Abstract: A downhole tool comprises a body defining a fluid inlet and two or more fluid outlets. A valve arrangement cycles the proportion of fluid directed from the inlet to each of the outlets. One of the outlets may be associated with a fluid pressure responsive device, such as a cleaning blade.

Abstract: An under-reamer includes a body and extendable cutters mounted on the body. The under-reamer is configured to be cycled between a first configuration in which the cutters are retracted and a second configuration in which the cutters are movable between retracted and extended positions. A control mechanism is provided and is configurable to prevent the under-reamer cycling between the first and second configurations and thus maintains the under-reamer in a selected one of the first and second configurations.

Abstract: A downhole valve comprises a tubular body and a valve member. The valve member is normally closed and in the closed position may prevent or restrict passage of a working fluid through the body. The valve member is movable to an open position, a first working fluid pressure differential being necessary to move the valve member from the closed position and a lower second working fluid pressure differential being necessary to maintain the valve member in the open position.

Abstract: A downhole apparatus comprises a body, extendable members mounted on the body and being movable between retracted and extended configurations, and a remotely operable retaining arrangement for maintaining the extendable members in the retracted configuration. The extendable members may be cutters, such that the apparatus may be a cutting apparatus, such as a reamer. An operator may control the apparatus to retain the cutting members in the retracted configuration, or prevent the extension of the cutting members.

Abstract: A downhole tool comprises a body, radially extendable members mounted to the body and movable between retracted and extended positions, a cam member operatively associated with the extendable members and movable relative to the body to extend the extendable members, and a support member configurable to permit retraction of the extendable members from an extended position. The tool may be an under-reamer, and the extendable members may be cutting blades.

Abstract: A drilling apparatus includes a cutting structure defined by a percussive action cutter and at least one other cutter. The percussive action cutter is adapted to be urged in a drilling direction by hydraulic pressure force, while the other cutter is urged in a drilling direction by mechanical force.

Abstract: A downhole tool comprises a body, radially extendable members mounted to the body and movable between retracted and extended positions, a cam member operatively associated with the extendable members and movable relative to the body to extend the extendable members, and a support member configurable to permit retraction of the extendable members from an extended position. The tool may be an under-reamer, and the extendable members may be cutting blades.

Abstract: A hydraulic tool assembly for a downhole tool comprises a body (12), first and second members (14, 16) mounted for independent movement with respect to the body, and first and second control fluid chambers (24, 26) associated with the respective first and second members. Movement of the first member (14) between a first position and a second position in response to an applied force displaces control fluid from the first chamber (24) into the second chamber (26), to move the second member from a first position towards a second position to execute a tool function.

Abstract: A method of freeing stuck objects (16) from a bore (14) comprises running a string (12) into the bore (14), the string (12) including a flow modifier, such as a valve, for producing variations in the flow of fluid through the string, and a device for location in the string and adapted to axially extend or contract in response to variations in the flow of fluid through the string. A portion of the string (12) engages the stuck object (16). Fluid is then passed through the string while applying tension to the string, whereby the tension applied to the stuck object varies in response to the operation of the flow modifier and the extending or retracting device.

Abstract: Directional drilling apparatus for use in drilling a deviated bore comprises a mandrel for mounting to a drill string and having a main axis. A non-rotating mass is rotatably mounted on the mandrel and has a center-of-gravity spaced from the mandrel axis. The apparatus further comprises an offsetting arrangement including a non-rotating offsetting portion rotatably mounted on the mandrel, coupled to the mass, and having an outer profile defining an offset relative to the mandrel axis, and a bearing portion rotatably mounted on the offsetting portion. In use, the apparatus is run into an inclined bore on a string, and the offsetting portion is oriented relative to the mass. When the string is rotated the mass tends towards an orientation with its center-of-gravity positioned towards the low side of the bore and thus tends to maintain the offsetting portion in a desired relative orientation in the bore, the bearing portion rotationally isolating the offsetting portion from the bore wall.

Abstract: A downhole tool (10) for mounting on a drill string comprises: a mandrel (16); a body (18) axially movably mounted on the mandrel; and radially extendable members, such as stabiliser blades or cutters (30), mounted in the body and being operatively associated with the mandrel such that relative axial movement of the mandrel and body induces radial movement of the members. Application of axial tension to the tool produces axial movement of the body relative to the mandrel, tending to retract the members from an extended configuration. The mandrel may be arranged to draw the members inwardly to permit positive retraction of the members from an extended configuration. Further, the body may define a channel (32) and the mandrel and the members include an arrangement (38, 39, 40, 42) for maintaining a desired orientation of the members relative to the body channel.

Abstract: A downhole drilling method comprises producing pressure pulses in drilling fluid using measurement-while-drilling (MWD) apparatus (18) and allowing the pressure pulses to act upon a pressure responsive device (16) to create an impulse force on a portion of the drill string.

