WO2005083231A1

WO2005083231A1 - Improvements in or relating to valves

Info

Publication number: WO2005083231A1
Application number: PCT/GB2005/000660
Authority: WO
Inventors: Michael Adam Reid; Irvine Cardno Brown
Original assignee: Red Spider Technology Limited
Priority date: 2004-02-24
Filing date: 2005-02-24
Publication date: 2005-09-09
Also published as: GB2427637A; GB2427637B; GB0404012D0; GB0616840D0

Abstract

A hydrostatic support valve for use above or below an electrical submersible pump (ESP) in a well bore. The valve includes oppositely arranged spring biased pistons (46, 48). The springs (44, 78) are selected so that a relatively strong spring is used to support a column of fluid and close the valve in the vent of loss of production fluid pressure. Increasing fluid pressure from surface can be used to switch the valve and allow fluid to be pumped through the valve to the formation below the ESP. A collet and key arrangement between the pistons is described which assists in switching the valve.

Description

Improvements in or relating to valves

The present invention relates to valves used in well bores and in particular, though not exclusively, to a valve which supports hydrostatic pressure at a pump and has the ability to be selectively pumped through when required.

In producing from an oil well a pump, typically an ESP (electrical submersible pump) , can be inserted in the work string to assist in driving the oil from the formation up the well bore. Normally a check valve is positioned above the pump to ensure that any drop in hydrostatic pressure does not result in oil and other material falling back into the pump. Any back flow may damage the operation of a pump.

A disadvantage in the use of a check valve or other one- way valve, is that it prevents any access to the pump or the well bore located below the pump. In a number of cases it is useful to turn off the pump and introduce fluids into the formation below the pump. This is prohibited if a check valve is used. An object of the present invention is to provide a hydrostatic support valve which can withstand a predetermined fluid column. Such a valve, located above or below an ESP supports the column in the event that the pump is stopped and extends the life of the pump.

A further object of the present invention is to provide a hydrostatic support valve which allows fluid to be selectively pumped through the valve.

According to a first aspect of the present invention there is provided a hydrostatic support valve, the valve comprising a substantially cylindrical body for connection in a work string, in which is located two oppositely directed pistons, each piston being biased by a spring, wherein the springs are selected such that fluid can travel through the body in a first direction and, by movement of the pistons under fluid pressure, first and second operating position are provided, wherein in the first operating position fluid is prevented from passing through the body in a reverse direction, and in the second operating position fluid travels through the body in the reverse direction.

Thus the valve can provide hydrostatic support when mounted at a pump and allow pump-through when required.

Preferably the springs are selected to provide a relatively strong spring and a relatively weak spring. More preferably the relatively strong spring acts in the reverse direction. The relatively weak spring will thus act in the first direction. In this way the relatively strong spring can be used to support a column of fluid in the work string. The springs may be formed as a combination of springs . The springs may be coiled springs, disc springs such as Belville spring stacks or the like. They need not be of identical type.

Preferably the fluid travels through a first flow path in the body in the first direction and a second flow path in the body in the reverse direction.

Preferably the valve includes one or more sleeves. The sleeves may be integral with the pistons. The sleeves may include flow ports therethrough such that their movement controls fluid flow through the valve. The one or more sleeves may be biased by the springs.

Preferably at least a portion of the first piston is located within the second piston. In this way the length of the combined piston assembly can be varied.

Preferably at least one piston includes a substantially conical drive face against which fluid pressure can act. Preferably also the face directs fluid towards a flow path.

Preferably the first and second flow paths are opposite. Advantageously the flow paths are substantially annular in cross-section to provide a significant flow area for production of the well through the valve.

Preferably the valve further comprises engaging means between the pistons. Such engaging means assists in switching the valve between the first and second operating positions. Preferably the engaging means 1 comprises one or more locking keys located on a first 2 piston and a collet located on a second piston. 3 Preferably the collet includes one or more retaining 4 elements having a ledge thereupon for selective 5 engagement with the one or more keys. 6 7 Alternatively the engaging means may comprise one or more 8 locking keys located on a first piston which each mate 9 with one of two grooves on a surface of a second piston. 10

11 Advantageously the valve is re-settable. The engagement

12 means may also be re-settable so that the valve may be

13 cycled to any of the operating positions any number of

14 times .

15 ^{' *}- .. _. ^•

16 According to a second aspect of the present invention

17 there is provided a method of accessing a formation in a

18 wellbore below a pump, the method comprising the steps:

19 (a) locating a hydrostatic support valve according to 20 the first aspect and an electrical submersible

21 pump on a workstring;

22 (b) running the workstring into a well bore and

23 pumping produced fluids from a formation via the

24 pump to the surface while directing fluid flow

25 through the valve;

26 (c) on a drop in the pressure of the production fluid

27 using the fluid pressure to switch the valve so

28 that it prevents flow towards the formation and 29. supports the fluid in the workstring above the

30 valve; and

31 (d) using fluid pressure to switch the valve to

32 provide access of fluids to the formation. 33 The valve may be located above or below the pump. The valve may be run on a lock or packer anchoring device.

Preferably the method includes the step of re-setting the valve so that pumping of produced fluids can recommence.

Embodiments of the present invention will now be described, by way of example only, with reference to the following drawings of which:

Figure 1 is a cross-sectional view through a hydrostatic support valve according to a first embodiment of the present invention;

Figure 2 is a cross-sectional view through a hydrostatic support valve according to a second embodiment of the present invention; and

Figure 3 is a cross-sectional view through a portion of a hydrostatic valve illustrating an alternative arrangement to the embodiment of Figure 2.

Referring initially to Figure 1 there is illustrated a hydrostatic support valve, generally indicated by reference numeral 10, according to the present invention. At an upper end 12 of the valve 10 there is a box section 14 for connecting the valve 10 to an anchoring device to anchor it within production tubing (not shown) . Production tubing is used to take produced fluids from formations in the well to the surface. At a lower end 16 of the valve 10 is located a nozzle 18. Below this, on the production tubing, a downhole pump e.g. an ESP would be located to pump production fluids up the tubing. Valve 10 has a cylindrical body 20 formed from the nozzle 18 and box 14 sections together with an outer sleeve 22. These pieces are threaded together. Located within the outer sleeve 22 is an inner sleeve 24. An annular passageway 26 is provided between the two sleeves 22,24. End stops 28,30 are provided at either end 12,16 of the body 20. The upper stop 28 is formed as an inward facing lip on the box section 14. The lower stop 30 is a ring, abutting the nozzle section 18 and an inward facing lip of the outer sleeve 22. Movement of the inner sleeve 24 is therefore limited to the distance between the end stops 28,30.

Toward the upper end 12, sleeve 24 includes a radially outward jutting portion 32. This provides a wiper seal 34 between the inner and outer sleeves 22,24. Downward of the seal 34, on a sloping section 36 of the inner sleeve 24, are arranged flow ports 38 through the inner sleeve 24. There are three equidistantly circumferentially spaced flow ports 38. It will be appreciated that any number of flow ports can be used and there number and dimensions can be selected to determine a flow area to the passageway 26.

Toward the lower end 16 of the valve 10 are a series of radial supports 40 which keep the inner and outer sleeves 22,24 a fixed distance apart without interfering with flow through the passageway 26. Above the jutting portion 32, between the sleeves 22,24 an annular channel 42 is formed. A spring 44 is located in the channel 42. The spring 44 biases the inner sleeve 24 against the lower end stop 30.

Within the inner sleeve 24, two pistons 46,48 are oppositely arranged. A first piston 46 faces the upper end 12 of the valve 10, while the second piston 48 is located below the first, facing the lower end 16. _. . The second piston 48 has a trailing sleeve 50 attached to its rear surface 52. A portion of the trailing sleeve 50 comprises a collet 54. Collet 54 is made up of a series of longitudinally arranged sprung legs, attached to the sleeve 50 at either end. They are formed by cutting rectangular portions through the sleeve 50 at regular intervals around the circumference of the sleeve 50. Midway on each leg is formed an inwardly facing ledge 56. The ledge faces the upper end 12 of the valve and has a sloping surface facing the lower end 16.

Above the collet 54, the trailing sleeve 50 extends radially outward to form an inner lip 58 or ledge within the central bore 60 of the valve 10. A back face 62 of. the first piston 46 can abut the lip 58. Above the lip 58, the trailing sleeve 50 includes a number of flow ports 63 therethrough. These provide a route for fluid to flow into the annular passageway 65 between the inner. sleeve 24 and the trailing sleeve 50. The trailing sleeve 50 is then connected to. the inner sleeve 24.

