Retrievable bridge plug and retrieving tool

Information

  • Patent Grant
  • 6244642
  • Patent Number
    6,244,642
  • Date Filed
    Tuesday, July 18, 2000
    24 years ago
  • Date Issued
    Tuesday, June 12, 2001
    23 years ago
Abstract
A retrievable bridge plug having an internal bypass passage and external retrieving lugs, and a retrieving tool therefor. When the bypass passage is sealed, both the top and bottom openings of the bypass passage are closed, preventing debris from entering the bypass passage through either opening. A directing shroud is provided adjacent the top opening of the bypass passage, such that when the bypass passage is opened, part of any fluid flowing uphole through the bypass passage is directed over the retrieving lugs, clearing them of any debris and facilitating latching by the retrieving tool. The shroud also prevents debris from packing around the top opening of the bypass passage. A retrieving tool is also provided, which retrieving tool, through cooperation of a sleeve having a “J” shaped slot, and an inner latch sleeve having a straight slot, locks the retrieving tool onto the retrieving lugs.
Description




FIELD OF THE INVENTION




The present invention relates to bridge plugs and retrieving tools therefor and in particular to retrievable bridge plugs which may be placed in pressurized oil and gas well bores to temporarily seal a portion of the well bore, and which require equalization before retrieval.




BACKGROUND OF THE INVENTION




Bridge plugs are tools which are typically lowered into a cased oil or gas well. When set in position inside the casing, a bridge plug provides a seal to isolate pressure between two zones in the well. Retrievable bridge plugs are often used during workover operations when a temporary separation of zones is required.




Typical bridge plugs are shown in U.S. Pat. No. 4,436,150 issued to Barker on Mar. 13, 1984; U.S. Pat. No. 4,898,239 issued to Rosenthal on Feb. 6, 1990; and U.S. Pat. No. 5,727,632 issued to Richards on Mar. 17, 1998. Retrievable bridge plugs typically have anchor elements and sealing elements. The anchor elements are used to grip the inside surface of the well casing, thereby preventing the bridge plug from moving up or down within the casing, once set. The sealing elements engage the inside surface of the well casing to provide the requisite seal between the plug and the casing. Typically, the bridge plug is set in position by radially extending the anchor elements and the sealing elements to engage the well casing. To retrieve the bridge plug from the well casing, a retrieving tool is lowered down the casing to engage a retrieving latch, which, through a retrieving mechanism, retracts the anchor elements and the sealing elements, allowing the bridge plug to be pulled out of the well bore.




During workover operations, a pressure differential across the plug often develops. It is desirable to equalize this pressure differential before the anchor and sealing elements are disengaged. Equalization prevents the loss of control over the bridge plug, wherein the tool may be blown up or down a well casing in response to the pressure differential. As exemplified by the prior art bridge plugs listed above, such equalization is typically effected through the opening of a bypass passage through the interior of the plug, prior to disengagement of the anchor and sealing elements.




However, a problem is often encountered with the effect of debris on the operation of the plug. Such debris may have an adverse effect on the operation of the plug. If sufficient debris remains on top of the plug, it may block the proper functioning of the mechanism used to open the bypass passage, making it very difficult, if not impossible for the pressure to equalize across the plug. Further, if a significant amount of debris accumulates on top of the bridge plug, it may be difficult, or impossible to engage the retrieving latch to retract the anchor and sealing elements. Finally, debris accumulation inside the bridge plug may adversely affect the relative movement of various parts within the bridge plug.




With prior art retrievable bridge plugs, even with the bypass passage sealed, fluid in the well is allowed to enter the interior of the plug. Further, no structure protects the uphole opening of the bypass passage, and debris is allowed to accumulate adjacent this opening. Moreover, no means are provided by the bridge plug to protect, or clear the retrieving latch used to disengage the anchor and sealing elements.




With known retrieving tools, once the retrieving tool has latched onto the bridge plug, accidental unlatching of the bridge plug may occur due to jarring motions, or forces imparted on the bridge plug or retrieving tool when the bypass passage is opened. Also, while the bridge plug is being lifted out of the well bore, jarring, or friction against the well casing may cause the anchor elements to move to their extended positions, locking the bridge plug in place within the casing, necessitating emergency recovery procedures. Once the retrieving tool and bridge plug have been removed from the well bore, it is difficult to separate the two, additional machinery often being required.




SUMMARY OF THE INVENTION




An object of the present invention is to provide a retrievable bridge plug and retrieving tool therefor which reduces the effect of debris on the proper operation of the plug.




According to a broad aspect, the present invention provides a bridge plug for use in a well bore having a well wall, the bridge plug comprising: (a) an elongated body having an internal bypass passage; (b) anchors mounted on said elongated body, said anchors being extendible from a retracted position, in which they are held out of contact with the well wall, to an extended position in which they engage the well wall; (c) a seal mounted on said elongated body, said seal being extendible from a retracted position, in which it is held out of contact with the well wall, to an extended position in which it engages the well wall and forms an annular seal between the elongated body and the well wall; (d) a setting mechanism operable to set and lock said anchors and seal in their extended positions; (e) a release mechanism operable to disengage said anchors and seal from the well wall; (f) said internal bypass passage having a top and a bottom opening, said top opening located uphole from said seal, said bottom opening located downhole from said seal; (g) a top bypass closure adjacent said top opening of the internal bypass passage, and a bottom bypass closure adjacent said bottom opening of the internal bypass passage, each of said top and bottom bypass closures being mounted on said elongated body for movement between a first position in which the internal bypass passage is open, and a second position in which the internal bypass passage is sealed, and the top and bottom openings of the internal bypass passage are closed, substantially preventing debris from entering the internal bypass passage; and (h) a bypass sealing mechanism operable to move said top and bottom bypass closures between said first and second positions.




According to another aspect, the present invention provides a bridge plug for use in a well bore having a well wall, the bridge plug comprising: (a) an elongated body having an internal bypass passage; (b) anchors mounted on said elongated body, said anchors being extendible from a retracted position, in which they are held out of contact with the well wall, to an extended position in which they engage the well wall; (c) a seal mounted on said elongated body, said seal being extendible from a retracted position, in which it is held out of contact with the well wall, to an extended position in which it engages the well wall and forms an annular seal between the elongated body and the well wall; (d) a setting mechanism operable to set and lock said anchors and seal in their extended positions; (e) a release mechanism operable to disengage said anchors and seal from the well wall, said release mechanism being operable by a retrieving tool acting upon retrieving tool engaging elements mounted on the elongated body; (f) said internal bypass passage having a top and a bottom opening, said top opening located uphole from said seal, said bottom opening located downhole from said seal; (g) a directing shroud located over the top opening of the internal bypass passage; (h) a bypass sealing mechanism operable to selectively open and seal said internal bypass passage, whereby the directing shroud substantially protects the top opening of the internal bypass passage from debris and, when the internal bypass passage is open, directs part of any fluid flowing uphole through the internal bypass passage over the retrieving tool engaging elements.




