Abstract: A downhole apparatus which can be used as multi-cycle circulating subs utilized in downhole drilling operations, includes a piston (242) slidably mounted in a body between positions in which at least one aperture in the body is opened and closed. Movement of the piston (242) is controlled by a pin (86), secured to one of the body and a control member, and a control groove (52) formed in the other of the body and control member for receiving a portion of the pin. An arrangement of elements (232, 276) respectively connected to the control member and body is such as to normally resist axial movement of the control member from a first axial position to a second axial position. A spring (44) is located in a chamber for biasing the piston (242). The chamber is vented by an opening in the body.

Abstract: An expandable drill bit for use with earth drilling equipment. The bit includes arms held in a closed position, so that the bit may be inserted through casing or a small bore hole. The arms are expandable to create an expanded drill bit having a crown profile common to a solid crown bit. The arrangement of the arms provides a short gauge length so that the expanded bit is steerable downhole. Embodiments of the expandable drill bit are detailed to show mechanisms for actuating the arms between the open and closed positions.

Abstract: An expandable reamer shoe is provided for use with expandable casing in a borehole. The reamer shoe has a number of reaming members in the form of blades which remain closed against the body of the shoe when inserted through casing, and can then be expanded to underream below the casing. Additionally, the expandable reamer shoe is made substantially of a drillable material so that the borehole can be extended beyond the point reached by the expandable reamer shoe.

Abstract: A tool for reducing torque on work string, eg for gas or oil production, comprises an upper clamp (2), a lower clamp (3) and connection means (4), the three components formed as a unitary structure (1). The tool also comprises bearing means, preferably made from an elastomeric compound, and an annular body (7) (see FIG. 4) held in place over the connection means by the clamps. The clamps may comprise spigots (5) for retaining the connection means. In a preferred embodiment the annular body is in two semi-annular components connected at one end to allow them to pivot, and the other end comprises mating castellations for receiving a fastening pin. The annular body may comprise a number of replaceable wear pads (14) which may be made of bronze or an elastomer. The unitary structure of the tool enhances the integral strength and efficiency of the clamps.

Abstract: An expandable drill bit for use with earth drilling equipment. The bit includes arms held in a closed position, so that the bit may be inserted through casing or a small bore hole. The arms are expandable to create an expanded drill bit having a crown profile common to a solid crown bit. The arrangement of the arms provides a short gauge length so that the expanded bit is steerable downhole. Embodiments of the expandable drill bit are detailed to show mechanisms for actuating the arms between the open and closed positions.

Abstract: An expandable reamer shoe is provided for use with expandable casing in a borehole. The reamer shoe has a number of reaming members in the form of blades which remain closed against the body of the shoe when inserted through casing, and can then be expanded to underream below the casing. Additionally, the expandable reamer shoe is made substantially of a drillable material so that the borehole can be extended beyond the point reached by the expandable reamer shoe.

Abstract: A tool for reducing torque on work string, eg for gas or oil production, comprises an upper clamp (2), a lower clamp (3) and connection means (4), the three components formed as a unitary structure (1). The tool also comprises bearing means, preferably made from an elastomeric compound, and an annular body (7) (see FIG. 4) held in place over the connection means by the clamps. The clamps may comprise spigots (5) for retaining the connection means. In a preferred embodiment the annular body is in two semi-annular components connected at one end to allow them to pivot, and the other end comprises mating castellations for receiving a fastening pin. The annular body may comprise a number of replaceable wear pads (14) which may be made of bronze or an elastomer. The unitary structure of the tool enhances the integral strength and efficiency of the clamps.

Abstract: This invention relates particularly but not exclusively to the secondary means for closing a bypass valve. A bypass valve (102) is provided which comprises a body (4) having a bore extending therethrough; at least one aperture (32) adapted to allow fluid communication between the bore and a chamber defined in the body (4); and at least one aperture adapted to allow fluid communication between the chamber and the exterior of the bypass valve. Fluid communication between the chamber and the bypass valve exterior is permitted when a piston (78) located in the chamber is in a first position, but is not permitted when the piston (78) is in a second position. Mechanism for selectively exposing the piston (78) to a pressure differential which moves the piston (78) is provided. A bypass valve is hereby provided which is more reliable than conventional bypass valve equipment.

Abstract: The invention relates to bypass valves for use in wellbores, particularly but not exclusively to bypass valves used during the setting of hydraulic anchor packers. The invention provides a bypass valve for selectively isolating the interior of a down-hole assembly from the exterior thereof, the bypass valve comprising guide pin in received slot being adapted to permit movement of a piston (30) from a first position to a second position in response to a predetermined pressure differential between a bore (58) of the piston (30) and the exterior of a body (4) but normally preventing movement of the piston (30) to a third position in which the bore (58) of the piston (30) is substantially isolated from the exterior of the body (4), and an extension of the guide slot for overriding the guide pins in the slot, so as to permit movement of the piston (30) to the third position.

Abstract: Apparatus for milling a well casing (15) includes an elongate guide member (1) having a leading end and a trailing end, the guide member having defined thereon a guide track (23) which, in the use position of the guide member, converges with the well casing to be milled from the trailing end of the guide member towards the leading end thereof. A support member (4) is selectively movable along the guide track from the trailing end towards the leading end of the guide member to converge with the well casing to be milled. A milling tool (5) has a leading end rotatably supported by the support member (4) and includes milling means (6) located rearwardly of its leading end.