Combined Anti-Rotation and Flow Control Tool

Abstract

A combined anti-rotation and flow control tool comprises a tubular housing for connection with an oil production tubing string. A flow port in the side wall of the housing is selectively covered by a collar rotatably mounted on the tubular housing and including corresponding ports therein for selective alignment with the flow ports as the collar is rotated. An anti-rotation mechanism includes a fixed jaw on the tubular housing and a floating jaw on the collar for rotation therewith to vary the overall diameter of the tool as the floating jaw rotates relative to the fixed jaw. The collar and the floating jaw are coupled for movement together so that the flow ports are always in the open position when the anti-rotation mechanism is in a set position anchored against righthand rotation of the tubing string.

Description

This application claims foreign priority benefits from Canadian Patent Application 2,555,023 filed Aug. 3, 2006.

FIELD OF THE INVENTION

The present invention relates to a flow control tool for connection in series with an oil production tubing string having an inline pump to selectively pump fluids through either ports in the tool or a bottom end of the tubing string, and more particularly, the present invention relates to a flow control tool which incorporates an anti-rotation mechanism for anchoring the tubing string relative to a surrounding well casing and for simultaneously operating condition of the flow ports of the flow control tool.

BACKGROUND

Oil production tubing strings supported in well casings commonly use an inline pump for producing oil from the well casing. The inline pump is typically a progressive cavity screw-type pump having a stator and a screw type rotor rotatably supported therein. The stator is connected on the tubing string with the rotor being connected to a series of rods extending through tubing string for driving rotation of the rotor in relation to the stator. The rotor is typically installed after the stator has been coupled to the tubing string and requires vertical placing within the tubing string. In this arrangement oil is typically produced by pumping the oil up through a bottom end of the tubing string.

A known occurrence in producing oil from a wall casing involves the well casing and tubing string becoming plugged with sand which slows the production of oil. The sand can also jam the rotor within the stator of the pump which may completely halt the production of oil. Circulation of the oil and sand within the well casing is then required to free the pump and clear the sand from the tubing string. Circulation however generally requires either pulling the tubing string from the well casing which is costly and desirably avoidable or pumping fluid down through the tubing string. Pumping fluid down through tubing string generally involves pulling the rotor from the stator and pumping fluids through the same cavities which have been plugged with sand. The rotor must then be replaced within the stator.

If an anti-rotation tool is used with the tubing string below the inline pump, the oil produced and the circulation fluids used must be pumped through a bottom of the anti-rotation tool similarly to the arrangement described above wherein the oil and fluids are pumped through a bottom end of the tubing string.

Canadian patent application 2,326,967 discloses a circulating apparatus for use with an oil production tubing string in which upper and lower housing portions are supported for rotation relative to one another and for connection in series with the tubing string. Relative rotation between the upper and lower housing portions causes flow ports to be opened and closed. In order to operate the circulating apparatus, a separate anti-rotation tool is required to anchor the lower housing portion in relation to the upper housing portion. The ant-rotation tool therefore must be mounted below the circulating apparatus so that the flow ports are spaced a considerable distance from the open bottom end of the tubing string which corresponds to either the bottom end of the anti-rotation tool or any additional tubing supported therebelow. Controlling the condition of the flow ports can be difficult as conventional anti-rotation tools are only able to secure against rotation in one direction. Furthermore the condition of the flow ports does not correspond necessarily to the condition of the anti-rotation tool and accordingly the user is not necessarily aware of the condition of the flow ports simply by setting or unsetting the anti-rotation tool.

U.S. Pat. No. 5,623,991 to Jani discloses an anti-rotation tool for anchoring a tubing string relative to a surrounding well casing using a series of drag slips which can be displaced between set and unset positions. The device can be operable to anchor against rotation in either direction relative to the well casing, however the tool requires disassembly and reassembly before use in order to be adapted from anchoring in one direction to the other. Accordingly when in use within a tubing string, the tool only operates for anchoring in one direction. No flow control ports are disclosed.