According to a further aspect, the present invention provides a retrieving tool having top and bottom ends, for retrieving downhole tools from a well bore, such downhole tools having a top end and a plurality of transversely extending retrieving lugs, the retrieving tool comprising: (a) a tubing attachment interface for detachably attaching the retrieving tool to tubing; (b) a retrieving lug guide having a bottom end, said retrieving lug guide comprising a sleeve defining a plurality of J-shaped slots extending upward from its bottom end, the number of said J-shaped slots being equal to or greater than the number of retrieving lugs on the downhole tool and, each of said J-shaped slots being sized to accommodate a retrieving lug, each J-shaped slot having a stem portion and a hook potion, said stem portion of each J-shaped slot extending upward and obliquely from said bottom end of the retrieving lug guide, said hook portion of each J-shaped slot extending downward, said bottom end of said retrieving lug guide being provided with downward-pointing spade-shaped profiles between entrances to each J-shaped slot; (c) a latch sleeve mounted for reciprocal longitudinal movement within the retrieving tool, said latch sleeve having a bottom end, at least a portion of said latch sleeve overlapping a sufficient portion of said retrieving lug guide so as to substantially overlap an interface between the hook portion and stem portion of the J-shaped slots of said retrieving lug guide; said latch sleeve defining a plurality of latch slots extending upward from the bottom end of said latch sleeve, the number of said latch slots being equal to or greater than the number of retrieving lugs, said latch slots being sized to accommodate the retrieving lugs, said latch slots being aligned with the hook portions of the J-shaped slots of the retrieving lug guide; (d) each of said retrieving lug guide and latch sleeve having an inner diameter large enough to allow the retrieving lug guide and latch sleeve to pass over all portions of the downhole tool above the retrieving lugs, but small enough to cause engagement with the retrieving lugs; (e) a latch sleeve alignment mechanism to prevent the latch sleeve from rotating relative to the retrieving lug guide; (f) a latch sleeve biasing element to bias the latch sleeve downward relative to the retrieving lug guide; and (g) a rotation mechanism to allow the retrieving lug guide, latch sleeve, latch sleeve alignment mechanism and biasing element to rotate relative to the tubing attachment interface, whereby as the retrieving tool is lowered into the well on the end of the tubing, the retrieving lugs on the downhole tool first contact the bottom end of the retrieving lug guide, the spade-shaped profile of the bottom end of the retrieving tool guide causing the retrieving tool guide, latch sleeve, latch sleeve alignment mechanism and biasing element to rotate relative to the tubing attachment interface as the retrieving tool is lowered further, still further lowering causing the retrieving lugs to enter the stem portions of the J-shaped slots and then to bear against the bottom end of the latch sleeve causing the latch sleeve to move upwards against the biasing force provided by the biasing element, further downward movement of the retrieving tool causing the retrieving lugs to enter the hook portion of the J-shaped slots allowing the biasing element to force and retain the latch sleeve back down relative to the retrieving lug guide as the retrieving lugs enter the latch slots, thereby locking the retrieving lugs within the hook portion of the J-shaped slots of the retrieving lug guide.




According to a still further aspect, the present invention provides a downhole tool/retrieving tool combination for use in a well bore having a well wall comprising: (a) a downhole tool comprising anchors extendible from a retracted position in which the anchors are held out of contact with the well wall, to an extended position in which the anchors engage the well wall; (b) said downhole tool further comprising an anchor retracting mechanism for retracting the anchors to their retracted positions; and (c) a retrieving tool adapted to actuate said anchor retracting mechanism to retract the anchors to their retracted positions, and to maintain said anchors in their retracted positions while the downhole tool is raised out of the well bore.




Advantageously, the retrievable bridge plug of the present invention prevents debris from entering the interior of the plug when the internal bypass passage is sealed. Further, the top opening of the bypass passage is protected against buildup of debris by the shroud. Additionally, when the bypass passage is opened after the workover operations, part of any fluid passing upward through the bypass passage is directed by the shroud over the retrieving tool engaging elements, to clear them of debris. These advantages allow the retrievable bridge plug of the present invention to reduce the effect of debris on the proper operation of the plug.




Advantageously, the retrieving tool of the present invention prevents inadvertent disengagement of the retrieving lugs once the retrieving lugs are locked into the hook portion of the “J” shaped slot of the retrieving lug guide. Further, once the user has retracted the anchors on the downhole tool using the retrieving tool, the anchors are retained in their retracted position while the downhole tool is raised out of the well bore. Finally, the downhole tool/retrieving tool combination of the present invention allows the user to easily detach the downhole tool from the retrieving tool.




Other objects, features and advantages will be apparent from the following detailed description taken in connection with the accompanying sheets of drawings.











BRIEF DESCRIPTION OF THE DRAWINGS




Preferred embodiments of the present invention will now be described with reference to the attached drawings in which:





FIG. 1

is a split longitudinal cross-sectional view of a bridge plug according to a preferred embodiment of the present invention, in an open run-in position;





FIG. 2

is a split longitudinal cross-sectional view of the bridge plug of

FIG. 1

in a sealed set position;





FIG. 3

is a split longitudinal cross-sectional view of the bridge plug of

FIG. 1

in a released position;





FIG. 4

is a fragmentary partial longitudinal cross-sectional view of the portion of the bridge plug of

FIG. 1

marked “A”;





FIG. 5

is a split longitudinal cross-sectional view of the prong assembly of the bridge plug of

FIG. 1

;





FIG. 6

is a longitudinal cross-sectional view of the prong ratchet assembly of the bridge plug of

FIG. 1

;





FIG. 7

is a split longitudinal cross-sectional view of the main mandrel assembly of the bridge plug of

FIG. 1

;





FIG. 8

is a longitudinal cross-sectional view of the anchor slip assembly of the bridge plug of

FIG. 1

;





FIG. 9

is a longitudinal cross-sectional view of the rubber seal assembly of the bridge plug of

FIG. 1

;





FIG. 10

is a longitudinal cross-sectional view of the ratchet assembly of the bridge plug of

FIG. 1

;





FIG. 11

is a radial cross-sectional view of the bridge plug of

FIG. 1

, taken along


11





11


;





FIG. 12

is a radial cross-sectional view of the bridge plug of

FIG. 2

, taken along


12





12


;





FIG. 13

is a radial cross-sectional view of the bridge plug of

FIG. 1

, taken along


13





13


;





FIG. 14

is a radial cross-sectional view of the bridge plug of

FIG. 2

, taken along


14





14


;





FIG. 15

is a radial cross-sectional view of the bridge plug of

FIG. 1

, taken along


15





15


;





FIG. 16

is a radial cross-sectional view of the bridge plug of

FIG. 1

, taken along


16





16


; and





FIG. 17

is a split longitudinal cross-sectional view of a retrieving tool according to an embodiment of the present invention.




In

FIGS. 1

,


2


,


3


,


5


, and


7


, the top half of the drawing shows the top portion of the bridge plug while the bottom half of the drawing shows the bottom portion of the bridge plug, with some overlap between the top and bottom halves of the drawing, as indicated.

FIG. 17

is a similar view of the retrieving tool.











DETAILED DESCRIPTION OF THE DRAWING




The retrievable bridge plug according to a preferred embodiment of the present invention is shown in

FIGS. 1 through 3

in different operational positions. In

FIG. 1

, the bridge plug is shown in the open run-in position, in

FIG. 2

, the bridge plug is shown in the sealed set position, while in

FIG. 3

, the bridge plug is in the released position.




The bridge plug


20


comprises a prong assembly, prong ratchet assembly, main mandrel assembly, anchor slip assembly, rubber seal assembly, and ratchet assembly. Each assembly includes a plurality of components that move or act together. In describing the components of the bridge plug, the terms “upper”, “lower”, “uphole”, “downhole”, “top” and “bottom” are used with reference to the orientation of the bridge plug in the well.




As better seen in

FIG. 5

, the prong assembly comprises a prong


21


, shear stud


22


, collar


23


, ported sleeve


24


, and by-pass piston


25


.




The prong


21


is an elongated solid cylinder which forms the core of the bridge plug


20


. The prong


21


is provided with a first set of external threading


25




a


at its upper end, and a second set of external threading


25




d


at the bottom end of the prong. A first


25




b


and second


25




c


set of circumferential unidirectional teeth are located intermediate the first


25




a


and second


25




d


sets of external threading. A cylindrical bore


27


is defined longitudinally through the bottom of the prong


21


, while a plurality of radial ventilation holes


28


are defined near the top end of the bore


27


to allow communication of fluids between the inside of the cylindrical bore


27


and the outside of the prong


21


.




A cylindrical shear stud


22


having a shear constriction


26


and external threading


26




a


and


26




b


at either end, is co-axially mounted to the top of the prong


21


. The internally-threaded collar


23


attaches the shear stud


22


to the top end of the prong


21


by way of the external threading


26




b


and


25




a


on the bottom of the shear stud


22


, and the top of the prong


21


respectively. The external threading


26




a


at the top of the shear stud


22


accommodates attachment of an insertion tool


26




c


(partially shown) prior to run-in. Once the bridge plug


20


has been run-in and set, sufficient upward or twisting force imparted on the insertion tool


26




c


allows the shear stud


22


to break at the shear constriction


26


allowing the insertion tool to be pulled out of the well bore with the top half of the shear stud


22


.




