Abstract:
A mud-saver valve having an independent means for blocking the flow of fluid through the bore of a ball valve. The mud-saver valve has a tubular body having a central through-bore, a rotatable ball having a through-bore, and pressure actuated right and left concave cup members that can rotate about the periphery of said ball regardless of the position of the ball. When the ball is in the open position, the concave cup members may be rotated from an open to a closed position along the outer surface of the ball, thereby blocking the through-bore of the ball and preventing the flow of fluid through such bore.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS:  
       [0001]     None  
       FEDERALLY SPONSORED RESEARCH:  
       [0002]     Not Applicable  
       SEQUENCE LISTING OF PROGRAM:  
       [0003]     Not Applicable  
       BACKGROUND OF THE INVENTION  
       [0004]     1. Field of Invention  
         [0005]     The present invention relates to internal blowout preventers used on oil and gas drilling rigs. More particularly, the present invention relates to a mud-saver valve that can be used in connection with internal blowout preventers on drilling rigs. More particularly still, the present invention relates to a mud-saver valve that can be used in connection with top drive units.  
         [0006]      2 . Description of Related Art  
         [0007]     Drilling rigs, such as those used to explore for oil and gas, are typically comprised of a supportive rig floor, a derrick extending vertically above said rig floor, and a traveling block which can be raised and lowered within said derrick. A wellbore typically extends downward beneath the derrick into subterranean strata. During drilling operations, such drilling rig equipment is used to move tubular goods into and out of said wellbore.  
         [0008]     Frequently, boring drill bits and/or other equipment are lowered into wellbores, and manipulated within said wellbores, via tubular drill pipe. For example, oil and gas wells are usually drilled by rotating a boring bit located at the bottom of a length of tubular components known as a drill string. Rotation of the drill bit is typically accomplished by applying torque to the drill string at the drilling rig and transmitting such torque via the drill string to the subsurface boring bit located within the wellbore. Such torque may be generated at the drilling rig by a rotary table and kelly or, alternatively, by a large motor known as a top drive unit.  
         [0009]     Top drive units, which are typically movable vertically within the derricks of drilling rigs, generally include a pipe gripping apparatus having at least one set of toothed inserts for gripping the outer surface of a section of pipe. Top drive units also typically include means for connecting to a section of pipe, as well as a motor for rotating or spinning such pipe about its longitudinal axis. In most cases, fluid can be communicated through such top drive units and into the inner flow path of pipe sections connected to such top drive units.  
         [0010]     During drilling operations, a fluid known as drilling mud is normally pumped down the longitudinally extending bore of the tubular drill string, and circulated up the annular space which is formed between the external surface of said drill string and the internal surface of the wellbore. In order for drilling mud to accomplish its intended objectives, it is often necessary to adjust or control certain characteristics of such drilling mud. Thus, chemicals and/or other additives are often mixed into such drilling mud. Common drilling mud additives include gelling agents (e.g., colloidal solids and/or emulsified liquids), weighting materials, and other chemicals which are used to maintain mud properties within desired parameters. On a rig equipped with a top drive unit, mud is often pumped through the top drive unit and into the drill string situated below the top drive unit.  
         [0011]     Many drilling muds, and/or drilling mud additives can be environmentally damaging. Further, exposure to such muds and/or additives can have a harmful effect on the health of rig personnel. Thus, it is often undesirable, and in many cases a violation of applicable environmental regulations, to release such muds and/or additives directly into the surrounding environment. As such, it is generally beneficial to limit or restrict spillage of drilling mud and mud additives on a rig.  
         [0012]     In the course of drilling, it is often necessary to disconnect and separate various components of the drill string, usually at or near the level of the drilling rig floor. When such components are disconnected and separated, drilling mud and/or other fluids situated within the drill string above the point of separation may spill out into the surrounding area. Such spillage is highly undesirable because it can have harmful effects on the environment, as well as the health of rig personnel working in the area.  
         [0013]     On “standard” drilling rigs utilizing a rotary table and kelly to rotate a drill string, a discrete mud-saver valve may be used to prevent such spillage of drilling mud and/or other fluids. On such rigs, mud-saver valves are typically installed between the kelly and drill string. On rigs employing top drive units, existing mud-saver valves have proven to be ineffective and/or unusable. In such cases, a device known as an internal blowout preventer (“IBOP”) is commonly used to prevent spillage of drilling mud and other fluids. However, use of IBOP&#39;s for this purpose is generally not desirable.  
