Patent Publication Number: US-9422790-B2

Title: Safety valve with lockout capability and methods of use

Description:
BACKGROUND 
     The present invention relates generally to operations performed and equipment utilized in conjunction with a subterranean well and, in particular, to a safety valve with a built-in lockout feature. 
     Subsurface safety valves are well known in the oil and gas industry and act as a failsafe to prevent the uncontrolled release of reservoir fluids in the event of a worst-case scenario surface disaster. Typical subsurface safety valves are flapper-type valves which are opened and closed with the help of a flow tube moving telescopically within the production tubular. The flow tube is often controlled hydraulically from the surface and is forced into its open position using a piston and rod assembly that may be hydraulically charged via a control line linked directly to a hydraulic manifold or control panel at the well surface. When sufficient hydraulic pressure is conveyed to the subsurface safety valve via the control line, the piston and rod assembly forces the flow tube downward, which compresses a spring and simultaneously pushes the flapper downward to the open position. When the hydraulic pressure is removed from the control line, the spring pushes the flow tube back up, which allows the flapper to move into its closed position. 
     Some safety valves are arranged thousands of feet underground and are therefore required to traverse thousands of feet of borehole, including any turns and/or twists formed therein, before arriving at its proper destination. Consequently, during its descent downhole, the control line may undergo a substantial amount of vibration or otherwise sustain significant damage thereto. In extreme cases, the control line may be severed or one of the connection points for the control line may become inadvertently detached either at a surface well head or at the safety valve itself, thereby rendering the safety valve powerless. Moreover, during prolonged operation in downhole environments that exhibit extreme pressures and/or temperatures, the hydraulic actuating mechanisms used to move the flow tube may fail due to mechanical failures such as seal wear or the like. As a result, some safety valves prematurely fail, thereby leading end users to request the ability to lock the damaged safety valve in the open position. 
     SUMMARY OF THE INVENTION 
     The present invention relates generally to operations performed and equipment utilized in conjunction with a subterranean well and, in particular, to a safety valve with a built-in lockout feature. 
     In at least one aspect, the disclosure provides a safety valve including a housing, a flapper coupled to the housing and being movable between an open position and a closed position, a flow tube movably disposed within the housing and having an extended position, the flow tube being configured to retain the flapper in the open position when in the extended position, a lockout rod coupled to the housing and being movable between a deployed position and a stored position, the lockout rod being configured to retain the flow tube in the extended position when the lockout rod is in the deployed position, and a lockout ratchet element arranged within the housing and coupled to the lockout rod, the lockout ratchet element being configured to retain the lockout rod in the deployed position. 
     In other aspects, the disclosure may provide a method of locking open a safety valve. The method may include moving a flapper of the safety valve to an open position, extending a flow tube of the safety valve to an extended position, wherein the flow tube is configured to retain the flapper in the open position when the flow tube is in the extended position, deploying a lockout rod of the safety valve to a deployed position, the lockout rod being configured to retain the flow tube in the extended position when the lockout rod is in the deployed position, and retaining the lockout rod in the deployed position with a lockout ratchet element arranged within the housing and coupled to the lockout rod. 
     In yet other aspects, the disclosure may provide a lockout tool including a top tube having an upper bore, an intermediate ring coupled to the top tube, wherein the top tube and the intermediate ring are configured to selectably block a longitudinal flow path of a housing of a safety valve when the lockout tool is disposed within the safety valve, the safety valve having a longitudinal up-down axis, and an exercise key coupled to the intermediate ring and configured to selectably engage keying features of a flow tube of the safety valve. 
     The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the preferred embodiments that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following figures are included to illustrate certain aspects of the present invention, and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to those skilled in the art and having the benefit of this disclosure. 
         FIG. 1  depicts an example safety valve with a valve assembly that includes a flapper and a valve seat, according to one or more embodiments. 
         FIG. 2  and the enlarged cross-sectional views in  FIGS. 2A-2F  are cross-sectional views of an exemplary safety valve, according to one or more embodiments. 
         FIG. 3  is a partial cross-sectional view of the safety valve in the closed position, according to one or more embodiments. 
         FIG. 4  is a partial cross-sectional view of the safety valve in the open position during normal operation of the safety valve, according to one or more embodiments. 
         FIG. 5  is a partial cross-sectional view of the safety valve in the locked-open position after completion of a lock-out operation using a lockout tool as disclosed herein, according to one or more embodiments. 
