A casing plug assembly

Abstract

There is provided a casing plug assembly (100) comprising a casing plug (1) and a running tool (10) releasably connected to the casing plug (1). The casing plug assembly (100) is operable between a plurality of operational states and comprises an actuation system (50) for operating the casing plug assembly (100) between the plurality of operational states (S1, S2, S3, S4, S5, S6, S7, S8). The actuation system (50) comprises: an upper J-slot mechanism (60) formed between the running tool (10) and an upper connector (9) of the casing plug (1), having a first set of positions (60P1, 60P2, 60P3, 60P4); a lower J-slot mechanism (80) formed between an upper housing section (4a) and a mandrel (2) of the casing plug (1), having a second set of positions (80P1, 80P2, 80P3, 80P4); and a locking mechanism (65) that prevents at least one combination of the positions (60P1, 60P2, 60P3, 60P4) of the first set of positions with the positions (80P1, 80P2, 80P3, 80P4) of the second set of positions so that a number of the combinations is equal to the number of operational states.

Description

[0001] A CASING PLUG ASSEMBLY

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a casing plug assembly.

[0004] BACKGROUND OF THE INVENTION

[0005] Casing plugs are used in a casing of a well, for the purpose of temporarily closing the well, for the purpose of pressure testing the casing etc. Casing plugs are typically run into the well in a radially retracted state by means of a drill pipe and subsequently radially expanded into contact with the inner surface of the casing by means of the drill pipe. The casing plug may be operated by means of the drill pipe by pushing the drill pipe down, by pulling the drill pipe up, by rotation of the well pipe clockwise or by rotation of the drill pipe counter-clockwise. Typically, the casing plug has an anchoring device for anchoring of the plug to the inner surface of the casing and a sealing device with an elastomeric sealing element for preventing fluid flow between a position below the sealing device and a position above the sealing device.

[0006] One object of at least some embodiments of the present invention is to provide a casing plug that can be radially expanded into the inner surface of the casing and then radially retracted again multiple times. This is often referred to as a resettable casing Plug.

[0007] The drill pipe is typically made by drill pipe elements that are threadedly connected to each other. Clockwise rotation connects two elements to each other, while counterclockwise rotation disconnects the two elements from each other. Another purpose of the present invention is to provide a resettable casing plug which can be operated by the drill string without any risk of disconnecting drill pipe elements from each other. Hence, one object of at least some embodiments of the invention is that there should be no need for counter-clockwise rotation of the drill pipe in order to operate the casing plug. A further object of at least some embodiments is that there should be that the actuation system should be able to be manipulated through its operational states substantially using longitudinal movement with as little rotation as possible.

[0008] WO2016 / 189123 describes a casing plug assembly for performing an operation in a well pipe. The assembly comprises a running tool for connection to a drill pipe, an equalizing module, a seal module, and an anchor module. A continuous fluid channel is formed through the casing plug assembly. The anchor module is configured to be set in the well pipe by pumping fluid through continuous fluid channel. The anchor module is, in the set state, providing a support in the well pipe used by the running tool to operate the seal module. The invention also relates to a method for operating the casing plug assembly in a well pipe. The invention also relates to an anchor module for anchoring to a well pipe.

[0009] US 4149594 discloses a retrievable well plug which is adaptable to be moved longitudinally within a well conduit. The plug contains normally retracted slip elements which are operated into engagement with the conduit by expander elements. An elastomeric packing element, of known construction, is expandable exteriorly around the well tool and is adapted to selectively seal with the well conduit. Booster means are provided for transmitting the compressive force defined by differential pressure acting across the packing element when the slips are in expanded position against the conduit and the packing element is sealed with the well conduit, such that the packing element is maintained in sealing relationship with the well conduit.

[0010] Another object of at least some embodiments of the invention is to provide a casing plug with an actuation system which makes it easy to operate the casing plug from topside and which makes it possible to verify the states of the casing plug during operation of the casing plug.

[0011] SUMMARY OF THE INVENTION

[0012] According to a first aspect, there is provided a casing plug assembly. The casing plug assembly comprises a casing plug and a running tool releasably connected to the casing plug. The casing plug assembly is operable between a plurality of operational states. The casing plug comprises: a mandrel with a through bore; a housing provided radially outside of at least parts of the mandrel, wherein the housing comprises an upper housing section and a lower housing section; an upper connector provided in an upper end of the upper housing section for releasably connecting to the running tool; an anchoring device provided radially outside of the mandrel, wherein the anchoring device is movable between a radially retracted state in at least one of the operational states of the casing plug assembly and a radially expanded state in at least another one of the operational states of the casing plug assembly; a sealing device provided radially outside of the mandrel and circumferentially around the mandrel wherein the sealing device is movable between a radially retracted state in at least one of the operational states of the casing plug assembly and a radially expanded state in at least another one of the operational states of the casing plug assembly; and a valve device movable between an open valve state, in which fluid flow through the bore is allowed, in at least one of the operational states of the casing plug assembly and a closed valve state, in which fluid flow through the bore is prevented, in at least another one of the operational states of the casing plug assembly. The casing plug assembly comprises an actuation system for operating the casing plug assembly between the plurality of operational states. The actuation system comprises: an upper J-slot mechanism formed between the running tool and the upper connector, the upper J-slot mechanism having a first set of positions; a lower J-slot mechanism formed between the upper housing section and the mandrel, the lower J-slot mechanism having a second set of positions; and a locking mechanism, wherein the locking mechanism prevents at least one combination of the positions of the first set of positions of the upper J-slot mechanism with the positions of the second set of positions of the lower J-slot mechanism so that a number of the combinations is equal to the number of operational states.

[0013] According to the above, it is achieved a casing plug assembly where a plurality of different states of the casing plug assembly can be achieved. These states are achieved by relative movement between the different components, particularly between the running tool and the casing plug, and between different parts of the casing plug. For example, at least parts of the housing are moveable relative to the mandrel. The provision of an upper J-slot mechanism and a lower J-slot mechanism enables combinations of different positions of the J-slot mechanisms, as is implemented by the locking mechanism, and therefore a higher number of operational states can be achieved. A higher number of operational states may allow greater functionality of the casing plug assembly, such as being able to expand / retract the anchoring device and the sealing device, and to open / close the valve device. Operational states including disconnection or reconnection of the running tool may be achieved. A higher number of operational states may also allow for validation or verification that a particular previous operational state or action has been achieved. For example, one of the operational states may be verification that the anchoring device and the sealing device have been radially expanded.

[0014] Utilizing J-slot mechanisms may also enable rotation of the casing plug assembly to be minimized. Elements of a drill string may be connected and disconnected by rotation between elements, with clockwise rotation leading to connection and counter-clockwise rotation leading to disconnection, so rotating a drill string counterclockwise may run the risk of disconnecting two elements. The J-slot mechanisms may utilize longitudinal movement of the drill string by an operator to move between positions. The J-slot mechanisms may also operate partially by clockwise movement between elements, with such movement being caused by the longitudinal movement of the drill string by the operator. Accordingly, rotation is only achieved between elements where absolutely necessary.

[0015] Providing two J-slot mechanisms and the locking mechanism may enable one J-slot mechanism to be held in a particular position while the other J-slot mechanism moves. This may allow independent movement of the J-slot mechanisms, so that the casing plug can be maintained in a set state while other operational states, such as the running tool being connected or disconnected, are achieved.

[0016] Allowing combinations of positions may enable reduced complexity in the J-slot mechanisms individually for a given number of operational states. This may reduce the likelihood of failure or of incorrect operation by a J-slot mechanism, and therefore may improve operation of the casing plug assembly overall. In addition, it is achieved that the casing plug assembly can be controlled from topside, via the use of J-slot mechanisms, without the use of fluid flow through the casing plug assembly.

[0017] The number of positions in the first set of positions and the number of positions in the second set of positions may be equal. The number of positions in the first set of positions may be less than the number of operational states. The number of positions in the second set of positions may be less than the number of operational states. The sum of the number of positions in the first set of positions and the second set of positions may be equal to the number of operational states.

[0018] The positions in the first set of positions and the positions in the second set of positions may be the same. In other words, the upper J-slot mechanism and the lower J-slot mechanism may have the same layout, so that the same positions are achieved.

[0019] The casing plug may have an upper section and a lower section. The upper section of the casing plug may be a region of the casing plug above a lower lock of the locking mechanism, while the lower section may be a region of the casing plug below the lower lock. The anchoring device may be provided in the lower section of the casing plug. The sealing device may be provided in the lower section of the casing plug. The valve device may be provided within the mandrel. The valve device may be provided in the upper section of the casing plug.

[0020] The lower housing section may be below the upper housing section along the length of the casing plug.

[0021] The locking mechanism may comprise an upper lock. The locking mechanism may comprise a lower lock in addition to the upper lock. The upper lock may have a first upper lock state, in which the running tool is locked to the upper connector and a second upper lock state, in which the running tool is released from the upper connector.

[0022] The upper lock therefore enables relative movement between the running tool and the upper connector in the second upper lock state and prevents relative movement between the running tool and the upper connector in the first upper lock state. As the upper J-slot mechanism is formed between the running tool and the upper connector, preventing relative movement of the upper connector and the running tool in the first upper lock state enables the locking mechanism to prevent a combination of positions between the upper J-slot mechanism and the lower J-slot mechanism by locking the upper J-slot mechanism in a particular position. In the second upper lock state, the upper connector may be locked to the mandrel. When the upper lock is in the second upper lock state, the running tool may be connected to or disconnected from the upper connector.

[0023] The upper lock may also have a third upper lock state. In the third upper lock state, the upper connector remains locked to the mandrel. The third upper lock state may differ from the second upper lock state by how the upper connector and the mandrel are locked together. In the second upper lock state, the upper connector may be locked to the mandrel by a feature of the upper lock. In the third upper lock state, the upper connector may be locked to the mandrel by the running tool.

[0024] The terms locked and released, as used herein, relate to longitudinal movement of the different features. In other words, the running tool being locked to the upper connector means that longitudinal movement of the running tool causes the upper connector to move longitudinally. The running tool being released from the upper connector means that the running tool can move independently of the upper connector.

[0025] The valve device, sealing device, and anchoring device may each or all be below the upper lock.

[0026] The running tool may releasably connect to the upper connector by means of the upper J-slot mechanism and the upper lock.

[0027] The upper lock therefore performs two functions; the first of locking the upper J-slot mechanism relative to the lower J-slot mechanism and the second function of enabling releasable connection between the running tool and the upper connector. Releasable connection between the running tool and the upper connector enables the running tool to be detached from and reattached to the casing plug.

[0028] The upper lock may comprise: a first mandrel recess provided in an outer surface of the mandrel; an upper locking element provided in a connector opening in the upper connector; and a running tool locking recess provided in an inner surface of the running tool above an inwardly protruding finger profile of the running tool. In the first upper lock state, the upper locking element may be in engagement with the running tool locking recess and out of engagement with the first mandrel recess. In the second upper lock state, the upper locking element may be in engagement with the first mandrel recess and out of engagement with the running tool locking recess.

[0029] In the third upper locking state, the upper locking element may be in engagement with the first mandrel recess and out of engagement with the running tool locking recess.

[0030] In the first upper lock state, relative longitudinal movement between the upper connector and the mandrel may be allowed as the upper locking element is out of engagement with the first mandrel recess. In addition, the running tool may be locked to the upper connector via the upper locking element in the first upper lock state.