At the connection between the two sleeves 24,50 a circumferential recessed channel 67 is formed, facing the central bore 60 of the valve 10. A sliding seal ring 69 is located in^' the recess ^'67. The ring 69 provides an inner surface 68 within the central bore 60. In an alternative embodiment, the ring 69 is biased toward the upper end 12 of the valve 10 by the incorporation of a spring within the recess 67 which abuts the inner sleeve 24.

The first piston 46 has a conical drive face 64 with a rounded apex 66. The piston 46 can abut the ring 69 to limit the upward movement of the piston 46. The first piston 46 is limited in movement across a distance dictated by the position of the ring 69 in recess 67 and the position of lip 58 located on the trailing sleeve 50. Piston 46 also has a cylindrical body 70 directed toward the lower end 16 of the valve 10. The body 70 extends through the trailing sleeve 50 and into the second piston 48. The second piston 48 is provided with a central through bore 72 to accommodate this movement. In one embodiment of the present invention, the body 70 may also include a bore extending to a rear surface of the first piston 46.

On an outer surface 74 of the body 70 there is located a raised portion 76. The raised portion 76 acts as a double sided stop. Below the portion 76 is located a spring 78. The spring 78 is bounded at its opposite end by the second piston 48. The spring 78 biases the two pistons 46,48 in opposite directions, away from each other.

Control of movement within the valve is undertaken by an engaging mechanism, generally indicated by reference numeral 80, located between the body 70 of the first piston 46 and the collet 54 of the second piston 48. Mechanism 80 comprises a ring 82 arranged on the outer surface of the body 70. The ring 82 includes six keys which can move radially with respect to the ring, such that they will extend radially from either side of the ring 82 when a surface abuts the opposite surface of the ring 82. In this way the keys can be made to reposition themselves within the valve 10. Any number of keys may be selected, but the number and location of the keys 84 must ensure that all of the ledges 56 on the collet 54 are engaged. A . The ring 82 is biased toward an upper edge 86, on the body 70, by virtue of a spring 88 located between the ring 82 and the raised portion 76. Spring 88 may be located at any position, against any ledge which provides the same bias to the body 70. The keys 84 and collet 54 are so arranged that when the keys 84 are pushed radially outward they will contact the ledges 56 on the collet.54. ^{■ "} ■ ^{■ •} Between the raised portion 76 and the edge 86, the. diameter of the body 70 changes. This change provides a step 90. On passing across the step 90, towards the raised portion 76, the keys are free to move radially inwards by virtue of a gap created between the body 70 and the ring 82 at this location. Operation of the mechanism 80 will be described hereinafter with respect to use of the valve 10. ^• .- ^• - . ^' In use, the valve 10 is located in a production string by use of the box 14 and nozzle 18 sections as is known in the art. In the preferred embodiment, the valve 10 will be positioned above or below a downhole pump e.g. an ESP. In this way produced fluids from a formation in the well, located below the pump, are lifted through the production string to the surface of the well by use of the pump. In order for the pump to function successfully, hydrostatic pressure must be maintained in the string above the pump to prevent produced fluids travelling back down the string, into the pump. The valve provides this function as follows .

On run in, the pistons 46,48 are located at their furthest distance apart, by virtue of the spring 78. Spring 44 will bias the inner sleeve 24 towards the lower end 16 of the valve 10. Spring 88 will move the keys 84 clear of the ledges 56 so that the ring 82 abuts the edge 86 and the piston 46 is pushed against the sliding seal ring 69, to a position where the ring 69 abuts the sleeve 24. There is no available flow path through the valve 10 and the upper side of the pump will be sealed from the upper end of the production tubing.