         FIG. 6  and the enlarged cross-sectional views in  FIGS. 6A-6C  illustrate an exemplary lockout tool, according to one or more embodiments. 
         FIG. 7  and the enlarged cross-sectional views in  FIGS. 7A-7C  show the exemplary lockout tool disposed in the safety valve and configured for a first step in the lock-out operation, according to one or more embodiments. 
         FIG. 8  and the enlarged cross-sectional views in  FIGS. 8A-8C  show the exemplary lockout tool disposed in the safety valve and configured for a second step in the lock-out operation, according to one or more embodiments. 
         FIG. 9  and the enlarged cross-sectional views in  FIGS. 9A-9D  show the exemplary lockout tool disposed in the safety valve and configured for a third step in the lock-out operation, according to one or more embodiments. 
         FIG. 10  and the enlarged cross-sectional views  FIGS. 10A-10B  illustrate the configuration of the safety valve after successful completion of a lockout operation, according to one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates generally to operations performed and equipment utilized in conjunction with a subterranean well and, in particular, to a safety valve with a built-in lockout feature. 
     The exemplary safety valves disclosed herein provide a downhole safety valve that incorporates a feature that, when used in conjunction with a lock-out tool as disclosed herein, permanently locks the safety valve in an open position. At least one advantage of the safety valves disclosed herein is that inclusion of a lockout capability requires only a minimal increase in the cost of the safety valve. Moreover, conventional safety valves can easily be retrofitted or otherwise modified with the embodiments disclosed herein. Another advantage is that the exemplary lockout tool described herein is a robust design that can be stored on-site for an extended period of time without a significant risk of degradation in operability. As can be appreciated, this decreases the operational time required to correct a failed safety valve. 
     As used herein, the term “pressure seal” is used to indicate a seal which provides pressure isolation between members which have relative displacement therebetween, for example, a seal which seals against a displacing surface, or a seal carried on one member and sealing against the other member, etc. A pressure seal may be elastomeric or resilient, nonelastomeric, metal, composite, rubber, or made of any other material. A pressure seal may be attached to each of the relatively displacing members, such as a bellows or a flexible membrane. A pressure seal may be attached to neither of the relatively displacing members, such as a floating piston. 
     In the following description of the representative embodiments of the disclosure, directional terms such as “above,” “below,” “upper,” “lower,” etc., are used for convenience in referring to the accompanying drawings. In general, “above,” “upper,” “upward” and similar terms refer to a direction toward the earth&#39;s surface along a wellbore, and “below,” “lower,” “downward” and similar terms refer to a direction away from the earth&#39;s surface along the wellbore. 
     Within this document, the phrase “flow tube” means an element that is extended to open or maintain in an open position a safety valve, such as a flapper valve. Elements with this function are sometimes referred to as a “control sleeve.” An alternate embodiment of a safety valve may utilize a different type of element to hold the flapper open. 
     Within this document, the term “lock open” or similar means that a movable device having an open position has been retained in or near the open position by a modification to the movable device or placement of a secondary device, such as a flow tube, so as to prevent the movable device from a large departure from the open position. The movable device may be allowed to move some distance from the open position, for example 10% of the motion required to move from the open position to a closed position, that is considered sufficiently similar to the open position of the movable device. 
     The safety valve  10  and/or lockout tool  300 , as described herein below, may include numerous seals to provide pressure-sealing capability between separate parts, fittings and fasteners to join separate parts, and multiple components that are manufactured separately, for example, for ease of manufacture, and assembled to provide certain elements of the safety valve  10  and/or lockout tool  300 . Within this document and the associated drawings, multiple components may be provided with a single reference identifier to indicate that the components are considered as a single functional element although, in certain embodiments, they may be fabricated as separate parts and assembled. In addition, the materials from which the various components of the safety valve  10  and/or lockout tool  300  are fabricated are selected based on the function, design, and service environment. The details of these types of features are known to those of skill in the art and are not described herein so as not to obscure the disclosure. 
       FIG. 1  depicts an example safety valve  10  with a valve assembly  30  that includes a flapper  34  and a valve seat  32 , according to one or more embodiments. The safety valve  10  may be used in an offshore oil and gas application, a land-based oil and gas rig, or a rig located at any other geographical site. It should be understood that the disclosure is not limited to any particular type of well. 
