Flow restrictor

1. A flow restrictor for restricting flow in an annulus, the flow restrictor comprising:

a body; and

a restrictor assembly mounted on the body,

wherein the flow restrictor is actuable by fluid flow over the restrictor assembly above a threshold flow rate actuating the restrictor assembly from a run-in configuration to a set configuration,

wherein the restrictor assembly has a fixed portion that remains fixed relative to the body and a movable portion that is movable from a stowed position in the run-in configuration to a radially splayed position in the set configuration to thereby substantially restrict flow in the annulus,

wherein said movable portion moves from said stowed position to said radially splayed position by pivoting relative to the fixed portion in response to the fluid flow across the restrictor assembly in a direction from the movable portion towards the fixed portion, and

wherein the flow restrictor has a central axis and at least a part of the restrictor assembly is inclined at an angle of incline relative to the central axis, the body being tapered to define the angle of incline of the at least part of the restrictor assembly.

2. The flow restrictor according to claim 1 , wherein a part of the restrictor assembly is deformable above the threshold flow rate to move the restrictor assembly from the run-in configuration to the set configuration.

3. The flow restrictor according to claim 1 , wherein the restrictor assembly is a frustoconical shape.

4. The flow restrictor according to claim 1 , wherein the angle of incline of the restrictor assembly is between one and seven degrees relative to the central axis.

5. The flow restrictor according to claim 1 , wherein the restrictor assembly comprises at least one layer of deformable material.

6. The flow restrictor according to claim 1 , comprising a backup mechanism to retain the restrictor assembly in the set configuration.

7. The flow restrictor according to claim 1 , wherein at least one of:

the flow restrictor is arranged to act as an annular seal in the set configuration;

the flow restrictor is arranged to act as a fluid flow diverter within the annulus;

the flow restrictor is arranged to act as an actuator;

the flow restrictor is mounted on a tubular proximate a tool such that the flow restrictor is slidable along the tubular when a predetermined flow rate acts against the flow restrictor in the set configuration to thereby act as an annular piston and actuate the tool;

the flow restrictor is a packer.

8. A method of restricting flow in an annulus, the method comprising the steps of:

providing a flow restrictor according to claim 1 ;

running the flow restrictor into a hole in the run-in configuration;

pumping fluid into the hole above the threshold flow rate;

flow actuating the flow restrictor from the run-in configuration to the set configuration in which the at least a portion of the restrictor assembly is radially splayed, by flowing the fluid over the restrictor assembly above the threshold flow rate.

9. The method according to claim 8 , including fixing a portion of the restrictor assembly relative to the body and providing a movable portion of the restrictor assembly and flowing fluid over the restrictor assembly in direction from the movable portion towards the fixed portion, thereby substantially restricting flow in the annulus.

10. The method according to claim 8 , including at least one of:

pumping fluid above the threshold flow rate into an annulus between the hole and a tubing; and

pumping fluid above the threshold flow rate into an annulus by pumping fluid through tubing having a port opening into the annulus.

11. The method according to claim 8 , including moving the flow restrictor from the run-in configuration to the set configuration by deforming the restrictor assembly in response to fluid flow above the threshold flow rate.

12. The method according to claim 8 , including providing a plurality of metal petals in the restrictor assembly and deforming the petals by flowing fluid over the restrictor assembly above the threshold value.

13. The method according to claim 8 , including selecting the value of threshold flow rate such that it exceeds flow rates to which the flow restrictor is exposed during running the flow restrictor into the hole.

14. The method according to claim 8 , including providing a backup mechanism to substantially restrict further deformation of the flow restrictor once the flow restrictor is in the set configuration and activating the backup mechanism by moving the restrictor assembly from the run-in to the set configuration.

15. The method according to claim 8 , including sealingly engaging the hole when the flow restrictor is in the set configuration.

16. The method according to claim 8 , including maintaining a pressure differential within the annulus when the flow restrictor is in the set configuration.

17. The method of stimulating a geological formation including the steps of:

opening a port in a tubing;

restricting flow in an annulus according to claim 8 , including pumping stimulating fluid above the threshold flow rate; and

stimulating the geological formation using the flow restrictor in the set configuration to substantially obturate the annulus and direct the flow of stimulating fluid into the geological formation.