         [0014]     In many cases, upper and lower IBOP&#39;s are installed as tubular components of the drill string within the structure of the top-drive unit itself. In such cases, the upper IBOP is typically actuated by an external hydraulic cylinder and linkage arrangement, while the lower IBOP is typically manually operated and includes a short tubular saver-sub at the lower threaded connection. The overall length and outside diameter of the upper IBOP/lower IBOP/saver-sub assembly cannot be increased because it must be positioned within the structure of the top-drive unit. As a result, there is no room to add an existing prior art mud-saver valve to the top drive unit or attached drill string.  
         [0015]     Due to such length restrictions, a common practice is to actuate an IBOP to control the spillage of drilling mud on top drive rigs when the top drive unit is separated from the drill string. However, IBOP&#39;s must control the flow of the well in the event of a blowout. Thus, IBOP&#39;s must be tested frequently and must not leak. If the IBOP&#39;s are repeatedly actuated in order to prevent mud spillage (that is, if the IBOP&#39;s are being used as mud-saver valves), the life and reliability of such IBOP&#39;s can be significantly reduced. Moreover, the position of the IBOP&#39;s within a top drive assembly makes such valves very difficult and time-consuming to replace.  
         [0016]     In light of the foregoing, it is evident that there exists a significant need for a mud-saver valve that can be used on top-drive rigs. Such a mud-saver valve should preserve the life and integrity of the upper and lower IBOP&#39;s, without adding to the combined length of said existing upper and lower IBOP&#39;s. Further, the mud-saver valve should be automatically actuated by change of pressure within the drill string, such as when mud pumps are turned off prior to disconnecting a top drive unit from a section of pipe.  
         [0017]     Ideally, a mud-saver valve for top-drive rigs should be integral to the lower IBOP, and operation of the mud-saver valve should not wear or damage the IBOP, or otherwise reduce or compromise the reliability or integrity of such IBOP. Furthermore, because the mud-saver valve must be positioned near the top of the drill string, the structure of the valve must be capable of transmitting the maximum loads that may be applied to the drill string. Such loads include internal hydraulic pressure, applied torsion, and axial loading from the weight of the drill string. In other words, inclusion of the mud-saver valve members should not significantly reduce the capacity of the system to handle loads commonly observed in the drilling process.  
         [0018]     Several objects and advantages of the present invention include, but are not necessarily limited to, the following: 
        (a) To provide a mud-saver valve integral to the lower IBOP used on top-drive rigs that does not increase the overall length or outside diameter of the IBOP assembly and related components of the top-drive unit;     (b) To provide a mud-saver valve that is automatically actuated by change of pressure within the drill string; and     (c) To provide a mud-saver valve that does not reduce the load-carrying capacity of the drill string.        
 
       SUMMARY OF THE INVENTION  
       [0022]     The mud-saver valve of the present invention comprises an independent means for blocking the flow of fluid through the inner bore of an IBOP, such as an IBOP attached to a top-drive unit. The mud-saver valve of the present invention generally comprises a tubular body having a central through-bore, a rotatable ball having a through-bore, and right and left rotating concave cup members. The ball is rotatably disposed within the through-bore of the body such that the ball may be rotated from an open to a closed position. When the ball is in the open position the through-bore of the ball is axially aligned with the through-bore of the body, thereby permitting the flow of fluid through the aligned bores of said ball and body. When the ball is in the closed position, the through-bore of the ball is oriented perpendicular to the through-bore of the body, thereby preventing fluid flow through the through-bore of such ball. When the ball is rotated, the mud-saver valve of the present invention operates much like existing ball valves or IBOP&#39;s which are generally known in the art.  