     The valve assembly  30  is located within a housing  19  that includes an upper sub  18  and a lower sub  16 . The safety valve  10  has a longitudinal up-down axis, as shown in  FIG. 1 , and the upper end of the upper sub  18  is configured to sealingly mate with production tubing  12  through which the oil and/or gas flows out of the well. One or more control lines  13  run parallel to the production tubing  12  and connect to a fitting  18 A (not shown in  FIG. 1 ). As discussed in more detail below, the one or more control lines  13  may be configured to actuate the safety valve  10 , for example, to maintain the safety valve  10  in an open position, or otherwise to close the safety valve  10  and thereby prevent a blowout in the event of an emergency. 
     In some embodiments, the one or more control lines  13  may be hydraulic conduits that provide hydraulic fluid pressure to the safety valve  10 . In operation, hydraulic fluid may be conveyed or otherwise applied to one or more of the control lines  13  from a hydraulic manifold (not shown) arranged at a remote location, such as at a production platform or a subsea control station. When properly applied, the hydraulic pressure derived from one or more of the control lines  13  may be configured to open and maintain the safety valve  10  in its open position, thereby allowing production fluids to flow through the tubing string. To move the safety valve  10  from its open position and into a closed position, the hydraulic pressure in the one or more control lines  13  may be reduced or otherwise eliminated. 
     While only one control line  13  is depicted in  FIG. 1 , it should be understood that more than one control line  13  may be employed without departing from the scope of the disclosure. It should also be understood that other means, besides hydraulic fluid pressure, may be used to actuate the safety valve  10 , in keeping with the principles of the disclosure. For example, the safety valve  10  could be at least partially electrically actuated, in which case the control line  13  could be an electrical or a fiber optic line that communicates with a servo or other subsea motor or actuator. In other embodiments, the safety valve  10  could be actuated using telemetry, such as mud pulse, acoustic, electromagnetic, seismic or any other type of telemetry. In yet other embodiments, the safety valve  10  could be actuated using any type of surface or downhole power source communicably coupled to the safety valve  10  via one or more control lines  13 . 
     Moreover, although the control line  13  is depicted in  FIG. 1  as being arranged external to the production tubing  12 , it will be readily appreciated by those skilled in the art that any hydraulic line may be used to convey actuation pressure to the safety valve  10 . For example, the hydraulic line could be internal to the production tubing  12 , or formed in a sidewall of the production tubing  12 . The hydraulic line could extend from a remote location, such as from the earth&#39;s surface, or another location in the wellbore (not shown in  FIG. 1 ). In yet other embodiments, the actuation pressure could be generated by a pump or other pressure generation device communicably coupled to the safety valve  10  via the control line  13 . 
       FIG. 2  and the enlarged views in  FIGS. 2A-2E  are cross-sectional views of an exemplary safety valve  10 , according to one or more embodiments. The safety valve  10  has a housing  19 , which includes a top sub  18  and a bottom sub  16 , and a valve assembly  30  having a flapper  34  and a valve seat  32 . The safety valve  10  also includes a flow tube  50  disposed within the housing  19 , the flow tube  50  having a center element  51 , a lower flow tube  54 , and an upper flow tube  56 . A closure spring  48  is disposed within the housing  19  and serves to bias the center element  51  upward. 
       FIG. 2A  is a cross-section of the portion of safety valve  10  indicated by the dashed-line box A in  FIG. 2 .  FIG. 2A  depicts the upper end of the top sub  18  where a no-go profile  15  is provided on the interior surface of an internal flow path  60  defined within the safety valve  10 , according to certain aspects of the present disclosure. In some embodiments, the profile  15  is a proprietary RPT® no-go profile commercially available through Halliburton Energy Services of Houston, Tex., USA. Below the no-go profile  15  is a honed bore  17  that is controlled in diameter and surface finish so as to provide a suitable surface for engagement of sealing features of various tools, such as the exemplary lockout tool  300  disclosed herein below. 
