Abstract: A fluid actuated downhole tool for inducing movement of a downhole apparatus is described. The tool comprises a body for coupling to downhole apparatus, the body being adapted to accommodate now of fluid therethrough and including a flow-modifying arrangement for modifying the flow of fluid through the body. The flow-modifying arrangement is configurable in an inactive configuration and in an active configuration. The fluid activated tool is selectively operated from the surface by varying an operating condition which causes the flow through the tool to either bypass or flow through the flow-modifying arrangement to induce movement of the downhole apparatus.

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 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 method of running a bore-lining tubing string into a bore includes running a tubing string, typically a liner string, into a bore while agitating the string. The agitation of the string reduces the friction between the string and the bore wall and thus facilitates the translation of the string into the bore. The agitation may also take place while the tubing is being cemented in the bore. Pressure pulses may be applied to fluid in the bore, which fluid may be cement slurry.

Abstract: Drilling apparatus comprises: a body; a pilot hole-drilling assembly (14) mounted to the body for drilling a pilot hole of a first diameter; and a hole-opening assembly (16) mounted to the body for opening the pilot hole to a larger second diameter. The apparatus is configured such that the pilot hole-drilling assembly (14) will drill at a faster rate than the hole-opening assembly (16) for a given unit loading. As the pilot hole- drilling assembly (14) has the capability to drill at a faster rate than the hole-opening assembly (16), the pilot hole-drilling assembly will tend to experience relatively low weight-on-bit (WOB). The pilot hole-drilling assembly (14) will thus tend to maintain a vertical orientation. The hole-opening assembly (16) will follow the path of the pilot hole, while opening the hole to the required diameter.

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 fluid actuated downhole tool for inducing movement of a downhole apparatus is described. The tool comprises a body for coupling to downhole apparatus, the body being adapted to accommodate now of fluid therethrough and including a flow-modifying arrangement for modifying the flow of fluid through the body. The flow-modifying arrangement is configurable in an inactive configuration and in an active configuration. The fluid activated tool is selectively operated from the surface by varying an operating condition which causes the flow through the tool to either bypass or flow through the flow-modifying arrangement to induce movement of the downhole apparatus.

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 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 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 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: Directional drilling apparatus having a non-rotating mass rotatably a centre-of-gravity spaced form the mandrel axis. An offsetting arrangement is coupled to the mass, and has an outer profile defining an offset relative to the mandrel axis, and a bearing portion rotatably mounted on the offsetting portion. The apparatus is run on a string, and the offsetting portion is oriented relative to the mass. When the towards an orientation with its centre-of-gravity positioned towards the low side of the bore and tends to maintain the relative orientation.

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 (22), such as a valve, for producing variations in the flow of fluid through the string, and a device (26) 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: 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.