Patent Publication Number: US-10323477-B2

Title: Seal assembly

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     Embodiments of the invention generally relate to tools having a seal assembly for sealing an annulus between a tubular seat in the wellbore and the outside of the tool disposed in the tubular seat. 
     Description of the Related Art 
     Surface-controlled, subsurface safety valves (SCSSVs) and plugs are commonly used to shut-in oil and/or gas wells. The SCSSV or plug fits into tubing in a hydrocarbon producing well and operates to block upward flow of formation fluid through the tubing. The tubing may include a landing nipple designed to receive the SCSSV or plug therein such that the SCSSV or plug may be installed and retrieved by wireline. During conventional methods for run-in of the SCSSV or plug to the landing nipple, a tool used to lock the SCSSV or plug in place within the nipple also temporarily holds the SCSSV or plug open until the SCSSV or plug is locked in place. 
     Most SCSSVs are “normally closed” valves, i.e., the valves utilize a flapper type closure mechanism biased to a closed position. During normal production, application of hydraulic fluid pressure transmitted to an actuator of the SCSSV maintains the SCSSV in an open position. A control line that resides within the annulus between production tubing and a well casing may supply the hydraulic pressure to a port in the nipple that permits fluid communication with the actuator of the SCSSV. In many commercially available SCSSVs, the actuator used to overcome the bias to the closed position is a hydraulic actuator that may include a rod piston or concentric annular piston. During well production, the flapper is maintained in the open position by a flow tube acted on by the piston to selectively open the flapper member in the SCSSV. Any loss of hydraulic pressure in the control line causes the piston and actuated flow tube to retract, which causes the SCSSV to return to the normally closed position. Thus, the SCSSV provides a shutoff of production flow once the hydraulic pressure in the control line is released. 
     The landing nipple within the tubing may become damaged by operations that occur through the nipple prior to setting the SCSSV or plug in the landing nipple. For example, operations such as snubbing and tool running using coiled tubing and slick line can form gouges, grooves, and/or ridges along the inside surface of the nipple as the operations pass through the nipple. Further, any debris on the inside surface of the nipple or any out of roundness of the nipple may prevent proper sealing of the SCSSV or plug within the nipple. Failure of the SCSSV or plug to seal in the nipple due to surface irregularities in the inner diameter of the nipple can prevent proper operation of the actuator to open the SCSSV and can prevent the SCSSV or plug from completely shutting-in the well when the SCSSV or plug is closed since fluid can pass through the annular area between the SCSSV or plug and the nipple due to the irregularities. Operating the well without a safety valve or with a safety valve or plug that does not function properly presents a significant danger. Thus, the current solution to conserve the safety in wells having damaged nipples includes an expensive and time consuming work over to replace the damaged nipples. 
     Therefore, a need exists for improved apparatus and methods for disposing a plug or SCSSV within tubing regardless of whether the tubing has a damaged or irregular inside surface. 
     SUMMARY OF THE INVENTION 
     Embodiments of the invention generally relate to a seal assembly for use in a tubular, comprising a mandrel, a compressible seal member disposed around the mandrel, a first piston assembly in contact with a first end of the compressible seal member, and a second piston assembly in contact with a second end of the compressible seal member. The first piston assembly may include a piston head, and a piston extension sealing member extending at least partially between the mandrel and of the compressible seal member, and integrally formed with the piston head. When at least one of the piston assemblies is urged towards the compressible seal member, the compressible seal member forms a seal with the tubular. 
     In one embodiment, the invention relates to an apparatus for use in a tubular, which may comprise a mandrel having a bore therethrough, a valve that is coupled to the mandrel, the valve selectively preventing fluid flow through the bore, and a seal assembly disposed around the mandrel. The seal assembly may include a compressible seal member and a piston assembly disposed on a first side of the compressible seal member. The piston assembly may include a piston head and a piston extension sealing member, the piston extension sealing member integrally formed with the piston head and extending at least partially between the mandrel and the compressible seal member. The piston assembly is movable to compress the compressible seal member from a first end, and the compressible seal member forms a seal with the tubular when the piston assembly moves toward the compressible seal member. 
     The invention also generally relates to method for creating a seal between an apparatus and a tubular, including positioning the apparatus in the tubular. The apparatus may include a seal assembly disposed around a mandrel, the seal assembly comprising a compressible seal member, a first piston assembly disposed on a first side of the compressible seal member, and a second piston assembly disposed on a second side of the compressible seal member. The first piston assembly may include a first piston head and a first piston extension sealing member, the first piston extension sealing member integrally formed with the first piston head and extending at least partially between the mandrel and the compressible seal member. The method for creating a seal between an apparatus and a tubular further includes moving at least one of the first or second piston assemblies towards the compressible seal member until the compressible seal member forms a seal with the tubular. 
     In one embodiment, the invention relates to a seal assembly for use in a tubular, which may comprise a mandrel, a compressible seal member disposed around the mandrel, a first sealing element at a first end of the compressible seal member, and a second sealing element at a second end of the compressible seal member. The compressible seal member forms a seal with the tubular when at least one of the first or second sealing elements is urged toward the compressible seal element. In addition, the first and second sealing elements may also form a seal with the tubular. 
     In one embodiment, the invention relates to a seal assembly for use in a tubular, comprising a mandrel and a compressible seal member disposed around the mandrel. The seal member comprises a plurality of concave sealing elements and a central sealing element. The seal assembly further comprises a first piston assembly in contact with a first end of the compressible seal member, the first piston assembly comprising a piston head and a piston extension sealing element extending at least partially between the mandrel and the compressible seal member, and integrally formed with the piston head. The seal assembly also comprises a second piston assembly in contact with a second end of the seal member, a first sealing element in contact with the first piston assembly, and a second sealing element in contact with the second piston assembly. When the first and second sealing elements are compressed, the sealing elements move the first and second piston assemblies toward the compressible seal member. Further, when at least one of the piston assemblies is urged towards the compressible seal member, the compressible seal member forms a seal with the tubular. 
     In one embodiment, the invention relates to a seal assembly for use in a tubular, comprising a mandrel, a compressible seal member, and a piston. The mandrel includes a first and second recess. The compressible seal member may be positioned around the first recess of the mandrel, and the compressible seal member may comprise a plurality of concave sealing elements and a central sealing element. The piston is in contact with the compressible seal member, and the piston may slide along the first and second recesses of the mandrel. The compressible seal member forms a seal with the tubular when the piston is urged toward the compressible seal member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the 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. 1  is a schematic of a production well having a surface controlled, subsurface safety valve (SCSSV) installed therein. 
         FIG. 2  is a sectional view of the SCSSV within a landing nipple during run-in of the SCSSV illustrating one embodiment of seal assemblies of the SCSSV in an uncompressed position. 
         FIG. 3  is a sectional view of the SCSSV set in the nipple and actuated to an open position illustrating the seal assemblies in a first compressed position. 
         FIG. 4  is a sectional view of the SCSSV set in the nipple and biased to a closed position illustrating the seal assemblies in a second compressed position. 
         FIG. 5  is a sectional view of one embodiment of a seal assembly that could be used in the SCSSV. 
         FIG. 6  is a sectional view of one embodiment of a seal assembly that could be used in the SCSSV. 
         FIG. 7  is a sectional view of one embodiment of a seal assembly that could be used in the SCSSV. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention generally relate to seal assemblies for any type of safety valve, dummy valve, straddle or plug designed to be landed and set within a tubular member. For some embodiments, the tubular member may form a ported landing nipple to enable fluid actuation of the safety valve, a side pocket mandrel, a sliding sleeve valve or a solid walled landing nipple. The seal assembly may be implemented with other variations of plugs, dummy valves, and subsurface safety valves different than exemplary configurations and designs shown and described herein since many operational details of these tools function independent of the seal assembly. For example, the seal assemblies may be used in all types of tools designed for landing in a nipple including wireline retrievable tools that may utilize flapper type valves or concentric type valves. 
       FIG. 1  illustrates a production well  12  having an SCSSV  10  installed therein according to aspects of the invention as will be described in detail herein. While a land well is shown for the purpose of illustration, the SCSSV  10  may also be used in offshore wells.  FIG. 1  further shows a wellhead  20 , surface equipment  14 , a master valve  22 , a flow line  24 , a casing string  26  and a production tubing  28 . In operation, opening the master valve  22  allows pressurized hydrocarbons residing in the producing formation  32  to flow through a set of perforations  34  that permit and direct the flow of hydrocarbons into the production tubing  28 . Hydrocarbons (illustrated by arrows) flow into the production tubing  28 , through the SCSSV  10 , through the wellhead  20 , and out into the flow line  24 . The SCSSV  10  is conventionally set and locked in a profile within the production tubing  28 . Surface equipment  14  may include a pump, a fluid source, sensors, etc. for selectively providing hydraulic fluid pressure to an actuator (not shown) of the SCSSV  10  in order to maintain a flapper  18  of the SCSSV  10  in an open position. A control line  16  resides within the annulus  35  between the production tubing  28  and the casing string  26  and supplies the hydraulic pressure to the SCSSV  10 . 
       FIG. 2  illustrates a sectional view of the SCSSV  10  within a landing nipple  100  as part of the production tubing. The SCSSV  10  is shown in a run-in position prior to setting of the SCSSV  10  within the landing nipple  100 . As shown, the SCSSV  10  includes an upper seal assembly  101  and a lower seal assembly  103  around its exterior, a packing mandrel  124  disposed inside the seal assemblies  101 ,  103 , and an actuator housing  152  connected to the lower end of the packing mandrel  124 . An exemplary actuator is a spring. The upper seal assembly  101  is compressible and includes an upper seal member  111  formed by upper concave seal elements  110  disposed on each side of an upper central sealing element  114 . The upper central sealing element  114  could be an o-ring, s-seal, or any other type of sealing element known in the art. Upper concave seal elements  110  could include V-seals, chevron seals, or any other type of sealing element known in the art. An upper first piston  102  is in contact with an upper end of the upper concave seal elements  110 , and an upper second piston  106  is in contact with a lower end of the upper concave seal elements  110 . The upper second piston  106  comprises an upper piston head  107 A and an upper piston extension sealing member  107 B which may be integrally formed and that extends between the upper seal member  111  and the mandrel  124 . In one embodiment, the upper piston extension sealing member  107 B of the upper second piston  106  may slide under a portion of the upper first piston  102 . 
     Similarly, the lower seal assembly  103  is compressible and includes a lower seal member  113  formed by lower concave seal elements  112  disposed on each side of a lower central sealing element  116 . The lower central sealing element  116  could be an o-ring, s-seal, or any other type of sealing element known in the art. Lower concave seal elements  112  could include V-seals, chevron seals, or any other type of sealing element known in the art. A lower first piston  104  is in contact with a lower end of the lower concave seal elements  112 , and a lower second piston  108  is in contact with an upper end of the lower concave seal elements  112 . The lower first piston  104  comprises a lower piston head  109 A and a lower piston extension sealing member  109 B that extends between the lower seal  113  and the mandrel  124 . In one embodiment, the lower piston extension sealing member  109 B of the lower second piston  104  may slide under a portion of the lower first piston  108 . The pistons  102 ,  106 ,  108 ,  104  are preferably annular pistons. While both the upper and lower seal assemblies  101 ,  103  are shown in the embodiment in  FIG. 2 , the SCSSV  10  may include only one of either the upper or lower seal assemblies  101 ,  103 . Additionally, other variations of the seal members  111 ,  113  may be used so long as the pistons  102 ,  106 ,  108 ,  104  can operate to force the seal members  111 ,  113  into sealing contact with the nipple  100 . 
     The packing mandrel  124  includes an upper sub  126  and a middle sub  128  connected together such as by threads. However, the packing mandrel  124  may be made from an integral member or any number of subs. An annular shoulder  138  on the upper sub  126  provides a decompression stop for the upper first piston  102 , which is slidable along a portion of an outer diameter of the upper sub  126 . The upper piston extension sealing member  107 B of the upper second piston  106  provides a compression stop for the upper first piston  102 . Likewise, the upper first piston  102  provides a compression stop for the upper second piston  106 . The upper second piston  106  is slidable along portions of the outer diameter of the upper sub  126  and the upper piston extension sealing member  107 B is slidable between the upper concave sealing elements  110  and the upper sub  126 . The middle sub  128  is fixed to the upper sub  126  and operates to longitudinally separate the upper and lower seal assemblies  111 ,  113 . The middle sub  128  provides a decompression stop for the upper second piston  106  and a decompression stop for the lower second piston  108 . The lower second piston  108  is slidable along a portion of the outer diameter of the middle sub  128 . The lower piston extension sealing member  109 B of the lower first piston  104  provides a compression stop for the lower second piston  108 . Likewise, the lower second piston  108  provides a compression stop for the lower first piston  104 . The lower first piston  104  is slidable along a portion of the outer diameter of the middle sub  128  and the lower piston cylinder  109 B is slidable between the lower concave sealing elements  112  and the middle sub  128 . An end face  144  of the actuator housing  152  provides a decompression stop for the lower first piston  104 . 
     The compression and decompression stops operate to limit the sliding movement of the pistons  102 ,  106 ,  108 ,  104  of the sealing assemblies  101 ,  103 . Inner seal members  120  A-D on the inside of the pistons  102 ,  106 ,  108 ,  104  provide a seal between each piston and the packing mandrel  124  that the pistons slide along. Outer seal members  118  A-D on the outside of the pistons  102 ,  106 ,  108 ,  104  provide an initial seal between each piston and the nipple  100 . The outer seals  118  may be soft o-rings, or any other type of seal known in the art, with a large cross section to help ensure a sufficient initial seal between the pistons  102 ,  106 ,  108 ,  104  and the nipple  100 . Thus, the initial seal provided by the outer seal members  118  sufficiently seals against the nipple  100  such that fluid pressure applied to the large surface areas of the pistons  102 ,  106 ,  108 ,  104  that are shown in contact with the decompression stops  138 ,  140 ,  142 ,  144  causes the pistons to slide along the packing mandrel  124  toward the respective seal  111 ,  113 . 
     In the run in position of the SCSSV  10  as shown in  FIG. 2 , the seal assemblies  101 ,  103  are in uncompressed positions with all the pistons  102 ,  106 ,  108 ,  104  contacting their respective decompression stops  138 ,  140 ,  142 ,  144 . Therefore, the upper and lower seal members  111 ,  113  are not compressed and may not provide sealing contact with the inside surface of the nipple  100  and the outside of the packing mandrel  124 . During run-in all parts of the SCSSV  10  are in equal pressure so that the pistons  102 ,  106 ,  108 ,  104  do not move. In the run-in position, the SCSSV  10  is temporarily held open by a running tool (not shown) using a run-in prong or other temporary opening member. Since the SCSSV  10  is open, wellbore fluid pressure does not act on the first pistons  102 ,  104  to compress the upper and lower seal members  111 ,  113 . Further, fluid pressure is not supplied through the control line  16  such that the second pistons  102 ,  106  are also not acted on to compress the upper and lower seal members  111 ,  113 . 
     Once the SCSSV  10  is set or locked in the nipple  100  by conventional methods, the temporary opening member disengages and permits normal functioning of the SCSSV  10 . Thus, the flapper  18  biases to a closed position unless fluid pressure is supplied through the control line  16  to a port  150  in the nipple  100  in order to actuate the SCSSV  10 . 
       FIG. 3  is a sectional view of the SCSSV  10  in an actuated open position with the seal assemblies  101 ,  103  in a first compressed position. Fluid pressure supplied through the control line  16  to the port  150  in the nipple  100  passes through a fluid passageway  154  into an annular area outside the upper sub  126 . The fluid pressure acts on a piston rod  158  connected to a flow tube  122  to force the flow tube down against the bias of a biasing member such as a spring  146 . The longitudinal displacement of the flow tube  122  causes the flow tube  122  to displace the flapper  18  and place the SCSSV  10  in the actuated open position. As an example of an SCSSV actuated by a concentric piston, the fluid pressure may alternatively act on an outward facing shoulder of a flow tube located concentrically within the packing mandrel to force the flow tube down and open a flapper. 