[0031] In the second upper lock state, relative longitudinal movement between the upper connector and the mandrel may be prevented as the upper locking element is in engagement with the first mandrel recess. In addition, the running tool may be no longer locked to the upper connector via the upper locking element in the first upper lock state.

[0032] In the third upper lock state, relative longitudinal movement between the upper connector and the mandrel may be prevented as the upper locking element is in engagement with the first mandrel recess.

[0033] The upper lock may further comprise: an upper connector recess provided in an outer surface of the upper connector below the connector opening; and a finger sleeve provided outside of the upper connector below the upper locking element. The finger sleeve may have an upper end and a lower end. The finger sleeve may comprise: a finger having a lower end secured to the lower end of the finger sleeve and an upper free end. The finger sleeve may have a plurality of fingers.

[0034] In the first upper lock state, the upper free end of the finger may be out of engagement with the upper connector recess and in engagement with the running tool locking recess. In the second upper lock state, the upper free end of the finger may be in engagement with the upper connector recess and out of engagement with the running tool locking recess.

[0035] In the third upper lock state, the upper free end of the finger may be out of engagement with the upper connector recess and in engagement with the running tool locking recess. In the third upper lock state, therefore, the upper locking element is in engagement with the first mandrel recess, as in the second upper lock state, and the finger is out of engagement with the upper connector recess, as in the first upper lock state.

[0036] In the first upper lock state, relative longitudinal movement between the upper connector and the finger sleeve may be allowed as the upper free end of the finger is out of engagement with the upper connector recess. In addition, the running tool may be locked to the upper connector via the upper end of the finger.

[0037] In the second upper lock state, relative longitudinal movement between the upper connector and the finger sleeve may be prevented as the upper free end of the finger is in engagement with the upper connector recess. In addition, the running tool may be no longer locked to the upper connector via the upper end of the finger.

[0038] The upper locking element and the upper free end of the finger may be in engagement with the first running tool locking recess in the first upper locking state. In the third upper lock state, the upper free end of the finger may be in engagement with the second running tool locking recess while outwardly movement of the upper locking element is prevented. The outward movement of the upper locking element may be prevented by the running tool, because the upper locking element is not in engagement with the second running tool locking recess when the second running tool locking recess is in engagement with the finger.

[0039] The first running tool locking recess and the second running tool locking recess may be provided adjacent to each other in the inner surface of the running tool. The upper lock may be brought between the first upper lock state and the third upper lock state by rotation of the running tool relative to the upper connector.

[0040] The finger sleeve may comprise a protrusion protruding outwardly from the finger sleeve below the upper free end of the finger and circumferentially adjacent to the finger. The inwardly protruding finger profile of the lower end of the running tool may be provided longitudinally between the protrusion and the upper free end of the finger in the first upper lock state.

[0041] The upper end of the finger sleeve may be preventing the upper locking element from being brought out of engagement with the first mandrel recess in the second upper lock state.

[0042] In first upper lock state, relative longitudinal movement between the upper connector and the mandrel may be allowed an upper lock distance before the upper locking element becomes engaged in the first mandrel recess.

[0043] As the upper connector is secured to the upper housing section, relative longitudinal movement between the upper housing section and the mandrel may be allowed in first upper lock state the upper lock distance before the upper locking element becomes engaged in the first mandrel recess. The upper lock distance allowed between the upper housing section and the mandrel in the first upper lock state is equal to a second travel distance moved by the lower J-slot mechanism between its third and fourth positions.

[0044] The upper free end of the finger may comprise an outwardly protruding lug engageable by the inwardly protruding finger profile of the lower end of the running tool. The upper free end of the finger may comprise an inwardly protruding lug engageable by the upper connector recess.

[0045] The upper lock distance may be greater than a first travel distance traveled by the running tool and the upper housing section as the lower J-slot mechanism is moved between two end positions.

[0046] Due to the geometry of the running tool locking recess, the running tool may be prevented from being disconnected from the upper connector unless the upper locking element is in the first mandrel recess and the outwardly protruding lug is in the upper connector recess. This may prevent unwanted disconnection.

[0047] The upper J-slot mechanism may comprise: a profile provided on an inside of the running tool; and a pin protruding radially outwardly from the upper connector. The pin may be engageable within and movable along the profile.

[0048] The running tool may comprise an outer housing and a through bore provided through the outer housing. The through bore may be defined by an inner surface of the outer housing. The profile of the upper J-slot mechanism may be provided as a recess in the inner surface. The through bore may be longitudinally aligned with the through bore of the mandrel.

[0049] The running tool may be connected to a lower end of a drill pipe by means of a connection interface provided in an upper end of the outer housing. The drill pipe may comprise a coiled tubing system. The casing plug may be set in a well pipe. The well pipe may be a casing type of well pipe. Alternatively, the well pipe may be a production tubing.

[0050] The first set of positions may comprise a first position, a second position, a third position, and a fourth position. The first position, the second position and the fourth position of the upper J-slot mechanism may be end positions of the profile. The third position of the upper J-slot mechanism may be an open-ended position of the profile, allowing the profile of the running tool to be moved away from the pin of the upper connector. The end positions may be referred to as closed-ended positions to differentiate from the open-ended position.

[0051] An end position or closed-ended position is a position at which the J-slot mechanism has a defined end point for relative longitudinal movement between the pin and profile. The profile may define end points for the pin at which further longitudinal movement of the pin within or relative to the profile is not possible.

[0052] An open-ended position is a position at which the pin is not at a defined end point of the profile of the J-slot mechanism. In other words, an open-ended position is a position at which further longitudinal movement of the pin relative to the profile is possible. In some cases, when in an open-ended position, the movement of the pin relative to the profile may be limited by a stop or end point elsewhere within the mechanism. In other cases, an open-ended position may allow unlimited movement of the pin relative to the profile.

[0053] The upper J-slot mechanism may move sequentially from the first position to the fourth position and then back to the first position. The upper J-slot mechanism may be defined with a first travel distance representing the relative longitudinal travel distance for the pin between two end positions of the first set of positions.

[0054] Where the first set of positions comprises four positions, the first travel distance may be between the first position and the second position, or between the fourth position and the first position.

[0055] The term “longitudinal” may refer to a direction being perpendicular to a longitudinal central axis of the casing plug assembly.

[0056] The upper J-slot mechanism may be defined with a second travel distance representing a relative longitudinal travel distance for the pin between an open-ended position of the first set of positions and an end position of the first set of positions.

[0057] Where the first set of positions comprises four positions, the first travel distance may be between the second position and the third position.

[0058] The first travel distance of the upper J-slot mechanism may be shorter than the second travel distance of the upper J-slot mechanism. The second travel distance of the upper J-slot mechanism may represent the distance between the running tool and the casing plug when the running tool has been disconnected from the casing plug.

[0059] The upper J-slot mechanism may be moved between the positions of the first set of positions using longitudinal movement of the running tool by the operator. The running tool and upper connector may rotate relative to one another due to said longitudinal movement.

[0060] The locking mechanism may comprise a lower lock having a second lower lock state, in which the upper housing section is released from the mandrel, and a first lower lock state, in which the upper housing section is locked to the mandrel.

[0061] The lower lock may therefore enable relative movement between the upper housing section and the mandrel in the second lower lock state and prevents relative movement between the upper housing section and the mandrel in the first lower lock state. As the lower J-slot mechanism is formed between the upper housing section and the mandrel, preventing relative movement of the upper housing section and the mandrel in the first lower lock state may enable the locking mechanism to prevent a combination of positions between the upper J-slot mechanism and the lower J-slot mechanism by locking the lower J-slot mechanism in a particular position.

[0062] The valve device may be above the lower lock. The sealing device and anchoring device may be below the lower lock.

[0063] The lower lock may comprise: a lower locking element provided in an opening in the upper housing section; a second mandrel recess provided in an outer surface of the mandrel; and a lower housing recess provided in an inner surface of the lower housing section. In the second lower lock state, the lower locking element may be out of engagement with the second mandrel recess and in engagement with the lower housing recess. In the first lower lock state, the lower locking element may be in engagement with the second mandrel recess and out of engagement with the lower housing recess. The second mandrel recess may be provided below the first mandrel recess.

[0064] In the second lower lock state, relative longitudinal movement between the mandrel and the upper housing section may be allowed a lower lock distance. The lower lock distance may be equal to the second travel distance of the lower J-slot mechanism. Moreover, a relative longitudinal movement between the upper housing section and the lower housing section is also allowed due to the longitudinal extent of the lower housing recess. Hence, when in the second lower lock state, the lower J-slot mechanism may not be locked, as the pin are allowed to move along the profile.

[0065] In the second lower lock state, relative longitudinal movement between the mandrel and the upper housing section may be prevented. Here, the lower J-slot mechanism may be locked, as the pin will not be able to move along the profile due to the mandrel being longitudinally locked to the upper housing section.

[0066] The opening may be provided in the lower end of the upper housing section.

[0067] The second mandrel recess may be provided below and adjacent to the sleeve of the lower J-slot mechanism.

[0068] The lower J-slot mechanism may comprise: a sleeve provided radially outside of the mandrel and radially inside of the upper housing section; a profile provided on an outside of the sleeve; and a pin protruding inwardly from the upper housing section; wherein the pin is engageable within and movable along the profile.

[0069] The sleeve may be rotationally movable relative to the mandrel. The sleeve may be rotationally movable relative to the upper housing section. The sleeve may be longitudinally movable relative to upper housing section.

[0070] The profile may be provided as a recess on an outwardly facing surface of the sleeve.

[0071] The second set of positions may comprise a first position, a second position, a third position, and a fourth position. The first position, the second position and the third position of the lower J-slot mechanism may be end positions of the profile. The fourth position of the lower J-slot mechanism may be an open-ended position. Alternatively, also the fourth position may be an end position of the profile. The second set of positions may have an additional fifth position and sixth position between the fourth position and the first position. The lower J-slot mechanism may move sequentially from the first position to the fourth position and then back to the first position. Alternatively, the lower J-slot mechanism may move sequentially from the first position to the sixth position and then back to the first position.

[0072] The lower J-slot mechanism may be defined with a first travel distance representing the relative longitudinal travel distance for the pin between two end positions of the second set of positions.

[0073] Where the second set of positions comprises four positions, the first travel distance may represent the relative longitudinal travel distance for the pin between the first position and the second position or between the second position and the third position.

[0074] The lower J-slot mechanism may be defined with a second travel distance representing the relative longitudinal travel distance for the pin between an end position and an open-ended position of the second set of positions.

[0075] Where the second set of positions comprises four positions, the second travel distance may represent the relative longitudinal travel distance for the pin between the third position and the fourth position.

[0076] The first travel distance of the lower J-slot mechanism may be shorter than the second travel distance of the lower J-slot mechanism.

[0077] The casing plug may further comprise: a drag block device provided radially outside of the mandrel; and a ratchet device for selectively locking at least part of the lower housing section to the mandrel.

[0078] The ratchet device may have a first ratchet state, in which relative longitudinal movement between at least part of the lower housing section and the mandrel is prevented, and a second ratchet state, in which relative longitudinal movement between at least part of the lower housing section and the mandrel is permitted, if a sufficient friction force is overcome. The drag block device may be connected to the lower housing section and may provide said friction force by interacting with the well pipe. The ratchet device can be moved between the first ratchet state and the second ratchet state by rotation of the running tool, which in turn may cause rotation of the housing relative to the mandrel. Such rotation may result in a ratchet ring of the ratchet device moving to a different portion of the mandrel where the force required to move the mandrel relative to the lower housing section is less.