The by-pass piston


25


is threadably mounted to the second set of external threading


25




d


at the bottom of the prong


21


. The by-pass piston is a cylinder having a cylindrical piston bore


29


defined longitudinally therethrough, such that once mounted on the prong


21


, fluid may flow through the bottom of the by-pass piston


25


, through the piston bore


29


defined therethrough, through the cylindrical bore


27


defined in the bottom of the prong


21


and out the radial ventilation holes


28


defined near the top of the cylindrical bore


27


. Resilient O-rings


30


are mounted in two grooves


32


defined on the outside surface of the by-pass piston


25


near the top and bottom of the by-pass piston


25


.




The ported sleeve


24


is an annular cylinder having a downwardly extending movable cover, the sand gate


34


. The portion of the sand gate


34


furthest from the annular cylinder portion of the ported sleeve


24


is a solid sleeve having an inner diameter greater than the outer diameter of the prong


21


such that there is space


35


between the prong


21


and this portion of the sand gate


34


. The portion of the sand gate


34


closest to the annular cylinder portion of the ported sleeve


24


is a sleeve having ports


36


. These ports may be better seen in the cross-sectional view of this portion of the bridge plug


20


shown in FIG.


11


. The ported sleeve


24


is threaded onto the second set of external unidirectional teeth


25




c


on the prong


21


.




The components of the prong ratchet assembly are shown in FIG.


6


. The prong ratchet assembly comprises a prong ratchet


38


, prong ratchet cap


40


, prong ratchet retainer


42


, and “C” ring


44


, and serves to control motion of the prong assembly relative to the remainder of the bridge plug


20


.




The prong ratchet


38


, a “C” collar having unidirectional teeth


46


defined on its inside surface, floats in an internal space formed by the prong ratchet retainer


42


below it, the prong ratchet cap


40


above it and external to it, and the prong


21


on its inside. The prong ratchet


38


is biased inwardly into contact with the external surface of the prong


21


. As the prong ratchet assembly slides up the prong


21


, the unidirectional teeth


46


defined on the inside surface of the prong ratchet


38


cooperate with the first set of circumferential unidirectional teeth


25




b


formed on the external surface of the prong, for ratcheting motion. Thus, although the prong ratchet


38


is allowed to travel up the prong


21


, it is prevented from travelling down the prong.




The prong ratchet retainer


42


is a collar located just below, and outside of the prong ratchet


38


. The prong ratchet retainer


42


is formed with an internal circumferential recess


50


at its bottom end to accommodate the upper end of the ported sleeve


24


, and internal threading


51


on an upwardly-extending outer sleeve portion at the top of the prong ratchet retainer.




The prong ratchet cap


40


is located above, and external to the prong ratchet


38


, and is provided with external threading


51




a


at its bottom end for threadably engaging the internal threading


51


on the prong ratchet retainer


42


. The prong ratchet cap


40


is provided with an internal recess


51




b


at its lower end to accommodate the ratchet


38


. The prong ratchet cap


40


also has an external circumferential rib


43


having a sloping upper surface


43




a


and a square lower surface


43




b.


The upper end of the prong ratchet cap is provided with a shoulder


52


which may abut against the lower end of the collar


23


to limit upward movement of the prong ratchet assembly.




The expanding “C” ring


44


is located between the lower square surface


43




b


of the circumferential rib


43


and the upper end of the prong ratchet retainer


42


. The “C” ring is biased outwardly.




The prong ratchet assembly is initially detachably fixed to the prong assembly by circumferentially-disposed prong-ratchet-assembly/prong-assembly shear pins


54


. These shear pins


54


are located within circumferentially-disposed orifices


56


located near the bottom end of the prong ratchet retainer


42


, and engage circumferentially-disposed recesses


58


provided near the upper end of the ported sleeve


24


. These shear pins


54


will shear and allow relative movement between the prong assembly and the prong ratchet assembly once a given amount of shear force is imparted thereon.




The components of the main mandrel assembly are shown in FIG.


7


. The main mandrel assembly comprises a main mandrel


60


, sand shroud


62


, “C” ring housing


64


, and lower cone


66


. The main mandrel assembly is mounted on the prong assembly and the prong ratchet assembly, and acts as the mount for the anchor slip assembly, rubber seal assembly, and ratchet assembly. The main mandrel assembly, together with the prong assembly, define the internal bypass passage


68


.




The main mandrel


60


is a hollow cylinder with an inner diameter greater than the outer diameter of the prong


21


. The annular space between the main mandrel


60


and the prong


21


forms the bypass passage


68


. As better seen in

FIG. 11

, near the upper end of the main mandrel


60


, four longitudinal slots are defined circumferentially around the main mandrel, forming the top opening


72


of the bypass passage


68


. As shown in

FIGS. 2 and 12

, when the bypass passage


68


is in the sealed set position, debris is prevented from entering the bypass passage through this top opening


72


by the sand gate


34


which slides under, and closes this opening. Hence, the sand gate


34


acts as a top bypass closure which may be moved from a first position in which the top opening is open, and a second position in which the top opening is covered by the sand gate


34


. Circumferential unidirectional teeth


73


are provided on the exterior surface of the main mandrel


60


at a location intermediate the top opening


72


and the lower cone


66


. Intermediate the unidirectional teeth


73


and the lower cone


66


, an external shoulder


73




a


is defined on the main mandrel


60


. External threading


73




b


is provided on the exterior surface of the main mandrel


60


at its bottom end. External threading


73




c


is also provided on the exterior surface of the main mandrel


60


at its upper end.




The sand shroud


62


is threadably mounted to the external threading


73




c


at the top of the main mandrel


60


. The sand shroud


62


has a perforated sleeve


74


extending downward overtop the top opening


72


of the bypass passage


68


, which sleeve portion is radially spaced from the main mandrel


60


. As better seen in

FIG. 4

, the perforated sleeve


74


of the sand shroud


62


is provided with perforations


76


. This perforated sleeve


74


of the sand shroud


62


prevents debris from packing around the top opening


72


of the bypass passage


68


, facilitating venting when the bypass passage is opened. When fluid flows upward through the bypass passage


68


, some of the fluid will be allowed to pass through the perforated sleeve


74


via the perforations


76


, while the rest of the fluid will be directed downward by the directing sand shroud


62


and the perforated sleeve out the bottom of the perforated sleeve. The upper end of the sand shroud


62


is provided with an inwardly extending lip


78


. When the prong ratchet assembly slides up relative to the main mandrel assembly, the sloped upper surface


43




a


of the external circumferential rib


43


of the prong ratchet cap


40


abuts against this inner lip


78


to stop further upward movement of the prong ratchet assembly relative to the main mandrel assembly.




The “C” ring housing


64


is located inside the sand shroud


62


just above the top end of the main mandrel


60


. When the bridge plug


20


is in the open run-in position, the “C” ring housing


64


is located outside the expanding “C” ring


44


, preventing further expansion of the “C” ring


44


. The “C” ring housing


64


is provided with an inner lip


80


at its upper end, which inner lip extends inside the inner surface


79


of the sand shroud


62


. This inner lip


80


is provided with a sloping lower surface


82


, while the top surface


84


of the inner lip is substantially perpendicular to the length of the “C” ring housing. Thus, as the prong ratchet assembly slides upward relative to the main mandrel assembly, the expanding “C” ring


44


slides along the inside surface of the “C” ring housing


64


. As the “C” ring


44


meets the inner lip


80


of the “C” ring housing


64


, the “C” ring is constricted by the sloping interface


82


. Once the “C” ring


44


passes under the inner lip


80


, it is allowed to expand once again, and the prong ratchet assembly is prevented from sliding back downward relative to the main mandrel assembly by the expanded “C” ring abutting against the top surface


84


of the inner lip


80


of the “C” ring housing


64


. The distance between this top surface


84


of the inner lip


80


and the inwardly extending lip


78


at the top end of the sand shroud


62


is such that the expanding “C” ring


44


slides under the inner lip


80


of the “C” ring housing


64


just as the external circumferential rib


43


of the prong ratchet cap


40


abuts against the inner lip


78


of the upper end of the sand shroud


62


. Hence, once the prong ratchet assembly slides upward sufficiently, relative to the main mandrel assembly, to achieve the position just described, the two assemblies are locked to each other as shown in

FIG. 2

, and no further relative movement between the two assemblies is permitted.




