Downhole apparatus and method

Abstract

A downhole apparatus comprising a body configured to be coupled to a production tubular and an upper opening and a lower opening. First and second flow paths are provided between the upper opening and the lower opening in the body, and a flow diverter is arranged to direct downward flow through the body towards the second flow path and away from the first flow path. A filter device in the second flow path filters or collects solid particles in the second flow path from passing out of the lower opening of the apparatus. The apparatus has particular application to artificial lift hydrocarbon production systems, and may be installed above a downhole pump in a production tubing to prevent solids from settling on the pump during pump shutdown. Embodiments for use with ESPs and PCPs are described.

Claims

1. A downhole production apparatus comprising: an outer tubular having an upper opening and lower opening, the outer tubular configured to be assembled into a production string above a downhole production pump; an inner tubular extending at least partially along the inside of the outer tubular, the inner tubular having a wall with at least one passageway; and annular space separating at least part of the outer tubular and at least part of the wall of the inner tubular, wherein the annular space is arranged to collect downward moving solid particles that have been directed away from the inner tubular and toward the annular space; a flow diverter arranged to direct downward moving solid particles toward the annular space and away from the inner tubular; wherein the at least one passageway extends from an inside of the inner tubular to the annular space such that fluid flowing upwardly into the inner tubular flows through the wall of the inner tubular and into the annular space, thereby causing solid particles that have been collected to be carried out of the annular space.

2. The apparatus of claim 1, further comprising at least one opening, wherein the at least one opening permits fluid flowing upwardly in the inner tubular to reach the upper opening of the outer tubular even if upward flowing fluid cannot flow through the at least one passageway in the wall of the inner tubular due to an accumulation of collected solid particles.

3. The apparatus of claim 1, wherein the at least one passageway comprises multiple passageways in the wall of the inner tubular, the multiple passageways arranged such that fluid flowing upwardly into the inner tubular flows out the multiple passageways and into the annular space, thereby causing solid particles that have been collected to be progressively carried out of the annular space.

4. The apparatus of claim 1, wherein the at least one passageway comprises a first passageway and a second passageway in the wall of the inner tubular, the first passageway positioned adjacent a first end of the wall and the second passageway positioned adjacent an end opposite of the first end such that the second passageway permits fluid flowing upwardly in the inner tubular to reach the upper opening in the outer tubular even if fluid cannot flow through the first passageway in the wall of the inner tubular due to an accumulation of collected solid particles.

5. The apparatus of claim 1, further comprising one or more holes arranged between a main flow path through the apparatus and a lower part of the annular space, the one or more holes arranged to receive upward flow of fluid from the main flow path and to stimulate upward flow at a bottom of the annular space, further assisting with carrying collected solids away from the lower part of the annular space.

6. The apparatus of claim 1, wherein the at least one passageway comprises a slot.

7. The apparatus of claim 6, wherein the slot has a dimension of approximately 0.5 millimeters.

8. The apparatus of claim 6, wherein the slot is a laser cut slot.

9. The apparatus of claim 1, wherein the at least one passageway comprises two or more slots having different orientations.

10. The apparatus of claim 9, wherein the two or more slots each have a dimension of approximately 0.5 millimeters.

11. The apparatus of claim 9, wherein the two or more slots are laser cut slots.

12. The apparatus of claim 1, further comprising a mesh or screen disposed over the at least one passageway.

13. The apparatus of claim 1, further comprising a downhole production pump, wherein the downhole production pump is an electric submersible pump (ESP) or progressive cavity pump (PCP) coupled beneath the lower opening of the tubular housing.

14. The apparatus of claim 1, wherein the flow diverter comprises a valve.

15. The apparatus of claim 14, further comprising at least one opening, wherein the at least one opening permits fluid flowing upwardly in the inner tubular to reach the upper opening of the outer tubular even if upward flowing fluid cannot flow through the at least one passageway in the wall of the inner tubular due to an accumulation of collected solid particles.

