Abstract:
A method and apparatus for sealing a tool for use in a wellbore is provided. The seal is configured to be disposed in a tool comprising a ported sliding sleeve and a ported housing. The tool may be actuable between a closed and an open position. The seal is configured so that one side of the seal acts as a flow restrictor to protect the other side of the seal from damage during actuation of the tool under pressurized conditions.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Embodiments of the present invention generally relate to a novel seal assembly for use in a wellbore tool. An upper end of the seal assembly acts as a flow restrictor protecting a lower end of the seal assembly from high pressure and/or high volume flow. 
   2. Description of the Related Art 
   Subsequent to the drilling of an oil or gas well, it is completed by running into such well a string of casing which is cemented in place. Thereafter, the casing is perforated to permit the fluid hydrocarbons to flow into the interior of the casing and subsequently to the top of the well. Such produced hydrocarbons are transmitted from the production zone of the well through a production tubing or work string which is concentrically disposed relative to the casing. 
   In many well completion operations, it frequently occurs that it is desirable, either during the completion, production, or workover stages of the life of the well, to have fluid communication between the annular area between the interior of the casing and the exterior of the production tubing or workstring with the interior of such production tubing or workstring for purposes of, for example, injecting chemical inhibitor, stimulants, or the like, which are introduced from the top of the well through the production tubing or workstring and to such annular area. Alternatively, it may be desirable to provide such a fluid flow passageway between the tubing/casing annulus and the interior of the production tubing so that actual production fluids may flow from the annular area to the interior of the production tubing, thence to the top of the well. Likewise, it may be desirable to circulate weighting materials or fluids, or the like, down from the top of the well in the tubing/casing annulus, thence into the interior of the production tubing for circulation to the top of the well in a “reverse circulation” pattern. 
   In instances as above described, it is well known in the industry to provide a well tool having a port or ports therethrough which are selectively opened and closed by means of a “sliding” sleeve element positioned interiorly of the well tool. Such sleeve typically may be manipulated between open and closed positions by means of wireline, remedial coiled tubing, electric line, or any other well known auxiliary conduit and tool means. 
   Typically, such ported well tools will have upper and lower threaded ends, which, in order to assure sealing integrity, must contain some sort of elastomeric or metallic sealing element disposed in concert with the threads to prevent fluid communication across the male/female components making up the threaded section or joint. A placement of such a static seal represents a possible location of a seal failure and, as such, such failure could adversely effect the sealing integrity of the entire production tubing conduit. 
   Additionally, in such well tools, a series of upper and lower primary seals are placed in the housing for dynamic sealing engagement relative to the exterior of a sleeve which passes across the seals during opening and closing of the port element. As with all seals, such primary sealing means also represent an area of possible loss of sealing integrity. 
   During movement of the sleeve to open the port in such well tool to permit fluid communication between the interior and exterior thereof, such primary seals positioned between the interior wall of the well tool housing and the exterior wall of the shifting sleeve will first be exposed to a surge of fluid flow which can cause actual cutting of the primary seal elements as pressure is equalized before a full positive opening of the sleeve and, in some instances, during complete opening of the sleeve. In any event, any time such primary seals are exposed to flow surging, such primary seals being dynamic seals, a leak path could be formed through said primary seals. 
   Accordingly, there is a need for a well tool wherein the leak paths are reduced, thus greatly reducing the chances of loss of sealing integrity through the tool and the tubular conduit. Secondly, there is a need for a well tool in which sensitive areas of the primary seal element are protected by substantially blocking fluid flow thereacross during shifting of the sleeve element between open and closed positions. 
   SUMMARY OF THE INVENTION 
   The present invention generally relates to a novel seal assembly for use in a wellbore tool. An upper end of the seal assembly acts as a flow restrictor protecting a lower end of the seal assembly from high pressure and/or high volume flow. 
   In one aspect, a tool for use in a wellbore is provided, comprising a tubular housing having a bore therethrough and at least one flow port disposed through a wall thereof; a sleeve slidably mounted within the housing, wherein the sleeve has a bore therethrough and at least one flow slot disposed through a wall thereof, the at least one slot selectively alignable with the at least one flow port; and a seal assembly disposed between the housing and the sleeve, wherein the seal assembly is configured so that a first portion of the seal assembly protects a second portion of the seal assembly from substantial damage during actuation of the tool. Preferably, the seal assembly comprises a center adapter. Preferably, either the length of the center adapter or that of the seal assembly substantially corresponds to the length of the sleeve flow slot and the center adapter comprises a plurality of protrusions disposed around both an inner side and an outer side thereof. Preferably, the seal assembly further comprises a first end adapter; a second end adapter, wherein the center adapter is disposed between the two end adapters; at least one first sealing element disposed between the first end adapter and the center adapter; and at least one second sealing element disposed between the second end adapter and the center adapter. 
   In another aspect, a seal assembly for use in a wellbore tool is provided, comprising a first end adapter; a second end adapter; a center adapter disposed between the two end adapters; at least one first sealing element disposed between the first end adapter and the center adapter; and at least one second sealing element disposed between the second end adapter and the center adapter, wherein the length of the seal assembly substantially corresponds to a length of a sleeve flow slot of the wellbore tool. Preferably, a plurality of protrusions are disposed around both sides of the center adapter. 
   In yet another aspect, a seal assembly for use in a wellbore tool is provided, comprising a tubular housing having a bore therethrough and at least one flow port disposed through a wall thereof; a sleeve slidably mounted within the housing, wherein the sleeve has a bore therethrough and at least one flow slot disposed through a wall thereof, the at least one slot selectively alignable with the at least one flow port; and a seal assembly comprising a center adapter, wherein the center adapter includes a structure configured for limiting fluid flow across the seal assembly during actuation of the tool. 
   In yet another aspect, a method of using a wellbore tool is provided, comprising providing the wellbore tool, wherein the tool comprises a tubular housing having a bore therethrough and at least one flow port disposed through a wall thereof; a sleeve slidably mounted within the housing, wherein the sleeve has a bore therethrough and at least one flow slot disposed through a wall thereof; and a seal assembly disposed between the housing and the sleeve; running the wellbore tool into a pressurized wellbore; and sliding the sleeve over the seal assembly, wherein a first portion of the seal assembly will restrict flow of pressurized fluid to a second portion of the seal assembly so that the second portion is not substantially damaged during sliding of the sleeve. 
   In yet another aspect, a method of using a wellbore tool is provided, comprising providing the wellbore tool, wherein the tool comprises a tubular housing having a bore therethrough and at least one flow port disposed through a wall thereof; a sleeve slidably mounted within the housing, wherein the sleeve has a bore therethrough and at least one flow slot disposed through a wall thereof; a seal assembly comprising a center adapter, wherein the center adapter includes a structure; running the wellbore tool into a pressurized wellbore; and sliding the sleeve over the seal assembly, wherein the structure of the center adapter will limit fluid flow across the seal assembly so that the seal assembly is not substantially damaged during sliding of the sleeve. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
       FIG. 1A  is a sectional view of a wellbore tool in a closed position.  FIG. 1B  is a sectional view of the wellbore tool in an intermediate pressure equalization position.  FIG. 1C  is a partial sectional view of the wellbore tool in an open position. 
       FIG. 2  is an enlarged view of a central portion of  FIG. 1A  displaying sealing features of the wellbore tool. 
       FIG. 3  is an enlarged view of a primary seal assembly displayed in an intermediate position of the tool between the positions displayed in  FIG. 1A  and  FIG. 1B . 
       FIG. 4  is a longitudinal sectional view of a subterranean well showing the well tool positioned above a well packer inside the well. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1A-1C  are ( 1 C partial) sectional views of a welibore tool  1  in its three actuatable positions: closed, equalization, and open, respectively. The wellbore tool  1  first comprises an upper housing  10 . The upper housing  10  is a tubular member with a flow bore therethrough. At a top end, the upper housing  10  is threaded for connection with a production string, workstring, or members thereof (not shown). At a bottom end, the upper housing  10  is threadedly connected to a lower housing  5 . The lower housing contains a lip (see  FIG. 3 ) at a top end that deforms against a tapered inside surface of the upper housing  10  when the two housings are connected, thereby forming a metal-to-metal seal. The lower housing  5  is a tubular member with a flow bore therethrough. At a bottom end, the lower housing  5  is threaded for connection with a production string, workstring, or members thereof (not shown). Concentrically disposed within the upper housing  10  and the lower housing  5  is a sleeve  15 . The sleeve  15  is a tubular member with a flow bore therethrough. A top end of the sleeve  15  is configured to form a shifting neck for receiving a shifting tool (not shown). The shifting tool may be run in on a wireline, coiled tubing, or other means. Once the shifting tool has engaged with the shifting neck, an actuation force may be exerted on the sleeve  15 . Alternatively, a lower end of the sleeve  15  proximate a latch  20  (see below) is also configured to form a shifting neck. The tool  1  may also be used upside down. 
   Three retainer grooves: upper groove  35 , middle groove  30 , and lower groove  25  are formed in a wall on an inner side of the lower housing  5 . The three grooves  25 ,  30 , and  35  correspond to the three positions of the tool  1 : closed, equalization, and open, respectively. A latch  20  is formed integrally with and extends outward from a lower side of the sleeve  15 . In  FIG. 1A , the latch  20  retains the sleeve  15  in the closed position. When it is desired to actuate the tool  1 , an upward actuating force will be applied to the sleeve  5 . This force will cause the latch member  20  to be compressed by an inner wall of the lower housing  5 . This will allow the sleeve to slide relative to the upper housing  10  and the lower housing  5  which is held in place by the workstring or an anchor (not shown). Once the sleeve is slid so that the latch  20  of the sleeve  15  is aligned with the middle groove  30  of the lower housing  5 , the latch will engage the middle grove  30 . The sleeve  15  will then be retained in the equalization position of the tool  1  (see  FIG. 1B ). The process may then be repeated to actuate the tool  1  into an open position (see  FIG. 1C ). The actuating force may be reversed to actuate the tool back to the equalization position and then again back to the open position. Alternatively, a retainer groove (not shown) may be formed in a wall on a lower side of the sleeve  15  instead of the latch  20 . A latch ring (not shown) may then be disposed between the retainer groove of the sleeve and the lower groove  25  (in the closed position) of the upper housing  5 . The actuation force would then cause the latch ring to be compressed within the retainer groove of the sleeve  15  during actuation of the sleeve. 
   Formed proximately below the groove  25  in the lower housing  5  is a shoulder. A corresponding shoulder (see  FIG. 1 ) is formed in the upper housing  10 . These two shoulders form rigid barriers to sliding of the sleeve in case of failure of the latch member  20  or operator error in applying the actuation force so that the sleeve  5  does not escape the confines of the tool  1 . 
   Referring now to  FIG. 2 , two flow ports  70  are disposed through a wall of the upper housing  10 . A seal recess  115  is disposed along an inner side of the upper housing  10 . At a bottom end, the seal recess  115  is bounded by an upper end  110  of the lower housing  5 . At a top end, the seal recess  115  is bounded by a shoulder  100  of the upper housing  10 . Disposed within the seal space  115  is a lower primary seal retainer  90 . The retainer  90  is restrained from sliding up the seal space by a shoulder that mates with a corresponding shoulder of the upper housing  10 . The retainer  90  is restrained from sliding downward by the upper end  110  of the lower housing  5 . Disposed in the seal space  115  proximately below the flow port  70  is an upper primary seal retainer  60 . The retainer  60  has a groove for seating a retainer screw  65  which is threadedly engaged to a corresponding hole formed through the upper housing  10 . Disposed in the seal space  115  between the two retainers  90 ,  60  is a primary seal assembly  55 . Disposed in the seal space  115  proximately above the flow port  70  is a secondary seal retainer  75 . Like the upper primary seal retainer  60 , the retainer  75  has a groove for seating a retainer screw  80  which is threadedly engaged to a corresponding hole formed through the upper housing  10 . Disposed in the seal space  115  between the retainer  75  and the shoulder  100  is a secondary seal assembly  85 . Alternatively, the retainer screws  65 ,  80  and their corresponding holes through the upper housing  10  may be replaced by retainer rings (not shown). Grooves (not shown) would be formed in an inner wall of upper housing  10  instead of the holes. The retainer rings would then seat in the grooves formed in retainers  60 ,  75  and the grooves formed in the inner wall of the upper housing  10 . Alternatively, further, flow ports  70  could be extended axially along the tool, by adding slots, to correspond to the retainers  60 ,  75  and the retainer rings could be ring portions with J-hooks at each of their ends to secure the retainer rings to the upper housing  10 . 
   Disposed through a wall of the sleeve  15  are a flow port  45  and an equalization port  50 . Both ports  45  and  50  comprise a series of slots disposed around the sleeve  15 . The slots of the equalization port  50  are smaller in comparison to the slots of the flow port  45 . Thus, under the same pressure the flow capacity of the equalization port  50  is less than that of the flow port  45 . 
     FIG. 3  illustrates an enlarged view of the primary seal assembly  55 . The seal assembly  55  first comprises an upper  55   a  and a lower  55   i  end adapter. The seal assembly further comprises a center adapter  55   e . Three Chevron-shaped, upper sealing elements  55   b - d  are disposed between the upper end adapter  55   a  and the center adapter  55   e . Likewise, three Chevron-shaped, lower sealing elements  55   f - h  are disposed between the center adapter  55   e  and the lower end adapter  55   i . The sealing elements  55   b - d ,  55   f - h  disposed above and below the center adapter  55   e  are subjected to an axial compressive force which flares the sealing elements radially outward slightly to engage, on one side, the upper housing  10 , and to engage, on the other side, sleeve  15 . Each sealing element is equipped with one male end and one female end. Each female end is equipped with a central cavity which is adapted for receiving other male ends. The center adapter  55   e  is equipped with two male ends and each end adapter is equipped with one female end. As shown, seal elements  55   b - d  and  55   f - h  are substantially identical. Alternatively, there may be variations in the shape of each of elements  55   b - d  and  55   f - h . Alternatively, further, the male ends of center adapter  55   e  may be lengthened and the female ends of elements  55   d, f  may be lengthened to surround the male ends of center adapter  55   e.    
   The adapters  55   a,e,i  may be made of any substantially hard nonelastomeric material, such as a thermoplastic polymer, or they may be made of metal. Examples of a suitable thermoplastic polymer are Polyetheretherkeytone (PEEK), PEK, PEKK, or any combination of PEEK, PEK, and PEKK. The sealing elements  55   b - d  and  55   f - h  may also be made of a thermoplastic polymer or they may be made of an elastomer. Preferably, the adapters  55   a,e,i  are constructed from a relatively hard material as compared to a preferable soft material of the sealing elements  55   b - d  and  55   f - h . Examples of the relatively soft material are TEFLON (Du-Pont Trademark) and rubber. 
   The adapters  55   a,e,i  comprise protrusions  55   j - m . The center adapter  55   e  has been narrowed and the protrusions  55   k,l  have been exaggerated for the purpose of illustration. Each protrusion is disposed around both an inner side and an outer side of the adapters  55   a,e,i . Preferably, the protrusions  55   j - m  are formed such that their cross-sections are substantially in the shape of a right-triangle, however, other cross-sectional shapes will suffice. The protrusions  55   j,k  are oriented such that the hypotenuse of each faces the upper end of the tool. Conversely, the protrusions  551   l - m  are oriented such that the hypotenuse of each faces the lower end of the tool. However, any orientation of the protrusions  55   j - m  should suffice. Alternately, the protrusions  55   j - m  may be disposed around only one side of the adapters  55   a,e,i . If the adapters  55   a,e,i  are constructed from metal, protrusions  55   j - m  may be disposed as separate softer pieces within grooves (not shown) formed in the adapters  55   a,e,i . A preferred configuration of seal assembly  55  is shown, however, the number of protrusions may be varied according to the design requirements of the seal assembly. Also, protrusions may be disposed around only the end adapter  55   a  or around only the center adapter  55   e . Further, there may be no protrusions at all. The secondary seal assembly  85  may be a conventional packing stack which is well known in the art so it will not be discussed in detail. 
   Operation of the tool  1  is as follows. Referring to  FIG. 4 , the tool  1  of the present invention is assembled within a workstring or production string. The workstring or production string may comprise one or two packers and other well tools. The workstring or production string is lowered into a cased wellbore containing pressurized fluid. The tool  1  is usually in a closed position (see  FIG. 1A ) when run in to the wellbore, however, it can also be run in an open position (see  FIG. 1C ). When run-in closed, the outside of the tool  1  will be exposed to the wellbore pressure Ph. Typically, the inside of the tool will be at a lower pressure Pl. Roughly, a lower end of the seal assembly  55  will be at Pl, while an upper end will be at Ph. Referring to  FIG. 1A , once the tool  1  is lowered within a pressurized wellbore, pressurized fluid will enter the flow ports  70  flow around/through the retainers  65  and  80 . The fluid will be prevented from entering the low pressure bore within the sleeve  15  by the primary  55  and secondary  85  seal assemblies. Fluid will be prevented from entering through the coupling between the upper  10  and lower  5  housings by the seal formed by the lip of the lower housing  5  and the tapered section of the upper housing  10 . 
   At some point, it will be desired to actuate the sleeve  15 . As the sleeve is being actuated from the closed position ( FIG. 1A ) to the equalization position ( FIG. 1B ), the equalization port  50  will expose the interior of the tool to pressure increasing from Pl to Ph. Referring to  FIG. 3 , when the flow port  45  passes under the lower sealing elements  55   f - h , the ends of the elements will expand into the port. It is at this point where the lower sealing elements  55   f - h  are at the greatest risk of being damaged. If there is a substantial pressure drop across the lower sealing elements  55   f - h  when a back lip  45   a  of the flow port  45  passes under them, the higher pressure acting on the expanded ends of seal elements will not allow the lower sealing elements to be compressed back into the seal space  115 . Instead, the back lip will shear material off of the ends of the lower sealing elements  55   f - h . Inevitably, this will shorten the useful life of the seal assembly  55 . This deleterious effect will be prevented by the design of seal assembly  55 .  FIG. 3  exhibits the sleeve  15  in an intermediate position between the closed position ( FIG. 1A ) and the equalization position ( FIG. 1B ), just before the back lip  45   a  of the sleeve will pass over the extended ends of the lower sealing elements  55   f - h . In order for the pressurized fluid from the wellbore to reach the expanded ends of the lower sealing elements  55   f - h , it must first flow around the upper end adapter  55   a  with protrusion  55   j , sealing elements  55   b - d , and center adapter  55   e  with protrusions  55   k,l . In order for the fluid to flow around sealing elements  55   b - d , it must expend energy to compress them. Additionally, the protrusions  55   j - l  will serve as choke points, further removing energy from the high pressure wellbore fluid. Thus, members  55   a - e  and  55   j - l  of the seal assembly  55  serve as flow restrictors protecting seal elements  55   f - h  from either high pressure and/or high volume flow. Further, the sleeve  15  will safely pass over the expanded ends of seal elements  55   f - h  compressing them back into seal space  115  rather than damaging them. 
   The length of the center adapter  55   e  corresponds substantially to that of the flow port  45 . However, the length of the center adapter  55   e  may be substantially longer or shorter than that of the flow port  45 . If a shorter center adapter  55   e  is desired, more sealing elements may be added so that the overall length of the seal assembly  55  at least substantially corresponds to that of the flow port  45 . The correspondence in length between the center adapter  55   e  and the flow port  45  ensures the protective members  55   a - e  of the seal assembly  55  are in position to shield the members  55   f - h  from high pressure and/or high volume flow during the transition between the closed and equalization positions of the tool  1 . 
     FIG. 1B  shows the wellbore tool  1  in an equalization position, with equalization port  50  in fluid communication with flow port  70 , for receiving fluid from the wellbore into the interior of the tool. In the preferred embodiment, equalization port  50  provides a restricted flow path, which allows for gradual diminishment of the pressure differential between the wellbore and the interior of the tool. Further, in this position, members  55   f - h  are not exposed to sleeve port  45  further ensuring their safety. Finally, as shown in  FIG. 1C , the tool  1  is in a flowing mode (open position) of operation. Flow port  45  is in alignment with flow port  70 , allowing the fluid to flow from the wellbore to interior of the tool  1 . 
   The seal assembly  55  is shown in wellbore tool  1 . However, the seal assembly  55  may be disposed in different tools that serve varying functions in the drilling and completion of a wellbore. 
   Referring to  FIG. 4 , there is schematically shown the apparatus of the present invention in a well  225  with a wellhead  200  positioned at the top and a blowout preventor  205  positioned thereon. 
   It will be appreciated that the apparatus of the present invention may be incorporated on a production string during actual production of the well in which the wellhead  200  will be in the position as shown. Alternatively, the apparatus of the present invention may also be included as a portion of a workstring during the completion or workover operation of the well, with the wellhead  200  being removed and a workover or drilling assembly being positioned relative to the top of the well. 
   As shown in  FIG. 4 , the casing  210  extends from the top of the well to the bottom thereof with a cylindrical fluid flow conduit  215  being cylindrically disposed within the casing  210  and carrying at its lowermost end a well packer  220 . The well tool  1  is shown being carried on the cylindrical fluid flow conduit  215  above the well packer  220 . 
   While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.