         [0023]     The rotating concave cup members of the present invention are rotatably disposed about the periphery of said ball valve. When the ball is in the open position, said concave cup members may be rotated from an open to a closed position along the outer surface of the ball, thereby obstructing and sealing the through-bore of said ball. Such concave cup members rotate in a manner similar to the closing of eyelids about an eyeball. In the closed position, such concave cup members block the flow of mud or other fluids through the body of the mud-saver valve regardless of the position of the ball. In the preferred embodiment, such concave rotating cup members are actuated by a spring-biased piston. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  depicts a side view of a typical prior art top drive unit comprising a pipe handler, an upper IBOP, a lower IBOP and a saver sub.  
         [0025]      FIG. 2  depicts a side cross-sectional view of the mud-saver valve assembly of the present invention.  
         [0026]      FIG. 2A  is a detail view of a portion of the side cross-sectional view of  FIG. 2 .  
         [0027]      FIG. 3A  is a side cross-sectional view of the mud-saver valve assembly with a ball in the open position, and bowl-shaped cups in the closed position.  
         [0028]      FIG. 3B  is a side cross-sectional view of the mud-saver valve assembly of the present invention with a ball in the open position, and bowl-shaped cups in the open position. 
     
    
     DETAILED DESCRIPTION OF INVENTION  
       [0029]      FIG. 1  shows a block sketch of a typical top drive unit  300  comprising, generally, top drive motor  310 , upper IBOP  320 , mud-saver sub  124  and pipe handler  330 . The positional relationship between top drive motor  310 , upper IBOP  320 , and pipe handler  330  is depicted. Note that these members, as well as tubular drill string  340 , are generic and are not specifically included in the present invention. Mud-saver valve  10 , and saver sub  124 , both of the present invention, are positioned between upper IBOP  320  and pipe handler  330 . As described previously, saver sub  124  must not extend below pipe handler  330 . Thus,  FIG. 1  illustrates the length restriction of the overall length of mud-saver  10  and saver sub  124  referenced previously.  
         [0030]      FIG. 2  depicts a side cross-sectional view of the preferred embodiment of mud-saver valve  10  of the present invention. Mud-saver valve  10  comprises a substantially cylindrical body  100  having a through-bore  166 , a ball  108  rotatably disposed within said body  100 , a seat  106 , and two stems  110  extending outward from the sides of ball  108 . Upper threaded member  168  is disposed at the top of body  100  to facilitate connection to other threaded components, such as an IBOP of a top drive unit. Ball  108  has through-bore  156  of approximately the same diameter as through-bore  166  of body  100 , and two parallel flat surfaces  158 . Flat surfaces  158  of ball  108  are parallel to the axis of through-bore  156  of ball  108 .  
         [0031]     Ball  108  is rotatably disposed within through-bore  166  of body  100 . In a first position, as depicted in  FIG.2 , through-bore  156  of ball  108  is axially aligned with through-bore  166  of body  100 . Stems  110  are rotatably and sealably disposed within body  100  and are retained by stem retainers  112 . Stem seal  146  is disposed on the outside diameter of each stem  110 . Stem  110 , stem retainer  112 , and stem seal  146 , as well as their relationship to ball  108 , are depicted in detail in  FIG. 2A .  
         [0032]     Referring back to  FIG.2 , boss  152  protrudes from the inner face of each stem  110  and mates in each flat surface  158  of ball  108 ; as such, rotation of stems  110  cause rotation of ball  108  between an open position and a closed position. The outer surface of stems  110  have hexagonal indentions  154  which may accept a standard wrench (not shown in  FIG. 2 ) to rotate stems  110  and thus, ball  108 .  
         [0033]     Seat  106  is disposed above ball  108  and is biased downward against the outer surface of ball  108  by wave spring  104 . Seat  106  has a concave surface  160  that sealingly engages against the outer surface of ball  108 . Spacer  102  is disposed between wave spring  104  and internal shoulder  164  of body  100 . As depicted in  FIG.2 , ball  108  remains in its open position, whereby through-bore  156  of ball  108  is axially aligned with through-bore  166  of body  100 . Right rotating cup member  115  (not depicted in  FIG. 2 ) and left rotating cup member  114  are rotatably disposed about the outer surface of ball  108 . Left rotating cup member  114  and right rotating cup member  115  are mirror images of one another.  
