gap is tightly sealed under the magnetic action; in addition, the automatic compensation function of magnetic fluid can also be realized.

A hybrid bit includes fixed blades and wheel support structures. The wheel support structure includes a wheel inserted into a slot between a leading support and a trailing support. One or more shims fill a gap between a flange and the leading supports. An elongated seal between the wheel and the supports is provided to seal the wheel support.