       FIG. 2B  is a cross-section of the portion of safety valve  10  indicated by the dashed-line box B in  FIG. 2 .  FIG. 2B  depicts a forcing ring  41  that may be disposed within the top sub  18  axially adjacent the closure spring  48  which pushes upward on the forcing ring  41 , according to certain aspects of the present disclosure. An actuation rod  40  is shown at the bottom, in the view of  FIG. 2B , and is disposed in a drilled passage  18 B fluidly connected to a control line port  18 A (shown in  FIG. 2D ). A lockout rod  70  is shown at the top, in the view of  FIG. 2B , and is disposed in a drilled passage  18 C. The lockout rod  70  is discussed in greater detail below with respect to  FIG. 2E . Both the actuation rod  40  and the lockout rod  70  are configured to push downward on the forcing ring  41 , according to certain aspects of the present disclosure. The center element  51  is configured to engage the forcing ring  41  such that a downward force may be applied by the flow tube  50  to the forcing ring  41  via the center element  51 . The actuation rod  40  and the closure spring  48  engage opposite sides of the forcing ring  41 . Providing hydraulic pressure to the control line  13  ( FIG. 1 ) will force the actuation rod  40  downward, thereby forcing the forcing ring  41  and the flow tube  50  downward. In contrast, releasing the pressure in the control line  13  will allow the closure spring  48  to force the forcing ring  41  and flow tube  50  back upward. One or more keying features  52  may be defined on the inner surface of the center element  51 . 
       FIG. 2C  is a cross-section of the portion of safety valve  10  indicated by the dashed-line box C in  FIG. 2 .  FIG. 2C  depicts the flapper  34  in the closed position against the valve seat  32 , according to certain aspects of the present disclosure. A flapper arm  36  may be in contact with the underside of the flapper  34  and also in contact with a flapper piston  38  that may be configured to engage a flapper spring  39 . Once the flow tube  50  is retracted, as generally described above, the combined action of the flapper arm  36 , flapper piston  38 , and flapper spring  39  may result in urging the flapper  34  towards the closed position, and thereby ceasing fluid flow through the internal flow path  60  ( FIG. 2A ). The lower edge  55  of the flow tube  50  is visible at the left of  FIG. 2C , with the flow tube  50  shown in the retracted position. 
       FIG. 2D  is a cross-section of the portion of safety valve  10  indicated by the dashed-line box D in  FIG. 2 .  FIG. 2D  depicts the actuation rod  40  disposed in the drilled passage  18 B and the lockout rod  70  disposed in the drilled passage  18 C, according to certain aspects of the present disclosure. As depicted, the drilled passage  18 B may be in fluid communication with the control line port  18 A. The details of drilled passage  18 C are discussed in greater detail below with respect to  FIG. 2E . 
       FIG. 2E  is a cross-section of the portion of safety valve  10  indicated by the dashed-line boxes jointly marked E in  FIG. 2D .  FIG. 2E  depicts the upper end and lower end of the lockout rod  70  disposed within the drilled passage  18 C in the top sub  18 , according to certain aspects of the present disclosure. The drilled passage  18 C is fluidically coupled to the flow path  60  of the safety valve  10  through a lockout activation port  18 D defined in the inner wall of the flow path  60  just above the flow tube  50  when in the retracted position. There is a pressure seal  71  near the top of the lockout rod  70  that seals the gap between the lockout rod  70  and the walls of the drilled passage  18 C such that pressure in the drilled passage  18 C above the lockout rod will force the lockout rod  70  downward. The lockout rod  70  has at least one shaped ridge  74 , and in certain embodiments, has a series of shaped ridges  74  arranged along the lockout rod  70 . The shaped ridges  74  are discussed in greater detail below with respect to  FIG. 2F . 
     At the bottom of the drilled passage  18 C is a lockout ratchet element  72  disposed about the lower end of the lockout rod  70 . In certain embodiments, the lower end of the drilled passage  18 C is enlarged to accommodate the lockout ratchet element  72 , thereby preventing the lockout ratchet element  72  from moving upward within the drill passage  18 C. The lockout rod  70  is shown in  FIG. 2E  in its stored, i.e. most upward, configuration. When the lockout rod  70  is forced downward, i.e. moved to its deployed position, the lockout rod  70  passes through the lockout ratchet element  72 . The interaction of the lockout rod  70  and the lockout ratchet element  72  is discussed below in greater detail with respect to  FIG. 2F . 
