A fracbot for fracturing a formation, comprising: a drill bit; a rotary swivel configured to rotate the drill bit; a motor configured to induce vibrations that create a spiral movement of the fracbot, wherein the spiral movement of the fracbot allows the fracbot to traverse existing fractures in the formation comprising a first fracture and a second fracture; a battery configured to power the fracbot; and a coating encompassing the fracbot configured to dissolve at a predefined temperature, wherein the fracbot is configured to create a channel that connects the first fracture and the second fracture.

Bottom hole assemblies for drilling through a lost circulation zone of a wellbore includes a drill string, a drill bit and a cladding seat coupled to the drill string, an expandable cladding sheath engaged with the cladding seat, a release mechanism coupling an uphole end of the expandable cladding sheath to the drill string, and an expander translatable axially along the drill string. The expandable cladding sheath is a fiber reinforced polymer. The cladding seat releasably couples a downhole end of the expandable cladding sheath to the drill string, and the release mechanism operates to release the uphole end of the expandable cladding sheath from the drill string. The expander deforms the expandable cladding sheath outward into contact with a wall of a wellbore when translated axially through a central cavity of the expandable cladding sheath. The bottom hole assembly may enable drilling ahead through a lost circulation zone.

Bottom hole assemblies for drilling through a lost circulation zone of a wellbore includes a drill string, a drill bit and a cladding seat coupled to the drill string, an expandable cladding sheath engaged with the cladding seat, a release mechanism coupling an uphole end of the expandable cladding sheath to the drill string, and an expander translatable axially along the drill string. The expandable cladding sheath is a fiber reinforced polymer. The cladding seat releasably couples a downhole end of the expandable cladding sheath to the drill string, and the release mechanism operates to release the uphole end of the expandable cladding sheath from the drill string. The expander deforms the expandable cladding sheath outward into contact with a wall of a wellbore when translated axially through a central cavity of the expandable cladding sheath. The bottom hole assembly may enable drilling ahead through a lost circulation zone.

A downhole device delivery and drive transfer system includes a sub which is arranged to attach to a drill string and a tool which is configured to enable it to travel through the drill string and releasably couple to the sub. The sub and the tool are arranged so that when they are releasably coupled to each other torque imparted to the drill string is transferred by the sub to the tool. The tool is arranged to carry one or more devices for performing one or more downhole functions such as core drilling, hole reaming or wedge placement for directional drilling. The system also has a guide mechanism that operates between the sub and the tool to guide the tool to a known rotational orientation relative to the sub as the tool travels into the sub. A fluid control system controls the flow of fluid through the tool through a downhole outlet and and a plurality of ports intermediate opposite ends of the tool.

Provided is a two part drilling and running tool, a well system, and a method for forming a well system. The two part drilling and running tool, in one aspect, includes a conveyance, and a smaller assembly coupled to an end of the conveyance. The two part drilling and running tool, in accordance with this aspect, further includes a larger bit assembly slidably coupled to the conveyance, the smaller assembly and larger bit assembly configured to slidingly engage one another downhole to form a combined bit assembly.

Provided is a two part drilling and running tool, a well system, and a method for forming a well system. The two part drilling and running tool, in one aspect, includes a conveyance, and a smaller assembly coupled to an end of the conveyance. The two part drilling and running tool, in accordance with this aspect, further includes a larger bit assembly slidably coupled to the conveyance, the smaller assembly and larger bit assembly configured to slidingly engage one another downhole to form a combined bit assembly.

A system can include a disconnect tool connected as part of a tubular string, the disconnect tool including an outer housing, and an inner mandrel in the outer housing, in which an abrasive slurry is directed to flow through the tubular string and from the inner mandrel to an annulus between the inner mandrel and the outer housing, and the abrasive slurry erodes through the outer housing. A method can include installing a tubular string in a well, then deploying a disconnect assembly into the tubular string, and flowing an abrasive slurry through the disconnect assembly, thereby parting the tubular string. A disconnect tool can include a rotational flow structure configured to induce rotational flow, and an inner diameter decrease downstream of the rotational flow structure.

A system can include a disconnect tool connected as part of a tubular string, the disconnect tool including an outer housing, and an inner mandrel in the outer housing, in which an abrasive slurry is directed to flow through the tubular string and from the inner mandrel to an annulus between the inner mandrel and the outer housing, and the abrasive slurry erodes through the outer housing. A method can include installing a tubular string in a well, then deploying a disconnect assembly into the tubular string, and flowing an abrasive slurry through the disconnect assembly, thereby parting the tubular string. A disconnect tool can include a rotational flow structure configured to induce rotational flow, and an inner diameter decrease downstream of the rotational flow structure.

A drilling unit for drilling a hole, wherein the drilling unit comprising a drilling head (1). Said drilling head (1) further comprising pulling means (2) for pulling a casing (7) into the hole, a pilot bit (3) for drilling a center hole, connecting means and a ring bit assembly (4) for reaming the center hole for the casing (7). Said ring bit assembly (4) being connected to said pilot bit (3) by the connecting means and to said casing (7) by the pulling means (2). Said ring bit assembly (4) comprising a carrier (5) comprising carrier coupling means (23) and a plurality of ring bit segments (6) movably attached to said carrier coupling means (23).

A drilling unit for drilling a hole, wherein the drilling unit comprising a drilling head (1). Said drilling head (1) further comprising pulling means (2) for pulling a casing (7) into the hole, a pilot bit (3) for drilling a center hole, connecting means and a ring bit assembly (4) for reaming the center hole for the casing (7). Said ring bit assembly (4) being connected to said pilot bit (3) by the connecting means and to said casing (7) by the pulling means (2). Said ring bit assembly (4) comprising a carrier (5) comprising carrier coupling means (23) and a plurality of ring bit segments (6) movably attached to said carrier coupling means (23).