[0079] Longitudinal movement of the mandrel relative to the lower housing section may result in movement of the ratchet device to a third ratchet state. In the third ratchet state, rotation of the mandrel relative to the housing may move the ratchet device back to the first ratchet state. The rotation to move the ratchet device between ratchet states may be clockwise rotation.

[0080] The ratchet device and drag block device may be below the lower lock, and may be below the sealing device and the anchoring device.

[0081] The casing plug may comprise one or more spline connections. A first spline connection may be provided between the upper housing section and the mandrel to rotationally lock the upper housing section and the mandrel. A second spline connection may be provided between parts of the lower housing section to rotationally lock those parts. The upper housing section and mandrel, or parts of the lower housing section may be rotationally locked using other means in other examples.

[0082] The lower housing section may comprise a first part, a second part, and a third part. The first part and the second part may be moveable longitudinally relative to one another. A restriction may prevent at relative longitudinal movement of the first and second parts beyond a particular distance in a particular direction. The restriction may comprise a nut. The sealing element may be provided between the first and second parts, and relative longitudinal movement of the first and second parts may bring the sealing element from the radially retracted state to the radially expanded state. The second and third parts may be moveable longitudinally relative to one another. The second and third parts may be rotationally locked, preferably using the second spline connection described above. The anchoring device may be provided between the second and third parts. Relative longitudinal movement of the second and third parts may bring the anchoring device from the radially retracted state to the radially expanded state.

[0083] The operational states may comprise: a first state in which the casing plug assembly is movable up or down within the well; a second state in which the casing plug is set in the well; a third state in which the setting of the casing plug is verified; a fourth state in which the valve device is closed; a fifth state in which the closing of the valve device is verified; a sixth state in which the running tool is disconnected from the casing plug; a seventh state in which the running tool is re-connected to the casing plug; an eighth state in which the valve device is opened.

[0084] The valve device may comprise a ball body with a through bore pivotably engaged within the mandrel. The through bore may be aligned with the bore in the open valve state to allow fluid flow through the bore and out of alignment with the bore in the closed valve state to prevent fluid flow through the bore. The ball body may comprise a profile engaged by a pin secured to the upper housing section. The profile may comprise a first section and a second section. The pin may be allowed to move within the first section without causing the ball body to pivot to the closed valve state. The ball body may be pivoted by the pin when the pin is moved within the second section.

[0085] The second section may be oriented at an angle of ca 30° - 60°, preferably ca 45°, with respect to the first section.

[0086] The first section may have a pin travel length. The pin travel length may be equal to or greater than the longitudinal first travel distance between the first position and the second position of the lower J-slot mechanism, so that the ball body does not rotate as the lower J-slot moves between the first and second position. In some examples, the pin travel length of the first section may be smaller than the longitudinal first travel distance between the first position and the second position of the lower J-slot mechanism. In such a circumstance, a pin travel length of the second section may be greater than the longitudinal first travel distance, so that movement of the lower J- slot mechanism between the first position and the second position is insufficient to fully rotate the ball body, meaning that the bore is not closed during such a movement.

[0087] The upper J-slot mechanism may comprise more than one pin. The upper J-slot mechanism may comprise 2-8 pins, preferably 3-6 pins, even more preferably 3 pins. The lower J-slot mechanism may comprise more than one pin. The lower J-slot mechanism may comprise more pins than the upper J-slot mechanism. The lower J- slot mechanism may comprise 4-24 pins, preferably 8-20 pins, even more preferably 10-12 pins.

[0088] When operating the upper J-slot mechanism, the upper connector is typically stationary in the rotational direction, while the running tool is rotating or stationary in the clockwise direction. Hence, counterclockwise rotation of the drilling string and the running tool connected to the running tool is avoided.

[0089] When operating the lower J-slot mechanism, the upper housing section is typically stationary in the rotational direction, while the sleeve is rotating in the counterclockwise direction.

[0090] According to a second aspect, there is provided a lock for selectively locking a housing and a mandrel of a casing plug. The lock may have some or all of the features of the upper lock described above.

[0091] The following definitions and terms are used throughout this specification. A J-slot mechanism is a type of mechanism commonly used in the setting and unsetting of downhole tools and equipment such as packers. The J-slot mechanism typically comprises a sleeve with a profile provided circumferentially in the outwardly facing surface or in the inwardly facing surface of the sleeve and one or more pins engaged within the profile. Most conventional downhole tools operate by upward or downward movement, rotation, or a combination of both. The profile creates a track for an actuating cam or pin that combines rotation and up or down movement to provide a simple yet reliable means of tool activation.

[0092] The terms “upper”, “above”, “below” and “lower” are used herein to define parts of the well tool, when the well tool is used in a well. “Upper” and “above” refer to a position relatively closer to the well opening and “below” and “lower” refer to a position relatively further away from the well opening. These terms apply both when the well has a vertical and horizontal orientation.

[0093] As used herein, the terms “radially retracted state / position” and “run state / position” are used interchangeably for the state / position in which the well tool is lowered to a desired location in the well. The terms “radially expanded state / position” and “set state / position” are used interchangeably for the state / position in which the well tool is engaged with the inner surface of the well at the desired location in the well.

[0094] As used herein, the term “anchoring device” refers to a part of the well tool which is radially expanded to be engaged with the inner surface of the well at the desired location in the well. The anchoring device may comprise a serrated surface which prevents the well tool from moving longitudinally within the well when engaged with the inner surface of the well.

[0095] As used herein, the term “sealing device” refers to a part of the well tool which is radially expanded into contact with the inner surface of the well at the desired location of the well. The function of the sealing device is to prevent or reduce longitudinal fluid flow at the desired location in the well, i.e. to prevent or reduce fluid from flowing between a location above the well tool and a location below the well tool.

[0096] It is commonly known that the anchoring device and / or sealing device are only capable of performing their function in their radially expanded state in the well. Moreover, it should be noted that a well tool is rated to a pressure level or pressure interval and / or a temperature level or temperature interval.

[0097] LIST OF DRAWINGS

[0098] Fig. la shows a cross-sectional view of a casing plug assembly in a first operational state corresponding to the run state;

[0099] Fig. lb illustrates the positions of the upper J-slot mechanism and the lower J-slot mechanism schematically, wherein the circle represents the pin of the respective J- slot mechanism, the solid line represents the profile in which the pin moves, and the dashed line represent the movement of the pin within the profile;

[0100] Fig. 2 shows a top view of the ball element of the valve device;

[0101] Fig. 3 shows a side view of the upper J-slot mechanism; Fig. 4a shows a side view of the lower J-slot mechanism;

[0102] Fig. 4b shows a perspective view of the lower J-slot mechanism;

[0103] Fig. 5a shows a perspective view of an upper lock in a first upper lock state;

[0104] Fig. 5b shows a perspective view of the upper lock in a second upper lock state;

[0105] Fig. 6a shows a cross-sectional view of the upper lock in the first upper lock state;

[0106] Fig. 6b shows a cross-sectional view of the upper lock in the second upper lock state;

[0107] Fig. 6c shows a cross-sectional view of the upper lock in a third upper lock state;

[0108] Fig. 7 shows a perspective view of the lower end of the running tool;

[0109] Fig. 8a shows a perspective view of a lower lock in a first lower lock state;

[0110] Fig. 8b shows a perspective view of the lower lock in a second lower lock state;

[0111] Fig. 9a shows a cross-sectional view of the lower lock in the first lower lock state;

[0112] Fig. 9b shows a cross-sectional view of the lower lock in the second lower lock state;

[0113] Fig. 10a shows a cross-sectional view of an upper section of the casing plug assembly in a first operational state;

[0114] Fig. 10b illustrates the positions of the upper J-slot mechanism and the lower J-slot mechanism in the first operational state;

[0115] Fig. I la shows a cross-sectional view of the upper section of the casing plug assembly in a second operational state;

[0116] Fig. 11b illustrates the positions of the upper J-slot mechanism and the lower J-slot mechanism in the second operational state;

[0117] Fig. 11c shows a cross-sectional view of the casing plug assembly in the second operational state;

[0118] Fig. 12a shows a cross-sectional view of the upper section of the casing plug assembly in a third operational state;

[0119] Fig. 12b illustrates the positions of the upper J-slot mechanism and the lower J-slot mechanism in the third operational state;

[0120] Fig. 13a shows a cross-sectional view of the upper section of the casing plug assembly in a fourth operational state;

[0121] Fig. 13b illustrates the positions of the upper J-slot mechanism and the lower J-slot mechanism in the fourth operational state; Fig. 14a shows a cross-sectional view of the upper section of the casing plug assembly in a fifth operational state;

[0122] Fig. 14b illustrates the positions of the upper J-slot mechanism and the lower J-slot mechanism in the fifth operational state;

[0123] Fig. 15a shows a cross-sectional view of the upper section of the casing plug assembly in a sixth operational state;

[0124] Fig. 15b illustrates the positions of the upper J-slot mechanism and the lower J-slot mechanism in the sixth operational state;

[0125] Fig. 16a shows a cross-sectional view of the upper section of the casing plug assembly in a seventh operational state;

[0126] Fig. 16b illustrates the positions of the upper J-slot mechanism and the lower J-slot mechanism in the seventh operational state;

[0127] Fig. 17a shows a cross-sectional view of the upper section of the casing plug assembly in an eighth operational state;

[0128] Fig. 17b illustrates the positions of the upper J-slot mechanism and the lower J-slot mechanism in the eighth operational state;

[0129] Fig. 18 shows a side view of the upper connector when the casing plug assembly is in the first operational state;

[0130] Fig. 19 shows a side view of the upper connector when the casing plug assembly is in the sixth operational state

[0131] Fig. 20 shows a side view of an alternative embodiment of the lower J-slot mechanism.

[0132] DETAILED DESCRIPTION

[0133] Fig. la shows a casing plug assembly 100 in a first operational state SI. The casing assembly 100 is shown in its first operational state SI in Fig. 1, but has and is operable between a plurality of operational states, which will be described later in relation to Figs. 10a to 17b.

[0134] Focusing initially on Fig. la, the casing plug assembly 100 comprises a casing plug 1 and a running tool 10. The casing plug 1 is a resettable casing plug, and so can be retrieved and reset multiple times.

[0135] The running tool 10 has an outer housing 11 with a bore 13 defined by its inner surface 12. The outer housing 11 defines a connection interface I la for connecting to a drill string (not shown). The running tool 10 is connected to the casing plug 1 in the first operational state SI, and is releasably connected to the casing plug 1, so that the casing plug 1 can be disconnected from the running tool 10 and reconnected again to allow setting and retrieval of the casing plug 1.

[0136] The casing plug 1 has an upper section 1US and a lower section ILS. The running tool 10 connects to the casing plug 1 at the upper section 1US. The lower section ILS includes features for engaging the well pipe, in use.

[0137] The casing plug 1 has a mandrel 2 with a through bore 3. The through bore 3 extends along a longitudinal axis LCA of the casing plug 1. The mandrel 2 extends between the upper section 1US and the lower section ILS of the casing plug 1.

[0138] The casing plug 1 also has a housing 4 that is provided radially outside part of the mandrel 2. The housing 4 is moveable longitudinally relative to the mandrel 2. The housing 4 has an upper housing section 4a and a lower housing section 4b. The upper housing section 4a is provided substantially in the upper section 1US of the casing plug 1, while the lower housing section 4b is provided substantially in the lower section ILS of the casing plug 1. The upper housing section 4a is rotationally locked to the mandrel 2 by a first spline connection 41.

