Abstract:
A flapper valve assembly is described having an equalizing port assembly with a bleed valve member that is moveable between an open position and a closed position. The equalizing port assembly features a structural support member in the form of a retainer key that is secured to the flapper valve member both axially and radially. Additionally, a compressible spring is located between the structural support member and provides biasing force upon the valve member to urge it toward a closed position. Additionally, the flapper valve member presents a pair of raised, substantially flat actuator contact portions upon its downstream face to meet an actuating tube in a mating contact arrangement and resist material deformation that could tend to clog or block the equalizing fluid flow port.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates generally to equalizing flapper type valves that are used, for example, as subsurface safety valves.  
         [0003]     2. Description of the Related Art  
         [0004]     Wellbores often include subsurface safety valves used to close off a section of production tubing in the event of an emergency. Flapper valve assemblies have long been employed as safety valves. Flapper valve assemblies typically consist of a curved metal valve member that is shaped to seat upon an annular valve seat within the tubing flowbore to block fluid flow through the flowbore. The valve member is hingedly attached to the inside of the tubing and rotates about the hinge point between open and closed positions. A closed flapper valve is usually opened by an axially shiftable actuation sleeve that contacts the downstream face of the flapper valve and urges the valve member toward its open position. It is, however, difficult to open a flapper valve that has been closed by a high pressure differential. The fluid pressure holding the valve member in the closed position can be very difficult to overcome. It is, therefore, necessary to reduce (i.e., equalize) the pressure differential prior to opening the flapper. This may be done by incorporating an equalizing, or bleed, valve assembly into the flapper valve member.  
         [0005]     Prior art equalizing flapper valves of this type are known. U.S. Pat. No. 4,478,286 issued to Fineberg and U.S. Pat. No. 6,644,408 issued to Ives are two examples of equalizing valves. Both of these patents are owned by the assignee of the present invention and both are incorporated herein by reference. Both patents describe flapper valve assemblies that have poppet-type equalizing valves retained therein to bleed off pressure from the upstream side of the flapper valve prior to opening the flapper valve assembly. While effective, these valve assemblies may not be well suited to high slam rate applications where the dynamic forces are so significant that they can damage the equalization valve element during closing (i.e., slamming) of the flapper. A particular problem that has been observed with prior art equalization valve assemblies is that the poppet valve components for the equalization valve assembly can be damaged as the flapper is slammed closed by fluid flow. As a result, the flapper may be unable to fully close off fluid flow as it is intended to do.  
         [0006]     U.S. Pat. No. 6,296,061 issued to Leismer describes an equalization flapper device that uses a pilot activator located within a pilot bore and retained in place only by a hinge spring. U.S. Pat. No. 6,079,497 issued to Johnston et al. describes an equalization flapper assembly having a retention member that is formed from a cantilevered beam. Neither of these arrangements is sufficiently robust to effectively resist potential damage during high slam rate applications. Additionally, a cantilevered beam may be unsuitable for effectively biasing closed the equalizing valve because the beam member may not have adequate shape memory, in the manner that a compression spring would have. As a result, the equalizing port may not be fully closed in the absence of a significant pressure differential and may tend to leak fluid in any event.  
         [0007]     A related problem with conventional equalizing flapper assemblies stems from damage caused to the upper (downstream) face of the flapper valve member from contact by the actuating sleeve. The axial faces of flapper valve members are curved and shaped as a natural consequence of forming the valve member to generally conform to the surrounding flow tube while in an open position. When a smaller, curved area of metal contacts the lower end of the actuating sleeve, the forces necessary to open the flapper element often deform the metal of the flapper element. Because the equalization valve is normally aligned with the lower end of the actuating sleeve, deformed metal can flow onto the equalization valve member itself, causing the valve member to become non-functional.  
         [0008]     The present invention addresses the problems of the prior art.  
       SUMMARY OF THE INVENTION  
       [0009]     The invention provides an improved equalizing flapper valve design which may be used within subterranean wellbores or other flow situations. The flapper valve of the present invention is particularly well suited for use in flowbores having high rates of fluid flow and high pressure differentials.  
         [0010]     An exemplary flapper valve assembly is described wherein an equalizing port assembly is incorporated into the flapper valve member. The equalizing port assembly includes a poppet-type bleed valve member that is moveable between an open position, wherein fluid can pass through the flapper valve body, and a closed position, wherein fluid flow across the flapper valve body is blocked. The exemplary equalizing port assembly also features a structural support member in the form of a retainer key that is secured to the flapper valve member both axially and radially. In a presently preferred embodiment, the retainer key is retained within a set of grooves formed into the upstream face of the flapper member to preclude the retainer key from moving axially with respect to the valve member. A retainer screw affixes the retainer key against radial movement with respect to the flapper valve body. Additionally, a compressible spring is located between the structural support member and provides biasing force upon the valve member to urge it toward a closed position.  
         [0011]     In a described embodiment, the flapper valve member presents a pair of raised, substantially flat actuator contact portions upon its downstream face. The contact portions are the first portions of the flapper valve member to contact the actuator tube as it is moved to open the flapper valve assembly. Because they are substantially flat, they meet the lower end in a mating contact arrangement and resist material deformation that could tend to clog or block the equalizing fluid flow port.  
         [0012]     In a further desirable aspect, the fluid flow port of the equalizing port assembly features a dual counterbore design that helps prevent metal that might be deformed by the lower end of the actuating sleeve from flowing onto the equalization valve member.  
         [0013]     It is believed that the equalizing valve assembly of the present invention provides a more suitable and secure valve arrangement in high slam applications than conventional equalizing valve assemblies that have heretofore been used in flapper valves. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a side, cross-sectional view of an exemplary flapper valve assembly constructed in accordance with the present invention with the flapper valve element in a closed position.  
         [0015]      FIG. 2  is a side, cross-sectional view of an exemplary flapper valve assembly constructed in accordance with the present invention with the flapper valve element in an open position.  
         [0016]      FIG. 3  is an isometric view of an exemplary equalizing flapper member.  
         [0017]      FIG. 4  is a plan view of the downstream face of the flapper member.  
         [0018]      FIG. 5  is a cross-sectional view depicting the use of double counterbore flowport configuration. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]      FIGS. 1 and 2  depict an exemplary equalizing flapper valve assembly  10  that is constructed in accordance with the present invention. The valve assembly  10  is typically incorporated into a production tubing string within a wellbore and used as a safety valve. The valve assembly  10  includes a valve housing  12  having a first axial end  14  with pin-type threading  16  for attachment to an adjacent section of production tubing (not shown) and a second axial end  18  with box-type threading  20  for attachment to an adjacent section of tubing (not shown). The valve housing  12  defines an axial flowbore  22  along its length having an enlarged central section  24 . An annular valve seat  26  is secured within the enlarged central section  24 . In this instance, it is desired to block fluid flowing from the second end  18  toward the first end  14 . Therefore, the second end  18  will be considered to be upstream from the first end  14 .  
         [0020]     A flapper valve member  28  is hingedly secured to the valve seat  26  by hinge pin  30 . The valve member  28  is rotationally moveable about the hinge pin  30  between an open position (shown in  FIG. 2 ) and a closed position ( FIG. 1 ), wherein the valve member  28  contacts and is seated upon the valve seat  26 . A torsion spring (not shown) biases the valve member  28  toward its closed position. When in the closed position depicted in  FIG. 1 , the valve assembly  10  blocks fluid flowing downstream from the second end  18  toward the first end  14  of the housing. An equalizing port assembly, the structure and function of which will be described shortly, is generally indicated at  32 .  
         [0021]     An axially shiftable actuation member, which may be a conventional actuation tube or sleeve,  34  is disposed within the flowbore  22  above the valve seat  26 . The actuation tube  34  may be axially shifted within the flowbore  22  by means of hydraulic fluid pressure, shifting tools, or using other methods known in the art. The actuation tube  34  is shiftable between an upper position (shown in  FIG. 1 ) and a lower position ( FIG. 2 ). The actuation tube  34  includes a lower engagement end  36  that may be substantially flat.  
         [0022]     The structure of the flapper valve member  28  and the equalizing port assembly  32  may be more fully understood with reference to  FIGS. 3 through 5 . The valve member  28  includes a main valve body  38  that is a generally saddle-shaped disc having a rounded radial perimeter  40 . The main valve body  38  is arcuately curved so as to provide a curvature that approximates that of the interior surface of the flowbore  22 . The valve body  38  presents upstream and downstream faces  42 ,  44 , respectively. A hinge portion  46  extends radially outwardly from the main valve body  38 . The upstream face  42  of the valve body  38  typically receives fluid pressure from the upstream direction.  
         [0023]     The downstream face  44 , shown in detail in  FIG. 4 , presents an outer rim portion  48  that is shaped and sized to contact and engage the valve seat  26  in a fluid sealing relation. Arcuate ramp areas  50  lie radially inwardly of the rim  48  and extend from end points  52  to substantially flat raised actuator contact portions  54  on either lateral side of the flapper member  28 . The flat actuator contact portions  54  serve the function of initially contacting the actuation tube  34  when the tube  34  is moved downwardly to urge the flapper member  28  toward its open position. The contact portions  54  should be substantially flat so that they will abut the flat lower end of the actuation tube  34  in a mating fashion. Experience has shown that, if curved, the end of the actuation tube  34  will tend to deform the contact portions  54  and cause metal to flow onto and hinder operation of the equalizing port assembly  32 .  
