Abstract: A downhole apparatus such as multi-cycle circulating subs used during downhole drilling operations includes a piston (42) slidably mounted in a body (4) between positions in which at least one aperture (40) in the body is opened and closed. Movement of the piston (42) is controlled by a pin (86) secured to one of the body and a control member, and a control groove (52) in which a portion of the pin is received formed in the other of the body and control member. An arrangement of elements (32,76) respectively connected to the control member and body is such that, as the control member moves axially, increasing lengths of the elements locate adjacent one another so as to provide resistance to relative rotation in at least one direction of the control member and body. The relative rotation is rotation which presses the control member against the control groove. The risk of damage to the control pin is thereby reduced.

Abstract: A downhole apparatus permitting separation of one part of downhole equipment from another part thereof includes a first part connected to a second part by a connecting member which limits axial and rotational movement of the first and second parts and has first and second ends connected respectively to the first and second parts. The connecting member includes a cross bar extending between the first and second ends having an aperture therein that results in a region of weakness, a portion of the cross bar spaced from the aperture minimizing stress at the region of weakness when torque is transmitted in use between the first and second parts via the connecting member.

Abstract: The present invention relates to methods and equipment for recovering use of a well-bore in circumstances where the well bore has become blocked by downhole equipment. The invention provides a method comprising the steps of separating, at a release joint, a portion of equipment from a jammed portion (6) of equipment; running the separated portion of equipment uphole out of the wellbore (100); running a deflector assembly (60) downhole into the wellbore (100); and deflecting a milling tool (64) from the wellbore into surrounding formation. The method is characterised by restricting relative movement between the deflector assembly (60) and the wellbore (100) by engaging, prior to deflecting the milling tool (64), the deflector assembly (60) with said jammed portion (6) of equipment.

Abstract: The present invention relates to methods and equipment for recovering use of a well-bore in circumstances where the well bore has become blocked by downhole equipment. The invention provides a method comprising the steps of separating, at a release joint, a portion of equipment from a jammed portion (6) of equipment; running the separated portion of equipment uphole out of the wellbore (100); running a deflector assembly (60) downhole into the wellbore (100); and deflecting a milling tool (64) from the wellbore into surrounding formation. The method is characterised by restricting relative movement between the deflector assembly (60) and the wellbore (100) by engaging, prior to deflecting the milling tool (64), the deflector assembly (60) with said jammed portion (6) of equipment.

Abstract: A downhole apparatus permitting separation of one part of downhole equipment from another part thereof includes a first part (4) connected to a second part (6) by connecting means which limits axial and rotational movement between the parts. The connecting means includes a connecting member (22) having first and second ends connected respectively to the first and second parts (4, 6). The connection of the first and second ends of the connecting member (22) is such as to limit axial and rotational movement relative to the respective first and second parts (4, 6). The connecting member (22) is provided between the first and second ends with a region of weakness in the connecting member provided by weakening means (28), and with means for minimizing stress generated in the connecting means at the region of weakness when torque is transmitted in use between the first and second parts (4, 6) via the connecting member (22).

Abstract: The present invention relates to downhole apparatus and particularly but not exclusively, to multi-cycle circulating subs used during downhole drilling operations. Apparatus is provided comprising a piston (42) slidably mounted in a body (4) between positions in which at least one aperture (40) in the body is opened and closed. Movement of the piston (42) is controlled by a pin (86) secured to one of the body and a control member, and a control groove (52) in which a portion of the pin is received formed in the other of the body and control member. An arrangement of elements (32, 76) respectively connected to the control member and body is such that, as the control member moves axially, increasing lengths of said elements locate adjacent one another so as to provide resistance to relative rotation in at least one direction of the control member and body. The relative rotation is rotation which presses the control member against the control groove.

Abstract: The present invention relates to downhole apparatus for limiting rotation of a rotor (4) relative to a stator (8) associated with said rotor (4). Apparatus according to the invention is provided with a locking member (12) movable from a first axial position to a second axial position by the application of a static fluid pressure to a differential area of said locking member (12). The apparatus is characterised by means for selectively applying static fluid pressure to said differential area of said locking member (12).