US20040173362A1 - Electric downhole safety valve - Google Patents

Abstract

An electrically actuated fail-safe valve for controlling fluid flow in deepwater drilling operations comprises a body having a bore therethrough, a closure element mounted in the bore and actuable between a closed position and an open position, a flow tube slidably mounted in the bore, the tube being actuable between a first position in which it does not interfere with the normal bias of the closure and a second position in which it opposes the normal bias of the closure, and a drive mechanism causing the tube to advance from its first to its second position. The drive mechanism comprises a gear drive, a rotating sleeve including a helical groove, and a follower pin on the flow tube and received in the helical groove. Power supplied to the drive causes the sleeve to rotate, bearing on the follower pin and advancing the flow tube to its second position.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation-in-part of U.S. Provisional Application Serial No. 60/437,070, filed Dec. 30, 2002 and entitled “Electric Downhole Safety Valve,” which is incorporated herein by reference.[0001]
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
• Not Applicable.[0002]
FIELD OF THE INVENTION
• The present invention relates generally to downhole safety valves and more particularly to a downhole safety valve that is electrically operated.[0003]
BACKGROUND OF THE INVENTION
• The invention relates to a surface controlled subsurface safety valve (SCSSV) for a sub-terranean well and, more particularly, to a safety valve utilizing an electrical actuation mechanism controlled from the surface or by a downhole intelligent controller.[0004]
• Oil and gas wells typically employ at least one safety valve that can be actuated to stop or control the flow of fluid through a pipe. These valves are normally positioned downhole to close the bore of the tubing string extending from one or more production zones to the well surface. Safety valves of this type include a spring that biases the valve to a fail-safe mode, such that an interruption in the force acting to keep the valve open will cause the valve to close.[0005]
• Conventional downhole safety valves are hydraulically operated. As oil and gas reserves are developed in deepwater, however, the column of fluid needed for hydraulic actuation becomes impractically long. Specifically, the hydrostatic head developed in a conventional hydraulically controlled valve results in high operating pressures and requires an unworkably large failsafe spring.[0006]
• Because of the problems with hydraulically controlled safety valves, electrically operated safety valves are an attractive alternative. In addition, intelligent completion systems are being developed that are equipped with a variety of electrically driven flow control devices. Hence, it is currently desirable to provide an all-electric control system and remove the requirement for any hydraulic supply. Electrically controlled downhole safety valves have been developed, but they generally require high power consumption and/or unfavorably large geometry, and are vulnerable to problems with electrical connections to the surface.[0007]
• Hence, it remains desirable to provide an electrically operated downhole safety valve that can operate effectively and reliably at deep setting depths, using available power downhole.[0008]
SUMMARY OF THE INVENTION
• The present invention provides an electrically operated downhole safety valve that can operate effectively and reliably using available power downhole. In a preferred embodiment, the present system fits into a casing no larger than would be required for a comparable hydraulic unit.[0009]
• The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention, and by referring to the accompanying drawings.[0010]
BRIEF DESCRIPTION OF THE DRAWINGS
• For a more detailed description of the preferred embodiments of the present invention, reference will now be made to the accompanying drawings, wherein:[0011]
• FIG. 1 is a schematic cross-section of a device constructed in accordance with a preferred embodiment of the present invention, showing the valve in a closed position;[0012]
• FIG. 2 is a schematic cross-section of the device of FIG. 1, showing the valve in a open position;[0013]
• FIG. 3 is a cross-section taken along lines[0014]3-3 of FIG. 2; and
• FIGS. 4 and 5 are cross-sections taken along lines[0015]4-4 and5-5 of FIG. 2, showing the restraining mechanism in its de-energized and energized states, respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
• Referring initially to FIG. 1, a device constructed in accordance with a preferred embodiment of the present invention comprises a generally[0016]cylindrical body10 having acentral bore12 therethrough and aconcentric flow tube50 slidably mounted inbore12.Body10 includes afirst end13 and asecond end14, and preferably includesfemale threads15 at each end. In addition,bore12 includes avalve receptacle16, aspring receptacle26, aneccentric gearbox receptacle36, and aguide groove46, all described in detail below.
• [0017]Flow tube50 comprises a cylindrical tube having a first end53 and asecond end54. The outer surface offlow tube50 includes a first,annular extension56 spaced a first distance from first end53 and a second,non-annular extension58 spaced a further distance from first end53. In addition, the outer surface offlow tube50 includes an outwardly extendingfollower pin59 betweenannular extension56 andnon-annular extension58.