U.S. application Ser. No. 11/115,14 to LaClare discloses a tubing string anchoring tool which is operable to resist rotation of a tubing string relative to the surrounding well casing when set in either one of two anchoring positions corresponding to anchoring in either clockwise or counter-clockwise rotational directions relative to the casing. No flow control ports are disclosed however.

SUMMARY OF THE INVENTION

According to one aspect of the invention there is provided an anti-rotation and flow control tool for use with an oil production tubing string in a stationary well casing, the tool comprising:

a tubular housing extending in a longitudinal direction between an open top end and an open bottom end, at least the top end being arranged for threaded connection in series with the oil production tubing string;

a flow port formed through a side wall portion of the tubular housing;

a cover member supported on the housing for movement between a closed position in which the cover member spans the flow port and an open position in which the flow port is substantially unobstructed by the cover member; and

an anti-rotation mechanism supported on the housing for movement between an unset position and a set position in which an overall diameter of the tool is greater than in the unset position for anchoring the tubular housing against rotation in one direction relative to the stationary well casing;

the cover member and the anti-rotation mechanism being coupled for movement together such that the cover member is in the open position when the anti-rotation mechanism is in the set position.

By providing an anti-rotation mechanism and a member which controls opening and closing of flow ports operable together within a common tool, the condition of the flow ports is always known and readily controlled as the condition of the flow ports can be made dependent upon the condition of the anti-rotation mechanism when the two are moveable together. By providing flow ports and an anti-rotation mechanism commonly on a single housing, the flow ports can also be provided as close as possible to the bottom of the tubing string as no additional tooling or tubing is required below the tool when both an anti-rotation mechanism and flow ports are provided commonly thereon.

Preferably the flow ports are fully open when the anti-rotation mechanism is set against righthand rotation of the tubing string in relation to the stationary well casing.

The anti-rotation mechanism may anchor the tubing string in two directions. In this instance the anti-rotation mechanism is operable from the unset position in a first direction into a first set position anchored against righthand rotation of the tubing string relative to the well casing and in a second direction into a second set position in which the tubing string is anchored against lefthand rotation in relation to the stationary well casing.

There may be provided a stop member selectively supported on the housing which is arranged to restrict movement of the anti-rotation mechanism in one of the first or second directions from the unset position.

The flow port may be nearer to the top end of the tubular housing than the bottom end.

When there is provided a rigid tag bar spanning diametrically across the tubular housing, the bar is preferably positioned adjacent the bottom end of the tubular housing substantially below the anti-rotation mechanism and below the flow port.

When there is provided a plurality of flow ports through the side wall portion of the tubular housing, they are preferably located at circumferentially spaced positions. When there are provided two flow ports, they are preferably located at diametrically opposed positions in the side wall portion of the tubular housing.

The cover member which operates the flow ports preferably comprises a collar rotatably supported about the tubular housing and including a corresponding port therein for selective alignment with the flow port in the tubular housing.

Preferably both the top and bottom ends of the tubular housing are threaded for connection in series with tubing of the tubing string, in which the top and bottom ends of the tubular housing are fixed in relation to one another.

The anti-rotation mechanism comprises a fixed jaw projecting radially from the tubular housing in fixed relation therewith and a floating jaw projecting radially from the housing for rotation about a central axis of the tubular housing.

The floating jaw portion of the anti-rotation mechanism may be supported on the same collar rotatable about the housing which operates the flow ports.

There may be provided a circumferential slot in one of the collar or the housing and a stop mounted on the other of the collar or the housing in which the stop member is slidable along the slot as the fixed jaw is displaced relative to the floating jaw.

The flow port may be in the open position when the fixed jaw is rotated from the unset position more than 90° in a righthand direction relative to the floating jaw. Preferably the flow port is fully open when the jaws are rotated near 110° degrees relative to one another.

The floating jaw preferably projects radially outwardly from a central axis of the tubular housing greater than the fixed jaw for gripping the well casing before the fixed jaw.

There may be provided a plurality of projections extending from the bottom end of the housing in the longitudinal direction of the housing at circumferentially spaced positions about the housing.

One embodiment of the invention will now be described in conjunction with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic elevational view of a tubing string within a stationary well casing.

FIG. 2 is an enlarged elevation view of the tool for connection in series with the tubing string according to a first embodiment.

FIG. 3 is a sectional view along the line 3-3 of FIG. 2.

FIG. 4 is a sectional view along the line 4-4 of FIG. 2 in an unset position of the tool.

FIG. 5 is a sectional view along the line 4-4 of FIG. 2 in which the tool is partially rotated towards one of the set positions.

FIG. 6 is a sectional view along the line 4-4 of FIG. 2 in which the tool is shown in one of the set positions.

FIG. 7 is an elevational view of a second embodiment of the tool.

FIG. 8 is a sectional view along the line 8-8 of FIG. 7 showing the tool in an unset position.

FIG. 9 is a sectional view along the line 8-8 of FIG. 7 showing the tool in a set position against further right hand rotation of the tubing string.

In the drawings like characters of reference indicate corresponding parts in the different figures.

DETAILED DESCRIPTION

Referring to the accompanying figures there is illustrated an anti-rotation and flow control tool generally indicated by reference numeral 10. Two embodiments of the present invention are shown in the accompanying figures and accordingly some of the features common to both embodiments will first be described herein.

The tool 10 is intended for use in anchoring and controlling circulation of fluids in a tubing string 12 supported within a well casing 14. The tool is typically used with a conventional tubing string 12 having an inline pump 16 and which is arranged to be suspended within the stationary well casing 14 by a dognut 20 located adjacent the wellhead.

The pump 16 is an inline progressive cavity pump having a stator 22 arranged to be coupled in series with the tubing string and a screw type rotor 24 rotatably supported therein. Rotation of the rotor 24 is driven by a series of rods 26 extending through the tubing string 12.

The tool 10 mounts directly below the pump 16 and operates to selectively control flow through ports in the tool or through the bottom end thereof comprising the bottom end of the string. In addition the tool operates to prevent righthand or clockwise rotation, as viewed from above, of the tubing string relative to the surrounding stationary well casing when set. Without any modification of the tool being required, the tool can also be unset and subsequently set into a second set condition in which the tool is instead anchored to the well casing so as to prevent further lefthand or counter-clockwise rotation to the tubing string relative to the well casing as viewed from above.

The tool 10 includes a tubular housing 28 which is elongate in a longitudinal direction between an open top end 30 and an open bottom end 32. At the top end, the housing 28 is threaded for connection threadably in series with the tubing string directly below the pump. At the opposing bottom end 32 the housing can also be threaded for threaded connection of additional tubing sections if desired. A hollow interior of the housing 28 has a substantially constant interior diameter between the open top and bottom ends.

Turning now to the first embodiment, an upper portion 34 of the outer surface of the housing however has a larger outer diameter than a remaining main portion 36 of the housing. Accordingly a downwardly facing shoulder 38 is defined at the intersection of the upper portion 34 and the main portion 36. The shoulder comprises an annular surface about the housing which is generally perpendicular to the longitudinal direction. Below the shoulder 38, the main portion 38 has a substantially constant outer diameter which is less than the outer diameter of the upper portion 34.

The top end of the housing is internally threaded and the bottom end of the housing is externally threaded according to the first embodiment.

A first collar 40 is supported on the outer surface of the main portion 36 of the housing for abutment against the shoulder 38. The collar is slidably mounted onto the main portion 36 from the bottom end of the housing and includes an interior diameter which is near to the dimension of the outer diameter of the main portion 36 of the housing. Once abutted against the shoulder 38 the first collar 40 remains freely rotatable about a central axis of the housing extending in the longitudinal direction, in relation to the housing.

A second collar 42 is also mounted on the main portion 36 of the housing by slidably mounting onto the housing over the bottom end thereof. The second collar has similar dimensions to the first collar so that the first and second collars together when abutted adjacent one another in the longitudinal direction substantially span the length of the main portion 36. The second collar 42 is fixed onto the main portion of the housing by suitable fasteners or welding so that the second collar 42 is secured against rotation and sliding movement in the longitudinal direction in relation to the housing. The first collar 40 is thus abutted between the shoulder 38 of the upper portion 34 of the housing and the second collar 42 therebelow which is also fixed in relation to the housing 28. Though fixed and prevented from sliding movement in the longitudinal direction, the first collar 40 remains rotatable about the central axis of the housing.

Also, in the first illustrated embodiment a tag bar 44 is mounted to extend through the main portion 36 of the housing and the second collar 42 to assist in fixing the second collar in relation to the housing. The tag bar 44 comprises a fixed and rigid bar which extends diametrically across the housing 28 adjacent the bottom end of the second collar 42. An enlarged head 46 at one end of the bar is received in a corresponding recess in the outer surface of the housing at one side thereof while a fastener secures a second portion of enlarged diameter 48 in a corresponding recess at a diametrically opposed position in the side wall of the housing once the tag bar is inserted through corresponding apertures in the housing and the second collar 42.

The tool further includes an anti-rotation mechanism 50 in the form of a floating jaw 52 supported on the first collar 40 and a fixed jaw 54 supported on the second collar 42. The floating jaw 52 extends in the longitudinal direction substantially the full length of the first collar and projects outwardly from the collar in a radial direction from one side thereof. A free end 56 of the floating jaw 52 lies generally parallel to the longitudinal direction of the housing and includes teeth 58 formed therein extending the length of the jaw with aggressive biting edges for griping the surrounding well casing. The floating jaw 52 is rotatable with the first collar fully about the housing 28.

The fixed jaw 54 supported on the second collar also extends in a longitudinal direction of the housing substantially the full length of the second collar. The fixed jaw 54 also extends radially outwardly to a free end 60 which lies generally parallel to the longitudinal direction. The fixed jaw 54 is fixed in orientation relative to the second collar which is in turn fixed to the housing so that the fixed jaw remains fixed in position in orientation relative to the tubular housing 28 of the tool. The free end 60 includes carbide inserts which are arranged to grip the surrounding well casing along the length of the fixed jaw, however the teeth 58 on the floating jaw project radially outwardly from the central axis of the tubular housing a distance which is slightly greater than the free end of the fixed jaw 54 so that the floating jaw will tend to grip the surrounding well casing before the fixed jaw.

As shown in FIG. 4, the anti-rotation mechanism is in an unset position when the fixed jaw 54 and the floating jaw 52 are generally aligned with one another. In this position the overall diameter of the tubing is substantially less than the interior diameter of the well casing so that the tubing string remains rotatable within the well casing. Due to the floating jaw having teeth which project radially and outwardly beyond the free end of the fixed jaw, when the tubing string is rotated in a clockwise or righthand direction as viewed from above as shown in FIG. 5, the floating jaw will tend to grip the well casing and remain relatively fixed in orientation relative to the well casing while the fixed jaw 54 rotates away from the floating jaw to increase the overall diameter of the tool.

Once the jaws are near approximately 110° of separation relative to the central axis of the tubular housing the overall diameter of the tool is sufficiently increased that the tool is wedged within the internal diameter of the well casing so that further clockwise or righthand rotation of the tubing string within the well casing is prevented by the anti-rotation mechanism 50. Rotation of the tubing string in the opposite direction or the lefthand or counter-clockwise direction will cause the fixed jaw to again return closer to the floating jaw to reduce the overall diameter of the tool and permit the tubing string to again be rotatable within the well casing. Rotation of the fixed jaw in the counter-clockwise or lefthand direction, as viewed from above, past the floating jaw will cause the overall diameter of the tool again to increase for subsequently reaching a second set position in which the jaws and the tubular housing are again wedged within the well casing to prevent further rotation in the lefthand or counter-clockwise direction.

The tubular housing also includes flow ports 62 extending through the side wall portion of the housing at two diametrically opposed positions so that the ports 62 are circumferentially spaced from one another. Each port 62 is elongate in the longitudinal direction and spans approximately the mounting location of the first collar between the upper portion 34 of the housing and the second collar 42 fixed thereon.

Two corresponding ports 64 are also located in the first collar 40 at two diametrically opposed positions therein. The corresponding ports 64 are also elongate in the longitudinal direction and are of the same size, shape and orientation as the flow ports 62 for alignment therewith. When rotating the first collar 40 the remaining wall portion of the collar acts as a cover member to selectively enclose and cover the flow ports 62 through a portion of rotation of the first collar. Alternatively when the corresponding ports 64 align with the flow port 62 the ports are fully opened for permitting fluid flows therethrough. The first collar 40 is thus rotatable between an open position in which the corresponding ports 64 are aligned with the flow ports 62 so that the flow ports are substantially unobstructed by the covering wall portion of the first collar and a closed position in which the wall portion of the first collar fully spans the flow ports and prevents fluid flow therethrough.

The floating jaw of the anti-rotation mechanism 50 is fixed in relation to the first collar 40 and the corresponding ports 64 thereon with the jaw being oriented in relation to the ports such that the flow ports 62 are in the open position when the anti-rotation mechanism is in the set position against further righthand rotation as shown in FIG. 6, while the ports are in the closed position when the anti-rotation mechanism is in the unset position with the jaws 52 and 54 aligned with one another. In the unset position of FIG. 4, the ports 64 of the first collar are offset circumferentially by 90° in relation to the flow ports 62 in the housing. The dimensions of the ports are arranged so that the tubing string must be rotated clockwise in relation to the first collar supporting the floating jaw thereon by more than 90°, and in the order of approximately 110° to fully open the ports into the set position against righthand or clockwise rotation as viewed from above. As shown in FIG. 5, the ports begin to open through approximately 60° of clockwise rotation of the tubing string relative to the floating jaw.

As noted above, the tool according to the first embodiment is assembled by first sliding the first collar onto the main portion of the housing over the bottom end of the housing, and then subsequently sliding the second collar onto the main portion of the housing again over the bottom end of the housing. The second collar is then fixed in place with the tag bar.

The tag bar location adjacent the bottom end of the second collar ensures that the tag bar is positioned below the flow ports and substantially below the anti-rotation mechanism. As the flow ports are operated between open and closed positions and as the anti-rotation mechanism is operated between set and unset positions, the threaded ends of the housing remain fixed relative to one another for connection in series with the tubing string.

Turning now to the embodiment of FIGS. 7 through 9, the fixed jaw 54 in this instance is supported on a collar 42 which instead is integrally formed with the housing 28 of the tool 10. The top end of the housing 28 in this instance is externally threaded and has an overall diameter which is near to the overall diameter of the main portion of the housing onto which the first collar 40 is slidably mounted for supporting the floating jaw 52 thereon. The second collar 42 in this instance comprises a portion of the housing which is enlarged in diameter to define a shoulder in the form of an annular end face 80 lying perpendicular to the longitudinal direction of the housing against which a bottom end of the first collar 40 is abutted.

An annular grove 82 is formed in the housing at the top end of the first collar 40 for receiving a split snap ring 84 therein to abut against the top end of the first collar 40 so that the first collar remains rotatable about the main portion of the housing while being fixed in the longitudinal direction in abutment between the snap ring 84 and the end face 80 of the second collar 42 integrally forming an enlarged diameter portion of the housing below the first collar 40. In further embodiments the second collar 42 may comprise a collar slidably mounted onto the housing which is instead fixed in relation to the housing by bolting or welding.

The first collar 40 can also be held in place longitudinally by a pair of stop members 86 received within respective circumferentially oriented slots 88 formed in the first collar. Two slots 88 are provided in the first collar 40 at opposing ends thereof to extend circumferentially only partway about the housing in the order of 110 degrees for example. In this instance, the ports 62 and 64 in the housing 28 and in the collar 40 respectively, along with the floating jaw 52 on the first collar 40 and the fixed jaw 54 on the housing, are arranged similarly relative to one another as in the previous embodiment. The stops 86 are mounted within the respective slots 88 for sliding movement along the slots when the housing is rotated relative to the first collar 40 as the stops 86 are fixed on the housing 28 for rotation therewith. The stops 86 comprise lugs which are threadably mounted within cooperating threaded bores in the housing so that the stops can be selectively separated or removed as desired for permitting free rotation of the first collar 40 about the housing or when removing the collar from the housing.

When the stops 86 are mounted on the housing, the slot orientation in relation to the stops is arranged so that the stops abut one end of the slots 88 in the unset position of the tool as shown in FIG. 8, while also being arranged for the stops to engage the opposing end of the respective slots 88 in the set position as shown in FIG. 9 in which the tool is set against further right-hand rotation of the tubing string relative to the floating collar 40 supporting the floating jaw 52 thereon. By arranging the stops to abut one end of the slots 88 in the unset position of FIG. 8, further rotation of the housing in a left-hand direction relative to the floating jaw on the collar 40 is prevented so that the tool cannot be set in the second direction into the second set position unless the stop members 86 are removed from the housing. Once the stops are removed, the first collar 40 is freely rotatable in either direction from the unset position to either one of two set positions as in the previous embodiment.

The embodiment of FIG. 7 also differs from the previous embodiment in that the first collar 40 and the corresponding ports 62 and 64 in the housing and collar respectively span much longer in the longitudinal direction in relation to the floating jaw 52 and the fixed jaw 54. Accordingly the ports in the second embodiment are in the order of twelve inches long while the floating collar 40 is near fourteen inches long in the longitudinal direction as compared to ports which are five inches long within a collar which is seven and a half inches long as shown in the previous embodiment. The ports are thus approximately twice the length of the jaws in the longitudinal direction and are arranged to span between the two slots 88 at opposing ends of the first collar 40.

At the bottom end of the housing 28, a tag bar 44 is provided diametrically across the housing similar to the previous embodiment, however the open bottom end of the housing is configured differently as compared to the previous embodiment. A plurality of projections 90 are provided at the bottom end which extend outward from the housing in the longitudinal direction beyond the bottom end at a plurality of evenly spaced circumferential positions about the housing. The projections 90 result in a varied contact area between the interior of the tubular housing and the surrounding well.

When installing the tool at the bottom of the tubing string, the flow ports are accordingly close to the open bottom end of the tubing string which corresponds to the open bottom end of the tool. Upon assembly of the tubing string, the rotor 24 of the pump is inserted into the tubing string until the bottom end of the rotor is engaged with the tag bar for locating the pump within the tubing string. Once the rotor has been engaged on the tag bar it may be raised into the stator by a predetermined vertical spacing to ensure the rotor is properly located. In order to produce oil from the well, the tubing string is rotated in a direction corresponding to righthand rotation until the anti-rotation mechanism of the tool 10 is set in an engaged position with the well casing for restricting further righthand rotation of the tubing string relative to the casing. The flow ports in this instance are automatically opened by the setting action of the anti-rotation mechanism for producing from two separate locations in the well corresponding to the flow ports and the open bottom end of the tubing string.

In the event that the tubing string and well casing become pulled with sand and circulation is required, the tubing string can be rotated in a direction corresponding to lefthand rotation as viewed from above so as to automatically both unset the tool 10 and close the ports to flush fluids down through the bottom end of the tubing string. Alternatively, the tool can remain in the set position of FIG. 6 or FIG. 9 with the flow ports open for flushing fluids through both the flow ports and through the bottom end of the housing. Pulling the rods and the rotor upwardly from the inline pump permits the circulating fluids to be pump down through the tubing string and through the tool 10 to the bottom end thereof for clearing the sand.

Once the sand has been sufficiently cleared from the tubing string, the string may once again be prepared for production by inserting the rotor 24 back into the stator 22, once again using the tag bar as a reference. Rotating the tubing string in a direction corresponding to righthand rotation will set the tool in an engaged position with the well casing and the flow ports will automatically be opened as shown in FIGS. 6 and 9. Setting the anti-rotation mechanism by rotating the tubing string in a lefthand direction as viewed from above will also ensure that the ports are closed if desired for a flushing operation. By locating both the corresponding ports that control opening and closing of the flow ports and the floating jaw of the anti-rotation mechanism on a common collar on the housing, the flow ports are always ensured to be in an open position when the anti-rotation mechanism is in a set position.

Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

Claims

1. An anti-rotation and flow control tool for use with an oil production tubing string in a stationary well casing, the tool comprising:

a tubular housing extending in a longitudinal direction between an open top end and an open bottom end, at least the top end being arranged for threaded connection in series with the oil production tubing string;

a flow port formed through a side wall portion of the tubular housing;

a cover member supported on the housing for movement between a closed position in which the cover member spans the flow port and an open position in which the flow port is substantially unobstructed by the cover member; and

an anti-rotation mechanism supported on the housing for movement between an unset position and a set position in which an overall diameter of the tool is greater than in the unset position for anchoring the tubular housing against rotation in one direction relative to the stationary well casing;

the cover member and the anti-rotation mechanism being coupled for movement together such that the cover member is in the open position when the anti-rotation mechanism is in the set position.

2. The tool according to claim 1 wherein the flow port is fully open when the anti-rotation mechanism is set against righthand rotation of the tubing string in relation to the stationary well casing.

3. The tool according to claim 1 wherein the anti-rotation mechanism is operable from the unset position in a first direction into a first set position anchored against righthand rotation of the tubing string relative to the well casing and in a second direction into a second set position in which the tubing string is anchored against lefthand rotation in relation to the stationary well casing.

4. The tool according to claim 3 wherein there is provided a stop member selectively supported on the housing which is arranged to restrict movement of the anti-rotation mechanism in one of the first or second directions from the unset position.

5. The tool according to claim 1 wherein the flow port is nearer to the top end of the tubular housing than the bottom end.

6. The tool according to claim 1 wherein there is provided a rigid bar spanning diametrically across the tubular housing, the bar being supported below the flow port.

7. The tool according to claim 1 wherein there is provided a rigid bar spanning diametrically across the tubular housing, the bar being positioned adjacent the bottom end of the tubular housing, substantially below the anti-rotation mechanism.

8. The tool according to claim 1 wherein there is provided a plurality of flow ports through the side wall portion of the tubular housing at circumferentially spaced positions.

9. The tool according to claim 1 wherein there is provided two flow ports at diametrically opposed positions in the side wall portion of the tubular housing.

10. The tool according to claim 1 wherein the cover member comprises a collar rotatably supported about the tubular housing and including a corresponding port therein for selective alignment with the flow port in the tubular housing.

11. The tool according to claim 10 wherein a portion of the anti-rotation mechanism is supported on the collar.

12. The tool according to claim 1 wherein the bottom end of the tubular housing is threaded for connection in series with tubing of the tubing string.

13. The tool according to claim 1 wherein the top and bottom ends of the tubular housing are fixed in relation to one another.

14. The tool according to claim 1 wherein the anti-rotation mechanism comprises a fixed jaw projecting radially from the tubular housing in fixed relation therewith and a floating jaw projecting radially from the housing for rotation about a central axis of the tubular housing.

15. The tool according to claim 14 wherein the cover member comprises a collar rotatably supported about the tubular housing and wherein the floating jaw is mounted on the collar for rotation with the collar relative to the housing.

16. The tool according to claim 15 wherein there is provided a circumferential slot in one of the collar or the housing and a stop mounted on the other of the collar or the housing, the stop member being slidable along the slot as the fixed jaw is displaced relative to the floating jaw.

17. The tool according to claim 14 wherein the flow port is in the open position when the fixed jaw is rotated from the unset position more than 90° in a righthand direction relative to the floating jaw.

18. The tool according to claim 17 wherein the flow port is fully open when the jaws are rotated near 110° degrees relative to one another.

19. The tool according to claim 14 wherein the floating jaw projects radially outwardly from a central axis of the tubular housing greater than the fixed jaw.

20. The tool according to claim 1 wherein there is provided a plurality of projections extending from the bottom end of the housing in the longitudinal direction of the housing at circumferentially spaced positions about the housing.