       FIG. 2F  is a cross-section of the portion of safety valve  10  indicated by the dashed-line box F in  FIG. 2E .  FIG. 2F  depicts the exemplary shaped ridges  74  of the lockout rod  70  and the exemplary retention features  76  of the lockout ratchet element  72 , according to certain aspects of the present disclosure. In one or more embodiments, the lockout rod  70  may have at least one shaped ridge  74  and the lockout ratchet element  72  may have at least one corresponding retention feature  76  configured to engage the at least one shaped ridge  74  as the lockout rod  70  moves from its stored configuration to its deployed configuration. In one or more embodiments, the at least one shaped ridge  74  and the at least one retention feature  76  may be configured to allow the at least one shaped ridge  74  to move past the at least one retention feature  76  in a first direction but prevent the at least one shaped ridge  74  from moving past the at least one retention feature  76  in a second direction that is opposite the first direction. In one or more embodiments, each shaped ridge  74  may have a lower sloped face  74 A and an upper flat face  74 B. Each retention feature  76  may have a lower flat face  76 A and an upper sloped face  76 B. In one or more embodiments, the slope of the lower sloped face  74 A may be generally the same as the slope of the upper sloped face  76 B. In one or more embodiments, the angles of the lower flat face  74 B and the upper flat face  76 B may be generally perpendicular to an axis of motion of the lockout rod  70 . In one or more embodiments, the angles of the lower flat face  74 B and the upper flat face  76 B may be complementary and undercut at complementary angles (not shown in  FIG. 2F ). 
     The lockout ratchet element  72  may be configured such that the sides may flex to allow the shaped ridges  74  to pass between the retention features  76  as the lockout rod  70  is forced downward, with the sloped faces  74 A and  76 A cooperating to allow the downward movement of the lockout rod  70  with respect to the lockout ratchet element  72 . Once the shaped ridges  74  have passed by the respective retention features  76 , the sides may then spring back toward the center. As a result, upward movement of the lockout rod  70  with respect to the lockout ratchet element  72  may be inhibited, and in certain embodiments prevented, by the interaction of the flat faces  74 B and  76 B. If the forcing ring  41  is moved to its lowest position, corresponding the flow tube  50  being fully extended and flapper  34  held open, the lockout rod  70  may be forced to a fully deployed position wherein the lower end of the lockout rod  70  is in contact with the forcing ring  41 . Once the lockout rod  70  is in this fully deployed position, the one or more retention features  76 , and in particular the flat faces  76 B, may interact with the one or more shaped ridges  74 , and in particular the flat faces  74 B, so as to prevent upward motion of the lockout rod  70 , thereby locking the flapper  43  in the open position. 
       FIG. 3  is a partial cross-sectional view of the safety valve  10  in the closed position, according to certain aspects of the present disclosure. As illustrated, the closure spring  48  is in its extended (e.g., expanded) position, forcing the flow tube  50  upward to its retracted position, thereby allowing the flapper  34  to move to its closed position against valve seat  32 , thereby preventing upward flow through the safety valve  10 . 
       FIG. 4  is a partial cross-sectional view of the safety valve  10  in the open position during normal operation of the safety valve  10 , according to certain aspects of the present disclosure. As illustrated, the flow tube  50  is in its fully extended position, wherein the lower edge  55  has extended past and below the flapper  34 , thereby forcing the flapper  34  open and maintaining the flapper  34  in its open position. The flow tube  50  in its extended position also protects the flapper  34  from accumulating debris within the oil and/or gas flowing through the flow path  60  of the safety valve  10 . As briefly described above, the closure spring  48  is compressed by downward motion of actuation rod  40  under pressure provided through the control line  13  ( FIG. 1 ) and is shown in its compressed configuration. 
       FIG. 5  is a partial cross-sectional view of the safety valve  10  in the locked-open position after completion of a lockout operation using the lockout tool  300  described below with reference to  FIG. 6 , according to certain aspects of the present disclosure. The fully deployed lockout rod  70  maintains the flow tube  50  in at least a partially extended position with lower edge  55  proximate to the flapper  34 , as shown in this example, that is sufficient that the lower flow tube  54  maintains the flapper  34  in the open position. As the lockout rod  70  cannot move upward, being restrained by the lockout ratchet element  72  ( FIG. 2E ), the safety valve  10  is permanently disabled with the flapper  34  locked in the open position. 
       FIG. 6  and the enlarged views in  FIGS. 6A-6C  illustrate an exemplary lockout tool  300 , according to one or more embodiments.  FIG. 6  depicts the entire lockout tool  300 , which includes a top tube  310 , an intermediate ring  320 , a middle tube  330 , a key expander mandrel  350 , and an opening prong  360 . Some of these elements may be formed, in certain embodiments, of multiple parts that are joined, for example by threaded couplings, to form a functional element. The embodiment shown in  FIG. 6  is only one example and the lockout tool  300  may be formed, in certain embodiments, from a single element or multiple alternate elements different from those shown herein. 
