Downhole anchor

1. An anchoring apparatus for use in an openhole wellbore having a wall, the anchoring apparatus comprising:

a mandrel having an uphole end and a downhole end, the mandrel having external recesses defined on an outer surface of the mandrel;

at least one movable wall engaging member configured to engage the wall of the openhole wellbore;

at least one lower sleeve located downhole relative to the at least one moveable wall engaging member and configured to contact the at least one movable wall engaging member at or near an upper end of the at least one lower sleeve; and

at least one actuating member located uphole relative to the at least one moveable wall engaging member and configured to move downwardly downhole and longitudinally relative to the mandrel, for moving the at least one movable wall engaging member from a retracted position to an expanded position;

wherein the at least one movable wall engaging member is movable from the retracted position to the expanded position to engage the wall,

wherein the at least one lower sleeve is detachably connected to a connector disposed between the at least one lower sleeve and the mandrel, the connector having internal protrusions engaged with the external recesses of the mandrel,

wherein the at least one lower sleeve is held stationary by the connector relative to the mandrel during deployment of the at least one movable wall engaging member from the retracted position to the expanded position,

wherein the at least one lower sleeve is configured to detach from the connector and is configured to release the at least one movable wall engaging member from the expanded position to the retracted position to disengage the wall, and

wherein the anchoring apparatus comprises a unidirectional or—non return—mechanism adapted to allow the at least one actuating member to move towards a respective one of the at least one movable wall engaging member, and prevent movement of the at least one actuating member in an opposite direction.

2. The anchoring apparatus of claim 1 ,

wherein the at least one movable wall engaging member is movable from a first of the retracted position to the expanded position to engage the wall, and is movable from the expanded position to a second of the retracted position to disengage the wall; and

wherein the first and second retracted positions are different.

3. The anchoring apparatus of claim 1 , wherein the anchoring apparatus comprises a plurality of the at least one movable wall engaging member, and wherein the movable wall engaging members are circumferentially arranged relative to the anchoring apparatus and/or wellbore.

4. The anchoring apparatus of claim 1 , wherein the anchoring apparatus comprises one of:

a plurality of the at least one movable wall engaging member; and

at least one stationary wall engaging member.

5. The anchoring apparatus of claim 1 ,

wherein the at least one movable wall engaging member comprises a first angled or tapered surface at or near a first end thereof, the first angled or tapered surface extending from an inner portion thereof to an outer portion thereof; and/or

wherein the at least one movable wall engaging member comprises a second angled or tapered surface at or near a second end thereof, the second angled or tapered surface extending from an inner portion thereof to an outer portion thereof.

6. The anchoring apparatus of claim 1 , wherein the at least one movable wall engaging member is radially movable relative to a housing and/or a mandrel of the apparatus.

7. The anchoring apparatus of claim 1 ,

wherein the at least one actuating member comprises a cam structure configured for engaging an upper angled or tapered surface of the at least one movable wall engaging member.

8. The anchoring apparatus of claim 1 , wherein the mandrel defines an inner portion or inner surface of the anchoring apparatus.

9. The anchoring apparatus of claim 1 ,

wherein the anchoring apparatus comprises at least one outer sleeve located on an upper side relative to the at least one movable wall engaging member; and

wherein the mandrel and the at least one outer sleeve define an annular space in which a respective actuating member is capable of moving longitudinally.

10. The anchoring apparatus of claim 1 , wherein in a first retracted configuration, the at least one actuating member is detachably attached to an at least one outer sleeve.

11. The anchoring apparatus of claim 10 , wherein, in use, the at least one actuating member is detachable from the at least one outer sleeve by application of a load on the at least one actuation member.

12. The anchoring apparatus of claim 1 , wherein, in use, application of a pulling force on the mandrel causes uphole movement of the mandrel and thus of a respective one of the at least one actuating member, allowing the respective movable wall engaging member to disengage the wall.

13. The anchoring apparatus of claim 1 , wherein the mandrel of the apparatus is provided with or comprises one or more first openings.

14. The anchoring apparatus of claim 13 , wherein the one or more first openings of the mandrel are similar in size or larger than one or more second openings of the at least one movable wall engaging member.

15. A method for disengaging an anchoring apparatus according to claim 1 from a wall of an openhole wellbore, the method comprising:

moving the at least one movable wall engaging member from the expanded position in which the at least one movable wall engaging member engages the wall, to the retracted position in which the at least one movable wall engaging member disengages the wall.

16. The method of claim 15 , wherein the at least one lower sleeve is connected to the connector by a frangible connection.

17. The anchoring apparatus of claim 1 , wherein the at least one lower sleeve is connected to the connector by a frangible connection.

18. An anchoring apparatus for use in an openhole wellbore having a wall, the anchoring apparatus comprising:

a mandrel having an uphole end and a downhole end, the mandrel having external recesses defined on an outer surface of the mandrel;

at least one movable wall engaging member configured to engage the wall of the openhole wellbore;

at least one lower sleeve located downhole relative to the at least one moveable wall engaging member and configured to contact the at least one movable wall engaging member at or near an upper end of the at least one lower sleeve; and

at least one actuating member located uphole relative to the at least one moveable wall engaging member and configured to move downwardly downhole and longitudinally relative to the mandrel, for moving the at least one movable wall engaging member from a retracted position to an expanded position;

wherein the at least one actuating member is movable by hydraulic actuation,

wherein the at least one movable wall engaging member is movable from the retracted position to the expanded position to engage the wall,

wherein the at least one lower sleeve is detachably connected to a connector disposed between the at least one lower sleeve and the mandrel, the connector having internal protrusions engaged with the external recesses of the mandrel,

wherein the at least one lower sleeve is held stationary by the connector relative to the mandrel during deployment of the at least one movable wall engaging member from the retracted position to the expanded position, and

wherein the at least one lower sleeve is configured to detach from the connector and is configured to release the at least one movable wall engaging member from the expanded position to the retracted position to disengage the wall.