The lower cone


66


is a cup-shaped element threadably affixed to the external threading


73




b


at the bottom of the main mandrel


60


. The lower cone


66


and the bypass piston


25


comprise the bypass sealing valve. As best seen in

FIG. 13

, the lower cone


66


is provided with a plurality of oblique orifices


92


located just below the bottom end of the main mandrel


60


. These oblique orifices act as the bottom opening for the bypass passage


68


. In its initial position, the bypass piston


25


is seated within the lower portion of the lower cone


66


such that the bypass passage


68


communicates with the exterior of the bridge plug


20


through the oblique orifices


92


. However, as shown in

FIGS. 2 and 14

, as the prong assembly moves upward relative to the main mandrel assembly, the bypass piston


25


slides upward within the lower cone


66


, such that the two O-rings


30


lie above and below the oblique orifices


92


, forming seals against the inner surface of the bottom end of the main mandrel


60


, and against the inner surface of the lower cone


66


. In this position, communication between the bypass passage


68


and the exterior of the bridge plug


20


is prevented, and the bypass passage is sealed. Of course, as shown in

FIG. 3

, once the prong assembly then slides downward relative to the main mandrel assembly, the bypass passage


68


is opened once again as the bypass piston


25


seats itself against the lower portion of the lower cone


66


, communication between the bypass passage


68


and the exterior of the bridge plug


20


is permitted again, and the bypass passage


68


is open. The bypass piston


25


, lower cone


66


, and O-rings


30


therefore comprise a bottom bypass closure, which is movable from a first position in which the bottom opening of the bypass passage


68


is open, and a second position in which the bypass passage is sealed, and the bottom opening is closed off. As the bypass piston


25


slides up and down within the lower cone


66


, undesirably high or low pressure in the area between the bypass piston and the bottom cavity of the lower cone is prevented by virtue of fluid communication between this bottom cavity, and the bypass passage


68


, through the piston bore


29


formed in the bypass piston


25


, the cylindrical bore


27


formed in the bottom of the prong


21


, and the ventilation holes


28


formed in the side of the prong. The lower cone


66


is provided with an inwardly sloping external surface


85


at its upper end. Cooperation of the lower cone


66


with the bypass piston


25


as described above comprise the sealing valve.




Cooperation of the main mandrel


60


, prong


21


, ported sleeve


24


, lower cone


66


and bypass piston


25


as described above comprise the bypass sealing mechanism.




The main mandrel assembly is initially detachably fixed to the prong ratchet assembly by circumferentially-disposed main-mandrel/prong-ratchet-assembly shear pins


86


. These shear pins


86


are located within circumferentially-disposed orifices


88


located near the top end of the main mandrel


60


and engage circumferentially-disposed recesses


90


located on the exterior surface of the prong ratchet retainer


42


. These shear pins


86


will shear and allow relative movement between the main mandrel assembly and the prong ratchet assembly once a given amount of shear force is imparted thereon.




The components of the anchor slip assembly are shown in FIG.


8


. The anchor slip assembly comprises anchor slips


94


, leaf springs


96


, upper cone


98


, anchor slip cage


100


and slip cage cap


102


. The anchor slip assembly is mounted on the main mandrel assembly, and when engaged, secures the bridge plug


20


to the casing.




As better seen in

FIG. 15

, the anchor slips


104


which act as the anchors for the bridge plug, are a series of four longitudinally-extending slips having teeth


104


defined on their external surface. Preferably, these teeth


104


are bidirectional, some pointing down, some pointing up to provide anchoring against either upward or downward forces. The anchor slips


104


are located just above and exterior to the upper end of the lower cone


66


, and are provided with sloping interior surfaces


105


as seen in

FIGS. 1 and 8

. The anchor slips


104


are biased toward their retracted positions toward the interior of the bridge plug


20


by virtue of anchor biasing elements comprising the leaf springs


96


.




The upper cone


98


is located above, and interior to the upper end of the anchor slips


94


. The lower end of the upper cone


98


is provided with a sloping exterior surface


99


. The upper portion of the upper cone


98


is a sleeve having external threading


106


at its upper end.




The sloping exterior surface


85


and


99


of the upper end of the lower cone


66


and the lower end of the upper cone


98


respectively, cooperate with the sloping interior surfaces


105


of the anchor slips


94


to push the anchor slips outward to an extended position when the lower cone and upper cone are moved toward each other. When the lower cone


66


and upper cone


98


are moved apart again, the leaf springs


96


pull the anchor slips


94


back to a retracted position.




The anchor slips


94


are held in position by the anchor slip cage


100


, a sleeve located exterior to the lower cone


66


, anchor slips and upper cone


98


, and having rectangular orifices to allow the anchor slips


94


to extend therethrough when the anchor slips are moved to the extended position. Downward movement of the anchor slip cage


100


relative to the upper cone


98


is limited through abutment of an interior lip


108


at the upper end of the cage with an external shoulder


110


defined on the exterior surface of the upper cone. Upward movement of the anchor slip cage


100


relative to the lower cone


66


is limited through abutment of the upper surface


101


of the slip cage cap


102


which is threaded to the bottom end of the slip cage, against an external shoulder


112


defined on the lower cone.




The components of the rubber seal assembly are best seen in FIG.


9


. The rubber seal assembly is comprised of rubber seal elements


114


, element spacer


116


, element mandrel


118


, upper


120


and lower


121


gauge rings and element mandrel cap


122


. The rubber seal assembly is located above the anchor slip assembly, and when engaged, provides a seal between the bridge plug


20


and the casing.




Rubber seal elements


114


which provide the seal between the bridge plug and the well wall, are two generally flat annular resilient elements separated by the element spacer


116


. The rubber seal elements


114


are supported by, and lie exterior to the element mandrel


118


, and are limited above and below by the two gauge rings


120


and


121


. The rubber seal elements


114


are sufficiently malleable such that when the two gauge rings


120


and


121


are moved toward each other, the rubber seal elements extrude outward from their retracted positions as shown in

FIG. 1

to their extended positions as shown in

FIG. 2

, to press against the well casing and form an annular seal between the bridge plug


20


and the well casing. Once the gauge rings


120


and


121


are separated again, the rubber seal elements


114


return to approximately their original shape and position as shown in FIG.


3


.




The lower gauge ring


121


is threaded onto the external threading


106


located at the upper end of the upper cone


98


and moves therewith. Each of the lower gauge ring


121


, element spacer


116


, and rubber seal elements


114


are slidably mounted on and lie exterior to the element mandrel


118


. The upper gauge ring


121


is threadably mounted on the element mandrel. Thus, when the lower gauge ring


121


is moved upward, each of the lower gauge ring


121


, element spacer


116


and rubber seal elements


114


slide upward on the element mandrel


118


relative to the upper gauge ring


120


. Downward movement of the lower gauge ring


121


is limited by abutment of the lower gauge ring against the element mandrel cap


122


threadably mounted to the bottom end of the element mandrel


118


. Near the upper end of the element mandrel


118


, an internal circumferential recess is provided, housing an O-ring


124


. This O-ring


124


prevents leakage of fluids which might otherwise circumvent the seal provided by the rubber seal elements


114


by travelling under the element mandrel


118


. The upper end of the element mandrel


118


is provided with internal threading.




The components of the ratchet assembly are best seen in FIG.


10


. The ratchet assembly comprises a ratchet


126


, ratchet release support


128


, ratchet release


130


and ratchet housing


132


. The ratchet assembly locks the anchor and rubber seal assemblies in their engaged positions until it is desirable to unset the bridge plug


20


. The ratchet assembly is located outside of the main mandrel assembly, above the rubber seal assembly, and below the prong ratchet assembly.