[0139] Within the upper section 1US of the casing plug 1, an upper connector 9 is provided at an upper end of the upper housing section 4a. The upper connector 9 surrounds at least an upper portion of the mandrel 2. The upper connector 9 is provided to releasably connect the casing plug 1 to the running tool 10.

[0140] The casing plug 1 also includes a valve device 8 in its upper section 1US. The valve device 8 allows for selective closure of the through bore 3. The valve 8 is moveable between an open valve state, as shown in Fig. 1 and a closed valve state. In the open valve state, fluid flow through the through bore 3, at least across the valve device 8, is allowed by the valve device 8. In the closed valve state, fluid flow through the through bore 3, at least across the valve device 8, is prevented by the valve device 8. The valve device 8 can be operated between the open valve state and the closed valve state by relative movement between the upper housing section 4a and the mandrel 2.

[0141] Turning briefly to Fig. 2, a view of the valve device 8 is shown. The valve device 8 comprises comprise a ball body 180 with a through bore. The through-bore is not visible in Fig. 2. When mounted as part of the casing plug 1, the ball body 180 is pivotably engaged within the mandrel 2 about pivot 185. The ball body 180 is rotated in use so that the through bore is aligned with the bore 3 of the mandrel 2, thereby achieving the open valve state to allow fluid flow through the bore 3, or so that the through bore is out of alignment with the bore 3, to achieve the closed valve state to prevent fluid flow through the bore 3. The ball body 180 also comprises a profile 182. The profile 182 has a first section 182a and a second section 182b. The second section 182b is oriented at an angle al 82, which in this example is 45 degrees, with respect to the first section 182a. A pin 183 secured to the upper housing section 4a engages the profile 182 and can move along the first section 182a and the second section 182b and can move between the first section 182a and the second section 182b. Movement of the pin 183 within the first section 182a does not cause any movement of the ball body 180. Movement of the pin 183 to the second section 182b begins to pivot the ball body 180 and further movement along the second section 182b rotates the ball body 180. Movement of the pin to the end of the second section 182b fully rotates the ball body 180 to the closed valve state. The first section 182a has a pin travel length DI 82.

[0142] Returning to Fig. la, within the lower section ILS, the lower housing section 4b is moveable rotationally and longitudinally relative to the upper housing section 4a, and is formed of a first part 4b 1, which overlaps the upper housing section 4a, a second part 4b2, and a third part 4b3. The first part 4b 1, second part 4b2, and third part 4b3 are also moveable relative to one another. The first part 4b 1 is moveable longitudinally and rotationally relative to the second part 4b2. The second part 4b2 prevents longitudinal movement of the first part 4b 1 relative to it beyond a certain point by virtue of a nut 42a connected to the second part 4b2 and a flange 42b of the first part 4b 1. The nut 42a interferes with the flange 42b to form a barrier to further relative longitudinal movement between the first part 4b 1 and the second part 4b2. The second part 4b2 is moveable longitudinally relative to the third part 4b3. The second part 4b2 and third part 4b3 are rotationally locked by a second spline connection 43.

[0143] The casing plug 1 also includes, in its lower section ILS, a sealing device 7, for selectively sealing against a well pipe so as to prevent longitudinal fluid flow between the housing 4 and the well pipe past the sealing device 7. The sealing device 7 is provided radially outside and circumferentially around the mandrel 2, and, in the example of Fig. 1, radially outside and circumferentially around the second part 4b2 of the lower housing section 4b. The sealing device 7 comprises an elastomeric sealing element 17 that, when compressed, radially expands to be in contact with the well pipe. Accordingly, the sealing device 7 is movable between a radially retracted state and a radially expanded state. The sealing device 7 is compressed between the first part 4b 1 and the second part 4b2 of the lower housing section 4b, when the first part 4b 1 and second part 4b2 move relative to and towards one another.

[0144] Further down the casing plug 1, also within the lower section ILS, is an anchoring device 6 for anchoring the casing plug 1 against the well pipe. The anchoring device 6 is provided radially outside of the mandrel 2. The anchoring device 6 comprises a plurality of slips elements that, in the example of Fig. 1, extend between the second part 4b2 and the third part 4b3 of the lower housing section 4b. Movement of the second part 4b2 and the third part 4b3 of the lower housing section 4b relative to one another will move the slips elements radially with respect to the mandrel 2, so that they can engage the well pipe in a radially expanded state. Accordingly, the anchoring device 6 can be said to be movable between a radially retracted state and a radially expanded state.

[0145] Further along the lower section ILS of the casing plug 1, radially outside of the mandrel 2 and in part of the third part 4b3 of the lower housing section 4b, the casing plug 1 includes a ratchet device 51. The ratchet device 51 is for selectively locking at least the third part 4b3 of the lower housing section 4b to the mandrel 2. When the ratchet device 51 locks the third part 4b3 to the mandrel 2, relative longitudinal movement between the third part 4b3 and the mandrel 2 is prevented. The ratchet device 51 achieves this by having threaded grooves or hatching that interlock with corresponding grooves on the mandrel 2. Different areas of grooves on the mandrel 2 require different amounts of force to move the ratchet device 51 past them.

[0146] The ratchet device 51 is moveable between three ratchet states: a first ratchet state, a second ratchet state, and a third ratchet state. In the first and third ratchet states, the ratchet device 51 locks the third part 4b3 and the mandrel 2 to prevent relative longitudinal movement. This is achieved by requiring a high force to dislodge the ratchet device 51 from the grooves of the mandrel 2. In the second ratchet state, the third part 4b3 and the mandrel 2 are unlocked and relative longitudinal movement is permitted. The force required to move the ratchet device 51 is therefore lower in this second ratchet state. The ratchet device 51 can be moved from the first ratchet state to the second ratchet state and from the third ratchet state to the second ratchet state by rotation of the mandrel 2 relative to the ratchet device 51 (and therefore the lower housing section 4b). The ratchet device 51 is moved from the second ratchet state to the third ratchet state and from the second state to the first state by longitudinal movement.

[0147] Below the ratchet device 51, the casing plug 1 also includes in its lower section ILS, a drag block device 5, comprising a plurality of drag blocks, provided radially outside of the mandrel 2 and connected to the third part 4b3 of the lower housing section 4b. The drag block device 5 is for providing a frictional force against the well pipe. The drag block device 5 is configured to prevent movement of the casing plug 1 relative to the well pipe. The drag block device 5 may prevent rotation of third part 4b3 of the lower housing section 4b of the casing plug 1 and / or may prevent longitudinal movement of the third part 4b3. As a result, the third part 4b3 can be held stationary in the well pipe by the drag block device 5 as other parts of the casing plug 1 are moved relative to it. The ratchet device 51 and drag block device 5 interact to enable longitudinal movement of the casing plug 1 and casing assembly 100, such that when the ratchet device 51 is in the first ratchet state, the drag block device 5 has an insufficient frictional force with the well pipe to hold the third part 4b3 relatively stationary and when the ratchet device 51 is in the second ratchet state, the drag block device 5 has a sufficient frictional force with the well pipe to hold the third part 4b3 stationary relative to the mandrel 2 and other parts of the casing plug 1.

[0148] The ratchet device 51, anchoring device 6, sealing device 7, and valve device 8 can be operated, i.e. moved between their different states, by moving different parts of the casing plug assembly 100 relative to one another. Operation of the ratchet device 51, anchoring device 6, sealing device 7, and valve device 8 can move the casing plug assembly 100 between a plurality of operational states.

[0149] To achieve movement of the parts of the casing plug assembly 100 relative to one another in a controlled and verifiable way, the casing plug assembly 100 includes an upper J-slot mechanism 60, a lower J-slot mechanism 80, and a locking mechanism 65. The upper J-slot mechanism 60 and the lower J-slot mechanism 80 each have a set of positions that they can be placed into. Combinations of the positions can be used to change the relative longitudinal positions between the running tool 10, upper housing section 4a, and mandrel 2, in order to operate the ratchet device 51, anchoring device 6, and sealing device 7, and valve device 8. The locking mechanism 65, which comprises an upper lock 70 and a lower lock 90, prevents at least one of the combinations of positions, so that the number of possible combinations is equal to the number of desired operational states of the casing plug assembly 100.

[0150] The upper J-slot mechanism

[0151] A portion of the upper J-slot mechanism is shown in Fig. lb, while a side view of the upper J-slot mechanism can be seen in Fig. 3. The upper J-slot mechanism 60 is formed between the running tool 10 and the upper connector 9 and controls relative movement between the upper connector 9 and the running tool 10. An interior part of the running tool 10 is shown in Fig. 3 to aid understanding. The parts of the running tool 10 shown are connected together by the housing 11, which is not shown here. Specifically, as can be seen in Fig. lb and Fig. 3, the running tool 10 includes a profile 62 that receives pins 63 formed in and protruding radially outwardly from the upper connector 9 in a plurality of one of a first set of positions 60P1 - 60P4.

[0152] Turning briefly to Fig. 3, the profile 62 is provided on an inside of the running tool 10, although only the profile 62 is shown here for clarity, and a plurality of pins 63 protruding radially outwardly from the upper connector 9. The pins 63 engage within and moves along the profile 62.

[0153] The upper J-slot mechanism 60 has a first set of positions, comprising the first position 60P1, the second position 60P2, the third position 60P3, and the fourth position 60P4. The part of the profile 82 defining the first to fourth positions 60P1 to 60P4 of the first set of positions, as shown in Fig. lb, is repeated around the circumference of the profile 62. The upper J-slot mechanism 60 defines a first travel distance D62a, which is the relative longitudinal travel distance for a pin 63 between two end positions, i.e. the first position 60P1 and the second position 60P2 of the first set of positions. The upper J-slot mechanism 60 also defines a second travel distance D62b, which is the relative longitudinal travel distance for a pin 63 between an open-ended position of the first set of positions and an end position of the first set of positions, i.e. between the second position 60P2 and the third position 60P3. The second travel distance D62b is greater than the first travel distance D62a.

[0154] The lower J-slot mechanism

[0155] A portion of the lower J-slot mechanism 80 is shown in Fig. lb, while a side view and a perspective view of the lower J-slot mechanism 80 are shown in Figs. 4a and 4b respectively. The lower J-slot mechanism 80 is formed between the upper housing section 4a and the mandrel 2. Specifically, the upper housing section 4a has a plurality of pins 83 that face radially inwardly. The pins 83 are received in a profile 82 formed by a sleeve 81 surrounding the mandrel 2. The sleeve 81 is longitudinally locked to the mandrel 2.

[0156] The lower J-slot mechanism 80 has a second set of positions, comprising the first position 80P1, the second position 80P2, the third position 80P3, and the fourth position 80P4. The part of the profile 82 defining the first to fourth positions 80P1 to 80P4 of the second set of positions, as shown in Fig. lb, is repeated around the circumference of the profile 82. Movement from the fourth position 80P4 to the first position 80P1 is a movement from one part of the profile 82 to a next part of the profile 82.

[0157] The lower J-slot mechanism 80 defines a first travel distance D82a, which is the relative longitudinal travel distance for a pin 83 between two end positions, i.e. the first position 80P1 and the second position 80P2 of the second set of positions. The lower J-slot mechanism 80 also defines a second travel distance D82b, which is the relative longitudinal travel distance for a pin 83 between an open-ended position of the second set of positions and an end position of the second set of positions, i.e. between the third position 80P3 and the fourth position 80P4. The second travel distance D82b is greater than the first travel distance D82a.

[0158] The pin travel distance DI 82 of the valve device 8 is less than the first travel distance D82a, although in other examples it may be equal to D82a.

[0159] The locking mechanism

[0160] Returning to Fig. la, the casing plug assembly 100 has eight operational states. The upper J-slot mechanism 60 has a first set of four positions, and the lower J-slot mechanism 80 has a second set of four positions. The locking mechanism holds the upper J-slot mechanism 60 in one of its positions while the lower J-slot mechanism 80 moves between its four positions. The locking mechanism subsequently holds the lower J-slot mechanism 80 in one of its four positions while the upper J-slot mechanism 60 moves between its four positions, so that eight different combinations of positions are achieved, and therefore eight operational states can be achieved.

[0161] The locking mechanism has an upper lock 70 and a lower lock 90. The upper lock 70 is operable to selectively lock the running tool 10 to the upper connector 9 or the upper connector 9 to the mandrel 2. The lower lock 90 is operable to selectively lock the mandrel 2 to the upper housing section 4a.

[0162] The upper lock

[0163] Figs. 5a and 5b, 6a to 6c, and 7 show parts of the upper lock 70 in more detail than is visible in Fig. la. Figs. 6a to 6c show the operation of the upper lock 70 through its upper lock states, with a first upper lock state 70S1 being shown in Fig. 6a, a second upper lock state 70S2 being shown in Fig. 6b, and a third upper lock state 70S3 being shown in Fig. 6c. Figs. 5a and 5b show the parts of the upper lock provided on the casing plug 1 as found in the first and second upper lock states 70S1, 70S2 respectively, while Fig. 7 shows the parts of the upper lock provided on the running tool 10.

[0164] The upper lock 70 is formed across the upper connector 9 and the upper housing portion 4a of the housing 4 of the casing plug 1 as well as by the mandrel 2 of the casing plug 1 and the running tool 10, in at least the first and third upper lock states 70S1, 70S3.

[0165] To form the upper lock 70, the upper connector 9 has a connector opening 9o. The connector opening 9o extends only part of the way around the upper connector 9. Within the connector opening 9o, there is provided an upper locking element 74. The upper locking element 74 is movable radially within the connector opening 9o, and is used to selectively lock the upper connector 9 to the running tool 10 or the mandrel 2, by interacting with separate recesses. The upper locking element 74 is shaped to interact with the different recesses, as well as other elements of the upper lock 70.

[0166] The mandrel 2 has a first mandrel recess 73a provided in an outer surface of the mandrel 2. The outer surface of the mandrel 2 is the surface facing, and in contact with, the upper connector 9. The running tool 10 has a running tool locking recess 73c provided in an inner surface of the running tool 10. The inner surface of the running tool 10 is a surface arranged to face, and be in contact with, the upper connector 9 when the running tool 10 is connected to the casing plug 1. The running tool 10 has an inwardly protruding finger profile 15, and the running tool locking recess 73c is longitudinally above the inwardly protruding finger profile 15. The running tool locking recess 73c comprises two parts, which can be described as a first running tool locking recess 73cl, shown in Figs. 6a and 7, and a second running tool locking recess 73c2, shown in Figs. 6c and 7. The first running tool locking recess 73cl has a longitudinal extent that is longer - it extends further, longitudinally, along the running tool 10 - than the second running tool locking recess 73c2. The first running tool locking recess 73 cl and the second running tool locking recess 73 c2 are at different rotational positions around the running tool 10.

[0167] The recesses described herein, such as the running tool locking recess 73 c and the first mandrel recess 73a, have tapered edges. The tapered edges allow interaction with corresponding tapered edges of the upper locking element 74, as well as sliding of the upper locking element 74 into and out of the recess to allow the upper locking element 74 to be removed from the recess.

[0168] The upper lock 70 further includes a finger sleeve 71 having a plurality of fingers 72. Only a single finger 72 is shown in Figs. 6a to 6c. The fingers 72 and finger sleeve 71 are provided to perform different functions in each of the upper lock states, as will be described below.

[0169] The finger sleeve 71 is provided outside of the upper connector 9 below the upper locking element 74. The finger sleeve 71 is moveable relative to the upper connector 9. The finger sleeve 71 has an upper end 71U and a lower end 71L. The upper end 71U is closer to the upper locking element 74 than the lower end 7 IL.

[0170] The fingers 72 each have a lower end 72L secured to the lower end 7 IL of the finger sleeve 71 and an upper end 72U, which is a free end and may therefore be referred to as the upper free end 72U. By “free end” it is meant that the end is unattached or unsecured to the finger sleeve 71 or another element of the upper lock 70. The upper free end 72U is therefore able to move radially relative to the finger sleeve 71. The finger sleeve 71 has an opening 75 for each finger 72, within which each finger 72 sits and which permits movement of the finger 72 radially above and below the finger sleeve 71.

[0171] The finger sleeve 71 comprises a plurality of protrusions 77 protruding outwardly from the finger sleeve 71 below the upper free end 72U of the fingers 72. The protrusions 77 are provided between and circumferentially adjacent to the fingers 72.

[0172] The upper free end 72U of each finger 72 comprises an outwardly protruding lug 72a and an inwardly protruding lug 72b. The protrusions 77 and the outwardly protruding lug 72a are configured to receive the inwardly protruding finger profile 15 longitudinally between them. The inwardly protruding lug 72b is configured to engage with an upper connector recess 73b. In the first upper lock state 70S1, shown in Figs. 5a and 6a, the upper locking element 74 is in engagement with the first running tool locking recess 73cl and out of engagement with the first mandrel recess 73a. Accordingly, the upper connector 9 is locked to the running tool 10, but is released from, and can therefore move relative to, the mandrel 2.

[0173] In the first upper lock state 70S1, the protrusions 77 of the finger sleeve 71 and the outwardly protruding lugs 72a of the fingers 72 are engaged with the inwardly protruding finger profile 15 of the lower end of the running tool 10. The upper end 71U of one of the finger sleeves 71 abuts the upper locking element 74 and is therefore prevented from moving relative to the upper locking element 74, and therefore the upper connector 9 and running tool 10.

[0174] To move to the second upper lock state 70S2, the upper connector 9 is moved an upper lock distance D71 relative to the mandrel 2, so that the upper locking element 74 comes into engagement with the first mandrel recess 73 a. When the upper locking element 74 comes into engagement with the first mandrel recess 73 a, the upper locking element 74 moves downwardly into the recess 73a and comes out of engagement with the first running tool locking recess 73cl. When the upper locking element 74 comes into engagement with the first mandrel recess 73 a, the upper locking element 74, by virtue of its shape, also releases the finger sleeve 71, allowing the finger sleeve to slide over the upper locking element 74. The finger sleeve 71 can therefore be moved towards the upper locking element 74 so that the upper end 71U of the finger sleeve 71 covers part of the upper locking element 74 and so that the inwardly protruding lug 72b comes into engagement with the upper connector recess 73b. In doing so, the finger 72 moves downwardly, taking the outwardly protruding lug 72a out of engagement with the running tool 10, so that the running tool 10 can be moved separately from the upper connector 9.

[0175] In the second upper lock state 70S2, therefore, as shown in Figs 5b and 6b, the upper locking element 74 is in engagement with the first mandrel recess 73a and out of engagement with the running tool locking recess 73c. Accordingly, the upper connector 9 is locked to the mandrel 2, but is released from, and can therefore move relative to, the running tool 10.

[0176] The upper locking element 74 is prevented from moving out of engagement with the mandrel 2 by the finger sleeve 71. The finger sleeve 71 is maintained in position by the finger 72 being in engagement with the upper connector recess 73b of the upper connector.

[0177] To reconnect the running tool 10, the running tool 10 is moved along the upper connector 9 into contact with the protrusions 77, with the second running tool locking recess 73c2 facing the upper locking element 74. The inwardly protruding finger profile 15 engages with the protrusions 77 and pushes the finger sleeve 71 downwardly, which removes the finger 72 from the upper connector recess 73b. The finger sleeve 71 therefore moves away from engagement with the upper locking element 74. However, the upper locking element 74 is prevented from moving because the second running tool locking recess 73c2 is shorter than the first running tool locking recess 73cl and so is not in engagement with the upper locking element 74.

[0178] When the running tool 10 is reconnected to the finger sleeve 71 and fingers 72 but the upper locking element 74 is prevented from being removed from the first mandrel recess 73a, the upper lock 70 is in the third upper lock state 70S3. Rotation of the running tool 10 to bring the first running tool locking recess 73 cl into engagement with the upper locking element 74 allows the upper locking element 74 to move out of engagement with the first mandrel recess 73a, so that the upper lock 70 can be returned to the upper lock state 70S1 by moving the running tool 10 upwardly.

[0179] The lower lock

[0180] Figs. 8a and 8b show part of the lower lock 90 between the upper housing section 4a and the mandrel 2. Figs. 9a and 9b show a view of the lower lock 90. Figs. 8a and 9a show the lower lock 90 in a first lower lock state 90S1. Figs. 8b and 9b show the lower lock 90 in a second lower lock state 90S2.

[0181] The lower lock 90 is formed between the upper housing section 4a, the lower housing section 4b, and the mandrel 2. The lower lock 90 comprises a lower locking element 94. The lower locking element 94 is provided in an opening 4o in a lower end of the upper housing section 4a and can move radially inward or outward within the opening 4o.

[0182] A second mandrel recess 93a is provided in an outer surface of the mandrel 2. The second mandrel recess 93a is below and adjacent to the sleeve 81 of the lower J-slot mechanism 80.

[0183] A lower housing recess 93b is provided in an inner surface of the lower housing section 4b. The second mandrel recess 93a and the lower housing recess 93b have tapered edges to allow sliding of the lower locking element 94 into and out of the recesses 93a, 93b.

[0184] In the first lower lock state 90S1, shown in Figs. 8a and 9a, the lower locking element 94 is in engagement with the second mandrel recess 93a and is out of engagement with the lower housing recess 93b. As a result, the lower locking element 94 is prevented from moving outwardly by the lower housing section 4b, and so cannot leave engagement with the second mandrel recess 93a. This means that, in the first lower lock state 90S1, the mandrel 2 is locked to the upper housing section 4a, as any longitudinal movement of the upper housing section 4a will be transferred to the mandrel 2 via the second mandrel recess 93 a. Movement of the upper housing section 4a and mandrel 2 downwardly aligns the second mandrel recess 93 a with the lower housing recess 93b, as shown in Fig. 9b, which allows the lower locking element 94 to slide into the lower housing recess 93b and out of engagement with the second mandrel recess 93a.

[0185] Therefore, in the second lower lock state 90 S2, as shown in Figs. 8b and 9b, the lower locking element 94 can be said to be out of engagement with the second mandrel recess 93a and in engagement with the lower housing recess 93b.

[0186] In the second lower lock state 90S2, relative longitudinal movement between the mandrel 2 and the upper housing section 4a may be allowed a lower lock distance D91, and relative longitudinal movement between the upper housing section 4a and the lower housing section 4b is also allowed due to the longitudinal extent of the lower housing recess 93b. The lower lock distance D91 is equal to the second travel distance D82b of the lower J-slot mechanism 80. Hence, when in the second lower lock state 90S2, the lower J-slot mechanism may not be locked, as the pins 83 are allowed to move along the profile 82. However, it should be noted that where the pins 83 are prevented from moving within the profile 82 of the lower J-slot mechanism 80, relative longitudinal movement between the mandrel 2 and the upper housing section 4a may also be prevented in the second lower lock state 90S2.

[0187] Operational states

[0188] Turning now to Figs. 10 to 17, Figs.10a, I la, 12a, 13a, 14a, 15a, 16a, and 17a show the upper section 1US of the casing plug 1 and the running tool 10 in each of the eight operational states of the casing plug assembly 100, beginning at Fig. 10a with a first operational state SI, and ending at Fig. 17a with an eighth operational state S8. Figs. 10b, 11b, 12b, 13a, 14b, 15b, 16b, and 17b show the positions of the upper J-slot mechanism 60 and the lower J-slot mechanism 80 for each respective operational state.

[0189] The first operational state SI

[0190] In Figs. 10a and 10b, the first operational state SI is shown. Fig. 3 also shows the upper connector 9 in the first operational state SI, while Fig. la, which has already been described above, shows the full casing plug assembly 100 in the first operational state SI. The first operational state SI is referred to as a run state in which the casing plug assembly 100 is movable up or down within the well.

[0191] In the first operational state SI, the upper J-slot mechanism 60 is in a first position 60P1 and the upper lock 70 is in a first upper lock state 70S1. In the first upper lock state 70S1 the running tool 10 is locked to the upper connector 9, and relative longitudinal movement between the running tool 10 and the upper connector 9 is prevented.

[0192] The ratchet device 51 is in a first ratchet state, where friction force between the drag block device 5 and the well is not sufficient to allow relative longitudinal movement between the third part 4b3 of the lower housing section 4b and the mandrel 2. This is because the friction force between the drag block device 5 and the well is less than the friction force between the ratchet device 51 and the mandrel 2. By preventing relative longitudinal movement, it is thereby achieved that the anchoring device 6 and the sealing device 7 are prevented from being radially expanded because relative longitudinal movement between the parts 4b 1, 4b2, 4b3 of the lower housing section 4b is required to expand the anchoring device 6 and sealing device 7.

[0193] Hence, the anchoring device 6 and the sealing device 7 are maintained in their radially retracted states, and the casing plug assembly 100 may be lowered into the well by gravity, as the weight of the casing plug 1 is hung off from the running tool 10 by means of the upper J-slot mechanism. The weight of the mandrel 2 and hence the lower part of the casing plug 1 is transferred to the upper housing section 4a and hence to the upper connector 9 at a weight transferring interface WT.

[0194] The lower J-slot mechanism 80 is here in a first position 80P1 and the lower lock 90 is in a first lower lock state 90S1. In the first lower lock state 90S1, the mandrel 2 is locked to the lower housing section 4b and relative longitudinal movement between the mandrel 2 and the lower housing section 4b is therefore prevented.

[0195] In this first operational state SI, the casing plug assembly 100 may also be pushed through restrictions such as a wear bushing in the well because the ratchet device 51 is in the first ratchet state.

[0196] As there is no relative movement between the mandrel 2 and the housing 4, the valve device 8 will not be rotated to the closed state. Specifically, movement of the pin 183 of the valve device 8 in the first section 182a will be minimal, and the pin 183 will not enter the second section 182b, meaning that the valve device 8 will not be rotated to the valve closed state.

[0197] The second operational state S2

[0198] Figs. I la, 11b, and 11c relate to the second operational state S2, with Fig. I la showing the upper section of the casing plug assembly 100, Fig. 11b showing the J- slot mechanisms, and Fig. 11c showing the full casing plug assembly 100. The second operational state S2 is referred to as a set state in which the anchoring device 6 and the sealing device 7 are radially expanded, although this is not visible in Fig. 11b. The sealing device 7 prevents longitudinal fluid flow in the well outside of the housing 4 past the sealing device 7 when it is radially expanded. In the second operational state S2, the upper J-slot mechanism 60 is still in the first position 60P1. The upper lock 70 is still in the first upper lock state 70S1. The anchoring device 6 and sealing device 7 have been radially expanded.

[0199] The casing plug assembly 100 is brought from the first operational state SI to the second operational state S2 by rotating the running tool 10 clockwise. It should be noted that this will rotate the upper connector 9 and the upper housing section 4a together with the running tool 10. The lower lock 90 is longitudinally locking the upper housing section 4a to the mandrel 2. The first spline connection 41 rotationally locks the upper housing section 4a to the mandrel 2. Hence, the mandrel 2 is rotated relative to the lower housing section 4b. This will bring the ratchet device 51 to a second ratchet state, where the friction force of the drag block device 5 is sufficient to allow relative longitudinal movement between parts of the lower housing section 4b and the mandrel 2. This is because the friction force between the drag block device 5 and the well is greater than the friction force between the ratchet device 51 and the mandrel 2 in the second state.

[0200] Hence, by subsequently moving the running tool 10 downwardly, a force is transferred to the upper housing section 4a via the upper lock 70 and from the upper housing section 4a to the mandrel 2 via the lower lock 90. The mandrel 2 will move downwardly relative to the lower housing section 4b. The movement of the mandrel 2 allows the lower lock 90 to move to be brought into a second lower lock state 90S2, in which relative longitudinal movement between the upper housing section 4a and the mandrel 2 and between the upper housing section 4a and the lower housing section 4b is achieved. The upper housing section 4a is moved relative to the mandrel and lower housing section 4b the lower lock distance D91, which is equal to the second travel distance D82b.

[0201] As relative longitudinal movement between the upper housing section 4a and the mandrel 2 is permitted when the lower lock 90 is in the second lower lock state 90S2, further downward movement of the running tool 10 and therefore upper housing section 4a will move the lower J-slot mechanism 80 into a second position 80P2. The mandrel 2 will be pushed down by the interaction of the pins 83 and profile 62 of the lower J-slot mechanism 80. This pushes the mandrel 2 further relative to the stationary drag block device 5, which will cause the the anchoring device 6 to be radially expanded into engagement with the well.

[0202] By moving the running tool 10 further down relative to the anchoring device 6, the sealing device 7 will also be radially expanded into contact with the well.

[0203] The ratchet device 51 will prevent relative longitudinal movement between the relevant parts of the lower housing section 4b and the mandrel 2 in the opposite direction. Hence, the anchoring device 6 and the sealing device 7 will stay radially expanded. The ratchet device 51 is now in a third ratchet state, having been moved longitudinally from the second ratchet state.

[0204] The movement of the mandrel 2 relative to the upper housing section 4a during the above transition is insufficient to rotate the valve device 8 to the closed valve state. Specifically, the pin 183 of the valve device 8 will only be moved in the first section 182a, meaning that the valve device 8 will not be rotated to the valve closed state.

[0205] The third operational state S3

[0206] Figs. 12a and 12b relate to the third operational state S3. The third operational state S3 is referred to as a “set verification state” in which the setting of the casing plug 1 is verified or can be verified by an operator of the casing plug assembly 100.

[0207] In the third operational state S3, the upper J-slot mechanism 60 is still in the first position 60P1. The upper lock 70 is still in the first upper lock state 70S1.

[0208] The casing plug assembly 100 is brought from the second operational state S2 to the third operational state S3 by pulling the running tool 10 upwardly. This will pull the upper housing section 4a upwardly, causing the lower locking element 94 to move from the lower housing recess 93b to the second mandrel recess 93a, and causing the lower J-slot mechanism 80 is brought to a third position 80P3. As a result, the lower lock 90 remains in the second lower lock state 90S2, but the upper housing section 4a is moved longitudinally relative to the lower housing section 4b.

[0209] It is now possible to try to pull the running tool 10 upwardly with a predetermined force, to verify that the anchoring device 6 of the casing plug 1 is holding the casing plug 1 stationary with respect to the well. Pulling the running tool 10 upwardly pulls against the sleeve 81, which is locked longitudinally to the mandrel 2. Because the mandrel 2 is prevented from moving in that direction relative to the lower housing section 4b by the ratchet device 51, and the lower housing section 4b is anchored to the wall by the anchoring device 6, pulling upwardly should result in minimal movement of the assembly 100, allowing it to be verified that the casing plug 1 is being held in the well by the anchoring device 6.

[0210] As in the second operational state S2, the movement of the mandrel 2 relative to the upper housing section 4a during the above transition is insufficient to rotate the valve device 8 to the closed valve state. Particularly, the pin 183 of the valve device 8 will only be moved within the first section 182a, so the valve device 8 will not be rotated to the valve closed state.

[0211] The fourth operational state S4

[0212] Figs. 13a and 13b relate to the fourth operational state S4. The fourth operational state S4 is referred to as a “valve closed state” in which the valve device 8 is closed. By pushing the running tool 10 down again, the casing plug assembly 100 will be brought to the fourth operational state.

[0213] Here, the upper J-slot mechanism 60 is still in the first position 60P1 and the lower J-slot mechanism 80 has been moved to a fourth position 80P4. The lower lock 90 has been moved back to the second lower lock state 90S2. As shown in Figs 4a and 4b, and in Fig. 13b, the pin 83 is now allowed to move a second travel distance D82b, which is longer than the previously moved first travel distance D82a, meaning that the upper housing section 4a is moving further relative to the mandrel 2 than previously. This further movement is sufficient to cause the valve device 8 to move from the open valve state to the closed valve state, by causing the pin 183 of the valve device 8 to move from the first section 182a and into the second section 182b, thereby causing the ball body 180 to rotate and bring the valve device 8 to the closed valve state.

[0214] The longer movement allowed by the lower J-slot mechanism 80 also causes the upper lock 70 to be brought to the second upper lock state 70S2. In the second upper lock state 70S2, the mandrel 2 is locked to the upper connector 9.

[0215] The fifth operational state S5

[0216] Figs. 14a and 14b relate to the fifth operational state S5. The fifth operational state S5 is referred to a “valve closed verification state” in which the closing of the valve device 8 is verified.

[0217] To transition from the fourth operational state S4 to the fifth operational state S5, the running tool 10 is moved further down relative to the mandrel and moves relative to the upper connector 9, due to the upper connector 9 being locked to the mandrel 2.

[0218] Hence, as seen from the topside, there is no difference between the fourth operational state S4 and the fifth operational state S5. However, as shown in Fig. 14b, the upper J-slot mechanism 60 now changes position from the first position 60P1 to a second position 60P2.

[0219] It is no longer possible to move the running tool 10 further down due to the upper J- slot mechanism 60 being in the second position 60P2, and this is a confirmation of the valve device 8 being closed. It is now possible to increase the pressure within the bore 3 in order to further verify that the valve is closed.

[0220] The upper lock 70 is still in the second upper lock state 70S2 and the lower lock 90 is still in the second lower lock state 90S2.

[0221] The sixth operational state S6

[0222] Figs. 15a and 15b relate to the sixth operational state S6. Fig. 19 also shows the upper connector 9 in the sixth operational state S6. The sixth operational state S6 is referred to as a “disconnected state” in which the running tool 10 is disconnected from the casing plug 1.

[0223] To transition from the fifth operational state S5 to the sixth operational state S6, the running tool 10 is pulled upwardly. The upper J-slot mechanism 60 will now be brought to a third position 60P3 which allows the running tool 10 to be disconnected from the upper connector 9 and pulled up from the casing plug 1.

[0224] This is possible due to the upper lock 70 being in the second upper lock state 70S2, where an inwardly protruding finger profile 15 in the lower end of the running tool 10 is allowed to be pulled up and past the upper end of the finger 72 and past the upper locking element 74.

[0225] Hence, the running tool 10 and the drill string (not shown) used to operate the casing plug 1 can be retrieved from the well, while the casing plug 1 is forming a barrier set in the well.

[0226] It should be noted that the upper end of the finger sleeve 71 here prevents outward movement of the upper locking element. The finger sleeve 71 will be maintained in this longitudinal position since the upper end 72U of the finger 72 is engaged in the upper connector recess 73b.