16. The apparatus of claim 14, wherein the at least one passageway comprises multiple passageways in the wall of the inner tubular, the multiple passageways arranged such that fluid flowing upwardly into the inner tubular flows out the multiple passageways and into the annular space, thereby causing solid particles that have been collected to be progressively carried out of the annular space.

17. The apparatus of claim 14, wherein the at least one passageway comprises a first passageway and a second passageway in the wall of the inner tubular, the first passage way positioned adjacent a first end of the wall and the second passageway positioned adjacent an end opposite of the first end such that the second passageway permits fluid flowing upwardly in the inner tubular to reach the upper opening in the outer tubular even if fluid cannot flow through the first passageway in the wall of the inner tubular due to an accumulation of collected solid particles.

18. The apparatus of claim 14, further comprising one or more holes arranged between a main flow path through the apparatus and a lower part of the annular space, the one or more holes arranged to receive upward flow of fluid from the main flow path and to stimulate upward flow at a bottom of the annular space, further assisting with carrying collected solids away from the lower part of the annular space.

19. The apparatus of claim 14, wherein the at least one passageway comprises a slot.

20. The apparatus of claim 19, wherein the slot has a dimension of approximately 0.5 millimeters.

21. The apparatus of claim 19, wherein the slot is a laser cut slot.

22. The apparatus of claim 14, wherein the at least one passageway comprises two or more slots having different orientations.

23. The apparatus of claim 22, wherein the two or more slots each have a dimension of approximately 0.5 millimeters.

24. The apparatus of claim 14, further comprising a mesh or screen disposed over the at least one passageway.

25. The apparatus of claim 22, wherein the two or more slots are laser cut slots.

26. The apparatus of claim 14, further comprising a downhole production pump, wherein the downhole production pump is an electric submersible pump (ESP) or progressive cavity pump (PCP) coupled beneath the lower opening of the tubular housing.

27. A downhole apparatus for a production tubing, the apparatus comprising: a tubular having an upper opening and a lower opening, and defining a first flow region between the upper opening and the lower opening, wherein the tubular is configured to be assembled into an outer tubular in a production string above a downhole production pump such that a second flow region is formed in a space between the first flow region and a wall of the outer tubular after assembly into the outer tubular, the second flow region being arranged to collect downward moving solid particles; a flow diverter adjacent the upper end of the tubular configured to direct solid particles moving downwardly in the outer tubular away from the first flow region; one or more passageways extending through a wall of the tubular, the one or more passageways arranged such that when the tubular is assembled into an outer tubular upward flowing fluid through the first flow region in an upward direction causes fluid flow in the second flow region, which carries collected solid particles out of the second flow region.

28. The apparatus of claim 27, wherein the one or more passageways comprises a slot.

29. The apparatus of claim 28, wherein the slot has a dimension of approximately 0.5 millimeters.

30. The apparatus of claim 28, wherein the slot is a laser cut slot.

31. The apparatus of claim 27, wherein the one or more passageways comprises two or more slots having different orientations.

32. The apparatus of claim 31, wherein the two or more slots each have a dimension of approximately 0.5 millimeters.

33. The apparatus of claim 31, wherein the two or more slots are laser cut slots.

34. The apparatus of claim 27, further comprising a mesh or screen disposed over the one or more passageways.

35. The apparatus of claim 27, further comprising a downhole production pump, wherein the downhole production pump is an electric submersible pump (ESP) or progressive cavity pump (PCP) coupled beneath the lower opening of the tubular housing.

36. The apparatus of claim 27 wherein the flow diverter comprises a valve.

37. The apparatus of claim 36, wherein the one or more passageways comprises a slot.

38. The apparatus of claim 37, wherein the slot has a dimension of approximately 0.5 millimeters.

39. The apparatus of claim 37, wherein the slot is a laser cut slot.

40. The apparatus of claim 36, wherein the one or more passageways comprises two or more slots having different orientations.