         [0034]     Actuating piston  116  is slidably disposed within through-bore  166  of body  100 , and translates axially within sleeve  120 . Piston seal  144  and lower piston seal  140  are disposed between the outer surface of actuating piston  116  and the inner surface of sleeve  120 . Upper sleeve seal  139  and lower sleeve seal  138  are disposed between the outer surface of sleeve  120  and inner surface of body  100 . Sleeve  120  is coaxial to body  100  and is prevented from movement by sleeve retaining pin  118 . Spring  122  biases actuating piston  116  upward toward ball  108 .  
         [0035]     Saver sub  124  is attached to the lower end of body  100 . Body  100  has lower threads  134  that engage upper threaded member  132  of saver sub  124 . Saver sub seal  136  is disposed between the outer surface of upper threaded member  132  of saver sub  124  and the inner surface of body  100 . Saver sub  124  has lower threads  130  that can engage an adjacent threaded component, such as a component of the drill string. In the event of a problem with lower threads  130 , saver sub  124  can be easily repaired or replaced without affecting the other components of mud-saver valve  10  of the present invention.  
         [0036]      FIG. 3A  and  FIG. 3B  depict cross-sectional views of certain components of mud-saver valve  10  of the present invention rotated 90° from the view depicted in  FIG. 2 . Rotating cup members  114  and  115  have a closed position shown in  FIG. 3A  and an open position shown in  FIG. 3B . Ball  108  is omitted from  FIG. 3A  to better show certain details of actuating piston  116  and rotating cup members  114  and  115 ; however, it is to be observed that mud-saver valve  10  of the present invention depicted in  FIG. 3A  contains ball  108 .  
         [0037]     Referring to  FIG. 3A , cup members  114  and  115  each have a concave shell member  222  and side members  220 . Each concave shell member  222  has a concave inner surface  224  and an outer surface  226 . Side members  220  of rotating cup members  114  and  115  are oriented parallel to flat surfaces  158  of ball  108  (best seen in  FIG. 2 ). Each side member  220  has an enlarged circular member  210  with a concentric through-hole  212 . A rounded lever  214  extends radially outward from each enlarged circular member  210 . Stems  110  of ball  108  are rotatably disposed within through-holes  212  of circular members  210 , allowing rotating cup members  114  and  115  to rotate independently about lateral stems  110 , and allowing concave shell members to rotate about the outer periphery of ball  108 . Although not depicted on  FIG. 3A , it is to be observed that such components also exist on the opposite side of mud-saver valve  10 , said components being obscured from view in  FIG. 3A .  
         [0038]     Application of downward vertical force to levers  214  will cause rotating cup members  114  and  115  to rotate to an open position, while upward vertical force applied to of levers  214  will cause rotating cup members  114  and  115  to rotate to a closed position. Lever  214  depicted in  FIG. 3A  is attached to left cup member  114 , while another such lever (not depicted in  FIG. 3A ) is attached to right cup member  115 .  
         [0039]     Spherical shell member  222  of each rotating cup member  114  and  115  has a forward sealing edge  230 . In a closed position, sealing edge  230  of right rotating cup member  115  bears against sealing edge  230  of left rotating cup member  114 . In the preferred embodiment, sealing edge  230  of left rotating cup member  114  has a circumferential recess  232  at outer spherical surface  226 . Sealing edge  230  of right rotating cup member  115  has a circumferential recess  228  at inner spherical surface  224 . In a closed position, sealing edge  230  of left rotating cup member  114  overlaps sealing edge  230  of right rotating cup  115 .  
         [0040]     Actuating piston  116  is sealably disposed within sleeve  120 . Actuating piston  116  has an upper piston seal  144  and a lower piston seal  140 . The outside diameter of upper piston seal  144  is larger than the outside diameter of lower piston seal  140 . As such, a cylindrical volume  240  is defined by the differential area between upper piston seal  144  and lower piston seal  140  and the axial length between upper piston seal  144  and lower piston seal  140 . Sleeve  120  has radial bore  242  disposed between upper sleeve seal  139  and lower sleeve seal  138 . Similarly, body  100  has radial bore  244 . In the preferred embodiment, cylindrical volume  240  between upper piston seal  144  and lower piston seal  140  communication with pressure observed outside of body  100 .  
         [0041]     Actuating piston  116  has a concave upper surface  248 . The radius of curvature of concave upper surface  248  is approximately equal to the radius of curvature of outer spherical surfaces  226  of rotating cup members  114  and  115 . Two elongated extension arms  218  extend upward from the upper surface of actuating piston  116  (although only one such extension arm  218  is visible in  FIG. 3A ). Each extension arm  218  has slot  216  to receive levers  214  of rotating cup members  114  and  115 , respectively. Actuating piston  116  has a first position, depicted in  FIG. 3A , wherein actuating piston  116  is in a fully upward position and rotating cup members  114  and  115  are in their closed position. Actuating piston  116  has a fully downward second position, depicted in  FIG. 3B , wherein rotating cup members  114  and  115  are in their closed position.  
         [0000]     Operation  
         [0042]     During drilling operations, fluid such as drilling mud is pumped through the bore of a top drive unit (including the mud-saver valve of the present invention) and drill string. Restriction to the flow of such fluid results in a higher pressure within the drill string and mud-saver valve  10  of the present invention compared to pressure observed on the outside of such components. When it is desired to disconnect or break-out a connection between components of the drill string at or near the rig floor, mud pumps are typically shut off, and pressure within the drill string and mud-saver valve  10  decreases to static head pressure; such static head pressure results from the vertical length of the fluid column within the drill string above the rig floor (i.e., the point where such drill string components are to be disconnected). On many rigs, this height may be 90 feet or more.  
         [0043]     As described previously, actuating piston  116  has a larger diameter at upper piston seal  144  than at lower piston seal  140 . Cylindrical volume  240  between upper piston seal  144  and lower piston seal  140  communicates with pressure observed outside body  100  via radial bore  244 . Actuating piston  116  is upwardly biased by spring  122 . When mud is being pumped, both the top and the bottom of actuating piston  116  are exposed to high internal pump pressure. As such, downward force is exerted by such internal pressure acting against the area of the larger upper piston seal  144 . A lesser upward force is exerted by the same internal pump pressure acting against the area of smaller lower piston seal  140 . The differential area between the larger upper piston seal  144  and the smaller lower piston seal  140  is acted upon by pressure communicated through radial hole  242  of sleeve  120  and radial hole  244  of body  100 . Spring  122  also exerts an upward force on actuating piston  116 .  
         [0044]     Compression spring  122  is designed such that internal pressure (such as, for example, internal pressure resulting from rig mud pumps) greater than a predetermined trip pressure overcomes the upward bias of spring  122 . Actuating piston  116  is held in a lower position, with extension arms  218  exerting downward force on levers  214  of rotating cup members  114  and  115 , thereby holding rotating cup members  114  and  115  in their open position.  
         [0045]     When such internal pressure drops, such as when rig mud pumps are shut off, pressure observed within mud-saver valve  10  drops below such predetermined trip pressure. Under this scenario, upward bias of spring  122  overcomes the net downward force of the internal pressure acting against the differential area between larger upper piston seal  144  and small lower piston seal  140 . Actuating piston  116  moves upward by the force exerted by spring  122 . As such, extension arms  218  exert upward force on levers  214  of rotating cup members  114  and  115 , thereby moving rotating cup members  114  and  115  into their closed Ooined) position.  
         [0046]     The net upward force applied to actuating piston  116  exerts upward force on lever  214  of rotating cup members  114  and  115 , causing sealing edges  230  of rotating cup members  114  and  115  to seal against each other. The net upward force of spring  122  also forces concave surface  248  of actuation piston  116  against outer surface  226  of shell members  222  of rotating cup members  114  and  115 , thereby creating a seal between rotating cup members  114  and  115  and actuating piston  116 . In the closed position, head pressure above mud-saver valve  10  is completely sealed, and fluid contained within the assembly is prevented from draining out of the assembly and on the rig floor or surrounding environment.  
         [0047]     The above disclosed invention has a number of particular features which should preferably be employed in combination, although each is useful separately without departure from the scope of the invention. While the preferred embodiment of the present invention is shown and described herein, it will be understood that the invention may be embodied otherwise than herein specifically illustrated or described, and that certain changes in form and arrangement of parts and the specific manner of practicing the invention may be made within the underlying idea or principles of the invention.