     The fluid pressure supplied through the control line  16  used to actuate and open the SCSSV  10  additionally operates to place the seal assemblies  101 ,  103  in the first compressed position. The fluid pressure supplied from the control line  16  enters the port  150  where the fluid enters the interior of the nipple  100  and acts on the second pistons  106 ,  108  to slide the second pistons  106 ,  108  toward the respective seal members  111 ,  113 . Any wellbore pressure on the first pistons  102 ,  104  is less than that on the second pistons  106 ,  108  such that the first pistons  102 ,  104  remain in contact with their respective decompression stops  138 ,  144 . The sliding movement of the second pistons  106 ,  108  pushes on the concave sealing elements  110 ,  112 , which in turn pushes on the central sealing elements  114 ,  116 . Compression of the seal members  111 ,  113  caused by the sliding of the second pistons  106 ,  108  forces the central sealing elements  114 ,  116  and/or the concave sealing elements  110 ,  112  into sealing contact with the inside surface of the nipple  100 . Preferably, the central sealing elements  114 ,  116  are soft o-rings with a large cross section made from a material such as Viton® (65 duro). However, the central sealing elements  114 ,  116  could be S-Seals or any other type of sealing element known in the art. Additionally, the chevrons  110 ,  112  are preferably made from a material such as Kevlar® filled Viton®, but also could be any other sealing element known in the art. Once the SCSSV is actuated open, wellbore fluid passes through the SCSSV  10  such that wellbore fluid pressure does not act to slide the first pistons  102 ,  104 , and the first pistons  102 ,  104  remain in contact with their respective decompression stops  138 ,  144 . 
       FIG. 4  is a sectional view of the SCSSV  10  set in the nipple  100  and biased to the closed position with the seal assemblies  101 ,  103  in a second compressed position and the flapper  18  blocking fluid flow through the SCSSV  10 . As fluid pressure bleeds from the control line  16  during closure of the SCSSV  10 , the fluid pressure acting on the second pistons  106 ,  108  approaches hydrostatic pressure, which along with the wellbore pressure acting on the first pistons  102 ,  104  keeps the seals  111 ,  113  compressed. When the wellbore pressure is greater than the pressure supplied by the control line  16 , the wellbore pressure acts on the first pistons  102 ,  104  to slide the first pistons  102 ,  104  toward the respective seal members  111 ,  113 . For example, wellbore fluid pressure above the SCSSV  10  acts on the upper first piston  102 , and wellbore fluid pressure below the SCSSV  10  acts on the lower first piston  104 . The second pistons  106 ,  108  slide into contact with their respective decompression stops  140 ,  142 . The sliding movement of the first pistons  102 ,  104  pushes on the concave sealing elements  110 ,  112 , which in turn pushes on the central sealing elements  114 ,  116 . Therefore, compression of the seal members  111 ,  113  caused by the sliding of the first pistons  102 ,  104  maintains sealing contact with the inside surface of the nipple  100  since the central sealing elements  114 ,  116  and/or the concave sealing elements  110 ,  112  remain forced against the inside surface of the nipple  100 . 
     In both the first and second compressed positions as illustrated by  FIGS. 3 and 4  respectively, the upper and/or the lower seal members  111 ,  113  form a fluid seal with an inside surface of the nipple  100  that may have irregularities, grooves, recesses, and/or ridges that would prevent prior SCSSVs from properly sealing within the nipple  100 . Additionally, the sealing ability of the upper and/or the lower seal members  111 ,  113  with the concave sealing elements  110 ,  112  around the central sealing members  114 ,  116  increases with increased pressure to the pistons  102 ,  106 ,  108 ,  104 . As shown, the SCSSV provides an annular recess to provide a flow path to operate the SCSSV, and the seal assemblies  101 ,  103  do not interfere with the flow path through the SCSSV  10 . 
     A method for sealing an SCSSV within a nipple located in a well is provided by aspects of the invention. The method includes locating the SCSSV in the nipple using conventional running methods. The SCSSV includes at least one seal assembly disposed about an outer surface thereof, and the at least one seal assembly includes a seal member, a first piston disposed on a first side of the seal member, and a second piston disposed on a second side of the seal member. Urging the first piston, the second piston or both the first and second pistons toward the seal member forces the seal member into sealing contact with an inside surface of the nipple. Urging the first piston is caused by wellbore fluid pressure applied to the first piston when the SCSSV is closed. Urging the second piston is caused by fluid pressure supplied from a control line to a fluid port in fluid communication with an inside portion of the nipple. 
     Other seal assemblies  111 ,  113  are also contemplated within the current invention.  FIG. 5  illustrates one embodiment of a seal assembly  200  that could be used in place of one or both of the seal assemblies  101 ,  103  shown in  FIGS. 2-4 . The seal assembly  200  may include a compressible sealing member  205  formed by a central sealing element  210  located between concave sealing elements  220  such as V-seals or chevrons, or any other sealing element known in the art on each side of the central sealing element  210 . A mandrel  124  includes a first, second, and third shoulder  230 ,  232 ,  234  (respectively), and further includes a first recess  235  located between the first and second shoulders  230 ,  232 , and a second recess  245  located between the second and third shoulders  232 ,  234 . The compressible sealing member  205  is positioned between the first recess  235  and the nipple  100  and is located at a first end of the first recess  235 . A piston  240  is adjacent the compressible sealing member  205 , and is located at a second end of the first recess, as well as within the second recess  245 . The piston  240  is slidable along the first and second recesses  235 ,  245 , and has end stops at the second and third shoulders  232 ,  234 . The piston  240  may include sealing elements  270 B,  280 B for providing an initial seal between the nipple  100  and the mandrel  124 . The piston  240  slides between the nipple  100  and the first and second recesses  235 ,  245  to compress the compressible sealing member  210 . As the piston  240  is moved toward the compressible sealing member  205 , a seal is formed between the nipple  100  and the first recess  235  of the mandrel  124 . 
       FIG. 6  illustrates another embodiment of a seal assembly  300  that could be used in place of one or both of the seal assemblies  101 ,  103  shown in  FIGS. 2-4 . Seal assembly  300  may include a compressible seal member  305  formed by a central sealing element  310  located between concave sealing elements  320  such as V-seals or chevrons, or any other sealing element known in the art on each side of the central sealing element  310 . A first sealing element  330  is in contact with a shoulder  335  adjacent to a first end of the concave sealing elements  320 , and a second sealing element  340  in contact with a second shoulder  345  adjacent to a second end of the concave sealing elements  220 . The first and second sealing elements  330 ,  340  may be o-rings, s-type seals, polypacks, or any other type of seal known in the art, and may provide an initial seal against the nipple  100  and the mandrel  124 . The mandrel  124  provides a stop to the first and second sealing elements  330 ,  340 . As pressure is applied to the first and second sealing elements  330 ,  340 , the first and second sealing elements  330 ,  340  are compressed and slide along packing sub  124 , which then compresses the concave sealing elements  320  and the central sealing element  310 . When the concave sealing elements  320  and the central sealing element  310  are compressed, a seal is formed against the inside surface of the nipple  100 . 
       FIG. 7  illustrates another embodiment of a seal assembly  400  that could be used in place of one or both of the seal assemblies  101 ,  103  shown in  FIGS. 2-4 . The seal assembly  400  may include a compressible seal member  405  formed by a central sealing element  410  located between concave sealing elements  420  such as V-seals or chevrons on each side of the central sealing element  410 . A first piston  430 , which comprises a sealing element such as an o-ring or any other sealing element known in the art, and a first packing retainer  450  are adjacent to a first end of the concave sealing elements  420 . A second piston  440 , which comprises a sealing element such as an o-ring or any other sealing element known in the art, and a second packing retainer  460  are adjacent to a second end of the concave sealing elements  420 . The second packing retainer  460  includes a packing retainer extension  465 , and the packing retainer extension  465  slides between the concave sealing elements  420  and the middle sub  128 , and provides a compression stop for first piston  430 . In addition to acting as pistons to the seal assembly  400 , the first and second pistons  430 ,  440  also provide an initial seal between the nipple  100  and the middle sub  128 . As pressure is applied to the first and second pistons  430 ,  440 , the first and second pistons  430 ,  440  are compressed, and move toward the compressible seal member  405 , thereby resulting in the compressible seal member  405  forming a seal against the nipple  100 . 
     While the foregoing is directed to embodiments of the 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.