41. The apparatus of claim 40, wherein the two or more slots each have a dimension of approximately 0.5 millimeters.

42. The apparatus of claim 40, wherein the two or more slots are laser cut slots.

43. The apparatus of claim 36, further comprising a mesh or screen disposed over the one or more passageways.

44. The apparatus of claim 36, further comprising a downhole production pump, wherein the downhole production pump is an electric submersible pump (ESP) or progressive cavity pump (PCP) coupled beneath the lower opening of the tubular housing.

45. The apparatus of claim 27, wherein the tubular is assembled into an outer tubular in a production string above a downhole production pump, thereby forming a second flow region in a space between the first flow region and a wall of the outer tubular.

46. A method of forming a hydrocarbon production system, the method comprising; assembling a downhole apparatus according to claim 27 into a production tubing above a downhole production pump.

47. A downhole production system comprising: a production string in a hydrocarbon formation; the apparatus according to claim 1 assembled into the production string; and an electrical submersible pump (ESP) or progressive cavity pump (PCP) assembled into the production string, beneath the apparatus.

48. A downhole production system comprising: a production string in a hydrocarbon formation; the apparatus according to claim 27 assembled into the production string; and an electrical submersible pump (ESP) or progressive cavity pump (PCP) assembled into the production string, beneath the apparatus.

49. The system of claim 48, wherein the flow diverter of the apparatus comprises a valve.

50. A method for washing away collected solid particles from a downhole apparatus, the method comprising: operating a downhole production pump, thereby causing fluid to flow upwardly into a first flow region of the downhole apparatus and induce fluid flow in a second flow region of the downhole apparatus via at least one passageway extending through an inner tubular wall separating the first flow region from the second flow region, the induced flow further causing collected solid particles that were directed toward the second flow region and away from the first flow region when the downhole production pump was shutdown to move upwardly, thereby washing collected solid particles from the downhole apparatus.

51. The method of claim 50, further comprising causing the fluid to flow up the inner tubular and out of a flow diverter, the flow diverter comprising a valve.

52. The method of claim 50, wherein the induced flow causes the collected solid particles to be progressively washed from the second flow region.

53. The method of claim 50, wherein the downhole production pump is an electrical submersible pump (ESP) or progressive cavity pump (PCP).

54. The method of claim 50, wherein the at least one passageway comprises a plurality of slots along the inner tubular wall.

55. The method of claim 54, wherein at least one of the plurality of slots has a dimension of approximately 0.5 millimetres.

56. The method of claim 54, wherein at least two of the plurality of slots have different orientations.

57. The method of claim 54, wherein the plurality of slots are laser cut slots.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There will now be described, by way of example only, embodiments of the invention with respect to the following drawings, of which:

(2) FIGS. 1A, 1B and 10 are sectional views of a downhole apparatus in accordance with a first embodiment of the invention in different phases of operation;

(3) FIGS. 2 and 3 are sectional views of downhole apparatus according to alternative embodiments of the invention;

(4) FIGS. 4A and 4B are respectively longitudinal section and cross-sectional views of a downhole apparatus in accordance with a further alternative embodiment of the invention;

(5) FIG. 5 is part-longitudinal section of a downhole apparatus in accordance with a further alternative embodiment of the invention;

(6) FIGS. 6A to 6C are sectional views of a downhole apparatus in accordance with a further alternative embodiment of the invention in different phases of operation;

(7) FIG. 7 is a cross-sectional view through a part of the downhole apparatus of FIGS. 6A to 6C;

(8) FIGS. 8, 9 and 10 are part-sectional views of vent configurations which may be used in different embodiments of the invention; and

(9) FIG. 11 is a sectional view of a downhole apparatus in accordance with an alternative embodiment of the invention in operation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(10) Referring firstly to FIGS. 1A to 1C, there is shown in longitudinal section a downhole apparatus according to a first embodiment of the invention, generally depicted at 10. The apparatus 10 is configured for use in an artificial lift hydrocarbon production system which uses an electrical submersible pump (ESP) to pump hydrocarbons upwards in a production tubing to surface.

(11) The apparatus 10 comprises a body 12 formed from a top sub assembly 14, a pressure retaining housing 16, and a bottom sub assembly 18. The body 12 defines a throughbore 20 between an upper opening 22 and a lower opening 24. The lower opening is coupled to a production tubing above a downhole pump such as an ESP (not shown). The apparatus 10 may be located immediately above the ESP in the production tubing, or there may be intermediate tubing (not shown) between the ESP and the apparatus 10. It is advantageous for the apparatus to be located close to the ESP and the tubing string.

(12) The apparatus 10 also comprises an inner tubular 26 which extends along a part of the body 12. The inner tubular 26 is concentric with the body 12, and is aligned with the lower opening 24 and the upper opening 22 so as to provide a continuation of a main bore of the production tubing. In this embodiment, the inner tubular 26 has an inner diameter approximately equal to the main bore of the production tubing. The inner tubular 26 divides the throughbore 20 into a first flow region 28a on the inside of the tubular and a second flow region 28b in an annular space 30 between the inner wall of the housing 16 and the inner tubular 26. The inner tubular 26 is vented such that the first flow region 28a and the second flow region 28b are in fluid communication. The inner tubular 26 is also provided with a mesh 31 to prevent the passage of solids having a size larger than the apertures in the mesh from passing between the first and second flow regions.

(13) At the upper end of the inner tubular 26 is a valve 34 which functions to divert flow in the apparatus 10. A spider 32 supports the inner tubular 26 and defines a valve seat 36 for a valve member 38. The valve 34 is operable to be moved between an open position, shown in FIGS. 1A and 10, and a closed position shown in FIG. 1B. The valve member 38 is biased towards the closed position shown in FIG. 1B by a spring located between a valve mount 40 and the valve member 38.

(14) Operation of the apparatus will now be described with reference to FIGS. 1A to 1C. In FIG. 1A, the apparatus 10 is shown in a production phase, with the downhole pump operating to cause production fluids to flow upwards through the throughbore (as depicted by the arrows), entering the lower opening 24 and leaving the upper opening 22. As fluid flows into the apparatus 10, it enters the first flow region 28a defined by the inner tubular 26. The fluids also enter the second flow region 28b through vents 33 in the inner tubular 26, such that fluid also flows upwards in the annular space 30 between the inner wall of the housing 16 and the inner tubular. Here it should be noted that there is no direct flow path from the lower opening 24 to the second flow region which does not pass through the first flow region. The pressure created by the downhole pump acts against the valve member 38 and opens the valve 34, such that fluid flows from the first flow region 28a past the valve 34 and out of the upper opening 22. Fluid flowing in the second flow region 28b flows past the spider 32 and exits the upper opening 22.

(15) FIG. 1B shows a shutdown phase of the hydrocarbon production system. In this configuration, the downhole pump has been switched off, and fluid is no longer pumped upwards through the apparatus 10. The absence of pressure on the lower surface of the valve member 38 causes the valve 34 to close. This prevents fluid from entering the first flow region from an upper part of the apparatus 10 or from production tubing above the apparatus. Fluid flows downwards in the apparatus 10, as depicted by the direction of the arrows, until the fluid column in the production string equalises with the fluid column in the wellbore annulus. During this downward fluid flow phase, the fluid is diverted into the second flow region 28b. Solid particles such as sands entrained in the fluid are also diverted into the second flow region 28b. The fluid is allowed to pass into the first flow region 28a through vents 33 in the inner tubular 26, and out through the lower opening 24. The mesh 31 functions to screen or filter solid particles such as sands from the fluid, and the solids are collected in the second flow region 28b. When the fluid column is at rest and no longer flows through the tool, solid particles continue to fall through the fluid by gravity acting on the solids. Solid particles flowing in the fluid are diverted away from the first flow region 28a by the closed valve and into the second flow region 28b where they are collected.

(16) FIG. 1C shows a subsequent production phase, after operation of the downhole pump has been resumed. Production fluid is caused to flow upwards through the apparatus 10 and the pump pressure opens the valve 34 to open the first flow region 28a. The accumulated solid particles do not generate any significant back pressure on the flow path through the apparatus: the back pressure of the apparatus and valve is known, and can be exceeded within the normal operating parameters of the downhole pump. As fluid flows in the first flow region 28a defined by the inner tubular, fluid is also vented to the second flow region 28b. This has the effect of inducing fluid flow in the second region 28b which lifts and carries sands and solids which have accumulated in the second flow region during the shutdown phase. The sands and solids are entrained in the flow upwards through the apparatus and out of the upper opening 22, into the production tubing. Therefore the accumulated sands and solids are washed from the apparatus during a subsequent production phase.

(17) The apparatus of this embodiment provides a filter system for solids in a production tubing which prevents the solids from settling on, or passing downwards through, a downhole pump. The downhole apparatus filters the solids in a way which does not provide a significant backpressure or resistance to subsequent operation of the pump. In addition, the solids are collected in a manner which allows them to be entrained into a production fluid flow during a subsequent production phase and therefore allows them to be washed from the apparatus. This allows the apparatus to be used for extended periods.

(18) FIGS. 2 and 3 are sectional views of upper parts of two alternative embodiments of the invention. FIG. 2 shows an upper part of an apparatus 40, and FIG. 3 shows an upper part of an apparatus 60. The apparatus 40 and 60 are similar to the apparatus 10, and will be understood from FIGS. 1A to 1C and the accompanying text. However, the apparatus 40 and 60 differ in the valve configuration.

(19) Referring to FIG. 2, the apparatus 40 comprises a ball valve 42, in place of the mushroom-type valve in the apparatus 10. The ball valve 42 comprises a ball 44 which rests on a valve seat 46 to seal the inner tubular 26. A retainer 48 prevents the ball 44 from passing too far upwards in the apparatus 40 under the fluid flow. The ball 44 is selected to be lifted by the fluid flow during a production phase (equivalent to FIGS. 1A and 1C) and rests on the valve seat 46 by gravity during a shutdown phase of the downhole pump (equivalent to FIG. 1B).

(20) FIG. 3 shows an upper part of an apparatus 60, which differs from the apparatus 10 and 40 in the configuration of the valve. In this embodiment, the valve 62 is a flapper-type valve having a valve member 64 which is pivotally mounted on the spider to move between an open position and a closed position on the valve seat 66. In the closed position, the valve prevents fluid flow into an upper part of the inner tubular 26. A biasing member is included in a hinge 68 such that in the absence of upward flow, the valve member 64 rests on the valve seat.

(21) Referring now to FIGS. 4A and 4B, there is shown a further alternative embodiment of the invention, which differs in its valve configuration. FIG. 4A is a longitudinal section through an upper part of an apparatus, generally depicted at 80, and FIG. 4B is a cross-section through the apparatus 80 at line B-B.

(22) The apparatus is similar to the apparatus 10, and will be understood from FIGS. 1A to 1C and the accompanying text. The apparatus 80 comprises a retrievable valve 84, which is of the mushroom-type, comprising a valve member 82 movable between an open and closed position on a valve mount 88. As before, a spring biases the valve member into a closed position on a valve seat 86.

(23) In this embodiment, the valve mount 88 comprises fins 90 (most clearly shown in FIG. 4B) which are held into the valve seat by shear screws 92. The upper part of the valve member 86 is provided with a standard fish neck formation 94, and is configured to engage with a wireline fishing tool having a complementary socket. Should it be required to remove the valve to gain full bore access to the production tubing, a wireline tool can be run down the production tubing to engage with the fish neck 94. By pulling on the wireline or imparting an upward jar, the shear screws 92 can be sheared and the valve mount 82 released from the valve seat 86. The valve member 82 and valve mount 88 can then be pulled to surface via the wireline. It will be appreciated that other valve types may be provided with a remote retrieval arrangement similar to that shown in FIGS. 4A and 4B.

(24) Referring now to FIG. 5, there is shown a further alternative embodiment of the invention, which differs in its valve configuration. FIG. 5 is a longitudinal section through an upper part of an apparatus, generally depicted at 200. The apparatus 200 is similar to the apparatus 10, and will be understood from FIGS. 1A to 1C and the accompanying description. The apparatus 200 comprises a flapper-type valve 220, having a valve member 240 which is pivotally mounted on the spider 232 to move between an open position and a closed position on the valve seat 260. A biasing member is included in a hinge 280 such that in the absence of upward flow, the valve member 240 rests on the valve seat 260. In the closed position, the valve prevents fluid flow into a first flow region 228a. A space 265 is provided to accommodate the valve member 240 in the open position.

(25) This particular embodiment enables an intervention to provide full bore access 250 without the need to remove any part of the apparatus. This is achieved by the presence of a sleeve 230, which connects the tubular above the valve to the tubular below it. FIG. 5 shows the sleeve 230 in a lower position, in which a window 270 in the sleeve accommodates the valve member 240 and allows it to move between the open and closed positions. The sleeve is held in the lower position by engaging formations 290 which are received in recesses 210 in the upper subassembly 214. An upper end 225 of the sleeve 230 is provided with a shoulder 235 which can be engaged by an actuating tool (not shown) to pull the sleeve upwards with respect to the body 212 of the apparatus. Upward movement of the sleeve 230 forces the valve member 240 into the open position. The sleeve is retained in an upper position by the engagement of the formations 290 with locking recess 255, and therefore the sleeve locks the valve member 240 into its open position.

(26) The above-described embodiments are particularly suited for use with downhole pumps which are operated by downhole motors, such as ESPs. FIGS. 6A to 6C and 7 illustrate an alternative embodiment of the invention suitable for use with a system which has a shaft extending through the apparatus. This is particularly useful in applications to production systems with progressive cavity pumps (PCPs) which are driven from surface by a drive shaft which extends down the production tubing

(27) In FIGS. 6A to 6C, an upper part of the apparatus, generally depicted at 100, is shown in longitudinal section in different phases of operation. FIG. 7 is a part-sectional view from above, showing the shaft and bore in cross section and the petals of the valve in a closed configuration. Again, the apparatus 100 is similar to the apparatus 10, and will be understood from FIGS. 1A to 1C and the accompanying description. Once again, the apparatus 100 differs in details of the valve configuration, which is designed to permit the passage of a drive shaft 101 for a PCP. In this embodiment, the valve comprises a rubber petal valve 104, which has a plurality of petals 106 arranged circumferentially around the drive shaft 101. The valve 104 is engineered to be biased towards the closed position, but the biasing force is sufficiently light so as not to unduly restrict the rotation of the drive shaft to drive the pump.

(28) FIG. 6A shows the apparatus 100 in a production phase. The downhole pump is operating to cause production fluids to flow upwards through the apparatus 100, and with the flow acting against the valve 104, the valve opens away from the drive shaft 101 and allows fluid to flow from the first flow region 28a towards the upper opening 22.

(29) FIG. 6B shows shutdown phase of the production system, in which the downhole pump has ceased. With no pressure acting from below, the valve 104 closes against the drive shaft 101 and prevents flow to the first flow region 28a from above. Fluids and/or entrained solids and sand flow downwards in the apparatus 101, and are diverted to the second flow region 28b in which the solids and sands accumulate.

(30) In a subsequent production phase, shown in FIG. 6C, the downhole pump resumes to pump fluid upwards through the apparatus 100 and open the valve 104. Fluid flow in the first flow region 28a also induces flow in the second flow region 28b to carry sands and solids upwards in the apparatus to rejoin the production flow.

(31) FIGS. 8 to 10 show a range of vent configurations which may be used in various embodiments of the invention, alone or in combination. FIG. 8 shows a first vent configuration 170, showing a wall 172 of the inner tubular comprising a plurality of circular holes 174 which vent the first flow region 28a to the second flow region 28b. The holes 174 are arranged in a helical pattern on the inner tubular, and are provided with a wire mesh filter or screen 176 on the outer surface to prevent solid particles moving from the second flow region to the first flow region.

(32) FIG. 9 shows an alternative arrangement 180, in which the wall 182 of the inner tubular is provided with a plurality of slots 186 which vent the first flow region to the second flow region. The slots 186 are finely cut in the wall 182, and are formed circumferentially in the tubular. In this arrangement, multiple groups 184 of slots 186 are provided, with multiple groups arranged helically around the tubular. It will be appreciated that the slots could be cut in other orientations in alternative embodiments of the invention, and in further alternatives, a wire mesh screen or filter may be provided over the slots 186.

(33) FIG. 10 shows a further alternative embodiment of the invention at 190. In this embodiment, the vents are circular holes 194 formed with rubber membrane covers 196 which are arranged to open to flow from the inside of the tubular to the outside, and to close to flow from the outside of the tubular to the inside. In use, the rubber membrane 196 covers the holes to prevent flow of fluid from the second flow region 28b into the first flow region 28a, and therefore prevents the passage of solids and sands downward through the apparatus.

(34) The vents may be arranged in a variety of different configurations, and in some applications it may be advantageous to arrange the vents in a non-uniform distribution or pattern on the apparatus. For example, improved operation may be achieved by increasing the quantity and/or size of vents (and therefore the fluid communication between the first and second flow paths) towards the lower part of the apparatus.

(35) It may also be advantageous to provide one or more additional flow paths which introduce an axial flow component at the lower part of the second flow path. For example, as shown in FIG. 11, the apparatus, generally depicted at 310, is similar to the apparatus 10 and will be understood from FIGS. 1A to 1C and the accompanying description. Like features are given like reference numerals incremented by 300. One or more holes 337 may be arranged between the lower part of the first flow path 328a and the second flow path 328b through the lower subassembly 318 to receive upward flow from the main flow path. This may stimulate flow at the bottom of the second flow path and assist with the solids from being washed away from a lower part of the second flow path.

(36) The invention provides a downhole apparatus comprising a body configured to be coupled to a production tubular and an upper opening and a lower opening. First and second flow paths are provided between the upper opening and the lower opening in the body, and a flow diverter is arranged to direct downward flow through the body towards the second flow path and away from the first flow path. A filter device in the second flow path filters or collects solid particles in the second flow path from passing out of the lower opening of the apparatus. The apparatus has particular application to artificial lift hydrocarbon production systems, and may be installed above a downhole pump in a production tubing to prevent solids from settling on the pump during pump shutdown. Embodiments for use with ESPs and PCPs are described.

(37) Various modifications may be made within the scope of the invention as herein intended, and embodiments of the invention may include combinations of features other than those expressly claimed. In particular, flow arrangements other than those expressly described herein are within the scope of the invention. For example, although the described embodiments include a first flow path corresponding to a main through bore of the apparatus, and a second flow path in an annular space, this is not essential to the invention. Other flow paths may be used. However, the flow arrangement of the described embodiments has been recognised by the inventors to efficiently allow solid particles and sands collected and accumulated in the second flow path to be entrained in the production flow during the subsequent production phase. Multiple downhole apparatus according to the invention may be used in combination in a production tubing. One apparatus may be provided in proximity to the downhole pump, with another further up in the tubing string. One or more of the apparatus may be configured for intervention (for example to recover full-bore access), but this may not be required for the lower apparatus.

(38) It will be appreciated that combinations of features from different embodiments of the invention may be used in combination.