       FIG. 6A  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box A in  FIG. 6 .  FIG. 6A  depicts a fishing neck  302  formed at the top end of the top tube  310 . An upper bore  319  passes through the top tube  310  with flow passages  314  defined in a wall of the top tube  310 . A no-go stop  312  is formed as part of the exterior features of the fishing neck  302  and is discussed in greater detail with respect to  FIG. 9A . The fishing neck  302  is configured to engage the lower end of a pulling tool  301 , shown in phantom in  FIG. 6A , that can be used to lower the lockout tool  300  into, or remove the lockout tool  300  from, the safety valve  10 . Upward and downward forces can be applied to the lockout tool  300  through the pulling tool  301  to “jar up” or “jar down” the lockout tool. 
       FIG. 6B  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box B in  FIG. 6 .  FIG. 6B  depicts an enlarged view of the intermediate ring  320  that is, at least in this embodiment, formed from four pieces that are fixedly joined (e.g., assembled) together. A pressure seal  324  is provided on an outside surface of the intermediate ring  320  and configured to sealingly mate with the honed bore  17  ( FIG. 2A ) of the safety valve  10 . The lower end of the top tube  310  is slidingly captured within the intermediate ring  320  and is shown in an upwardmost position, wherein an upward force on the top tube  310  will transfer the upward force to the intermediate ring  320 . 
     The lower end of the top tube  310  may have a tapered nose seal surface  316  that sealingly mates with a pressure seal  322  of the intermediate ring  320  when the top tube  310  is moved downward with respect to the intermediate ring  320 . The top tube  320  may also define one or more flow passages  318  such that fluid can pass down the upper bore  319  defined within the top tube  320 , through the various flow passages  318 , and down through the lower bore  326  defined within the middle tube  330  when the nose seal surface  316  is not mated with the pressure seal  322 . When the lockout tool  300  is engaged in the safety valve  10  with the pressure seal  324  engaged with the honed bore  17  ( FIG. 2A ) of the safety valve  10 , the only longitudinal flow path through the housing  19  passes from the upper bore  319  of the top tube  310  through the intermediate ring  320  and into the lower bore  326  of the middle tube  330 . This flow path is blocked when the top tube  310  is moved downward with respect to the intermediate ring  320  into a downward position wherein the nose seal surface  316  is mated with the pressure seal  322  ( FIG. 8A ). 
       FIG. 6C  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box C in  FIG. 6 .  FIG. 6C  depicts an enlarged view of the key expander mandrel  350  that is, at least in this embodiment, formed of two pieces that are fixedly coupled or otherwise assembled together. The middle tube  330  and the opening prong  360  are fixedly coupled to top and bottom ends, respectively, of the key expander mandrel  350 . An exercise key  340  is disposed around the key expander mandrel  350 . The key expander mandrel  350  includes, in this example, two key expander ridges  352  on an exterior surface of the key expander mandrel  350  wherein the key expander ridges  352  are positioned in the configuration of  FIG. 6C  under two relief clearances  344  on an interior surface of the exercise key  240 , wherein the relief clearances  344  have similar profiles to the key expander ridges  252  such that the key expander ridges  352  and the relief clearances are not in contact. The exercise key  340  can slide with respect to the key expander mandrel  350  and can be expanded or otherwise flexed outward upon application of a radial outward force. The exercise key  340  also includes a set of keying features  342  on an external surface. The function of the keying features  342  is discussed in greater detail with respect to  FIG. 8B  below. 
       FIG. 7  and the enlarged views in  FIGS. 7A-7C  show the exemplary lockout tool  300  disposed in the safety valve  10  and configured for a first step in the lock-out operation, according to one or more embodiments. In the configuration of  FIG. 7 , the lockout tool  300  has been lowered into the safety valve  10  until the bottom of the opening prong  360  is generally in contact with the closed flapper  34 . 
       FIG. 7A  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box A in  FIG. 7 .  FIG. 7A  depicts an enlarged view of the intermediate ring  320  with the pressure seal  324  engaged with the honed bore  17  of the upper sub  18  below the no-go profile  15 . The top tube  310  is shown in an uppermost position with respect to the intermediate ring  320 . With the pressure seal  324  engaged, the only flow path from the production tubing  12  down to the flapper  34  (not shown in  FIG. 6A ) is through the lower bore  326 . When the top tube  310  is in the uppermost position, or in a lower position wherein the nose seal surface  316  is not mated with the pressure seal  322 , the flow path from the production tubing  12  to the lower bore  326  is open. 
       FIG. 7B  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box B in  FIG. 7 .  FIG. 7B  depicts an enlarged view of the key expander mandrel  350  and the exercise key  340  disposed proximate to the forcing ring  41 . The relief clearances  344  of the exercise key  340  are still aligned with the key expander ridges  352  of the key expander mandrel  350  and the keying features  342  are offset from the keying features  52  of the center element  51  of the safety valve  10 . The closure spring  48  is visible at the right, or downstream, side of  FIG. 7B  in the expanded position and the actuation rods  40  are visible at the left, or upstream, side of the upper sub  18 . 
       FIG. 7C  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box C in  FIG. 7 .  FIG. 7C  depicts an enlarged view of the area around the flapper  34 . The lower flow tube  54  is shown within the bottom sub  16  with the lower edge  55  above the flapper  34 . The opening prong  360  is disposed within the lower flow tube  54  and generally in contact with the hemispherical portion of the flapper  34 , which is in the closed position. 
       FIG. 8  and the enlarged views in  FIGS. 8A-8C  show the exemplary lockout tool  300  disposed in the safety valve  10  and configured for a second step in the lock-out operation, according to one or more embodiments. While in the configuration of  FIG. 7 , wherein there is a flow path from the production tubing  12  to the flapper  34 , the pressure within the safety valve  10  above the flapper  34  may be increased to be approximately balanced with the pressure below the flapper  34 . The lockout tool  300  may then be lowered, through one or more of the weight of the lockout tool  300 , jarring down the top tube  310  until the nose seal surface  316  is mated with the pressure seal  322 , after which further jarring down will cause the entire lockout tool  300  to move downward, and the application of additional pressure in the production tubing  12  after the nose seal surface  316  is mated with the pressure seal  322 . Any of these techniques applies a downward force to the entire lockout tool  300 , thereby forcing the opening prong  360  to push the flapper  34  to the open position. 
       FIG. 8A  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box A in  FIG. 8 .  FIG. 8A  depicts an enlarged view of the intermediate ring  320  showing how the top tube  310  has moved downward with respect to the intermediate ring  320  until the nose seal surface  316  is mated with the pressure seal  322 , thereby blocking the flow path from the upper bore  319  through the flow passages  318  to the lower bore  326 . If the pressure in the upper bore  319  is greater than the pressure in the lower bore  326 , a downward force may be applied to the intermediate ring  320 , thereby forcing it downward within the upper sub  18 . 
       FIG. 8B  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box B in  FIG. 8 .  FIG. 8B  depicts the key expander ridges  352  being displaced downward from the relief clearances  344  of the exercise key  340  so as to force the exercise key  340  to expand radially outward from a retracted position to an expanded position. The keying features  342  of the exercise key  340  are shown engaged with the keying features  52  of the center element  51 . Note that the keying features  342  and  52  are configured such that the keying features  342  will move downward over the keying features  52  until the respective features  342 ,  52  are aligned, whereupon further downward motion of the exercise key  340  relative to the center element  51  is prevented by engagement of the keying features  342  and  52 . Once the lockout tool  300  is in the configuration shown in  FIGS. 8-8C , additional downward force applied to the top tube  310  is transferred through the middle tube  330  to the key expander mandrel  350  and then through the exercise key  340  to the center element  51  that in turn transfers the downward force to the forcing ring  41 . 
       FIG. 8C  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box C in  FIG. 8 .  FIG. 8C  illustrates that the opening prong  360  has moved the flapper  34  to the open position as the opening prong  360  descended past the flapper  34  while the lower flow tube  54  remains in the most upward, i.e. the retracted position. 
       FIG. 9  and the enlarged views in  FIGS. 9A-9D  show the exemplary lockout tool  300  disposed in the safety valve  10  and configured for a third step in the lock-out operation, according to one or more embodiments. The flow tube  50  has been moved downward within the housing  19 , e.g. by jarring down, until the flow tube  50  is in its lowest, i.e. extended, position. 
       FIG. 9A  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box A in  FIG. 9 .  FIG. 9A  illustrates that the no-go stop  312  of the top tube  310  of the lockout tool  300  is in contact with the no-go profile  15  of the upper sub  18  of the safety valve  10  at a downwardmost position of the top tube  310  within the safety valve  10 . While the ability of the top tube  310  to move relative to the intermediate ring  320  may allow a lower portion of the lockout tool  300  (i.e. the intermediate ring  320 , the middle tube  330 , the exercise key  340 , the key expander mandrel  350 , and the opening prong  360 ) to move further downward within the safety valve  10 , the engagement of the exercise key  340  with the forcing ring  41  may prevent this further downward motion when the closure spring  48  is fully compressed. The lockout tool  30  is configured to prevent damage to the safety valve  10  from further downward motion of any portion of the lockout tool  300  within the safety valve  10  once the no-go stop  312  engages the no-go profile  15 . 