• Referring still to FIG. 2 and in particular to bore[0018]12 inbody10,valve receptacle16 comprises a first increased diameter portion inbore12.Valve receptacle16 is bounded by a lower,frustoconical shoulder17 and an upper,annular shoulder18. The inside diameter ofvalve receptacle16 is greater than the outer diameter offlow tube50, creating achamber19 therebetween. Aclosure element20 is housed inchamber19, along with aspring22.Closure element20 is pivotally mounted such that it can pivot about a transverse axis between a closed position, shown in FIG. 1, in which it bears onannular shoulder18, and an open position, shown in FIG. 2. In its closed position,closure element20 preferably substantially obstructs the flow of fluid throughbore12 and in its open position it does not. It will be understood that the closed and open positions need not be completely closed or completely open. In other words, the closed and open positions may be merely relative; namely, the closed position being one in which less fluid is allowed to pass than is allowed in the open position.Spring22 is preferably mounted betweenclosure element20 andbody10 such that it bears on closure element and urges it into its closed position.Sprint22 is shown as a coil spring, but it will be understood thatspring22 can comprise any suitable biasing member.
• [0019]Spring receptacle26 comprises a second increased diameter portion inbore12 spaced farther fromend13 thanvalve receptacle16.Spring receptacle26 is bounded by a lowerannular shoulder27 and an upperannular shoulder28. The inner diameter ofspring receptacle26 is greater than the outer diameter offlow tube50, creating anannular chamber29 therebetween. Acoil spring30 is preferably disposed inchamber29 between lowerannular shoulder27 ofspring receptacle26 andannular extension56 offlow tube50.Spring30 is preferably sized such that it is compressed and urgesflow tube50 away fromfirst end13 even whenannular extension56 bears on upperannular shoulder28.
• [0020]Eccentric gearbox receptacle36 comprises a third enlarged portion inbore12 and is spaced farther fromend13 thanspring receptacle26.Eccentric gearbox receptacle36 comprises alower portion37 and an upper portion38.Lower portion37 houses at least one and preferably a plurality ofdrive motors40,gearboxes42, andgears44. Upper portion38 houses a rotatingsleeve46.Rotating sleeve46 includes a loopedgroove48, which includes ahelical portion47, a short,transverse portion51, and astraight portion49. Loopedgroove48 receivesfollower pin59 onflow tube50. Whenclosure element20 is in the closed position shown in FIG. 1,follower pin59 is disposed at a junction betweenstraight portion49 andhelical portion47.
• [0021]Drive motors40,gearboxes42,gears44 and rotatingsleeve46 are preferably operably connected such that power supplied to drivemotors40 causesmotors40drive gearboxes42, which inturn drive gears44, which in turn cause rotatingsleeve46 to rotate about the axis ofbody10 andflow tube50. FIG. 3 is a cross-sectional view along the axis of the device with therotating sleeve46 removed so as to show the plurality ofgearboxes42 andgears44. FIG. 3 also illustrates the extension offollower pin59 from the outer surface offlow tube50.
• [0022]Guide groove46 extends longitudinally along a portion ofbore12 and receivesnon-annular extension58 offlow tube50. Referring briefly to FIGS. 4 and 5,guide groove46 preferably is wide enough to include at least a pair of retainingmembers68. Retainingmembers68 are actuable between an open position, shown in FIG. 4, and a closed position, shown in FIG. 5. In their closed position, retainingmembers68 engageextension58 so as to preventflow tube50 from moving relative tobody10.
• Retaining[0023]members68 and drivemotors40 receive electrical power fromelectrical leads7,9, respectively.Conductors7,9 preferably enterbody10 throughelectrical penetrator8.Conductors7,9 electrically connect to alocal control unit100, which is in turn electrically connected to aremote control unit102.
• A plurality of[0024]seals70 are preferably provided betweenbody10 and flowtube50 so as to isolateguide groove46,eccentric gearbox receptacle36, andspring receptacle26 and prevent the ingress of fluid thereinto.
• Operation[0025]
• When it is desired to open[0026]bore12 and allow fluid flow therethrough, a preferred first step is to equalize pressure on both sides ofclosure element20. With pressure equalized, power is supplied tomotors40 viaconductors9.Motors40drive gearboxes42, which in turn advance gears44, causingsleeve46 to rotate such thatfollower pin59 enters thehelical portion47 ofloop48. Assleeve46 rotates,helical groove47 bears onpin59, urgingflow tube50 towardfirst end13 ofbody10. Becauseflow tube50 is prevented from rotating by engagement ofextension58 withguide groove46, the rotation ofsleeve46 causes flowtube50 to advance longitudinally throughbody10. Asflow tube50 advances relative tobody10 in response to the force applied by rotatingsleeve46,annular extension56compresses spring30 and first end53 bears onclosure element20, forcing it open. If pressure is not equalized before the opening sequence, more power may be required to open the valve.
• When the opening process is complete, the tool is in the position shown in FIG. 2. Specifically, end[0027]53 offlow tube50 rests onfrustoconical shoulder17 andclosure element20 is contained betweenbody10 and flowtube50.Bore12 is open along the length of the tool,spring30 is compressed, andfollower pin59 rests at the juncture ofhelical portion47 andstraight portion49, as shown in phantom. At this point, power is supplied to retainingmembers68, causing them to come together and engageextension58 offlow tube50 so as to prevent it from moving axially withinbody10. Rotation ofsleeve46 is then preferably continued, without further advancingflow tube50, asfollower pin59 traversestransverse portion51 ofloop48, untilfollower pin59 rests at the juncture oftransverse portion51 andstraight portion49, as shown in FIG. 2.