Abstract: Downhole flow pulsing apparatus comprises a housing (14) for location in a drillstring, the housing (14) defining a throughbore to permit passage of fluid through the housing. A valve (27, 30) is located in the bore and defines a flow passage (29, 31). The valve includes a valve member (27) which is movable to vary the area of the passage (29, 31) to provide a varying fluid flow therethrough. A fluid actuated positive displacement motor (15, 16) is associated with the valve member (27). In a preferred embodiment, the apparatus is provided in combination with a drill bit (5) and a pressure responsive device, such as a shock-sub (3), which expands or retracts in response to the varying drilling fluid pressure created by the varying flow passage area. The expansion or retraction of the shock-sub (3) provides a percussive effect at the drill bit.

Abstract: A downhole drilling assembly (10) comprises a body (11) for mounting on a drillstring, the body defining a fluid conduit. A drilling fluid driven motor (12) is mounted in the body (11) and is coupled to a flow restricting device (14) axially movably mounted to the body (11). The device is coupled to a drill bit (16). In use, the flow restricting device (14) is driven by the motor (12) to vary the flow of drilling fluid through the body and produce a varying fluid pressure force to induce axial movement of the device (14) relative to the body (11), and thus provide a percussive or hammer drilling effect. The flow restricting device (14) may be coupled to the drill bit (16) by a mandrel (46) splined or otherwise coupled to the body. Alternatively, the flow restricting device (68) may be coupled to the drill bit (72) by a rotatable shaft (70), such that the motor (64) may also rotate the drill bit (72).

Abstract: A percussion drill 10 has a tubular fluid transmitting body 14, with a drill bit 16 mounted on a drill bit support 20 itself mounted in body 14 via a spring 22 and salines 24. A mass 28 is spring mounted in the body 14 and is movable to impact on a face 26 of the support 20. Mounted to the mass 28 is a rotating valve 32 comprising two valve plates 34, 36. Each plate 34, 36 defines a slot 38, 40, such that rotation of one of the valve plates 36 relative to the other moves the slots 38, 40 into and out of alignment; the change in alignment of the slots 38, 40 alters the flow of drilling fluid through the valve 32, so altering the drilling fluid pressure force acting on the mass 28, so causing mass 28 to push against the spring 30, and impact on the drill bit support 20 providing a percussive act ion at the drill bit 16.

Abstract: A downhole drilling method comprises producing pressure pulses in drilling fluid using measurement-while-drilling (MWD) apparatus (18) and allowing the pressure pulses to act upon a pressure responsive device (16) to create an impulse force on a portion of the drill string.

Abstract: Downhole flow pulsing apparatus comprises a housing (14) for location in a drillstring, the housing (14) defining a throughbore to permit passage of fluid through the housing. A valve (27, 30) is located in the bore and defines a flow passage (29, 31). The valve includes a valve member (27) which is movable to vary the area of the passage (29, 31) to provide a varying fluid flow therethrough. A fluid actuated positive displacement motor (15, 16) is associated with the valve member (27). In a preferred embodiment, the apparatus is provided in combination with a drill bit (5) and a pressure responsive device, such as a shock-sub (3), which expands or retracts in response to the varying drilling fluid pressure created by the varying flow passage area. The expansion or retraction of the shock-sub (3) provides a percussive effect at the drill bit.

Abstract: Directional drilling apparatus (26) for location on a drill string (20) comprises a stabilizer (32) having a mandrel (38) for connection to the drill string (20) and an eccentric non-rotating element (46) mounted on the mandrel (38) for offsetting the string (20) in the bore (22) and a non-rotating offset mass (34) for maintaining the element (46) at a selected orientation relative to the bore (22) as the drill string (20) rotates.

Abstract: A mounting arrangement for a pendulum in a downhole drift indicator comprises a plunger and a pendulum defining respective normally spaced apart first and second surfaces, and a pivot connection between the plunger and pendulum including a connecting pivot member. On the pivot connection being subject to a predetermined load the first and second surfaces engage to limit the load experienced by the pivot member. Also disclosed is a drift Indicator biassing arrangement, the arrangement including a housing partially defining a volume for containing a fluid reservoir, a signalling plunger and floating piston defining respective wall portions of the volume and being moveable relative to the housing. A spring acts on the piston to compress the fluid in the volume and move the signalling plunger relative to the housing.

Abstract: Downhole flow pulsing apparatus comprises a housing (14) for location in a drillstring, the housing (14) defining a throughbore to permit passage of fluid through the housing. A valve (27, 30) is located in the bore and defines a flow passage (29, 31). The valve includes a valve member (27) which is movable to vary the area of the passage (29, 31) to provide a varying fluid flow therethrough. A fluid actuated positive displacement motor (15, 16) is associated with the valve member (27). In a preferred embodiment, the apparatus is provided in combination with a drill bit (5) and a pressure responsive device, such as a shock-sub (3), which expands or retracts in response to the varying drilling fluid pressure created by the varying flow passage area. The expansion or retraction of the shock-sub (3) provides a percussive effect at the drill bit.