As best seen in

FIG. 16

, the ratchet


126


is a cluster of longitudinally-elongated elements


133


having unidirectional teeth


134


on an inner surface near the bottom of the elements. These unidirectional teeth


134


cooperate with the unidirectional teeth


73


on the external surface of the main mandrel


60


to permit the ratchet assembly to move downward relative to the main mandrel, while at the same time preventing upward movement. The elongated elements of the ratchet


126


are biased inwardly by a “C” spring


135


located on an outside surface of the ratchet


126


near its bottom end. The lower end of the ratchet


126


is provided with an external lip


136


having a bottom surface


137


sloping downward and outward.




The ratchet assembly is unlocked by the ratchet release


130


. The ratchet release


130


is located below the ratchet


126


. The top end of the ratchet release


130


is provided with a sloping surface


138


which slopes downward and outward. When this sloping surface


138


bears against the sloping surface


137


on the bottom of the external lip


136


of the ratchet


126


, the bottom portions of the elongated elements


133


comprising the ratchet are forced outward to disengage the unidirectional teeth


134


on the inner surface of the ratchet, from the external unidirectional teeth


73


on the main mandrel


60


, thereby allowing the ratchet assembly to move upward relative to the main mandrel assembly. The ratchet release


130


is provided with an interior shoulder


140


near its upper end. An internal recess


142


is provided at the bottom of the ratchet release


130


. This recess


142


accommodates the upper end of the element mandrel


118


.




Movement of the ratchet release


130


is guided by the ratchet release support


128


which lies interior to the ratchet release. The lower end of the ratchet release support


128


is threadably affixed to the upper end of the element mandrel


118


. As the ratchet release


130


slides upward relative to the ratchet release support


128


, such upward movement is limited by abutment of the interior shoulder


140


of the ratchet against an exterior shoulder


144


located near the upper end of the ratchet release support.




The ratchet


126


is forced downward during setting of the bridge plug


20


by the ratchet housing


132


. The ratchet housing


132


is threadably affixed to the upper end of the ratchet release


130


, and is provided with an interior recess


146


which accommodates the ratchet


126


. The upper end of this recess


146


defines a shoulder


148


which limits upward movement of the ratchet


126


relative to the ratchet housing


132


. The ratchet housing


132


is provided with two external retrieving lugs


150


near its upper end. These retrieving lugs act as retrieving tool engaging elements, the engagement points for unsetting the bridge plug. The retrieving lugs


150


are radial protrusions of circular cross-section. These retrieving lugs are used as latch points for the setting tool


26




a


and the retrieval tool


200


.




The ratchet assembly is initially detachably fixed to the rubber seal assembly by circumferentially-disposed ratchet-assembly/rubber-seal-assembly shear pins


152


. These shear pins


152


are located within circumferentially-disposed orifices


156


located near the bottom ends of the ratchet release


130


, and engage circumferentially-disposed external recesses


154


located near the top end of the element mandrel


118


. These shear pins


152


will shear and allow relative movement between the ratchet assembly and the rubber seal assembly once a given amount of shear force is imparted thereon.




The ratchet assembly is also initially detachably fixed to the main mandrel assembly by circumferentially-disposed ratchet-assembly/main-mandrel-assembly shear pins


158


. These shear pins


158


are located within circumferentially-disposed orifices


160


located near the top end of the ratchet housing


128


just below the retrieving lugs


150


, and engage circumferentially-disposed external recesses


162


located on the main mandrel


60


. These shear pins


158


will shear and allow relative movement between the ratchet assembly and the main mandrel assembly once a given amount of shear force is imparted thereon.




The components of the various assemblies required to move the rubber seals


114


and anchor slips


94


from their retracted positions to their extended positions, and lock them in their extended positions comprise the bridge plug setting mechanism.




In use, the bridge plug progresses through 5 positions—the open run-in position, the sealed run-in position, the sealed set position, the open set position and the released position.




In the open run-in position as shown in

FIG. 1

, relative movement between the assemblies of the bridge plug


20


is prevented by the shear pins


54


,


86


,


152


and


158


. The anchor slips


94


and rubber seals


114


are retracted, and the bypass passage


68


is open, since the bypass piston


25


is seated at the bottom of the lower cone


66


, and the ports of the ported sleeve


36


are aligned with the top opening


72


of the bypass passage, thus allowing fluid communication between the bypass passage


68


and the exterior of the bridge plug


20


.




The insertion tool


26




c


is threaded onto the external threading


26




a


at the upper end of the shear stud


22


, while an external portion of the insertion tool


26




c


(not shown) abuts the retrieving lugs


150


. The bridge plug


20


is then lowered into the well bore. Because the bypass passage


68


is open, fluid in the bore is allowed to flow through the bypass passage, thereby minimizing fluid resistance, and increasing the speed at which the bridge plug


20


may be lowered into the well bore.




Once the bridge plug


20


is placed in its desired position, the insertion tool


26




c


imparts an upward force on the shear stud


22


, while imparting downward force on the retrieving lugs


150


. Once sufficient opposing force is imparted on the bridge plug


20


, the main-mandrel/prong-ratchet-assembly shear pin


86


will shear, allowing relative movement between the prong and prong ratchet assemblies on the one hand, and the main mandrel, anchor slip, rubber seal and ratchet assemblies on the other. As the prong assembly moves upward relative to the main mandrel assembly, the sand gate


34


of the ported sleeve


24


slides under the top opening


72


of the bypass passage


68


, closing off the top opening, thereby preventing any debris from entering the interior of the bridge plug


20


through this top opening. Since the prong ratchet assembly moves upward along with the prong assembly, once the upper surface


43




a


of the circumferential rib


43


on the prong ratchet cap


40


abuts against the inwardly extending lip


78


at the top end of the sand shroud


62


, further upward movement of the prong and prong ratchet assemblies relative to the remainder of the bridge plug


20


is prevented. As described above, in this position, abutment of the “C” ring


44


against the inner lip


80


at the top end of the “C” ring housing


64


prevents any downward movement of the prong and prong ratchet assemblies relative to the rest of the bridge plug


20


, and all assemblies of the bridge plug are locked together once again. At the same time, the by-pass piston


25


slides upward within the lower cone


66


until the O-rings


30


mounted on the bypass piston straddle the oblique orifices


92


on the lower cone. The bypass passage


68


is then sealed, with no fluid flow being permitted therethrough. Further, the seal formed at the bottom of the bypass passage


68


prevents any debris from entering the bypass passage. Thus, in this, the sealed run-in position, the bypass passage


68


is closed and sealed, debris is prevented from entering the bypass passage


68


from either the top opening


72


or the oblique orifices


92


, and both the anchor slips


94


and rubber seals


114


are still in their retracted positions. Engagement of the “C” ring


44


against the inner lip


80


at the top end of the “C” ring housing


64


as described above prevents inadvertent re-opening of the bypass passage


68


.




Further upward force on the shear stud


22


, along with downward force on the retrieving lugs


150


commences the setting sequence by virtue of the setting mechanism. This opposing force causes the ratchet-assembly/main-mandrel-assembly shear pin


158


to shear. Movement then occurs between the prong assembly, prong ratchet assembly and main mandrel assembly on the one hand, and the anchor slip assembly, rubber seal assembly, and ratchet assembly on the other. The resulting movement of the ratchet assembly toward the lower cone


66


causes the upper cone


98


to move toward this lower cone


66


thereby causing the anchor slips


94


to move outward to their extended positions from their retracted positions to engage the well casing, as more fully described above. Continued opposing force causes the upper gauge ring


120


to move toward the lower gauge ring


121


thereby causing the rubber seals


114


to extrude outward to their extended positions, also as more fully described above. Thus, the engagement of each of the anchor slips


94


and rubber seals


114


against the well casing secures the bridge plug


20


against upward or downward movement within the well bore, while providing a seal between the bridge plug


20


and the well casing. At the same time, as the ratchet assembly moves downward relative to the main mandrel assembly, the unidirectional teeth


134


on the ratchet


126


also moves downward along the unidirectional teeth


73


on the main mandrel


60


. Thus, once the anchor slips


94


and rubber seals


114


have fully engaged the well casing, the anchor slip assembly and rubber seal assembly are locked in position by the engagement of the unidirectional teeth


134


on the ratchet


126


with the unidirectional teeth


73


on the main mandrel, as more fully described above. This provides the locking portion of the setting mechanism for locking the anchor slips


94


and rubber seals


114


in their extended positions. The bridge plug


20


is now in the sealed set position, as shown in

FIG. 2

with the bypass passage


68


closed and sealed, and the anchor slips


94


and rubber seals


114


locked in their extended positions.




While the bridge plug


20


is in the well casing, debris which may fall on top of the bridge plug as a result of the setting procedure, the workover operation, the retrieval procedure, or which is intentionally placed atop the plug to protect it, is prevented from accumulating adjacent the top opening


72


of the bypass passage


68


by the sand shroud


62


which directs debris away from this top opening.




Once it is desired to unset the bridge plug


20


and remove it from the well bore, a retrieval tool


200


is inserted down the well bore and fluid is circulated in the region above the bridge plug to remove as much of the debris packed on top of the plug as possible. Before unsetting the bridge plug


20


, the bypass passage


68


is first opened to equalize pressure across the bridge plug.




The retrieval tool


200


first imparts a downward force on the sheared end of the shear stud


22


. With sufficient downward force, accompanied by the resistance offered by the anchor slips


94


which hold the bridge plug


20


in place within the well casing, the prong-ratchet-assembly/prong-assembly shear pin


54


shears allowing the prong assembly to move downward relative to the remainder of the bridge plug


20


. The bypass piston


25


moves downward within the main mandrel assembly until it once again seats against the bottom of the lower cone


66


allowing fluid communication between the exterior of the bridge plug


20


and the bypass passage


68


through the oblique orifices


92


of the lower cone. At the same time, the sand gate


34


of the ported sleeve


24


which was located under the top opening


72


of the bypass passage


68


moves downward until the ports


36


of the ported sleeve align with the top opening of the bypass passage, allowing fluid communication between the bypass passage and the exterior of the bridge plug


20


through this top opening. The bypass passage


68


is then open.




The bypass passage


68


is locked in its open position by engagement of the unidirectional teeth


46


on the inside surface of the prong ratchet


38


with the unidirectional teeth


25




b


on the exterior of the prong


21


. As the prong assembly moves downward relative to the remainder of the bridge plug


20


, the prong ratchet assembly moves upward relative to the prong assembly. Thus, the prong ratchet


38


moves upward to engage the first set of unidirectional teeth


25




b


on the prong


21


. Once the bypass piston


25


had seated against the bottom of the lower cone


66


, upward movement of the prong assembly relative to the remainder of the bridge plug is prevented due to the engagement of the unidirectional teeth


46


of the prong ratchet


38


with the first set of unidirectional teeth


25




b


on the prong


21


, as more fully described above. Thus, inadvertent sealing of the bypass passage


68


is prevented.




Since pressure is normally higher in the area below the plug, once the bypass passage


68


is opened, fluid flows from this area below the plug, through the oblique orifices


92


of the lower cone


66


, up the bypass passage


68


, past the ports


36


of the ported sleeve


24


and out the top opening


72


. As the fluid exits the top opening


72


, often at a high flow rate, some of the fluid flows through the perforations


76


of the perforated sleeve


74


of the sand shroud


62


, while the remainder of the fluid is forced downward by the directing sand shroud and onto the retrieving lugs


150


. This rapid flow of fluid over the retrieving lugs


150


assists in clearing the retrieving lugs of debris, such that the retrieving tool


200


may more easily and more securely latch onto them.




The bridge plug is then in the open set position with the bypass passage


68


open, but with the anchor slip assembly and rubber seal assembly still engaged.




Once pressure has been equalized across the bridge plug


20


, the retrieving tool is then allowed to engage the retrieving lugs


150


.




The retrieving tool


200


then imparts an upward force on the retrieving lugs of the bridge plug


20


. With sufficient upward force, the ratchet-assembly/rubber-seal-assembly shear pins


152


shear, allowing the ratchet housing


132


and ratchet release


130


to move upward relative to the remainder of the bridge plug


20


. The rubber seal assembly and anchor slip assembly are held in their engaged positions by the ratchet


126


which still engages the unidirectional teeth


73


on the main mandrel


60


. The ratchet release


130


moves up until the sloping surface


138


at the top of the ratchet release bears against the sloping surface


137


of the external lip


136


at the bottom of the ratchet


126


. Further upward movement of the ratchet release


130


, along with cooperating action between the two sloping surfaces


138


and


137


forces the bottoms of the elements


133


of the ratchet


126


outward, disengaging the unidirectional teeth


134


of the ratchet from the unidirectional teeth


73


on the main mandrel


60


. Thus, the lock provided by engagement of the unidirectional teeth


134


and


73


is released. This provides the unlocking portion of the release mechanism for unlocking the anchor slips


94


and rubber seals


114


, allowing them to return to their retracted positions.




Release of the ratchet


126


from the main mandrel


60


unsets the bridge plug, as it allows the various components of the rubber seal assembly and the anchor slip assembly to move upward relative to the main mandrel assembly and in particular the lower cone


66


. The upper gauge ring


120


of the rubber seal assembly moves away from the lower gauge ring


121


, and the rubber seal elements


114


are allowed to relax and retract away from the well casing. The upper cone


98


likewise moves away from the lower cone


66


allowing the leaf spring


96


to pull the anchor slips


94


into a retracted position. This provides the unsetting portion of the release mechanism for urging the anchor slips


94


and rubber seals


114


to their retracted positions.




The bridge plug


20


is now in the released position with the rubber seal and anchor slip assemblies disengaged, and the bridge plug can be removed from the well bore.




Although the operation of the bridge plug


20


of the present invention has been described with the plug being inserted into the well casing in its open run-in position, it is to be understood that the plug may also be inserted into the well casing in its sealed run-in position so as to prevent any debris from entering the interior of the plug and interfering with the proper operation of the plug.




The retrieving tool


200


according to an embodiment of the present invention is shown in FIG.


17


.




The retrieving tool


200


is comprised of the retrieving tool mandrel assembly, retrieving tool main sleeve assembly, and the retrieving tool latch assembly.




The retrieving tool mandrel assembly is comprised of a top sub


202


, mandrel


204


, and shear ring


206


. A tubing attachment interface is provided by the top sub


202


which is an internally threaded collar which is partially screwed onto the top portion of the mandrel


204


. The upper portion of the top sub


202


is screwed onto a threaded bottom portion of tubing (not shown). The retrieving tool


200


is lowered into the well bore on this tubing. The mandrel


204


is a sleeve having an external circumferential rib


208


defined near its bottom end. This circumferential rib


208


has a top surface


210


perpendicular to the length of the mandrel


204


. The shear ring


206


, is an annular band located on the outside surface of the mandrel at a point intermediate the top sub


202


and the circumferential rib


208


. The shear ring


206


is detachably affixed to the mandrel


204


by circumferentially-disposed shear ring shear screws


212


.




The retrieving tool main sleeve assembly is comprised of a sleeve cap


214


, main sleeve


216


, main sleeve spring


218


and guide cap


220


. The sleeve cap


214


is a sleeve located outside the mandrel


204


. The sleeve cap


214


has an internal lip


222


contacting the external surface of the mandrel


204


. This lip


222


is located between the top sub


202


and the shear ring


206


. Upward and downward movement of the remainder of the retrieving tool


200


is limited by abutment of this internal lip


222


against the bottom end of the top sub


202


and the top surface of the shear ring


206


. The sleeve cap extends downward past the circumferential rib


208


on the mandrel


204


. The sleeve cap is also provided with an external circumferential groove


224


, above which is external threading


226


.




The main sleeve


216


is threaded onto the external threading


226


on the sleeve cap


214


. The main sleeve


216


is secured in place by set screws


228


threaded through orifices


230


in the main sleeve to seat in the circumferential groove


224


provided on the sleeve cap


214


. The bottom portion


232


of the main sleeve


216


is recessed and is provided with external threading


234


. A circumferential external lip


235


is provided at the bottom of the main sleeve


216


.




The guide cap


220


is located inside the main sleeve


216


for longitudinal reciprocal movement therein and is adapted to accommodate the shear stud


22


of the bridge plug


20


. The guide cap is provided with multiple longitudinal orifices


235


to allow fluid communication therethrough. The guide cap


220


is initially secured near the bottom of the main sleeve


216


by shear screws


236


. Further downward movement of the guide cap


220


relative to the main sleeve


216


is prevented by abutment of an external shoulder


238


on the guide cap


220


against an internal shoulder


240


on the main sleeve. The guide cap


220


is biased towards a position away from the sleeve cap


214


by a guide cap biasing element comprising the main sleeve spring


218


located within the main sleeve


216


which bears against the bottom end of the sleeve cap and a top surface of the guide cap.




The retrieval tool latch assembly comprises a retrieving lug guide


242


, latch sleeve


244


, latch spring


246


and outer sleeve


248


. The retrieving lug guide


242


is threaded onto the external threads


234


near the bottom end of the main sleeve


216


. The retrieving lug guide


242


is secured in place by set screws


250


located within circumferentially-disposed orifices


252


. These set screws


250


prevent downward movement of the retrieving lug guide


242


relative to the main sleeve


216


by abutment of the set screws against the internal lip


235


at the bottom of the main sleeve. The bottom portion of the retrieving lug guide is slightly recessed. This bottom portion of the retrieving lug guide is provided with two “J” shaped slots


254


spaced 180° apart circumferentially, extending upward from a bottom end of the retrieving latch guide


242


. Each “J” shaped slot


254


has an upward and obliquely-extending stem portion


256


, and a hook portion


258


extending downward from the upper end of the stem portion. Each “J” shaped slot


254


is sized to accommodate the retrieving lugs


150


of the bridge plug


20


. The very bottom of the retrieving lug guide is provided with two downward pointing spade-shaped profiles


260


180° apart circumferentially.




The latch sleeve


244


is mounted for reciprocal longitudinal movement within the retrieving lug guide


242


. The latch sleeve


244


is provided with two latch slots


262


spaced 180° apart circumferentially. These latch slots


262


extend upward from the bottom of the latch sleeve


244


, and are sized to accommodate the retrieving lugs


150


of the bridge plug


20


. The latch sleeve


244


is initially located within the retrieving lug guide


242


at a location such that the hook portion


258


of the “J” shaped slots


254


substantially align with the latch slots


262


, and the remainder of the latch sleeve substantially covers an interface between the hook portion


258


and stem portion


256


of the “J” shaped slots


254


of the retrieving lug guide


260


. Further downward progress of the latch sleeve


244


within the retrieving lug guide


242


is prevented by abutment of an external lip


264


at the top of the latch sleeve against an internal shoulder


266


on the retrieving lug guide just above the bottom portion of the retrieving lug guide. The latch sleeve


244


is biased downward relative to the main sleeve


216


by a latch sleeve biasing element comprising the latch spring


246


. The latch spring


246


bears against the external lip


264


at the top of the latch sleeve


244


and against the bottom end of the main sleeve


216


. Circumferential rotation of the latch sleeve


244


within the retrieving lug guide


242


is prevented by a latch sleeve alignment mechanism comprising circumferentially-disposed guide screws


268


located within circumferentially-disposed orifices


270


and


272


in each of the outer sleeve


246


and the retrieving lug guide


242


respectively and which slide along longitudinal grooves


274


defined in the latch sleeve.




The outer sleeve


248


is affixed to the retrieving lug guide


242


by the guide screws


268


, and extends downward.




In use, once it is desired to remove the bridge plug


20


which is in its sealed set position, from the well bore, the retrieving tool is screwed onto the tubing, with the inner threads of the upper portion of the top sub


202


engaging the external threading at the lower end of the coil tubing. The retrieving tool


200


is then lowered into the casing. Once the bottom of the retrieving tool


200


nears the broken portion of the shear stud


22


, clean-out fluids are flowed through the interior of the retrieving tool. The clean-out fluids are flowed through the interior of the hollow tubing, through the mandrel


204


, main sleeve


216


, the orifices


235


in the guide cap


220


, the retrieving lug guide


242


, latch sleeve


244


and outer sleeve


248


. Since further downward flow of the clean-out fluids is blocked by the bridge plug


20


, the clean-out fluids are then pushed up through the annular space between the retrieving tool


200


and the casing wall. As the retrieving tool


200


is slowly lowered further, the clean-out fluids serve to clean the top portion of the bridge plug


20


of any debris.




With further lowering of the retrieving tool


200


, the shear stud


22


contacts the guide cap


220


. Because the guide cap is affixed to the main sleeve


216


by the shear pins


236


, the guide cap imparts a downward force on the shear stud


22


, which downward force is transferred to the prong


21


. As described above, as the prong is pushed downward, the bypass passage


68


in the bridge plug


20


is forced open allowing pressure to equalize across the bridge plug


20


.




Once the bypass passage


68


of the bridge plug


20


is completely open, abutment of the lower end of the collar


23


against the upper end of the prong ratchet cap


40


resists any further downward movement of the prong


21


relative to the remainder of the bridge plug


20


. With further downward force imparted on the retrieving tool


200


, the shear pins


236


will shear, allowing the guide cap to travel upwards within the main sleeve


242


, compressing the main sleeve spring


218


. This allows the retrieving tool


200


to move lower relative to the bridge plug


20


. The outer sleeve


248


is sized such that it will slide over and past the retrieving lugs


150


on the bridge plug


20


.




The retrieving lugs


150


will then contact the spade-shaped profile


260


portion of the retrieving lug guide


242


. With further downward movement of the retrieving tool


200


, this spade-shape imparts an angular force on the retrieving tool latch assembly, forcing it to rotate one way or the other, depending on the location of the spade-shaped profile


260


the retrieving lugs


150


first contact. This angular force is transferred to the retrieving tool main sleeve assembly. By virtue of a rotation mechanism provided by the interaction between the internal lip


222


of the sleeve cap


214


with the shear ring


206


, the retrieving tool main sleeve assembly and retrieving tool latch assembly are allowed to rotate relative to the retrieving tool mandrel assembly and the coil tubing. Thus, as the retrieving tool


200


moves lower, the retrieving lugs


150


slide along the bottom surface of the spade-shaped profile


260


of the retrieving lug guide


242


, all the while forcing the retrieving tool latch assembly and retrieving tool mandrel assembly to rotate. Once the retrieving lugs


150


enter the stem


256


of the “J”-shaped slots


254


of the retrieving lug guide


242


, the retrieving lugs bear against the bottom surface of the latch sleeve


244


. With further lowering of the retrieving tool


200


, the latch sleeve


244


is forced upward against the downward biasing force provided by the latch spring


246


. The latch sleeve


244


is prevented from rotating relative to the retrieving lug guide


260


through cooperation of the guide screw


268


with the longitudinal grooves


274


in the latch sleeve. The upward movement of the latch sleeve


244


allows the retrieving lugs


150


to continue up the stem


256


of the “J” shaped slots


254


. Once the retrieving lugs


150


reach the top of the “J” shaped slots


254


, the retrieving lugs


150


no longer bear against the bottom surface of the latch sleeve


244


, and the retrieving lugs are allowed to enter the latch slots


262


, allowing the latch spring


246


to push the latch sleeve


244


back down to its original position. The retrieving lugs


150


are then locked within the hook portions


258


of the “J” shaped slots


254


.




The various components of the retrieving tool


200


are sized such that it is not possible for the retrieving lugs


150


of the bridge plug


20


to become locked within the hook portions


258


of the “J” shaped slots


254


until the prong


21


has been pushed down relative to the remainder of the bridge plug


20


sufficiently to open the bypass passage


68


, thus preventing a situation where the bridge plug


20


would become unset while the bypass passage


68


is still sealed.