       FIG. 9B  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box B in  FIG. 9 .  FIG. 9B  shows the position of the intermediate ring  320  within the safety valve  10  after the flow tube  50  has been moved to its extended position such that the lockout rod  70  can be deployed. The pressure seal  324  is engaged with the honed bore  17  of the housing  18  and the nose seal surface  316  of the top tube  310  is mated with the pressure seal  322  of the intermediate ring  320 , thereby blocking the flow path  60  at a point between the lockout activation port  18 D and the bottom  18 E of the drilled passage  18 C. In this position and configuration of the lockout tool  300 , there can be a pressure differential between the lockout activation port  18 D and the bottom  18 E of the drilled passage  18 C. Provision of an activation pressure in the production tubing  12  when the lockout tool  300  is configured as shown in  FIG. 9  will cause such a pressure differential, which will apply a net downward force on the lockout rod  70  and move the lockout rod  70  from its stored position to the deployed position.  FIG. 9B  depicts the lockout rod  70  in the deployed position. In certain circumstances, the pressure in the safety valve  10  below the intermediate ring  320  may increase when the flow path  60  is blocked at a point between the lockout activation port  18 D and the bottom  18 E of the drilled passage  18 C. The activation pressure in the production tubing may be selected to create a first pressure at the lockout activation port  18 D that is greater than a second pressure that is present at the bottom  18 E of the drilled passage  18 C when the flow path  60  is blocked at a point between the lockout activation port  18 D and the bottom  18 E of the drilled passage  18 C. 
       FIG. 9C  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box C in  FIG. 9 .  FIG. 9C  shows how the forcing ring  41  has been moved to its lowest position, thereby compressing the closure spring  48 , by forces applied through the exercise key  340  and center element  51 . The actuation rod  40  is shown in the extended, i.e. most downward, position that opens the flapper  34  (not shown in  FIG. 9C ) in normal operation. The lockout rod  70  is also shown in its deployed, i.e. most downward, position upon provision of pressure in the production tubing  12  that, with reference to  FIG. 2E , entered through port  18 D into the drilled passage  18 C and force the lockout rod  70  downward. The shaped ridges  74  of the lockout rod  70  are engaged with the retention features  76  of the lockout ratchet element  72  (not shown in  FIG. 9C ) such that the lockout rod  70  cannot be retracted once it is in its deployed position. 
       FIG. 9D  is a cross-section of the portion of lockout tool  300  indicated by the dashed-line box D in  FIG. 9 .  FIG. 9D  shows how the lower flow tube  54  has been extended around the outside of the opening prong  360  and past the flapper  34 . 
       FIG. 10  and the enlarged cross-sectional views  FIGS. 10A-10B  illustrate the configuration of the safety valve  10  after successful completion of a lockout operation, according to one or more embodiments. The flow tube  50  is in its fully extended, i.e., most downward, position thereby holding the flapper  34  in its open position. 
       FIG. 10A  is a cross-section of the portion of safety valve  10  indicated by the dashed-line box A in  FIG. 10 .  FIG. 10A  shows the flow tube  50  with the actuation rod  40  and the lockout rod  70  fully deployed. 
       FIG. 10B  is a cross-section of the portion of safety valve  10  indicated by the dashed-line box B in  FIG. 10A .  FIG. 10B  shows the top of the lockout rod  70  within the drilled passage  18 C in the upper sub  18 . The upper shaped ridges  74  are engaged with the retention features  76  of the lockout ratchet element  72 , thereby preventing the lockout rod  70  from retracting. 
     Those skilled in the art will readily recognize the several possible configurations for proper actuation and operation of the exemplary safety valve  10  configured with a lockout capability, as generally disclosed herein. For example, the drilled passage  18 C of the lockout rod  70  may be connected to a separate lockout control line (not shown), rather than communicating to the production tubing  12 , such that the lockout rod  70  is deployed by provision of pressure in the separate lockout control line. As an additional example, the lockout system may include a secondary mechanism (not shown) configured to prevent deployment of the lockout rod  70  until pressure is provided through a secondary lockout control line to release the secondary mechanism. Other variations and combinations will be apparent to those skilled in the art. 
     Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present invention. The invention illustratively disclosed herein suitably may be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein. While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted.