Patent Publication Number: US-6983803-B2

Title: Equalizer valve and associated method for sealing a fluid flow

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Application Ser. No. 60/381,419, filed May 17, 2002, entitled Equalizer Valve, which is hereby incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to oil and gas well drilling systems. More particularly, the present invention relates to fluid valves used to regulate or control fluid flows and pressures in a downhole environment. In one aspect, the present invention relates to an equalization valve used for sealing high differential pressure in a drilling environment during ancillary drilling operations. 
     2. Background of the Invention 
     During the drilling and completion of oil and gas wells, the downhole environment tends to be harsh and unforgiving. These harsh conditions include vibration and torque from the drill bit, exposure to drilling mud, drilled cuttings, and formation fluids, hydraulic forces of the circulating drilling mud, and scraping of sensitive equipment against the sides of the wellbore. Extreme pressures and temperatures are also present. Such harsh conditions can damage and degrade portions of the drill string, especially the equipment found in various tool strings. 
     Generally the drilling fluid flow is downward through the inner flow bore of the drill string, out through the drill bit, and back up through the annulus formed between the drill string and the borehole wall. However, often times it is required that the fluid flow, or portions thereof, be diverted, whether the fluid flow is found in the inner flow bore or in the annulus. For example, portions of the fluid flow may be diverted to provide hydraulic power to an independent system within the drill string, such as a packer module, to maintain continuous circulation of the drilling mud when primary drilling operations have been temporarily stopped, or to create or equalize a pressure drop between certain zones in the downhole environment. To achieve diversion of the fluid flow, particularly the fluid flow in the annulus, various valves have been developed. 
     Valves used in drilling operations are inherently susceptible to the harsh downhole conditions because they require the use of seals and moving parts. Valves that interact with the drilling mud flow are especially susceptible to the drilling mud, the deleterious debris carried by the drilling mud, and significant pressure drops. Unlike valves contained in closed systems, which typically interact only with a clean hydraulic oil, valves that interact with well fluids, called “dirty” fluid valves, are necessarily exposed to greater wear and degradation. The debris contained in well fluids tend to damage traditional valves using elastomeric seals. Thus, dirty fluid valves must be designed differently in order to compensate for their exposure to the debris in well fluids. 
     Often dirty fluid valves are exposed to the drilling environment because they are needed to create or diffuse a differential pressure between the drilling environment and some system that has been closed off from the drilling environment. This type of valve is typically called an equalizer valve. The function of the equalizer valve is to either isolate or connect the annulus of the borehole with a flowline of the valve internal to the drill string. When the annulus is isolated from the internal flowline, a significant pressure drop is created on the order of thousands of psi&#39;s. If the default position of the valve is to connect the annulus with the internal flowline, then the valve is considered normally open. If the default position is isolation, then the valve is considered normally closed. 
     Because the pressure differential is so great when the annulus is isolated from the internal flowlines of the drill string, valve and other seals are susceptible to blow-out and rapid degradation. Thus, equalizer valves are used to balance the pressure differentials. In order to reduce the wear on the seals, these valves are often normally open-type valves (connecting the annulus with internal flowlines). Despite being normally open, equalizer valves remain inherently susceptible to the abrasive nature of the well fluids that the valves interact with. Thus, the industry would welcome a reliable, normally open, dirty fluid valve for sealing high differential pressure in a drilling environment which is also field replaceable without disturbing the hydraulics circuit or other structure used to actuate the valve. 
     BRIEF SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     The preferred embodiments of the present invention include a dirty fluid valve for sealing high differential fluid pressures in a drilling environment, and methods for using such a valve. One embodiment of the valve includes a seal cartridge having several openings for directing a fluid path through the cartridge, a spring connected at one end of the seal cartridge and extending through the fluid path, and a seal member connected to the other end of the spring. The seal is actuatable between an open position and a closed position so that it covers one of the openings in the seal cartridge when it is in the closed position, thereby sealing off the fluid flow through the seal cartridge fluid path. The spring provides a pre-loading force to the seal member so that the seal member always has sufficient contact with the surfaces surrounding the opening that the seal covers. The spring also has a snap action for assisting with crisp movement between the open and closed positions. The spring and seal member combination cause a shear seal which is leak-free in a dirty fluid environment. 
     In another embodiment of the valve, the seal cartridge includes several opposing rod members that are reciprocally disposed within bores adjacent the seal member. The rod members contact the seal member, and can be moved back and forth to actuate the seal member between the open and closed positions. 
     In yet another embodiment of the valve, the valve includes a reciprocating sleeve member supported by the housing of a tool string. The sleeve member includes an aperture having an inner surface. The seal cartridge is place into the aperture, transverse to the longitudinal axis of the sleeve member and the tool string. The housing receives the seal cartridge via a radial bore. The outer portions of the rod members contact opposite ends of the inner surface of the sleeve member aperture. The sleeve member is hydraulically actuatable back and forth, thereby pushing the rod members and actuating the seal member between the open and closed positions. Use of the sleeve member to actuate the seal member allows the seal cartridge to be field replaceable without perturbing the hydraulic system. 
     A preferred embodiment of the method of the present invention includes directing a fluid flow through a seal cartridge; supporting a spring such that the spring extends into the fluid flow; pre-loading a seal member using the spring; and actuating the seal member between an open position and a closed position, where the fluid is allowed to flow through the seal cartridge when the seal member is in the open position and the fluid is sealed when the seal member is in the closed position. 
     Another embodiment includes disposing the seal cartridge within an aperture formed in a sleeve member, the aperture comprising an inner surface; engaging the inner surface of the aperture with the seal member; and actuating the sleeve member between an open position and a closed position, thereby actuating the seal member. 
     A further embodiment includes raising the seal cartridge to the surface of a wellbore and replacing the seal cartridge with a new seal cartridge at the surface of the wellbore. 
     These and other advantages and advances provided by the various embodiments of this invention will be readily apparent to those skilled in the art upon a review of the specification and drawings which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-section view of the equalizer valve in an open position; 
         FIG. 2  is an additional cross-section view of the equalizer valve of  FIG. 1 ; 
         FIG. 3  is a cross-section view of the valve of  FIG. 2  taken at the plane  1 — 1 ; 
         FIG. 4A  is a cross-section view of the valve of  FIG. 2  taken along the plane  2 — 2 ; 
         FIG. 4B  is the valve of  FIG. 4A  in a closed position; 
         FIG. 5  is the valve of  FIG. 2  in a closed position; and 
         FIG. 6  is a cross-section view of the valve of  FIG. 1  in a closed position and disposed a larger formation testing apparatus. 
     
    
    
     NOTATION AND NOMENCLATURE 
     Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, one skilled in the art may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. In addition, reference to up or down will be made for purposes of description with “up,” “upward,” or “upper” meaning toward the surface of the well and “down,” “downward,” or “lower” meaning toward the bottom of the primary wellbore or any lateral borehole. Furthermore, the term “couple” or “couples” is intended to mean either an indirect or a direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect electrical connection via other devices and connections. 
     This exemplary disclosure is provided with the understanding that it is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that illustrated and described herein. In particular, various embodiments of the present invention provide a number of different constructions and methods of operation. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to  FIGS. 1-4 , the valve  10  includes a sealing assembly or cartridge  20  and an actuator assembly  40  mounted in a housing  12 . The longitudinal axis of the actuator assembly  40  goes from left to right in  FIG. 1  while the longitudinal axis of the sealing assembly  20  goes from top to bottom and is transverse to the longitudinal axis of the actuator assembly  40 . The housing  12  includes a first port  14  whose longitudinal axis generally coincides with the longitudinal axis of the sealing assembly  20 . The port  14  communicates with a fluid under pressure and a second port  16  communicating with a passageway  18 . The valve  10  controls communication of fluid from the first port  14  to the second port  16  by opening and closing that communication to fluid flow. 
     The sealing assembly  20  includes a seal plate  22 , a seal  24 , a cage  26 , a spring cap  28 , a seal spring  30 , a plug  32 , a close push rod  52 , and an open push rod  54 . The sealing assembly  20  forms a field replaceable seal cartridge which is disposed in through an aperture  34  in the wall  36  of the housing  12 , across a cylindrical bore  38  in the housing  12  and into a counterbore  42 . The longitudinal axis of aperture  34  generally coincides with those axes of the port  14  and the sealing assembly  20 . The cylindrical bore  38  is transverse to the axis of the aperture  34  and the counterbore  42  which are co-axial. The plug  32  and the aperture  34  are threaded at  35  to removably connect the seal cartridge  20  to the housing  12 . 
     The actuator assembly  40  includes a slide member  50 , a return spring  56 , a close piston  58 , and an open piston  60 . As best shown in  FIGS. 1 ,  4 A and  4 B, the slide member  50  includes a slotted aperture  62  therethrough with first and second arcuate edges  64 ,  66 , respectively, adjacent the aperture  34  and the counterbore  42 , respectively. The slotted aperture  62  is an oblong hole in the slide member  50 . The first and second arcuate edges  64 ,  66 , respectively, are formed as the result of cutting the slotted aperture  62  through the cylindrical body of the slide member  50 . The actuator assembly  40  is disposed within the cylindrical bore  38  as hereinafter described in further detail. The sealing assembly  20  extends through the slotted aperture  62  between the aperture  34  and the counterbore  42 . 
     Referring particularly to  FIG. 1 , the seal plate  22  is received within the counterbore  42  and is sealed to the bottom of the counterbore  42  by the seal members  68 , such as o-rings. The seal plate  22  has a sealing surface on the side opposite seal members  68 . The seal plate  22  includes a fluid passage  70  extending therethrough communicating with the second port  16 . Cage  26  is generally cup shaped forming a cavity  72  and has an annular flange  74  extending around a reduced diameter end  76  of the seal plate  22 . An offset slotted hole  78 , having side and end walls, extends through the bottom of the cage  26 . The seal plate fluid passage  70  communicates with the cavity  72  via the slotted hole  78 . 
     The seal  24  is a solid cylindrical shaped member having a tang  80  extending from one end and a sealing surface on the other end. The seal  24  has a diameter slightly greater than the diameter of the mouth of the seal plate fluid passage  70 , whereby when the seal  24  is centered on the passage  70 , the sealing surface of the seal  24  seals with the sealing surface of the seal plate  22  to prevent flow through the passage  70  and the valve  10 . The seal  24  reciprocates in the slotted hole  78  in the bottom of the cage  26 . The side walls of the slotted hole  78  maintain the seal  24  in alignment with the passage  70  during reciprocation while the end walls serve as stops to the reciprocal movement of the seal  24  in the slotted hole  78 . 
     The close push rod  52  and open push rod  54  are reciprocably housed in bores  90 ,  92 , respectively, through the sides of the cage  26 . The close push rod  52  has a larger cross-section than the open push rod  54  so that the push rods cannot be assembled incorrectly. The push rod  54  is captured within slot  150  in the slide member  50 ; the close push rod  52 , having a larger cross-section, cannot fit in the slot  150 . The push rods  52 ,  54  are positioned to be in alignment with the seal  24  such that the inner ends of the rods  52 ,  54  bear against the seal  24  and the outer ends of rods  52 ,  54  bear against the end walls of the slide member  50  formed by the slotted aperture  62 . This positioning ensures that as the slide member  50  shifts axially, the rods  52 ,  54  also shift axially and the seal  24  is moved between the open and closed positions. The slide member  50  acts as a shuttle piston. Each end of the slide member  50  includes a cylinder  94 ,  96 , respectively. Close piston  58  and open piston  60  are received within cylinders  94 ,  96 , respectively, and are stationary members affixed to the housing  12 . Seals  104  are provided between the pistons  58 ,  60  and the housing  12 , and seals or O-rings  106  are provided between the pistons  58 ,  60  and the walls of the cylinders  94 ,  96 , respectively. 
     The spring cap  28  includes a reduced diameter portion which is received in a counterbore in the open end of the cage  26  to affix the cage  26  to the cap  28 . A plurality of fluid passageways  84 ,  85  extend through the spring cap  28 . A spring retaining bore  82  is centered on the reduced diameter portion and receives one end of the seal spring  30  with the other end of the seal spring  30  receiving the tang  80  projecting from the seal  24 . 
     The plug  32  is a disc-like member which is threadingly received by the threaded aperture  34  and which bears against the spring cap  28  to maintain the spring assembly, i.e., the seal cartridge  20 , in the housing  12 . The plug  32  includes a plurality of passages  86  therethrough to communicate the port  14  with the passageways  84 ,  85  in the spring cap  28  and the cavity  72  in the cage  26 . The inner side of the passages  86  are enlarged at  88  to ensure alignment and fluid communication between passages  86  and passageways  84  and  85 . It should be appreciated that fluids may flow through the passages  85  around the outside of the cage  26  and through the slotted aperture  62 , and that fluids may pass into the cylindrical bore  38 . 
     The close piston  58  is threadingly connected to the housing  12  at threads  98  in a threaded bore  100  in the housing  12 . The bore  100  is a hydraulic port which communicates with a supply of hydraulic fluid  170 . The close piston  58  also includes an aperture  102  therethrough communicating with the hydraulic port  100  such that the close cylinder  94  may be pressurized to hydraulically actuate the slide member  50  to the closed position. 
     The open piston  60  is threadingly connected to the housing  12  at threads  108  in a threaded bore  110  in the housing  12 . The open cylinder  96  is a hydraulic chamber which communicates with a supply of hydraulic fluid  160  via fluid passageway  112 . The open cylinder  96  may be pressurized to hydraulically actuate the slide member  50  to the open position. The open cylinder end of the slide member  50  has a reduced diameter portion  114  to form a spring annulus to house the return spring  56 . The return spring  56  bears against the stationary open piston  60  at one end, and against an annular shoulder  118  formed by the reduced diameter portion  114  at the other end. Preferably the return spring  56  will return the slide member  50  to the open position upon the reduction of fluid pressure in the close cylinder  94 . Hydraulic pressure via the hydraulic supply  160  through the fluid passageway  112  in the open cylinder  96  is preferably used to assist return spring  56  when needed. A return spring has only been provided on one side of the slide member  50  because the valve  10  is normally open. The valve  10  may be hydraulically actuated in both directions, but is normally open. Alternatively, the valve  10  can be constructed so that it operates as a normally closed valve. 
     Operation of the Valve 
     Referring now to  FIG. 1 , the valve  10  is shown in the open position with the slide member  50  being shifted all the way to the right by the return spring  56 . With the slide member  50  to the right, the cylinder  96  is enlarged and the open push rod  54  has pushed the seal  24  to the right and clear of the passage  70  in the seal plate  22 . This configuration opens the passageway defined by the port  14 , the passages  86 , the passageways  84 ,  85 , the cavity  72 , the slotted hole  78 , the passage  70 , and the second port  16  to the passageway  18 . The threads  98 ,  108  maintain the pistons  58 ,  60 , respectively, in a stationary position as the sleeve member  50  with the cylinders  94 ,  96  shuttles the seal  24  back and forth in response to hydraulic fluid forces applied either through the fluid passageway  102  or the passageway  112 . 
     Referring now to  FIG. 5 , the fluid in the bore  100  is pressurized via hydraulic fluid from the hydraulic supply  170  through the passageway  102  until the pressure on the bottom of the cylinder  94  overcomes the force of the return spring  56  on the shoulder  118  as well as the force due to friction caused by O-rings  106  on pistons  58  and  60  as seen in FIG.  1 . The slide member  50  then moves to the left with the close push rod  52  forcing the seal  24  to slide across the sealing surface  120  of the seal plate  22 . The rod  52  pushes the seal  24  from the open position shown in  FIG. 1  to the closed position shown in FIG.  5 . The seal  24  is pressed against the seal plate  22  by the seal spring  30 . As the slide member  50  moves to the left, the return spring  56  is compressed as shown in FIG.  5 . 
     To reopen the valve  10 , the hydraulic pressure in the bore  100  is reduced. The return spring  56  then de-compresses to move the slide member  50  back to the right. In addition, hydraulic fluid from hydraulic supply  160  is supplied through the passage  112 , and the pressure acts on the bottom shoulder of the cylinder  96  to assist the movement of slide member  50  back to the right. In the case where spring  56  fails to open the valve  10 , this secondary hydraulic supply  160  will act to close valve  10 . 
     In the closed position shown in  FIG. 3 , the seal spring  30  is straight and cylindrical, and in the open position shown in  FIGS. 1 and 2 , the seal spring  30  is deformed whereby the ends of spring  30  are no longer co-axial because tang  80  and counterbore  82  are no longer co-axial. The spring  30  is allowed to twist and turn with the movement of the seal  24 . 
     As the actuator assembly  40  shuttles the seal  24  back and forth within the slotted hole  78  and over the mouth of the passage  70 , it is important that proper flatness and surface finish are maintained so that there is no leakage past the seal created by the seal  24  and the seal plate  22  when the valve  10  is in the closed position. Thus, the contact surfaces (bottom surface of the seal  24  and top sealing surface  120  of the seal plate  22 ) are manufactured flat to 2 He lightbands or better. When the seal  24  is shuttled to the closed position, forces from the high pressure annulus fluid column push on the top side of the seal  24  at the tang  80 . Consequently, the portions of the seal  24  which overlap the mouth of passage  70  bear down on the seal plate  22 , creating what is known as a shear seal. 
     Although shear seals have been successfully employed in dirty fluid environments, in a preferred embodiment of the present invention the seal spring  30  is present to ensure that a proper shear seal is created. The seal  24  is only connected to the seal spring  30  at the tang  80 . It is not connected to the push rods  52 ,  54  or any of the other structure surrounding the seal  24 . Alternatively, the seal  24  could be connected to one or both of the push rods  52 ,  54 , but this would restrain the seal  24  in such a way as to possibly cause an off-axis load or misalignment on the seal  24 . An off-axis load on or a misalignment of the seal  24  would prevent the annulus pressure from causing the seal  24  to properly bear down on the seal plate  22 , thus preventing a shear seal. 
     Instead, the seal  24  is restrained only by the seal spring  30 . The seal spring  30  continuously provides force to the top of the seal  24  at the tang  80 , thereby providing a proper pre-load to the seal  24 . A “snap-acting” spring is used for the seal spring  30  to maintain the continuous force on the seal  24  whether the seal  24  is in the open position, closed position, or any position in between. As the seal  24  moves from the open position of  FIG. 1  to the closed position of  FIG. 5 , the seal spring  30  compresses with a snap action. As the seal  24  moves back to the open position, the seal spring also decompresses with a snap action. The snapping action assists the actuator assembly and push rods with crisp movement of the seal  24 . However, and more importantly, the snapping characteristic of the seal spring  30  allows the spring to apply the necessary pre-loading forces to the seal  24  despite the spring&#39;s contorted or twisted condition in the open position. The pre-loading force is especially important when the seal  24  moves from the open to the closed position. 
     It should be understood that the valve  10  may be used in any application requiring the sealing of a fluid flow. The valve  10  is particularly useful in oilfield operations and tools. For example, the valve  10  may be used as an equalizer valve in an oilfield tool which communicates with the surrounding annulus in a downhole environment. One such application of the valve  10  is in formation testing. Valve  10  is particularly well suited for use in the formation tester described in provisional patent application Ser. No. 60/381,243 filed May 17, 2002, entitled Formation Tester, and in the patent application filed concurrently herewith via Express Mail No. EV324573681US and entitled MWD Formation Tester, which claims priority to the previously reference provisional application, both applications hereby incorporated by reference herein for all purposes. 
     The valve  10  can seal dirty fluid (debris laden fluid) leak-free, and may be reopened while there is a pressure differential of up to 8,000 p.s.i. between first port  14  and second port  16 . For example, the shear seal provided by valve  10  can be used in a formation test tool that requires a leak-free equalizer valve in an environment containing dirty or debris laden fluid. Valve  10  can also be used in a formation tester that makes formation pressure tests with a pressure differential up to 8,000 p.s.i. between the annulus fluid and the formation fluid in the chamber of the formation tester. 
     Referring now to  FIG. 6 , there is shown an application of the valve  10  as an equalizer valve  130  in a formation tester  132 . The first port  14  is aligned with an aperture  134  through the wall of the housing  136  of the formation tester  132  such that the port  14  is open to the annulus  138  formed between the formation tester  132  and the wall of the borehole being drilled. The annulus  138  is filled with drilling mud and well fluids which pass through the aperture  134  and into the valve  130  via the port  14 . A screen  140  may be placed over the aperture  134  to prevent deleterious debris from passing into the equalizer valve  130 . The screen  140  is retained in the housing  136  by retaining ring  144 . 
     The equalizer valve  130  is normally open allowing annulus fluids to flow through the valve  130  from the port  14  to the port  16  and into the passage  118  in the internal member  142 . The formation tester  132  includes a motor driving a pump to actuate actuation assembly  40  to move the seal  24  between the open and closed positions. In the case of the formation tester  132 , the valve  130  may be closed to allow the formation tester to perform a test. 
     The seal cartridge  20  is inserted through the aperture  134  of the housing  136  and through port  14  of member  142  that forms part of the internal components of the formation tester  132 . As shown in  FIG. 6 , the internal member  142  is disposed within the housing  136  of the formation tester  132 . The cartridge  20  may be replaced in the field if necessary. Referring now to both  FIGS. 1 and 6 , the threads at  35  of  FIG. 1  allow the operator to isolate and remove the seal cartridge  20 . First, the operator may remove the screen  140  by removing the retaining ring  144  from the housing  136  and then removing the screen  140 . The cartridge  20  can be grabbed by screwing two small screws into the spring cap  28  and lifting the cartridge  20  out of the valve  10 . The hydraulic system, including the actuator assembly  40 , is unperturbed. When installing a replacement cartridge, the push rods  52 ,  54  assist the operator with orienting the cartridge  20  properly. As mentioned before, the open push rod  54  is smaller in diameter than the close push rod  52 , allowing the operator to align the open push rod  54  with the slot  150  in the slide  50 . 
     Thus the equalizer valve  10  combines shear seal technology with a snap-acting seal design that is field replaceable without disturbing-the hydraulics circuit used to actuate the valve. This design combines performance in a dirty fluid environment with maintainability should a seal failure occur. 
     The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. While the preferred embodiment of the invention and its method of use have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described herein are exemplary only, and are not limiting. Many variations and modifications of the invention and apparatus and methods disclosed herein are possible and are within the scope of the invention. Accordingly, the scope of protection is not limited by the description set out above, but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims.