Abstract
A rotary drive apparatus (24) for a downhole tool (22), the rotary drive apparatus (24) comprising a drive stage (36a) comprising a rotor (40a) and a stator (42a) and a connecting stage (38a) for connecting to the drive stage (36a). The connecting stage (38a) comprises a rotor connector (44a) suitable for connecting to the rotor (40a) and a stator connector (46a) suitable for connecting to the stator (42a).
Claims
1. A rotary drive apparatus for a downhole tool, the rotary drive apparatus, comprising: a drive stage comprising a rotor and a stator; and a connecting stage for connecting to the drive stage, wherein at least one of the rotor, the stator and the connecting stage is configured to flex in response to a force applied to the rotary drive apparatus to move the rotary drive apparatus from a first configuration to a second configuration.
2. The apparatus of claim 1, wherein the connecting stage comprises a rotor connector configured to connect to the rotor of the drive stage.
3. The apparatus of claim 2, wherein the rotor connector is configured to flex in response to the force applied to the rotary drive apparatus.
4. The apparatus of claim 1, wherein the rotor connector is at least partially constructed from at least one of: a polymeric material; a plastic material; and a composite material.
5. The apparatus of claim 1, wherein the connecting stage comprises a stator connector configured to connect to the stator of the drive stage.
6. The apparatus of claim 5, wherein the stator connector is configured to flex in response to the force applied to the rotary drive apparatus.
7. The apparatus of claim 5, wherein the stator connector is at least partially constructed from at least one of: a polymeric material; a plastic material; and a composite material.
8. The apparatus of claim 1, comprising a plurality of the connecting stages.
9. The apparatus of claim 8, wherein two or more of the connecting stages are configured to be connected in series.
10. The apparatus of claim 8, wherein two or more of the connecting stages are configured to connect to respective ends of the drive stage.
11. The apparatus of claim 8, wherein at least two of the connecting stages are of different flexibility, compressibility and/or elasticity.
12. The apparatus of any preceding claim, wherein at least one of the stator and the rotor are at least partially constructed from: a polymeric material; a plastic material; and/or a composite material.
13. The apparatus of claim 1, wherein the drive stage is fluid powered.
14. The apparatus of claim 1, wherein the drive stage comprises or defines a motor.
15. The apparatus of claim 14, wherein the drive stage comprises a positive displacement motor.
16. The apparatus of claim 1, wherein the drive stage is arranged such that the rotor surrounds the stator.
17. The apparatus of claim 1, comprising a plurality of the drive stages.
18. The apparatus of claim 1, wherein at least part of the rotary drive apparatus is configured to facilitate drilling through the rotary drive apparatus.
19. The apparatus of claim 1, comprising an access bore therethrough.
20. The apparatus of claim 1, comprising or operatively associated with a pressure relief device.
21. The apparatus of claim 20, wherein the pressure relief device comprises a valve, comprising: a valve body; an actuator; and an arrangement for fluid pressure surge mitigation.
22. The apparatus of claim 20, wherein the pressure relief device comprises an anti-surge valve comprising: a valve body; a valve member disposed in the valve body, the valve member axially moveable relative to the valve body between a first configuration in which fluid passage through the anti-surge valve is prevented and a second configuration in which fluid passage through the anti-surge valve is permitted.
23. A pressure relief device comprising an anti-surge valve for a downhole tool, the anti-surge valve comprising: a valve body; and a valve member disposed in the valve body, the valve member axially moveable relative to the valve body between a first configuration in which fluid passage through the anti-surge valve is prevented and a second configuration in which fluid passage through the anti-surge valve is permitted.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0333] These and other aspects will now be described, by way of example only, with reference to the accompanying drawings, in which:
[0334] FIG. 1 is a schematic side view of a downhole system according to an embodiment of the present invention;
[0335] FIG. 2A is a side view of a reaming tool according to an embodiment of the present invention, suitable for use in the downhole system of FIG. 1;
[0336] FIG. 2B is a part-cutaway side view of the reaming tool shown in FIG. 2A;
[0337] FIG. 3A is a perspective view of the rotary drive apparatus of the reaming tool shown in FIGS. 2A and 2B;
[0338] FIG. 3B is a cross sectional view of a drive stage of the rotary drive apparatus shown in FIG. 3A;
[0339] FIG. 3C is a longitudinal section view A-A of the drive stage shown in FIG. 3B;
[0340] FIG. 4A is a perspective view of another embodiment of the rotary drive apparatus of the reaming tool shown in FIGS. 2A and 2B;
[0341] FIG. 4B is a cross sectional view of a drive stage of the rotary drive apparatus shown in FIG. 4A;
[0342] FIG. 4C is a longitudinal section view B-B of the drive stage shown in FIG. 4B;
[0343] FIG. 5A is a cross sectional view of a drive stage according to another embodiment;
[0344] FIG. 5B is a longitudinal section view C-C of the drive stage shown in FIG. 5A;
[0345] FIG. 6A is a cross sectional view of a drive stage according to another embodiment;
[0346] FIG. 6B is a longitudinal section view D-D of the drive stage shown in FIG. 6A;
[0347] FIG. 7A is a cross sectional view of a drive stage according to another embodiment;
[0348] FIG. 7B is a longitudinal section view E-E of the drive stage shown in FIG. 7A;
[0349] FIG. 8A is a cross sectional view of a piston pressure relief valve according to an embodiment of the invention, in a deactivated position;
[0350] FIG. 8B is a sectional view of an arrangement for fluid pressure surge mitigation of the relief valve shown in FIG. 8A;
[0351] FIG. 9A is a cross sectional view of the piston pressure relief valve shown in FIG. 8A, in an activated position;
[0352] FIG. 9B is a sectional view of the arrangement for fluid pressure surge mitigation, in the activated position;
[0353] FIG. 10A is a cross sectional view of the piston pressure relief valve, in the deactivated position;
[0354] FIG. 10B is a cross sectional view of the piston pressure relief valve shown in FIG. 10A, in the activated position;
[0355] FIG. 11 shows an anti-surge valve to an embodiment of the invention, in a closed position;
[0356] FIG. 12 shows the anti-surge valve of FIG. 11;
[0357] FIG. 13 shows the anti-surge valve of FIG. 14, in an open position;
[0358] FIG. 14 is a perspective view of an anti-surge valve according to an alternative embodiment, in a closed position;
[0359] FIG. 15 is a cross sectional view of the anti-surge valve of FIG. 14, in the closed position;
[0360] FIG. 16 is a perspective view of the anti-surge valve of FIG. 14, in an open position;
[0361] FIG. 17 is a cross sectional view of the anti-surge valve of FIG. 14, in the open position;
[0362] FIG. 18 is a cross sectional view of the anti-surge valve of FIG. 17 in the open position according to an embodiment of the invention; and
[0363] FIG. 19 is a cross sectional view of an anti-surge valve of FIG. 17 in the closed position according to an embodiment of the invention.
DETAILED DESCRIPTION
[0364] Referring first to FIG. 1 of the accompanying drawings, there is shown a schematic side view of a downhole system 10 according to an embodiment of the present invention, the system 10 configured to be run into a borehole 12. As can be seen from FIG. 1, the borehole 12 has been drilled and lined with bore-lining tubulars 14. The distalmost bore-lining tubular 14 comprises a liner which terminates in a shoe 16. In the embodiment shown in FIG. 1, the liner comprises a 7 inch (193.68 mm) diameter tubular, though any suitable tubulars may be used. The borehole 12 has subsequently been extended beyond the shoe 16, in the illustrated embodiment in a substantially horizontal direction, this unlined section 18 of the borehole 12 extending through a hydrocarbon-bearing formation 20. It will be readily understood that the unlined section 18 of the borehole 12 may be of any required length, and may extend for several kilometres through the formation.
[0365] A reaming tool 22 is provided at a distal leading end of the downhole system 10 and the reaming tool 22 is run into the borehole 12 with the downhole system 10. The reaming tool 22 comprises a rotary drive apparatus 24, and a reamer shoe 26 comprising a reaming body 28 and a reaming nose 30. In use, fluid is directed to the rotary drive apparatus 24 to drive rotation of the reamer shoe 26 to facilitate reaming of the borehole 12 by the reaming tool 22.
[0366] As described further below, the rotary drive apparatus 24 is configured to flex in response to a force applied to the rotary drive apparatus 24 exceeding a selected threshold, this providing a degree of passive articulation at a distal end of the system 10 which provides hole-finding capability, for example but not exclusively permitting the system 10 to pass through tortuous well trajectories, soft formations, ledges and any other wellbore deviations that would otherwise create resistance or obstruction while running into the borehole 12 and/or while performing downhole operations.
[0367] FIGS. 2A and 2B show an exemplary reaming tool 22 for use in the downhole system 10 shown in FIG. 1. FIG. 2A shows the reaming tool 22 in a first configuration and FIG. 2A shows the reaming tool 22 in a second, flexed, configuration, the reaming tool 22 being configured to be reconfigurable from the first configuration to the second configuration in response to the force applied to the reaming tool 22.
[0368] As described above with reference to FIG. 1, reaming tool 22 comprises rotary drive apparatus 24 connected to reaming shoe 26 having reaming body 28 and reaming nose 30. As shown in FIGS. 2A and 2B, reaming shoe 26 comprises a number of radially extending and circumferentially arranged blades 32 for reaming the borehole section 18. A number of circumferentially arranged ports 34 are provided in the reaming shoe 26, the ports 34 in the illustrated embodiment being provided in the nose 30. In use, fluid may be directed through the ports 34 to lubricate passage of the reaming tool 22 through the borehole 12 and/or to assist in the removal of debris and cuttings during operation.
[0369] The rotary drive apparatus 24 forms the power section of the reaming tool 22 and has a drive stage 36a and a connecting stage 38a for connecting to the drive stage 36a. The drive stage 36a comprises a rotor 40a and a stator 42a and the connecting stage 38a comprises a rotor connector 44a and a stator connector 46a.
[0370] In the illustrated embodiment, the rotor 40a is disposed radially inwards of the stator 42a such that in use the rotor 40a rotated within the stator 42a. However, it will be recognised that in other embodiments the rotor 40a may alternatively be disposed radially outwards of the stator 42a and configured in use to rotate around the stator 42a.
[0371] The exemplary arrangement shown in FIGS. 2A and 2B shows two connecting stages 38a, 38b and three drive stages 36a, 36b, 36c. However, it will be understood that a rotary drive apparatus according to other embodiments may comprise a single drive stage and a single connecting stage, or any number of drive stages and connecting stages.
[0372] As shown in the cut-away portion of FIG. 2B, in the illustrated embodiment, the connecting stage 38a is flexible, that is at least one of the rotor connector 44a and the stator connector 46a is configured to flex in response to the force applied to the reaming tool 22 exceeding the selected threshold. The rotor connector 44a and the stator connector 46a are, in the rotary drive apparatus 24, formed by plastic or composite tubing having a lower stiffness than conventional metallic bore-lining tubulars, the cut-away portion of FIG. 2B showing the relatively rigid rotor 40a and stator 42a of drive stages 36a, 36b, 36c connected to the flexible connecting stages 38a, 38b.
[0373] As noted above, the reaming tool 22 shown in FIGS. 2A and 2B exemplifies the hole finding capability of the reaming tool 22 and/or the system 10 due to the rotary drive apparatus 24 flexing due to the flexing of only the connecting stages 38a, 38b. However, in other embodiments the ability to flex the rotary drive apparatus 24 may alternatively or additionally be provided by the drive stage, at least one of the rotor and the stator being configured to flex in response to the applied force exceeding a selected threshold.
[0374] Referring now also to FIGS. 3A to 3C of the accompanying drawings, there is shown an exemplary rotary drive apparatus 24 of the reaming tool 22. As described above, the illustrated rotary drive apparatus 24 comprises two connecting stages 38a, 38b (connecting stage 38a being shown in FIG. 3A) and three drive stages 36a, 36b, 36c (drive stages 36a,36b being shown in FIG. 3A).
[0375] As shown in FIGS. 3A-3C, the stators 42a, 42b have a substantially cylindrical exterior surface and the rotors 40a, 40b are hollow, such that the interior surface of the rotors 40a, 40b form a substantially tubular shape, forming an access bore 48 located about an axis X. The diameter of the stators 42a, 42b as measured from the exterior surface is larger than the diameter of the rotors 40a, 40b as measured from the interior surface of the rotor. The rotors 40, 40b are arranged such that they are surrounded by the stators 42a, 42b along the axis X. The exterior surface of the rotors 40a, 40b comprises elongated lobes 50 and the interior surface of the stators 42a, 42b comprise lobes 52 which together form substantially helical shapes. A passage 52 between the rotors 40a, 40b and the stators 42a, 42b permits the flow of fluid. In the illustrated embodiment, the rotors 42a, 42b comprise four lobes 50 and the stators 42a, 42b comprise five lobes 52.
[0376] As described above, the rotors 40a, 40b are hollow, such that fluid may flow within the rotors 40a, 40b. In operation, drilling fluid, such as mud, may be pumped, circulated or otherwise directed into the passage 52 between the rotors 40a, 40b and the stators 42a, 42b to drive rotation of the drive stages of the rotary drive apparatus 24.
[0377] In use, the shoe is adapted to rotate at a selected speed, although higher speeds may be used where appropriate, thus facilitating efficient reaming of the wellbore. The nose is constructed from a metallic material, such as aluminium or brass, though other materials such as ferrous materials, or ceramics may be used where appropriate. Fluid, such as drilling fluid or mud or the like, is directed from the drive stage to the reamer shoe and through the ports to assist in removing material from the bore. The fluid may then be recirculated to surface via an annulus (not shown) between the shoe and the bore. The ribs engage the interior surface of the wellbore or tubular component, rotation of the shoe reaming the wellbore to the required dimension and surface texture. Abrasive particles provided on the ribs and nose further assist in performing the operation. The number of lobes may be selected to produce the desired torque or rotational speed of the rotary drive. The stator always has one more lobe than the rotor when the rotary drive is a positive displacement motor. The number of complete twists that the substantially helical shaped and circumferentially distributed lobes of the exterior surface of the rotor makes in a single drive stage may be selected to produce a desired torque at a given fluid flow rate. On completion of the reaming operation, the shoe, the drive stages and the connecting stages can be drilled through to permit extension of the bore or permit location of tools or pipe though the bore. At least some of the components of the reaming shoe are sacrificial, that is they are suitable for drilling through.
[0378] It will be understood that the rotary drive apparatus may take a number of different forms.
[0379] Referring now to FIG. 4A to 4C of the accompanying drawings, there is shown an alternative rotary drive apparatus 124 of the reaming tool 22. The illustrated rotary drive apparatus 124 comprises two connecting stages 138a, 138b (connecting stage 138a being shown in FIG. 4A) and three drive stages 136a, 136b, 136c (drive stages 136a, 136b being shown in FIG. 4A).
[0380] As shown in FIGS. 4A-4C, the stators 142a, 142b have a substantially cylindrical exterior surface and the rotors 140a, 140b are hollow, such that the interior surface of the rotors 140a, 140b form a substantially tubular shape, forming an access bore 148 located about an axis X. The diameter of the stators 142a, 142b as measured from the exterior surface is larger than the diameter of the rotors 140a, 140b as measured from the interior surface of the rotor. The rotors 140a, 140b are arranged such that they are surrounded by the stators 42a, 42b along the axis X. The exterior surface of the rotors 140a, 140b comprises elongated lobes 150 which form substantially helical shapes. A passage 152 between the rotors 140a, 140b and the stators 142a, 142b permits the flow of fluid. As described above, the rotors 140a, 140b are hollow, such that fluid may flow within the rotors 140a, 140b. In operation, drilling fluid, such as mud, may be pumped, circulated or otherwise directed into the passage 152 between the rotors 140a, 140b and the stators 142a, 142b to drive rotation of the drive stages of the rotary drive apparatus 124.
[0381] In this embodiment, the rotors 140a, 140b comprise seven lobes 150 and the stators comprise eight lobes 152. Such an arrangement serves to minimise the cross-sectional area of the passage 152 between the rotors 140a, 140b and the stators 142a, 142b. The reduced cross-sectional area of the passage 152 results is a greater fluid flow velocity and greater motor speed and/or torque. The reduced cross-sectional area of the stators 140a, 140b also requires less material for manufacture and results in an apparatus which is lighter and/or more economical to manufacture.
[0382] The number of lobes may be selected to produce the desired torque or rotational speed of the drive stage. The number of complete twists that the substantially helical shaped and circumferentially distributed lobes of the interior surface of the stator makes in a single drive stage may be selected to produce a desired torque at a given fluid flow rate. A higher number of lobes increases the torque characteristics. The higher number of lobes leads to larger diameter rotor and lower wall-thickness stator. This may allow the rotor to be hollow.
[0383] Referring now to FIG. 5A to 7B of the accompany drawings, there are shown alternative rotary drive apparatus 324, 424 and 524 of the reaming tool 22.
[0384] In the embodiment shown in FIGS. 5A and 5B, rotor 340 comprises four lobes 350 and the stator 342 comprises five lobes 352. The stator 342, 342 also has substantially helical shaped and circumferentially distributed lobes 54 on its exterior surface. The provision of the substantially helical shaped and circumferentially distributed lobes 54 on the exterior surface of the stator 242 beneficially increases the flow rate of fluid within the annulus between the apparatus 324 and the borehole 12.
[0385] In the embodiment shown in FIGS. 6A and 6B, the apparatus 424 comprises a housing 56 and the rotor 440 has a circular cross-section (equivalent to a single lobe) and the stator 442 has an elongated circular shaped cavity defined by its interior surface (equivalent to a two lobes). The ratio of rotor lobes to stator lobes is 1:2, resulting in a high speed, low torque configuration.
[0386] In the embodiment shown in FIGS. 7A and 7B, the rotor 540 comprises five lobes 550 and the stator 542 comprises six lobes 552. Moreover, as described above, the rotor may in some embodiments be disposed radially outwards of the stator and configured to rotated around the stator and in the embodiment shown in FIGS. 7A and 7B, the rotor 540 is disposed radially outwards of the stator 542.
[0387] FIG. 8A is a cross sectional view of a piston pressure relief valve 1000, in a deactivated position. In the deactivated position, the valve actuator 1001 is positioned within the valve body 1002 such that the valve piston 1005 seals the radial openings 1015, thus preventing the flow of fluid through the piston pressure relief valve 1000. The o-rings 1012, 1013 ensure the valve actuator 1001 forms a seal with the valve body 1002. A radial spring or coil spring 1006 retains the valve actuator 1001 in a position which retains the valve 1000 in the deactivated state in the absence of a pressure or pressure differential equal to or greater than a selected value. Slotted set screws 1011 with long dog points are positioned to restrict movement of the valve actuator 1001 and piston valve beyond a defined position. The valve body 1002 comprises a collar or spring support 1007 to support the radial spring or coil spring 1007. The valve actuator 1001 comprises a top collar or top spring support 1008 to support the radial spring or coil spring 1007. The top collar or top spring support 1008 is maintained in position by screws 1009. A valve guide pin 1014 guides the valve piston 1005 when the valve actuator 1001 is moving. The valve guide pin 1014 beneficially ensures that there is no rotational movement of the valve actuator 1001 which could have the detrimental effect of misaligning the indentations on the valve actuator 1001 with the valve balls 1004. The exemplary arrangement shows an arrangement for fluid pressure surge mitigation comprising radial spring plugs 1010. The radial spring plugs 1010 are positioned circumferentially around the valve actuator 1001. Associated with each radial spring plug 1010 is a ball spring 1003 and a valve ball 1004. In the deactivated state, the valve ball or ball 1004 is held by the ball spring 1003 in an associated indentation or circumferential groove in the valve actuator 1001. The ball 1004, thus, inhibits movement of the valve actuator 1001 until a force is applied to the valve actuator 1001 sufficient to compress the ball spring 1003, permitting the valve ball 1004 to exit the associated indentation or circumferential groove in the valve actuator 1001.
[0388] FIG. 8B is a sectional view of an arrangement for fluid pressure surge mitigation of the valve shown in FIG. 8A, in the deactivated position. This exemplary arrangement shows the provision of five radial spring plugs 1010, ball springs 1003 and valve balls 1004.
[0389] FIG. 9A is a cross sectional view of the piston pressure relief valve 1000 of FIG. 8A, shown in an activated position. The valve actuator 1001 is positioned such that the radial openings 1015 are aligned with openings 1016 in the valve piston 1005, thus permitting the flow of fluid through the piston pressure relief valve 1000. The ball 1004, has moved radially outwards from the indentation of circumferential groove in the valve actuator 1001, compressing the ball spring 1003, as a result of a pressure force applied to the valve 1000. FIG. 9B, which is a sectional view of the arrangement for fluid pressure surge mitigation of FIG. 8B, in an activated position according, more clearly shows the position of the valve balls 1004 and ball springs 1003 when the valve 1000 is in the activated state.
[0390] FIGS. 10A and 10B are cross sectional views of the piston pressure relief valve 1000, in the deactivated and activated positions respectively, and showing the positioning of the valve 1000 within a housing 1021.
[0391] Referring to FIG. 11 of the drawings, there is shown an anti-surge valve, generally indicated by reference numeral 2000, according to an embodiment of the present invention.
[0392] As shown in FIG. 11, the anti-surge valve 2000 comprises a valve body 2002 and a valve member 2004. The valve body 2002 comprises two distinct sections, 2002a, 2002b. First section 2002a of the valve body 2000 is affixed to the top of the downhole tool. The second section 2002b of the valve body 2000 is affixed to the first section 2002a by means of shear pins 2006. The second section 2002b houses the valve member 2004. A seal is maintained between the first section 2002a and the second section 2002b by means of an o-ring 2008.
[0393] The valve member 2004 is axially moveable relative to the valve body 2002 between a first, open configuration in which fluid passage through the anti-surge valve 2000 is prevented and a second, closed configuration in which fluid passage through the anti-surge 2000 valve is permitted. The valve body comprises a cap 2001. The cap 2001 is affixed to the valve body 2002. The cap 2001 comprises inflow ports 2011, permitting fluid to flow between the throughbore 2013 and the interior 2014 of the anti-surge valve. The valve body is substantially cylindrical.
[0394] The valve body comprises a plurality of circumferentially arranged inflow ports 2010.
[0395] The anti-surge valve 2000 comprises a rupture disc assembly. The rupture disc assembly 2009 is detachably affixed to the valve member 2004 by means of a retainer nut 2003.
[0396] A seal is maintained between the valve member 2004 and the valve body 2002 by a wiper seal 2007.
[0397] The operation of the anti-surge valve can be seen from FIGS. 12 and 13, which show the direction of the flow of fluid relative to the anti-surge valve 2000.
[0398] The anti-surge valve 2000 is designed to operate under hydraulic flow. When the reamer tool is run into the wellbore, the anti-surge valve 2000 is directed or forced to be in the open position, as shown in FIG. 13. When running in the wellbore, fluid in the wellbore flows upward into the valve body 2002 and pushes against the valve member 2004. This moves the valve member 2004 into the open position and the fluid flows through the anti-surge valve 2000 through the in-flow ports 2010. By this operation, the anti-surge valve 2000 will remain open during the running-in operation. When the running-in operation is stopped, for example to add additional lengths of casing to the string, the valve member 2004 may close by gravity. On resumption of the running-in operation the anti-surge valve 2000 it will open as previously described.
[0399] When the drilling fluid is pumped under pressure into the wellbore 2013 the anti-surge-valve 2000 is directed or forced by flow and pressure differential to move to a closed position, as shown in FIG. 13. Arrows 2012 denote the direction of fluid flow. The valve member 2004 is moved by fluid flow and pressure differential into the closed position, and forming a seal by a circular knife edge feature 2018 against the interior flat face of valve body 2002 and will remain in this position under fluid flow. It can be seen that the valve member 2004 is positioned such that it obstructs the flow of fluid through the flow through ports 2010.
[0400] Referring now to FIGS. 14 to 19, there is shown an anti-surge valve, generally denoted 3000, according to an alternative embodiment. As shown, the anti-surge valve 3000 comprises a valve body 3001 which houses a valve member 3002. The valve member 3002 may slide within the valve body 3001, configuring the anti-surge valve 3000 to be in an open or closed configuration. The range of movement of the valve member is limited by at least two parallel pins 3008. This differs from the embodiment of FIG. 11, where the range of movement of the valve member 2004 is limited by a cap 2001 affixed to the valve body 2002. In the second embodiment, cap 3004 is fixedly attached directly to the valve member 3002. The cap 3004 comprises inflow ports 3020, permitting fluid to flow between the throughbore and the interior of the anti-surge valve 3000. The movement of the valve member 3002 within the valve body 3001 is guided by at least two spring guides 3003. The spring guides 3003 are affixed to the valve body, and slidably inserts into an associated slot in the valve member 3002. A collar 3021 on the valve member inhibits movement of the spring 3023 of the spring guide 3003 into the slot. A seal is maintained between the valve member 3002 and the valve body 3001 by a swan seal 3007.
[0401] When the reamer tool is run into the wellbore, the anti-surge valve 3000 is directed or forced to be in the open position.
[0402] The valve body 3001 comprises a plurality of circumferentially arranged inflow ports 3025. The inflow ports 3025 are arranged such that the valve body is, effectively, perforated.
[0403] The anti-surge valve 3000 is designed to operate under hydraulic flow.
[0404] When running in the throughbore, fluid in the throughbore flows upward into the valve body 3001 and pushes against the valve member 3002. This moves the valve member 3002 in a path guided by the spring guides 3003 into the open position, wherein further movement of the valve member 3002 in the opening direction is inhibited by the parallel pins 3008, and the fluid flows through the anti-surge valve through the in-flow ports 3025. Similarly, when fluid is pumped under pressure into the throughbore the anti-surge-valve 3000 is directed or forced by flow and pressure differential to move to a closed position.
[0405] FIG. 18 is a cross sectional view of the anti-surge valve 3000, the closed position, and shows the anti-surge valve 3000 positioned at the top of a downhole tool 3100, such as the reaming tool 22 described above. The anti-surge valve 3000 is located within a perforated section of inner-casing 3200. It can be seen that the valve member 3002 is positioned such that it obstructs the flow of fluid through the flow through ports 3025.
[0406] FIG. 19 shows a cross-sectional view of the anti-surge valve 3000, in the open configuration, and also illustrates the path of the flow of fluid that would results in the anti-surge valve 3000 moving to the closed position. Fluid pumped or circulated into the throughbore flows through the screen or perforated side walls of the casing into an annulus 3050, and subsequently into the downhole tool 3100. The fluid in the throughbore is pressurised, primarily for the purposes of powering the downhole tool 3100. A restricted amount of fluid may initially flow through the inflow ports 3025 of the anti-surge valve. In this scenario, the fluid pressure within the anti-surge valve and within at least the top of the downhole tool is less than the pressure in the throughbore outside the anti-surge valve 3000, resulting in a pressure differential. When the pressure differential is sufficient to overcome the compression force of the guide-springs 3003, the valve member 3002 will move to a closed position.
[0407] It should be understood that the embodiments described are merely exemplary of the present invention and that various modifications may be made without departing from the scope of the invention.