[0227] The seventh operational state S7

[0228] Figs. 16a and 16b relate to the seventh operational state S7. The seventh operational state S7 may be referred to as a “re-connection state” in which the running tool 10 is re-connected to the casing plug 1.

[0229] To transition from the sixth operational state S6 to the seventh operational state S7, the running tool 10 has been moved down again and has reconnected to the upper connector 9. The upper J-slot mechanism 60 is brought to a fourth position 60P4 by this movement.

[0230] The inwardly protruding finger profile in the lower end of the running tool 10 will meet the protrusion 77 of the finger sleeve 71 and push the finger sleeve 71 down. This will bring the upper end 72U of the finger 72 out of engagement with the upper connector recess 73b, forcing the upper end 72U of the finger 72 radially outwardly and into the running tool locking recess 73c, specifically, the second running tool locking recess 73c2. The upper lock 70 is in the third upper lock state 70S3. Outward movement of the upper locking element 74 is prevented, and hence it is avoided that the upper locking element 74 will be moved out of the first mandrel recess 73 a.

[0231] The lower J-slot mechanism 80 is still in the fourth position 80P4 and the lower lock 90 is in the second lower lock state 90S2. The eighth operational state S8

[0232] Figs. 17a and 17b relate to the eighth operational state S8. The eighth operational state S8 may be referred to as a “re-connection verification state” in which the reconnection of the running tool 10 to the casing plug 1 can be verified.

[0233] To transition from the seventh operational state S7 to the eighth operational state S8, the running tool 10 has been pulled upwardly, bringing the upper J-slot mechanism 60 to the first position 60P1 again. This will also rotate the running tool 10 relative to the upper connector 9, causing the first running tool locking recess 73cl to be provided radially outside of the upper locking element 74.

[0234] As seen in Fig. 17a, the upper locking element 74 is still provided in the first mandrel recess 73a.

[0235] The lower J-slot mechanism 80 is still in the fourth position 80P4 and the lower lock 90 is in the second lower lock state 90S2.

[0236] Transition from the eighth operational state S8 to the first operational state SI

[0237] From the eighth operational state S8, by pulling the running tool 10 further upwardly, the upper locking element 74 will move out of engagement with the first mandrel recess 73a and hence the upper lock 70 will go back to the first upper lock state 70S1.

[0238] During this upwardly movement of the running tool 10, the upper housing section 4a is moved upwardly relative to the mandrel 2. This movement is sufficient to cause the valve device 8 to transition from the closed valve state to the open valve state, by causing the pin 183 of the valve device 8 to move from the second section 182b to the first section 182a, thereby rotating the ball body 180 back and bringing the valve device 8 to the open valve state.

[0239] The pressure inside the bore 3 above the valve device 8 now becomes equalized with the pressure inside the bore 3 below the valve device 8. Typically, the bore 3 is open towards the well below the casing plug 1, and hence also the pressure in the well above the casing plug 1 becomes equalized with the pressure in the well below the casing plug 1.

[0240] By subsequently rotating the running tool 10, the ratchet device 51 will be brought from the third ratchet state to the first ratchet state, allowing relative longitudinal movement between the housing and the mandrel in the lower section ILS of the casing plug 1. Hence, by pulling the running tool 10 upwardly, the anchoring device 6 and the sealing device 7 will be brought from their radially expanded states to their radially retracted states.

[0241] As a result, the casing plug assembly 100 is brought to the first operational state SI again. Again, as seen from the topside, there is no difference between the eighth operational state S8 and the first operational state SI as the running tool is moved upwardly. Of course, the valve device 8 is brought to the open state, which can be detected upside as a change in fluid pressure or fluid flow rate through the bore. The operator may pressurize the drill string when the casing plug assembly 100 is in the seventh operational state S7 or in the eighth operational state S8. Pressurizing the drill string may allow the operator to verify when the valve device 8 is closed and when it opens as the casing plug assembly 100 moves from the seventh operational state S7 to the eighth operational state S8 and then to the first operational state SI again.

[0242] It is now possible to retrieve the casing plug assembly 100 from the well. Alternatively, it is possible to move the casing plug assembly 100 to a new position within the well, and repeat the above procedure to set the casing plug 1 at this new position.

[0243] Alternative examples

[0244] Fig. 20 shows a profile 281 for an alternative lower J-slot mechanism 280 that may be used instead of the lower J-slot mechanism 80 described above. As in the lower J- slot mechanisms described above, the profile 281 will be formed within a sleeve around the mandrel, with the profile 281 interacting with at least one pin 80 formed in the upper housing section 4a.

[0245] The alternative lower J-slot mechanism 280 has an alternative second set of positions, comprising a first position 280P1, a second position 280P2, a third position 280P3, a fourth position 280P4, a fifth position 280P5, and a sixth position 280P6. The first position 280P1, second position 280P2, and third position 280P3 are the same as in the corresponding first to third positions 80P1-80P3 of the lower J-slot mechanism 80 described above. The fourth position 280P4 differs from the fourth position 80P4 of the lower J-slot mechanism 80 described above, while the fifth position 280P5 and sixth position 280P6 are new. The fourth position 280P4, fifth position 280P5, and sixth position 280P6 are similar to the first position 280P1, second position 280P2, and third position 280P3 respectively except that they are mirrored. The fourth position 280P4, fifth position 280P5, and sixth position 280P6 represent end positions for a pin (not shown) of the alternative lower J-slot mechanism 280.

[0246] The changed fourth position 280P4 and the fifth and sixth positions 280P5, 280P6 allow an additional function, which is to allow reconnection of the running tool 10 to be verified by an operator while also preventing the valve device 8 from opening. Once verified, the running tool 10 can be disconnected and reconnected once more, at which point the valve device 8 is allowed to be opened. This additional function can provide a safety measure against unintentional opening of the valve device 8 during reconnection due to heave. The pin of the lower J-slot mechanism 280 is pushed down into the fourth position 280P4, which is a closed end position during movement between the third and fourth operational states S3, S4. Subsequently, the running tool 10 is disconnected in the sixth operational state S6, reconnected in the seventh operational state S7, and the reconnection is verified in the eighth operational state S8. After the eighth operational state S8, further verification can be achieved by performing an overpull on the running tool 10. The overpull moves the lower J-slot mechanism 280 from its fourth position 280P4 to the fifth position 280P5. Because the distance between the fourth and fifth positions 280P4, 280P5 is relatively small compared to the pin travel length required to open the valve device 8, the valve device 8 does not open during this movement. Accordingly, reconnection of the running tool 10 can be verified without unintentionally opening the valve device 8, because the relative movement of the mandrel 2 and the upper housing section 4a is limited by the lower J-slot mechanism 280. The operator may verify the reconnection based on pressure. The drill string may be pressurized when the casing plug assembly 100 is in the seventh operational state S7 or the eighth operational state S8. The drill string is therefore pressurized against the closed valve device 8. If there is no change in pressure when performing the overpull, then it can be verified by the operator that the reconnection was successful and the valve device 8 remains closed. Alternatively, in some circumstances, the operator may be provided with confirmation that the reconnection was successful based on an amount of longitudinal movement of the drill string attached to the running tool 10 during the overpull.

[0247] Subsequently, the running tool 10 may be pushed down again. This will move the upper J-slot mechanism from its first position 60P1 to the second position 60P2, and continued pushing down will move the lower J-slot mechanism 280 from the fifth position 280P5 to the sixth position 280P6.

[0248] After this movement, the running tool 10 may be overpulled again, which will result in disconnection of the running tool 10 from the casing plug 1. The upper J-slot mechanism moves from its second position 60P2 to the third position 60P3, while the lower J-slot mechanism remains in the sixth position 280P6. The drill string will be able to be pulled much further than during the previous overpull, providing further confirmation of disconnection to the operator. The operator is therefore able to know, based on the sequence of movements where in the process they are.

[0249] The running tool 10 has therefore been reconnected once and disconnected twice. It can now be reconnected again. When reconnecting this time, the upper J-slot mechanism moves from its third position 60P3 to its fourth position 60P4, while the lower J-slot mechanism remains in the sixth position 280P6, which is similar to the seventh operational state S7. Pulling up again moves the upper J-slot mechanism to its first position 60P1, with the lower J-slot mechanism remaining in the sixth position 280P6. This may provide verification of reconnection. Further pulling up of the running tool 10 brings the lower J-slot mechanism from the sixth position 280P6 to the first position 280P1, which will consequently open the valve device 8. This can also provide verification of the successful reconnection and opening the valve device 8, because there will be a change in pressure as the valve device 8 opens. The lower J-slot mechanism 280 therefore provides additional states and functionality, that are particularly useful during situations with heave. The lower J- slot mechanism 280 is in one of the fourth position 280P4 or the sixth position 280P6 during each disconnection and reconnection. During this functionality, as the lower J-slot mechanism 280 moves between the fourth and sixth positions 280P4, 280P6, the upper J-slot mechanism 60 cycles once through each of its positions 60P1-60P4.

[0250] LIST OF REFERENCE NUMBERS

[0251] 1 casing plug

[0252] 2 mandrel

[0253] 3 bore

[0254] 4 housing

[0255] 4a upper housing section

[0256] 4b lower housing section

[0257] 4b 1 first part of the lower housing section

[0258] 4b2 second part of the lower housing section 4b3 third part of the lower housing section

[0259] 40 opening

[0260] 5 drag block device

[0261] 6 anchoring device

[0262] 7 sealing device

[0263] 8 valve device

[0264] 9 upper connector

[0265] 9o connector opening

[0266] 10 running tool

[0267] 11 outer housing

[0268] I la connection interface

[0269] 12 inner surface

[0270] 13 bore

[0271] 15 inwardly protruding finger profile

[0272] 17 elastomeric sealing element

[0273] 41 first spline connection

[0274] 42a nut

[0275] 42b flange

[0276] 43 second spline connection

[0277] 50 actuation system

[0278] 51 ratchet device

[0279] 60 upper J-slot mechanism

[0280] 60P1 first position of upper J-slot mechanism 60P2 second position of upper J-slot mechanism 60P3 third position of upper J-slot mechanism 60P4 fourth position of upper J-slot mechanism

[0281] 62 profile

[0282] 63 pin

[0283] 65 locking mechanism

[0284] 70 upper lock

[0285] 7051 first upper lock state

[0286] 7052 second upper lock state

[0287] 7053 third upper lock state

[0288] 71 finger sleeve

[0289] 7 IL lower end

[0290] 71U upper end

[0291] 72 finger

[0292] 72L lower end

[0293] 72U upper free end

[0294] 72a outwardly protruding lug 72b inwardly protruding lug 73a first mandrel recess

[0295] 73b upper connector recess

[0296] 73c running tool locking recess

[0297] 73 cl first running tool locking recess

[0298] 73 c2 second running tool locking recess

[0299] 74 upper locking element

[0300] 75 opening

[0301] 77 protrusion

[0302] 80 lower J-slot mechanism

[0303] 80P1 first position of lower J-slot mechanism

[0304] 80P2 second position of lower J-slot mechanism

[0305] 80P3 third position of lower J-slot mechanism

[0306] 80P4 fourth position of lower J-slot mechanism

[0307] 81 sleeve

[0308] 82 profile

[0309] 83 pin

[0310] 90 lower lock

[0311] 9051 first lower lock state

[0312] 9052 second lower lock state

[0313] 93a second mandrel recess

[0314] 93b lower housing recess

[0315] 94 lower locking element

[0316] 100 casing plug assembly

[0317] 180 ball body

[0318] 181 bore

[0319] 182 profile

[0320] 182a first section

[0321] 182b second section

[0322] 183 pin

[0323] 185 pivot

[0324] 280 alternative lower J-slot mechanism

[0325] 280P1 first position of alternative lower J-slot mechanism 280P2 second position of alternative lower J-slot mechanism 280P3 third position of alternative lower J-slot mechanism 280P4 fourth position of alternative lower J-slot mechanism 280P5 fifth position of alternative lower J-slot mechanism 280P6 sixth position of alternative lower J-slot mechanism