• Because the present invention is normally closed, it is a fail-safe valve. Once the device has attained the open state shown in FIG. 2, flow can continue through it until either the device is closed deliberately, the power supplied to retaining[0028]members68 is interrupted, or retainingmembers68 fail. When any of these events occurs, retainingmembers68 cease to holdextension58 and thus cease to preventflow tube50 from moving axially. This allowsspring30 to driveflow tube50 away fromfirst end13. Asflow tube50 advances towardsecond end14,follower pin59 traversesstraight portion49 ofloop48.Flow tube50 is sized such that whenannular extension56 bears on upperannular shoulder28, its first end53 clears upperannular shoulder18, allowingclosure element20 to fullyclose bore12.
• Because the device preferably includes a plurality of[0029]motors40, a plurality ofgearboxes42, and a plurality ofgears44, it is multiply redundant, ensuring that it remains operable even in the event that one or more of its components fail. In addition, the gear train may be fitted with multiple slip clutches that will allow the device to operate even if one or more of the redundant drive motors fail.
• Retaining[0030]members68 can be any electrically actuable device and are shown as a pair of electrically actuated dogs. In a preferred embodiment, retainingmembers68 each comprise at least one flux carrier in conjunction with at least one coil. The coils are connected toconductors7. When power is supplied to the coils, they induce flux in the flux carriers, which in turn advance towardextension58 and ultimately engage it. By using electrical actuation and electrical power, the present device avoids the need for hydraulic systems.
• [0031]Flow tube50 preferably includes a static sealing member at its first end53, which forms a seal withfrustoconical shoulder17 when the device is open.Flow tube50 can be rotated to remove deposits that would otherwise impede travel of the tube. In some embodiments, flowtube50 includes a toothed cutting edge to facilitate removal of deposits.
• In still another alternative embodiment, the relative positions of the drive mechanism and[0032]spring30 may be reversed, such that the flow tube is pulled into the open position against the spring force. In this embodiment it is still preferred that the device be normally closed, so that it can function as a fail-safe device. Nonetheless, it is contemplated that in other embodiments, the configuration may be modified such that the device is normally open. In these embodiments, the relative positions ofspring30 and the drive mechanism may again be such that the drive mechanism either pulls or pushes the flow tube into the closed position.
• While certain preferred embodiments of the present invention has been shown and described, it will be understood that a variety of modifications could be made thereto without departing from the scope of the present invention. For example, the guiding and retaining functions performed by[0033]extension58 could be performed by separate elements.Closure element20, shown above as a single component could comprise multiple components and/or could operate in various other ways. For example,closure element20 could comprise a shutter-type closure, a ball valve, a stopcock-type closure, or any other suitable closure device. Likewise, the spring- loaded pivoting mechanism described above could comprise any suitable biasing means such as are known in the art.
• The drive mechanism described above as formed by the combination of gears, rotating sleeve, and follower pin could be replaced with a drive mechanism comprising solely gears, with the drive motors rotating a set of gears to either directly or indirectly advance the flow tube. For example, the flow tube could include gear teeth on a portion of its outer surface. Similarly, a plurality of powered drive mechanisms can be included and can include one-way drive clutches. The drive mechanism(s) can be configured so as to allow nonfunctioning drive mechanisms to be mechanically decoupled.[0034]
• [0035]Coil spring30 can be replaced with a biasing means that is better suited to operate in tension, rather than in compression, if desired.Flow tube50 can be replaced with a non-tubular element, although a tubular element is preferred because it is mechanically robust and protects the various components of the device from contact with the fluid. Similarly, retainingmembers68 could be replaced with a single member, or multiple members, mounted inline withextension58, which when face to face withextension58 can retainextension58 when energized.
• The embodiments described herein are exemplary only and are not limiting. One skilled in the art will understand that the mechanisms described herein could each be replaced with alternative mechanisms, so long as the invention is within the scope of the claims that follow. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims which follow, the scope of which shall include all equivalents of the subject matter of the claims. Also, in the claims that follow, the sequential recitation of steps is not intended to require that the steps be performed in the order recited, or that any given step be completed before another step is begun.[0036]