Once the retrieving lugs


150


are locked within the hook portions


258


of the “J” shaped slots


254


, the retrieving tool is then pulled up. This upward movement seats the retrieving lugs


150


within the bottom end of the hook portions


258


of the “J” shaped slots


254


, thereby imparting an upward force on the retrieving lugs


150


while the main sleeve spring


218


provides a downward force on the shear stud


22


and therefore the prong


21


. The prong


21


is also held in place by the anchor slip assembly, which is still engaged. As better described previously, these opposing forces serve to disengage both the rubber seal assembly and the anchor slip assembly, allowing both the retrieving tool and the bridge plug to be raised out of the well bore.




The hollow nature of the retrieving tool


200


allows clean-out fluid to continue to flow through the retrieving tool throughout the retrieving process, effecting an improved well clean out.




The opposing forces imparted on the retrieving lugs


150


and the prong


21


also serve to ensure that the lower cone


66


remains well apart from the upper cone


98


. In cooperation with the leaf spring


96


, the anchor slips


94


are thereby prevented from inadvertently engaging the casing wall during retrieval.




The locking of the retrieving lugs


150


within the hook portions


258


of the “J” shaped slots


254


of the retrieving lug guide


242


of the retrieving tool


200


prevents inadvertent release of the retrieving lugs during retrieval.




If the pulling force on the retrieving lugs


150


exceeds the expected force necessary to normally disengage the rubber seal assembly and anchor slip assembly, the shear ring shear screws


212


shear allowing the shear ring


206


to slam against the upper surface


210


of the circumferential rib


208


of the mandrel


204


quickly and with considerable force. This jarring action will aid disengagement of the rubber seal assembly and anchor slip assembly. If these assemblies still do not disengage, the retrieving tool


200


can then be lowered and then jarred upward again and again to achieve release of these assemblies.




Once the retrieving tool


200


with attached bridge plug


20


has been extracted from the well bore, the bridge plug may be separated from the retrieving tool in the following manner. First, the guide screw


268


is removed. This allows the latch sleeve


244


to rotate relative to the retrieving lug guide


242


. By first pushing the bridge plug


20


into the retrieving tool


200


, and then rotating it ¼ turn relative to, while pulling it away from, the retrieving tool, the retrieving lugs


150


are allowed to slide to the top of the J-shaped slots


254


, and then to exit the J-shaped slots via the stem portion


256


of the J-shaped slots. Hence, the bridge plug


20


is disengaged from the retrieving tool


200


.




Although the retrieving tool


200


has been described as being adapted to retrieve a bridge plug, it is to be understood that the retrieving tool can also be used to retrieve other downhole tools adapted to be engaged by it, a packer for example.




Although each of the bridge plug and retrieving tool have been described in great detail, it is to be understood that numerous modifications, variations, and adaptations may be made to the particular embodiments of the invention described above without departing from the scope of the invention which is defined in the claims.



Claims
  • 1. A retrieving tool having top and bottom ends, for retrieving downhole tools from a well bore, such downhole tools having a top end and a plurality of transversely extending retrieving lugs, the retrieving tool comprising:(a) a tubing attachment interface for detachably attaching the retrieving tool to tubing; (b) a retrieving lug guide having a bottom end, said retrieving lug guide comprising a sleeve defining a plurality of J-shaped slots extending upward from its bottom end, the number of said J-shaped slots being equal to or greater than the number of retrieving lugs on the downhole tool and, each of said J-shaped slots being sized to accommodate a retrieving lug, each J-shaped slot having a stem portion and a hook portion, said stem portion of each J-shaped slot extending upward and obliquely from said bottom end of the retrieving lug guide, said hook portion of each J-shaped slot extending downward, said bottom end of said retrieving lug guide being provided with downward-pointing spade-shaped profiles between entrances to each J-shaped slot; (c) a latch sleeve mounted for reciprocal longitudinal movement within the retrieving tool, said latch sleeve having a bottom end, at least a portion of said latch sleeve overlapping a sufficient portion of said retrieving lug guide so as to substantially overlap an interface between the hook portion and stem portion of the J-shaped slots of said retrieving lug guide; said latch sleeve defining a plurality of latch slots extending upward from the bottom end of said latch sleeve, the number of said latch slots being equal to or greater than the number of retrieving lugs, said latch slots being sized to accommodate the retrieving lugs, said latch slots being aligned with the hook portions of the J-shaped slots of the retrieving lug guide; (d) each of said retrieving lug guide and latch sleeve having an inner diameter large enough to allow the retrieving lug guide and latch sleeve to pass over all portions of the downhole tool above the retrieving lugs, but small enough to cause engagement with the retrieving lugs; (e) a latch sleeve alignment mechanism to prevent the latch sleeve from rotating relative to the retrieving lug guide; (f) a latch sleeve biasing element to bias the latch sleeve downward relative to the retrieving lug guide; and (g) a rotation mechanism to allow the retrieving lug guide, latch sleeve, latch sleeve alignment mechanism and biasing element to rotate relative to the tubing attachment interface, whereby as the retrieving tool is lowered into the well on the end of the tubing, the retrieving lugs on the downhole tool first contact the bottom end of the retrieving lug guide, the spade-shaped profile of the bottom end of the retrieving tool guide causing the retrieving tool guide, latch sleeve, latch sleeve alignment mechanism and biasing element to rotate relative to the tubing attachment interface as the retrieving tool is lowered further, still further lowering causing the retrieving lugs to enter the stem portions of the J-shaped slots and then to bear against the bottom end of the latch sleeve causing the latch sleeve to move upwards against the biasing force provided by the biasing element, further downward movement of the retrieving tool causing the retrieving lugs to enter the hook portion of the J-shaped slots allowing the biasing element to force and retain the latch sleeve back down relative to the retrieving lug guide as the retrieving lugs enter the latch slots, thereby locking the retrieving lugs within the hook portion of the J-shaped slots of the retrieving lug guide.
  • 2. The retrieving tool of claim 1 wherein the biasing element is a coil spring.
  • 3. The retrieving tool of claim 1 wherein the latch sleeve lies interior to the retrieving lug guide.
  • 4. The retrieving tool of claim 3 wherein the latch sleeve alignment mechanism is at least one guide screw located within an orifice in the retrieving lug guide and engaging a longitudinal slot defined in the latch sleeve.
  • 5. The retrieving tool of claim 4 wherein said guide screw may be disengaged from the longitudinal slot allowing the latch sleeve to rotate relative to the retrieving lug guide.
  • 6. The retrieving tool of claim 5 wherein the biasing element is a coil spring.
  • 7. The retrieving tool of claim 1 further comprising a guide cap mounted for reciprocating longitudinal movement within the retrieving tool, said guide cap being urged downward relative to the remainder of the retrieving tool by a guide cap biasing element, said guide cap engaging a central prong protruding from the top end of said downhole tool, and imparting a downward force thereon as the retrieving tool is lowered.
  • 8. The retrieving tool of claim 7 wherein the guide cap biasing element is a coil spring.
RELATED APPLICATION

The present application is a divisional of application Ser. No. 09/175,595, filed Oct. 20, 1998. The benefit of the earlier filing date of the aforementioned application Ser. No. 09/175,595 is hereby claimed.

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3393002 Woolley Jul 1968
3785690 Hutchinson Jan 1974
4185689 Harris Jan 1980
4436150 Barker Mar 1984
4595052 Kristiansen Jun 1986
4648446 Fore et al. Mar 1987
4671356 Barker et al. Jun 1987
4693309 Caskey Sep 1987
4862961 Neff Sep 1989
4898239 Rosenthal Feb 1990
4898245 Braddick Feb 1990
4928762 Mamke May 1990
5058684 Winslow et al. Oct 1991
5074361 Brisco et al. Dec 1991
5441111 Whiteford Aug 1995
5613560 Jelinski et al. Mar 1997
5678635 Dunlap et al. Oct 1997
5727632 Richards Mar 1998
5810410 Arterbury et al. Sep 1998
Foreign Referenced Citations (1)
Number Date Country
2148197 Sep 1995 CA