When the valve 10 is in position and the pump pushes fluid up towards the valve 10 during production, fluid pressure will impinge on all the downward facing surfaces of the valve 10. Pressure on the second piston 48, will cause it to move upwards together with the inner sleeve against the spring 42. Pressure on the body 70 of the first piston 46, will assist in this movement as piston 46 moves against the sliding seal ring 69, which in turn pushes the inner sleeve 24 upwards. This movement causes the inner sleeve 24 to rise away from the end stop 30 and in doing so exposes the annular passageway 26 to the central bore 60 at the lower end 16 of the valve 10. Production fluid travels up the passageway 26 and re- enters the central bore 60 through the flow ports 38 in the inner sleeve 24. As long as the pressure is maintained on the second piston 48, the valve 10 will pass production fluid upwards towards the surface of the well. If the pressure of the production fluid drops i.e. hydrostatic pressure increases, valve 10 will close. Pressure will now be upon the first piston 46 and the sliding seal ring 69. The surface area 68 of the sliding seal ring 69 which is exposed to the central bore 60 is greater than the surface are of the face 64 and apex 66 of the piston 46. As a result, with the two surfaces abutting, the seal ring 69 will force the piston 46 downwards. The keys 84 will come to rest upon the ledges 56 of the collet 54. At the same time, with the compression now off spring 44, the inner sleeve 24 moves downwards until it abuts the end stop 30. In this position, fluid entering the valve 10 from above will be stopped at the piston 46. Fluid will be able to pass through the flow ports 38 and down the passageway 26, but it will not be able to exit the valve 10, as there is no through path at the lower end 16 of the valve. The valve 10 therefore supports fluid in this position and^'back- flow to the pump is prevented.

If fluid needs to be pumped through the valve 10 towards the pump, this is achieved by increasing pressure to the valve 10 from above. As the sealing ring 69 has a greater surface area than the piston 46, the ring 69 will force the piston downwards until the seal reaches the lower end of the recess 67. Increased pressure on the piston will force the keys 84 against the ledges 56. The ledges will move radially outwards by virtue of the sprung legs on which they are mounted. The keys 84 will pass the ledges 56 and allow the piston to move downwards, compressing spring 78. The piston 46 will ultimately come to rest as the rear surface 62 of the piston 46 meets the lip 58 on the sleeve 50. In this position, the piston 46 has moved and exposed the flow ports 63 in the trailing sleeve 50. This provides a fluid flow path down through the tool from the central bore 60, into the trailing sleeve 50, through flow ports 63, into the passageway 65 between the sleeve 50 and the sleeve 24, passed the supports 49 which align the piston 48 in the sleeve 50, and out through the central bore 60 at the lower end 18 of the valve 10.

The valve 10 can be reset to allow production fluid to recommence flow upwards through the valve. Re-setting will position the valve back to the configuration on run in. To reset the valve 10, pressure is released or reduced at the upper end 12 of the valve 10. Release of pressure causes the spring 78 to expand and push the piston 46 upwards. Piston 46 will rise until the keys 84 meet the lower side of the ledges 56 and its face 64 meets the seal ring 69 again. Further movement of the piston 46 will cause the body 70 of the piston 46 to pass through the ring 82 in which the keys 84 are held. Spring 88 will now be compressed. The ring 82 will pass over the step 90 on the body 70. The reduced diameter will allow the ledges 56 to push the keys 84 backwards into the ring 82 against the body 70. The ledges 56 can then pass over the keys 84 and allow the piston 46 and seal ring 69 to move upwards until ring 69 reaches the upper end of the recess 67. Spring 88 is now free to push the ring 82 and keys 84 back up the step 90. The valve 10 is now is the position it was on run in. 1 Reference is now made to Figure 2 of the drawings which 2 illustrates a second embodiment of a hydrostatic pressure 3 valve, generally indicated by reference numeral 110, 4 according to a second embodiment, of the present 5 invention. Valve 110 has many like parts to the valve 10 6 of the first embodiment and these have been given the 7 same reference numeral with the addition of 100. Valve 8 110 operates in an identical manner to valve 10, except 9 instead of using a spring collet 54 to support the fluid

10 column, a disc spring stack 90 is used which can be

11 compressed until the keys 184 are expanded outward into a

12 first groove 92, to control action of the valve. The disc

13 spring stack 90 could be a Belville® spring stack.

14 . _, , , ' ^•

15 Disc spring 90 rests between the pistons 146,148. The

16 trailing sleeve 150 now has an inner surface 94 in which

17 are arranged parallel circumferential grooves 92,96. The

18 grooves 92,96 are sized to allow the keys 184 to expand

19 into when they are aligned with either groove 92,94. 20

21 In use, valve 110 is- run in the well bore and the pistons

22 146,148 are located at their furthest distance apart,- b

23 virtue of the . springs 90,95,97. Disc spring 90 forces

24 face 98 of the first piston 146 against a split ring stop

25 99 located on the trailing sleeve 150. Spring 97 acts

26 between the stop 99 and a ledge 93 on the body 170 of the

27 first piston 146. It is noted that the first piston 146

28 now has a bore.91 running through its body 170. Spring 95

29 acts between a face 162 of piston 146 and a ledge 87 on

30 • the body 170. Springs 95,97 are chosen so that the keys

31 184 rest on a ridge 85 between the grooves 92,96. As with

32. the first embodiment, the piston 146 is pushed against

33 the sliding seal ring 169, to a position where the ring 169 abuts the sleeve 124. There is no available flow path through the valve 110 and the upper side of the pump will be sealed from the upper end of the production tubing. ^{■ ' •} When the valve 110 is in position and the pump pushes fluid up towards the valve .110 during production, fluid pressure will impinge on all the downward facing surfaces of the valve 110. Pressure on the second piston 148, will cause it to move upwards together with the trailing sleeve 150 and the inner sleeve 124 against the spring 142. Pressure on the body 170 of the first piston 146, will assist in this, movement as piston 146 moves against the sliding seal ring 169, which in turn pushes the inner sleeve 124.upwards . This movement causes the inner^' sleeve 124 to rise away from the end stop 130 and in doing so exposes the annular passageway 126 to the central bore.. . . 160. Production fluid travels up the passageway 126 and re-enters the central bore 160 through the flow ports 138 in the inner sleeve 124. As long as the pressure is maintained on the second piston 148, the valve 110 will pass production fluid upwards towards the surface of the well. ^'. If the pressure of the production fluid drops i.e. hydrostatic pressure increases, valve 110 will close. Pressure will now be upon the first piston 146 and the sliding seal ring 169. The surface area^" 168 of the sliding seal ring 169 which is exposed to. the central bore 160 is greater than the surface are of the face 164 and apex 166 of the piston 146. As a result, with the two surfaces abutting, the seal ring 169 will force the piston_.146 downwards. The keys 184 are located at the portion 85 between grooves 92,96. The keys 184 are at the portion 85 by virtue of the disc spring stack 90 and spring 95. Piston 146 will be subsequently supported by the shoulder 83 abutting the keys 184. In this position, fluid entering the valve 110 from above will be stopped at the piston 146. Fluid will be able to pass through the flow ports 138 and down the passageway 126, but it will not be able to exit the valve 110, as there is no through path at the lower end 116 of the valve . Fluid loading on the piston 146 is supported by the Belville spring stack 90. The valve 110 therefore supports fluid in this position and back-flow to the pump is prevented.

If fluid needs to be pumped through the valve 110 towards the pump, this is achieved by increasing pressure to the valve 110 from above. As the sealing ring 169 has a greater surface area than the piston 146, the ring 169 will force the piston downwards until the seal reaches the lower end of the recess 167. Increased pressure on the piston will force the portion 83 passed the keys 184 by pushing them downward and then outward into groove 92. The keys 184 then return inward to relocate in the ridge 85. This allows the portion 83 to pass over the keys 184 and allow the piston 146 to move downwards, compressing spring 90. In this position, the piston 146 has moved and exposed the flow ports 163 in the trailing sleeve 150. This provides a fluid flow path down through the tool from the central bore 160, into the trailing sleeve 150, through flow ports 163, into the passageway 65 between the sleeve 150 and the sleeve 124, passed the supports 149 which align the piston 148 in the sleeve 150, and out through the central bore 160 at the lower end 118 of the valve 110. The valve 110 can be reset to allow production fluid to recommence flow upwards through the valve. Re-setting will position the valve back to the configuration on run in. To reset the valve 110, pressure is released or reduced at the upper end 112 of the valve 110. Release of pressure causes the spring 95 to expand and push the piston 146 upwards. Piston 146 will rise until the raised portion 83 passes the keys 184 by lifting the keys 184 and then pushing them outward into the groove 96. The keys 184 then expand inwards from the body 170 as the springs 95,97 move the piston 46 back to reposition the keys 184 at the ridge 85. The valve 110 is now in the position it was on run in.

A further feature of the second embodiment is the incorporation of debris filters 201,202 at either end of the bore 91 through the first piston 146. These are incorporated to prevent debris reaching the disc spring 90.

As an alternative to the incorporation of debris filters 201,202 a fluid by pass path can be incorporated through the first piston 146. This is illustrated in Figure 3, which shows a section of the valve 110 at the upper end of the piston 146. Ports 301 are provided on the piston 146 so that fluid may pass from the bore 91 through the ports 163 on the trailing sleeve 150 of the second piston 148. This flow path carries debris through and out of the valve 110. It will be apparent that in this embodiment seals will be required between moving parts of the piston 146 to prevent the ingress of debris to the springs. The principal advantage of the present invention is that it provides a hydrostatic support valve which can selectively be pumped through when required.

A further advantage of the present invention is that it provides a hydrostatic support valve which can be cycled between support and pump through.

A yet further advantage of an embodiment of the present invention is that it provides a hydrostatic valve which, when pumped through, the strong spring collet on the inner sleeve becomes redundant so that minimal pressure is required during pump through.

It will be appreciated by those skilled in the art that various modifications may be made to the invention herein described without departing from the scope thereof. In particular, although the description and statements have referred to the terms ^λup' and 'down' it will be appreciated that these are relative and that the valve could be used at any orientation in a well bore. Additionally the numbers of keys, sprung legs and supports can be varied to suit the scale of the valve in use.

Claims

1. A hydrostatic support valve, the valve comprising a substantially cylindrical body for connection in a work string, in which is located two oppositely directed pistons, each piston being biased by a spring, wherein the springs are selected such that fluid can travel through the body in a first direction and, by movement of the pistons under fluid pressure, first and second operating position are provided, wherein in the first operating position fluid is prevented from passing through the body in a reverse direction, and in the second operating position fluid travels through the body in the reverse direction.

2. A hydrostatic support valve as claimed in Claim 1 wherein the springs are selected to provide a relatively strong spring and a relatively weak spring .

3. A hydrostatic support valve as claimed in Claim 2 wherein the relatively strong spring acts in the reverse direction and the relatively weak spring acts in the first direction.

4. A hydrostatic support valve as claimed in any preceding Claim wherein the fluid travels through a first flow path in the body in the first direction and a second flow path in the body in the reverse direction.

5. A hydrostatic support valve as claimed in any preceding Claim wherein the valve includes one or more sleeves, integral with the pistons.

6. A hydrostatic support valve as claimed in Claim 5 wherein the sleeves include flow ports therethrough such that their movement controls fluid flow through the valve.

7. A hydrostatic support valve as claimed in any preceding Claim wherein at least a portion of the first piston is located within the second piston. ^'

8. A hydrostatic support valve as claimed in any preceding Claim wherein at least one piston includes , a substantially conical drive face against which . fluid pressure can act.

9. A hydrostatic support valve as claimed in any one of Claims 4 to 8 wherein the flow paths, are substantially annular in cross-section to provide a significant flow area for production of the well- through the valve.

10. A hydrostatic support valve as claimed in any preceding Claim further comprising engaging means between the pistons.

11. A hydrostatic support valve as claimed in Claim 10 wherein. the engaging means comprises one or more ^' locking keys located on a first piston and a collet located on a second piston.

1 12. A hydrostatic support valve as claimed in Claim 11 2 wherein the collet includes one or more retaining 3 elements having a ledge thereupon for selective 4 engagement with the one or more keys. ⁵ 6

13. A hydrostatic support valve as claimed in Claim 10 7 wherein the engaging means comprises one or more 8 locking keys located on a first piston which each 9 mate with one of two grooves on a surface of a second 10 piston.

11

12 14. A hydrostatic support valve as claimed in any

13 preceding Claim wherein the valve is re-settable. 14

15 15. A method of accessing a formation in a wellbore belo

16 a pump, the method comprising the steps:

17 a) locating a hydrostatic support valve according to

18 , the first aspect and an electrical submersible

19 pump on a workstring;

20 b) running the workstring into a well bore and

21 pumping produced fluids from a formation via the

22 pump to the surface while directing fluid flow

23 through the valve;

24 c) on a drop in the pressure of the production fluid

25 . ^' using the fluid pressure to switch the valve so 26. that it prevents flow towards the formation. and

27 supports the fluid in the workstring above the

28 . , valve; and

29 d) using fluid pressure to switch the valve to 30 provide access of fluids to the formation. 31

32 16. A method as claimed in Claim 15 wherein the valve is

33 located above the pump.

17. A method as claimed in Claim 15 wherein the valve is located below the pump.

18. A method as claimed in any one of Claims 15 to 17 wherein the valve is run on a lock or packer anchoring device.

19. A method as claimed in any one of Claims 15 to 18 wherein the method includes the step of re-setting the valve so that pumping of produced fluids can recommence .