A system and method for installing casing in a blind horizontal well for blind horizontal directional borings. The system and method may include an example of an offset transmitter sonde assembly that contains an open central passage through which well casing can be inserted, and an example of a drill bit assembly that may be remotely uncoupled from a drill string, leaving the bit in the bore created. Remote uncoupling of the drill bit assembly tends to allow a casing to be installed in the bore while the drill string and bit remain in the bore for support during casing installation. After installation of the casing the drill bit assembly may be uncoupled from the drill string, allowing the drill string to be withdrawn from the bore, with the drill bit assembly remaining in the bore.

A drive sub for a drilling assembly includes a tubular body configured to receive and releasably engage a drilling tool. The body has inner and outer faces and further has a castellated edge provided on its operative downhole end, which edge defines a plurality of lugs separated from each other by intervening slots. In one aspect the drive sub has a contour profile provided at least partially along a circumference of the castellated edge, wherein the contour profile traverses the castellated edge substantially from the inner face to the outer face. In another aspect the drive sub has a channel provided in each of the lugs, wherein the channel at least partially traverses the lugs and leads from an inlet opening on the castellated edge to an outlet opening on the outer face. The contour profile and/or channel facilitate flow of drilling fluid and cuttings past the lugs during use.

A drive sub for a drilling assembly includes a tubular body configured to receive and releasably engage a drilling tool. The body has inner and outer faces and further has a castellated edge provided on its operative downhole end, which edge defines a plurality of lugs separated from each other by intervening slots. In one aspect the drive sub has a contour profile provided at least partially along a circumference of the castellated edge, wherein the contour profile traverses the castellated edge substantially from the inner face to the outer face. In another aspect the drive sub has a channel provided in each of the lugs, wherein the channel at least partially traverses the lugs and leads from an inlet opening on the castellated edge to an outlet opening on the outer face. The contour profile and/or channel facilitate flow of drilling fluid and cuttings past the lugs during use.

An apparatus and method for pulling a drill string out from a wellbore and lowering the drill string back into the wellbore, with minimal or no disassembly of the drill string, are provided. The apparatus has a first tension mechanism, a second tension mechanism, an up-hole cable, a down-hole cable and a guide. To pull a drill string out from a wellbore, the up-hole cable is connected to an up-hole end of the drill string and the drill string is pulled upwardly into and through the guide. To lower the drill string into the wellbore, the down-hole cable is connected to the mid-section (and/or the up-hole end) of the drill string and the drill string is pulled downwardly from the guide back into the wellbore.

A down-the-hole drilling device, being meant for drilling a hole with and a casing part is described. The drilling device comprises in its drilling head: a drilling arrangement, having first drilling means for drilling a center hole and second drilling means for reaming the center hole for the casing part; and a flushing flow arrangement for feeding of a flushing medium onto a drilling surface of the drilling arrangement by one or more feed channels and for discharging the same from the drilling surface together with drilling waste. The casing part is arranged to be pulled into the hole to be drilled by power influence directed thereto from the drilling arrangement. A feed channel of the flushing flow arrangement at least partly ends up on the drilling surface at a flushing channel that exists in the longitudinal direction of the drilling device essentially behind a rearmost part of the drilling surface of at least of the first drilling means. The flushing flow arrangement comprises on the bottom of the flushing channel a supplementary flushing groove that extends from the feed channel towards the outer periphery of the drilling arrangement.

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).

A top surface drilling device has a core bit and a drill head disposed in the core bit. The drill head has a smaller diameter than that of the core bit, and the core bit and the drill head can be driven at different angular speeds.

A top surface drilling device has a core bit and a drill head disposed in the core bit. The drill head has a smaller diameter than that of the core bit, and the core bit and the drill head can be driven at different angular speeds.

A directional casing drilling system includes a casing string, a drilling rig and a retrievable Bottom Hole Assembly (BHA). The drilling rig includes a casing drive for rotating the casing string in the borehole, a control system for controlling the casing drive, and a mud pump for pumping a continuous flow of drilling mud into the casing string. The BHA includes a torque transfer section, with which it is secured in the casing string, and a drill bit section held in a drilling position in the torque transfer section. It further includes a mud drive that rotates the drilling position of the drill bit section about the longitudinal axis of the torque transfer section, and a communicating device for communicating the orientation of the drill bit to the control system. The BHA is steered by adjusting the rotational speed of the casing string.