18. A flow restrictor for restricting flow in an annulus, the flow restrictor comprising:

a body; and

a restrictor assembly mounted to the body,

wherein the flow restrictor is actuable by fluid flow over the restrictor assembly above a threshold flow rate actuating the restrictor assembly from a run-in configuration to a set configuration,

wherein the restrictor assembly has a fixed portion that remains fixed relative to the body and a movable portion that is movable relative to the fixed portion from a stowed position in the run-in configuration to a radially splayed position in the set configuration to thereby substantially restrict flow in the annulus,

wherein said movable portion moves from said stowed position to said radially splayed position by pivoting relative to the fixed portion in response to the fluid flow across the restrictor assembly in a direction from the movable portion towards the fixed portion, and

wherein the restrictor assembly has at least two layers of interweaved elongate elements deformable to move between the run-in and set configurations, the elongate elements from a first layer of the at least two layers of interweaved elongate elements being alternately interweaved with elongate elements from a second layer of the at least two layers of interweaved elongate elements, a leading edge of each elongate element overlaying a trailing edge of an adjacent elongate element on one side, and a trailing edge of each elongate element overlaid by a leading edge of an adjacent elongate element on the other side.

19. The flow restrictor according to claim 18 , wherein the at least two layers of elongate elements are interweaved such that radial splay of one elongate element acts on the adjacent elongate elements to urge radial splay of adjacent elongate elements.

20. The flow restrictor according to claim 18 , wherein at least one of:

the elongate elements are metal elongate elements; and

the elongate elements comprise petals extending outwardly from a collar.

21. The flow restrictor according to claim 18 , whereby deformation of elongate elements is actuable by at least one of:

fluid flow above a threshold flow rate; and

a mechanical mechanism.

22. The flow restrictor according to claim 5 , wherein at least one of:

the restrictor assembly comprises a plurality of layers of the deformable material;

at least one of layer of the deformable material is metal;

at least one layer of the deformable material has a plurality of petals arranged to radially splay when exposed to the fluid flow rates above the threshold flow rate value;

the restrictor assembly has at least two interweaved deformable layers of metal; and

the restrictor assembly comprises a plurality of deformable sealing layers.

23. The flow restrictor according to claim 6 , wherein at least one of:

the backup mechanism is arranged such that movement of the restrictor assembly to the set configuration actuates the backup mechanism; and

the backup mechanism supports at least a portion of the length of the restrictor assembly and restricts further movement of the restrictor assembly in the direction of fluid flow once the flow restrictor is in the set configuration.

24. The flow restrictor according to claim 18 , wherein the restrictor assembly is a frustoconical shape.

25. The flow restrictor according to claim 18 , wherein the flow restrictor has a central axis and at least a part of the restrictor assembly is inclined at an angle relative to the central axis.

26. The flow restrictor according to claim 18 , wherein the restrictor assembly comprises at least one layer of deformable material.

27. The flow restrictor according to claim 26 , wherein the restrictor assembly comprises a plurality of layers of the deformable material.

28. The flow restrictor according to claim 27 , wherein the restrictor assembly comprises a plurality of deformable sealing layers.

29. A method of restricting flow in an annulus, the method comprising the steps of:

providing a flow restrictor according to claim 18 ; and

flow actuating the restrictor assembly between the run in configuration and the set configuration by: flowing fluid over the restrictor assembly above a threshold flow rate, and deforming the interweaved elongate elements to the set configuration in which the at least a portion of the restrictor assembly is splayed to thereby substantially restrict flow in the annulus.

30. The method according to claim 29 , comprising deforming the elongate elements using a mechanical mechanism.

31. The method according to claim 29 , comprising deforming the elongate elements by fluid flow above a threshold value selected to exceed the flow rates to which the flow restrictor is exposed while the flow restrictor is run in to a bore.

32. The method according to claim 31 , wherein the elongate elements comprise petals extending outwardly from a collar, and the method comprises selecting the length and thickness of the petals according to the threshold flow rate.

33. The flow restrictor according to claim 1 , wherein the flow restrictor is actuable by the fluid flow over at least a portion of an outer surface of the restrictor assembly above the threshold flow rate.

34. The method according to claim 8 , wherein flow actuating the flow restrictor comprises flowing fluid over at least a portion of an outer surface of the restrictor assembly above the threshold flow rate.