Claims (21)

What is claimed is:

1. An electrically actuated fail-safe valve for controlling fluid flow in a deepwater drilling operation, comprising:

a body having a bore therethrough;

a closure element mounted in the bore and actuable between a closed position in which said bore is relatively obstructed and an open position in which said bore is relatively open, said closure element being biased to one of said closed and open positions;

a flow tube slidably mounted in said bore, said flow tube being actuable between a first position in which said flow tube does not interfere with the normal bias of said closure element and a second position in which said flow tube opposes the normal bias of said closure element so as to maintain said closure element in the other of said closed and open positions;

an electrically powered drive mechanism mounted in said body and engaging said flow tube so as to advance said flow tube from said first position to said second position.

2. The valve according toclaim 1 wherein said closure element is biased into said closed position and said drive mechanism advances said flow tube such that said flow tube actuates said closure element to said open position.

3. The valve according toclaim 1, further including a plurality of powered drive mechanisms, said drive mechanisms including one-way drive clutches and allowing nonfunctioning drive mechanisms to be mechanically decoupled.

4. The valve according toclaim 1 wherein the drive mechanism comprises:

a gear drive,

a rotating sleeve mounted in said body, said rotating sleeve including a helical groove, and

a follower pin mounted on said flow tube and received in said helical groove;

such that electrical power supplied to said gear drive causes said rotating sleeve to rotate, which in turn bears on said follower pin and advances said flow tube to said second position.

5. The valve according toclaim 4 wherein the helical groove includes a straight portion substantially parallel to the longitudinal axis of said bore.

6. The valve according toclaim 4 wherein the helical groove includes a transverse portion substantially perpendicular to the longitudinal axis of said bore.

7. The valve according toclaim 4, further including means for preventing longitudinal rotation of said flow tube.

8. The valve according toclaim 1, further including an electrically actuable retaining mechanism mounted in said body and actuable between an engaged position in which said retaining mechanism engages said flow tube and prevents axial movement of said flow tube relative to said body and a disengaged position in which said retaining mechanism allows axial movement of said flow tube relative to said body.

8. The valve according toclaim 1, further including a biasing means urging said flow tube into said first position.

9. An electrically actuated fail-safe valve for controlling fluid flow in a deepwater drilling operation, comprising:

a body having a bore therethrough;

a closure element mounted in the bore and actuable between a closed position in which said bore is relatively obstructed and an open position in which said bore is relatively open, said closure element being biased to said closed position;

a flow tube slidably mounted in said bore, said flow tube being actuable between a first position in which said flow tube does not interfere with the normal bias of said closure element and a second position in which said flow tube opposes the normal bias of said closure element so as to maintain said closure element in the other of said closed and open positions;

an electrically powered drive mechanism mounted in said body and engaging said flow tube so as to advance said flow tube from said first position to said second position such that said flow tube actuates said closure element to said open position, said drive mechanism comprising:

a gear drive,

a rotating sleeve mounted in said body, said rotating sleeve including a helical groove, and

a follower pin mounted on said flow tube and received in said helical groove;

wherein power supplied to said gear drive causes said rotating sleeve to rotate, which in turn bears on said follower pin and advances said flow tube to said second position.

10. The valve according toclaim 1, further including a plurality of powered drive mechanisms, said drive mechanisms including one-way drive clutches and allowing nonfunctioning drive mechanisms to be mechanically decoupled.

11. The valve according toclaim 9 wherein the helical groove includes a straight portion substantially parallel to the longitudinal axis of said bore.

12. The valve according toclaim 9 wherein the helical groove includes a transverse portion substantially perpendicular to the longitudinal axis of said bore.

13. The valve according toclaim 9, further including means for preventing longitudinal rotation of said flow tube.

14. The valve according toclaim 9, further including an electrically actuable retaining mechanism mounted in said body and actuable between an engaged position in which said retaining mechanism engages said flow tube and prevents axial movement of said flow tube relative to said body and a disengaged position in which said retaining mechanism allows axial movement of said flow tube relative to said body.

15. The valve according toclaim 9, further including a biasing means for urging said flow tube into said first position.

16. A method for controlling fluid flow in a deepwater drilling operation, comprising:

a) providing a tool having a bore therethrough, the tool including a closure element actuable between a closed position in which the closure element closes said bore and an open position in which the closure element allows fluid flow through the bore, the closure element being biased normally closed, the tool further including a flow tube slidably mounted in said bore, the flow tube being actuable between a first position in which the flow tube does not prevent the closure element from being in its normally biased position and a second position in which the flow tube opposes the normal bias of the closure element so as to actuate the closure element to the open position;

b) selectively actuating said flow tube so as to actuate the closure element to the open position.

17. The method according toclaim 16 wherein the tool further includes a rotating sleeve and a follower pin extending from the flow tube and engaging a helical groove in said rotating sleeve and wherein the actuating step comprises rotating the sleeve such that engagement of the follower pin in the helical groove advances the flow tube from the first position to the second position.

18. The method according toclaim 16 wherein the tool further comprises a releasable locking mechanism and said helical groove includes a longitudinal straight portion such that when the follower pin lies in the longitudinal straight portion of the groove and the locking mechanism is released, the biasing of the closure element causes the flow tube to move to the first position.

19. The method according toclaim 18 wherein the locking mechanism is electrically actuated.

20. The method according toclaim 16 wherein the flow tube is actuated using electrical power.

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