[0326] 281 sleeve of alternative lower J-slot mechanism

[0327] 282 profile of alternative lower J-slot mechanism DI 82 pin travel length

[0328] D62a first travel distance

[0329] D62b second travel distance

[0330] D71 upper lock distance

[0331] D82a first travel distance

[0332] D82b second travel distance

[0333] D91 lower lock distance

[0334] LCA longitudinal central axis

[0335] S1-S8 first-eighth operational states al 82 angle

Claims

CLAIMS1. A casing plug assembly (100), wherein the casing plug assembly (100) comprises a casing plug (1) and a running tool (10) releasably connected to the casing plug (1) and wherein the casing plug assembly (100) is operable between a plurality of operational states; wherein the casing plug (1) comprises:- a mandrel (2) with a through bore (3);- a housing (4) provided radially outside of at least parts of the mandrel (2), wherein the housing (4) comprises an upper housing section (4a) and a lower housing section (4b);- an upper connector (9) provided in an upper end of the upper housing section (4a) for releasably connecting to the running tool (10);- an anchoring device (6) provided radially outside of the mandrel (2), wherein the anchoring device (6) is movable between a radially retracted state in at least one of the operational states of the casing plug assembly (100) and a radially expanded state in at least another one of the operational states of the casing plug assembly (100);-a sealing device (7) provided radially outside of the mandrel (2) and circumferentially around the mandrel (2) wherein the sealing device (7) is movable between a radially retracted state in at least one of the operational states of the casing plug assembly (100) and a radially expanded state in at least another one of the operational states of the casing plug assembly (100); and- a valve device (8) movable between an open valve state, in which fluid flow through the bore (3) is allowed, in at least one of the operational states of the casing plug assembly (100) and a closed valve state, in which fluid flow through the bore (3) is prevented, in at least another one of the operational states of the casing plug assembly (100); characterized in that the casing plug assembly (100) comprises an actuation system (50) for operating the casing plug assembly (100) between the plurality of operational states (SI, S2, S3, S4, S5, S6, S7, S8), the actuation system (50) comprising:- an upper J-slot mechanism (60) formed between the running tool (10) and the upper connector (9), the upper J-slot mechanism (60) having a first set of positions (60P1, 60P2, 60P3, 60P4);- a lower J-slot mechanism (80) formed between the upper housing section (4a) and the mandrel (2), the lower J-slot mechanism (80) having a second set of positions (80P1, 80P2, 80P3, 80P4); and- a locking mechanism (65), wherein the locking mechanism (65) prevents at least one combination of the positions (60P1, 60P2, 60P3, 60P4) of the first set of positions of the upper J-slot mechanism (60) with the positions (80P1, 80P2, 80P3, 80P4) of the second set of positions of the lower J-slot mechanism (80) so that a number of the combinations is equal to the number of operational states.

2. The casing plug assembly (100) according to claim 1, wherein the locking mechanism (65) comprises an upper lock (70) having a first upper lock state (70S1), in which the running tool (10) is locked to the upper connector (9) and a second upper lock state (70S2), in which the running tool (10) is released from the upper connector(9).

3. The casing plug assembly (100) according to claim 2, wherein the running tool(10) releasably connects to the upper connector (9) by means of the upper J-slot mechanism (60) and the upper lock (70).

4. The casing plug assembly (100) according to claim 2 or claim 3, wherein the upper lock (70) comprises:- a first mandrel recess (73 a) provided in an outer surface of the mandrel (2);- an upper locking element (74) provided in a connector opening (9o) in the upper connector (9);- a running tool locking recess (73 c) provided in an inner surface of the running tool (10) above an inwardly protruding finger profile (15) of the running tool (10); wherein, in the first upper lock state (70S1), the upper locking element (74) is in engagement with the running tool locking recess (73c) and the upper locking element (74) is out of engagement with the first mandrel recess (73a); and wherein, in the second upper lock state (70S2), the upper locking element (74) is in engagement with the first mandrel recess (73a) and is out of engagement with the running tool locking recess (73c).

5. The casing plug assembly (100) according to claim 4, wherein the upper lock (70) comprises:- an upper connector recess (73b) provided in an outer surface of the upper connector (9) below the connector opening (9o);- a finger sleeve (71) provided outside of the upper connector (9) below the upper locking element (74), wherein the finger sleeve (71) has an upper end (71U) and a lower end (7 IL); wherein the finger sleeve (71) comprises a finger (72) having a lower end (72L) secured to the lower end (7 IL) of the finger sleeve (71) and an upper free end (72U); wherein, in the first upper lock state (70S1), the upper free end (72U) of the finger (72) is out of engagement with the upper connector recess (73b) and the upper free end (72U) of the finger (72) is in engagement with the running tool locking recess (73c); and wherein, in the second upper lock state (70S2), the upper free end (72U) of the finger (72) is in engagement with the upper connector recess (73b) and the upper free end (72U) of the finger (72) is out of engagement with the running tool locking recess (73c).

6. The casing plug assembly (100) according to claim 5, wherein the running tool locking recess (73c) comprises a first running tool locking recess (73cl) and a second running tool locking recess (73 c2), wherein the first running tool locking recess (73cl) has a longitudinal extent being longer than the second running tool locking recess (73c2); wherein the upper locking element (74) and the upper free end (72U) of the finger (72) are in engagement with the first running tool locking recess (73cl) in the first upper locking state; wherein the upper lock (70) has a third upper lock state in which the upper free end (72U) of the finger (72) is in engagement with the second running tool locking recess (73c2) while outwardly movement of the upper locking element (74) is prevented.

7. The casing plug assembly (100) according to claim 6, wherein the first running tool locking recess (73c 1) and the second running tool locking recess (73 c2) are provided adjacent to each other in the inner surface of the running tool (10); wherein the upper lock (70) is brought between the first upper lock state (70S1) and the third upper lock state by rotation of the running tool (10) relative to the upper connector (9).

8. The casing plug assembly (100) according to any one of claims 5 to 7, wherein the finger sleeve (71) comprises a protrusion (77) protruding outwardly from the finger sleeve (71) below the upper free end (72U) of the finger (72) and circumferentially adjacent to the finger (72); wherein the inwardly protruding finger profile (15) of the lower end of the running tool (10) is provided longitudinally between the protrusion (77) and the upper free end (72U) of the finger (72) in the first upper lock state (70S1).

9. The casing plug assembly (100) according to any one of claims 5 to 8, wherein the upper end (71U) of the finger sleeve (71) is preventing the upper locking element (74) from being brought out of engagement with the first mandrel recess (73a) in the second upper lock state (70S2).10 The casing plug assembly (100) according to any one of claims 4 to 9, wherein, in first upper lock state (70S1), relative longitudinal movement between the upper connector (9) and the mandrel (2) is allowed a distance (D71) before the upper locking element (74) becomes engaged in the first mandrel recess (73a).

11. The casing plug assembly (100) according to any one of the preceding claims, wherein the upper J-slot mechanism (60) comprises:- a profile (62) provided on an inside of the running tool (10); and- a pin (63) protruding radially outwardly from the upper connector (9); wherein the pin (63) is engageable within and movable along the profile (62).

12. The casing plug assembly (100) according to claim 11, wherein the upper J- slot mechanism (60) is defined with a first travel distance (D62a) representing the relative longitudinal travel distance for the pin (63) between two end positions of the first set of positions.

13. The casing plug assembly (100) according to claim 12, wherein the upper J- slot mechanism (60) is defined with a second travel distance (D62b) representing a relative longitudinal travel distance for the pin (63) between an open-ended position of the first set of positions and an end position of the first set of positions.

14. The casing plug assembly (100) according to any one of the preceding claims, wherein the locking mechanism (65) comprises a lower lock (90) having a second lower lock state (90S2), in which the upper housing section (4a) is released from the mandrel (2), and a first lower lock state (90S1), in which the upper housing section (4a) is locked to the mandrel (2).

15. The casing plug assembly (100) according to claim 14, wherein the lower lock (90) comprises:- a lower locking element (94) provided in an opening (4o) in the upper housing section (4a);- a second mandrel recess (93a) provided in an outer surface of the mandrel (2); and- a lower housing recess (93b) provided in an inner surface of the lower housing section (4b); wherein, in the second lower lock state (90S2), the lower locking element (94) is out of engagement with the second mandrel recess (93a) and in engagement with the lower housing recess (93b); and wherein, in the first lower lock state (90S1), the lower locking element (94) is in engagement with the second mandrel recess (93a) and out of engagement with the lower housing recess (93b).

16. The casing plug assembly (100) according to any one of the preceding claims, wherein the lower J-slot mechanism (80) comprises:- a sleeve (81) provided radially outside of the mandrel (2) and radially inside of the upper housing section (4a);- a profile (82) provided on an outside of the sleeve (81); and- a pin (83) protruding inwardly from the upper housing section (4a); wherein the pin (83) is engageable within and movable along the profile (82).

17. The casing plug assembly (100) according to claim 16, wherein the lower J- slot mechanism (80) is defined with a first travel distance (D82a) representing therelative longitudinal travel distance for the pin (83) between two end positions of the second set of positions.

18. The casing plug assembly (100) according to claim 17, wherein the lower J- slot mechanism (80) is defined with a second travel distance (D82b) representing the relative longitudinal travel distance for the pin (83) between an end position and an open-ended position of the second set of positions.

19. The casing plug assembly (100) according to any one of the preceding claims, wherein the casing plug (1) further comprises:- a drag block device (5) provided radially outside of the mandrel (2); and- a ratchet device (51) for selectively locking at least part (4b3) of the lower housing section (4b) to the mandrel (2).

20. The casing plug assembly (100) according to any one of the preceding claims, wherein the operational states (SI, S2, S3, S4, S5, S6, S7, S8) comprises:- a first state (SI) in which the casing plug assembly (100) is movable up or down within the well;- a second state (S2) in which the casing plug (1) is set in the well;- a third state (S3) in which the setting of the casing plug (1) is verified;- a fourth state (S4) in which the valve device (8) is closed;- a fifth state (S5) in which the closing of the valve device (8) is verified;- a sixth state (S6) in which the running tool (10) is disconnected from the casing plug (i);- a seventh state (S7) in which the running tool (10) is re-connected to the casing plug (i);- an eighth state (S8) in which the valve device (8) is opened.

21. The casing plug assembly (100) according to any one of the preceding claims, wherein the valve device (8) comprises a ball body (180) with a through bore (181) pivotably engaged within the mandrel (2); wherein the through bore (181) is aligned with the bore (3) in the open valve state to allow fluid flow through the bore (3) and out of alignment with the bore (3) in the closed valve state to prevent fluid flow through the bore (3); and wherein the ball body (180) comprises a profile (182) engaged by a pin (183) secured to the upper housing section (4a); wherein the profile (182) comprises a first section (182a) and a second section (182b), wherein the pin (183) is allowed to move within the first section (182a) without causing the ball body (180) to pivot to the closed valve state.

22. The casing plug assembly (100) according to claim 20, wherein the ball body (180) is pivoted by the pin (183) when the pin (183) is moved within the second section (182b).

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