         [0024]     The equalizing port assembly  32  is disposed through the flapper member  28  such that it is located within one of the actuator contact portions  54  (see  FIG. 4 ). The equalizing port assembly  32  features a fluid flow port  56 , best seen in  FIG. 5 , which passes through the flapper valve member  28 . The flow port  56  features a dual counterbore design, which is pictured in  FIG. 5 . The flow port  56  has a central portion  58  and a first enlarged diameter portion  60  near the upstream axial end of the flow port  56 . Additionally, there is a second enlarged diameter portion  62  at the upstream axial end of the flow port  56 . The diameter of the second portion  62  is greater than the diameter of the first portion  60 , and both portions  60 ,  62  are greater in diameter than the central portion  58 . The presence of the enlarged diameter portions, or counterbores,  60 ,  62  at the axial upstream end is highly advantageous because it helps to prevent metal from the flapper valve member  28  that is deformed and displaced from flowing onto the bleed valve member  64  that is retained within the flow port  56  when the lower end of the actuation tube  34  contacts the flapper member  28 . Rather than two counterbores, a single counterbore or a tapered counterbore might be used as well, so long as it provides the needed separation gap from the bleed valve member  64  to the surrounding flapper valve material. The preferred size of the gap may vary depending upon the particular materials used to fashion the body of the flapper valve member  28  and the size of the flow port  56  and bleed valve member  64 . However, the gap should be sufficient to substantially prevent deformed and displaced metal from the flapper member  28  from flowing onto and contacting the bleed valve member  64  or interfering with its function.  
         [0025]     The port assembly  32  also includes a bleed valve member  64  that is reciprocally retained within the flow port  56 . Defined within the bleed valve member  64  is an axial flow passage  66  and lateral flow apertures  68 . Also, the bleed valve member  64  presents an enlarged downstream end  70  and an upstream end  72 .  
         [0026]     On the upstream face  42  of the flapper valve member  28  (see  FIG. 3 ) is a laterally disposed, substantially rectangular slot  74 . Immediately upstream of the slot  74  is a shaped retainer recess  76  and a groove or guide track  78 . A retainer key  80  is retained within the retainer recess  76 . The retainer key  80  has a lateral flange  82  that is seated within the guide track  78 . This seating of the flange  82  within the guide track  78  secures the retainer key  80  against axial movement with respect to the flapper member  28 . A retainer screw  84  secures the retainer key  80  to the flapper member  28  so that the retainer key  80  cannot move radially with respect to the flapper member  28 .  
         [0027]     The bleed valve member  64  is movably disposed within the flow port  56  between an open position, wherein fluid can pass through the axial flow passage  66  and out through the lateral apertures  68 , and a closed position (shown in  FIG. 5 ) wherein the lateral apertures  68  are blocked against fluid flow. A compression spring member  86  resides within the slot  74  below the retainer recess  76  between the retainer key  80  and the bleed valve member  64 . The compression spring member  86  contacts the enlarged end  70  of the bleed valve member  64  and biases the bleed valve member  64  toward a closed position, such that fluid is unable to pass through the apertures  68 . In this closed position (illustrated in  FIG. 5 ), the downstream end  72  of the bleed valve member  64  projects above the flat actuator contact portion  54 .  
         [0028]     In operation, the flapper valve assembly  10  is opened by moving the flapper member  28  from the closed position shown in  FIG. 1  to the open position depicted in  FIG. 2 . To accomplish this, the actuation tube  34  is moved axially downwardly (i.e., in the upstream direction) until its lower end  36  contacts the downstream end  70  of the bleed valve member  64 . The actuation tube  34  then urges the bleed valve member  64  toward its open position, compressing the spring  86 . Fluid can now pass through the bleed valve member  64  so that the pressure differential across the flapper valve member  28  is reduced or equalized. Upon further downward movement of the actuation tube  34 , the lower end  36  of the actuator tube  34  is brought into mating contact with both actuator contact portions  54  of the flapper member  28 . Further downward movement of the actuation tube  34  then opens the flapper valve assembly  10 .  
         [0029]     To close the flapper assembly  10 , the actuation tube  34  is moved upwardly within the valve housing  12 . The torsion spring (not shown) urges the flapper member  28  toward its closed position. When the production tubing that incorporates the valve assembly  10  contains fluid that is at a high flow rate or under significant pressure, the flapper member  28  can slam shut against the valve seat  26  with considerable force. The construction of the equalizing port assembly  32  makes it highly unlikely that any components of the equalizing port assembly  32  will become dislodged from the flapper member  28 . The retainer key  80  is secured both axially and radially with respect to the flapper member  28 . The retainer key  80  provides a solid structural support that ensures that the bleed valve member  64  will remain disposed within the flow port  56 , even during slamming of the flapper member  28  because the retainer key  80  physically blocks the bleed valve member  64  from removal on the upstream side  42  of the flapper valve member  28 . Additionally, the enlargement at the end  70  of the bleed valve member  64  ensures that the bleed valve member  64  cannot pop free from the downstream side  44  of the flapper member  28 .  
         [0030]     Those of skill in the art will recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.