Abstract:
An internal blowout preventer used in drilling rigs for the discovery and production of hydrocarbons from the earth is disclosed. The internal blowout preventer has two independently and remotely operable blowout preventer valves in the same body, providing for greater service life and higher reliability during drilling operations. The two valves are loaded into the internal blowout preventer housing from a single end, and are operable by an actuator assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Application No. 61/312,786, filed Mar. 11, 2010, the entire contents of which are expressly incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This disclosure relates to the field of oilfield drilling equipment. In particular, this disclosure is drawn to an internal blowout preventer of a top drive system used in drilling rigs for the discovery and production of hydrocarbons from the earth. 
     2. Description of the Related Art 
     Internal blowout preventers (IBOPs) are valves designed to contain down-hole pressure and prevent blowouts in high pressure drilling applications. The IBOP includes a valve that can be closed in order to contain fluid from flowing out of the well. Regulations in some geo-political areas require two IBOPs (referred to as an upper IBOP and a lower IBOP) at the top of the well, for safety redundancy. Both the lower and the upper IBOP are tested periodically, such as weekly, to confirm that both valves hold a sufficient pressure without leaking. Other than this periodic testing, the lower IBOP valve is typically used only in the event of an emergency, such as a well blow-out. However, the upper IBOP valve is also used as a mud saver valve to contain hydrostatic or mud pump pressure from above. That is, each time a stand of pipe (typically three pipe segments threaded together) is added to the string and lowered into the wellbore, the upper IBOP is closed prior to disconnecting the top drive from the drill string, in order to contain the drilling fluid or mud flowing through the top drive. With the upper IBOP closed, the top drive is disconnected from the drill string and the entire assembly is raised to accept a new stand of pipe. Thus the upper IBOP valve may be cycled many times per day as a mud saver valve, in addition to weekly testing and emergency use. 
     Due to this repeated cycling, the upper IBOP valve tends to be high maintenance, and has been known to fail in the field due to the turbulent and corrosive flow of mud or drilling fluid through the valve. Additionally, as mentioned above, both the upper and lower IBOP valves are subject to periodic hydrostatic pressure testing, and a test failure requires immediate replacement of the valve, leading to lost drilling time. The upper IBOP valve in particular is subject to frequent repair or replacement. 
     A typical known IBOP assembly includes both a lower IBOP and an upper IBOP, each IBOP including a single blow-out preventer valve. The two IBOPs may be coupled together through multiple separate assemblies. In many cases, regulations require the redundancy of an upper and a lower IBOP, as a safety requirement. In use, the seals on these valves are subject to high strain and wear, causing frequent failure. Because a back-up valve is always required, if one of the valves fails (such as failing a weekly pressure test), the backup is then put in operation only until it is possible to shut down the drilling operation to repair or replace the first failed valve. When one of these valves fails, drill operations must be suspended while the entire IBOP unit is replaced or while repairs are performed. Neither of these options is particularly appealing, however, due to cost and loss of time on the drill site. Repair or replacement of an upper IBOP valve is a time consuming process. 
     IBOP valves are important parts of a top drive system which is used to drill for oil and gas. Known top drive systems typically have an upper IBOP valve and a lower IBOP valve, as regulations require, which become parts of the drill string during drilling. Each IBOP typically has only a single valve. IBOP valves are used as pressure control valves in case of a pressure kick from the well bore. The upper and lower IBOPs are typically used in tandem to provide the required safety redundancy, which necessarily involves numerous additional pipe connections and steps, and adds additional length in the assembly. The upper IBOP valve is remotely operated and is also used as a mud saver valve when a drill string connection is broken to add a new section of drill pipe. 
     BRIEF SUMMARY OF THE INVENTION 
     According to embodiments of the present invention, a dual upper IBOP valve is provided, having two valves, such as ball valves, within a single housing. This dual upper IBOP assembly provides a second redundancy in the system, by providing both a main upper IBOP valve and a back-up upper IBOP valve. An actuator sleeve is provided to operate crank mechanisms for each valve, to open or close the valve as necessary. A dual upper IBOP valve with a quick engagement crank mechanism allows the upper IBOP to continue to be used even after failure of the first upper IBOP valve, by switching to the second upper IBOP valve. A dual upper IBOP can improve the drilling situation considerably by allowing the rig crew to schedule repair work on the problematic valve to a convenient time, rather than needing an immediate emergency repair or replacement. 
     The dual upper IBOP valve disclosed herein is an improvement over the existing single upper IBOP valve and can be used as a direct replacement of either a single upper IBOP valve (which does not provide the second redundancy) or two single upper IBOP valves connected in series (which add considerable length and additional connections to the assembly). In case of a failure of the first upper IBOP valve, the second upper IBOP valve in the dual upper IBOP can be used, thereby saving valuable drilling time until a repair or replacement procedure can be scheduled. The dual valves can be operated such that only one of the two valves in the dual upper IBOP valve is functional at a time, and the other is set up as a back-up valve. The dual upper IBOP valve is a candidate to improve performance, efficiency, and reliability of top drive systems. 
     During drilling operations and under normal maintenance of equipment, it is a requirement that the upper and lower IBOP valves be periodically pressure tested to maintain credibility. If either IBOP fails the test, it is mandatory that a new valve be installed immediately, before drilling may resume, even if the other IBOP passes the test. This requirement is mandatory so that the system always operates with two fully functional valves, for safety redundancy. As the upper IBOP valve is used far more frequently than the lower IBOP valve, for mud saving, the upper IBOP valve is more likely to fail a pressure test due to repeated wear. Replacing or repairing an upper IBOP valve is very time consuming, and the valve test failure may occur at a critical time of the drilling program. With only a single upper IBOP valve, drilling must be stopped regardless of the timing so that the valve can be replaced. This situation may compromise safety to achieve the required results and may also incur considerable expenses and delay. With the use of a dual upper IBOP, this kind of an emergency will be, for the most part, eliminated, as the back-up upper IBOP valve may be used until a repair or replacement can be scheduled at a convenient and safe time. The system can continue to operate with the required safety redundancy, by operating with the back-up upper IBOP valve and the lower IBOP valve, until the main upper IBOP valve can be repaired. 
     In the above described situation, a top drive system equipped with a new dual upper IBOP valve with its unique design allows the drilling crew to quickly switch to the back-up upper IBOP valve and continue drilling. The switch to the backup upper IBOP valve is achieved by disengaging the faulty upper IBOP valve and engaging the back-up upper IBOP valve with minimal effort and time. This capability allows the replacement or repair of the dual upper IBOP valve to be scheduled and performed when convenient. 
     According to one embodiment of the invention, a dual internal blowout preventer for oilfield drilling operations includes two complete independent blowout preventer assemblies independently operable in a single housing. In one embodiment, at least one of the internal blowout preventer assemblies is adapted to be operated remotely. In one embodiment, both of the internal blowout preventers are adapted to be operated remotely. In one embodiment, a single-end loaded, dual ball, upper internal blowout valve is provided for drilling operations. A quick change crank mechanism is also provided for use with a single end loading, dual ball, upper internal blowout valve. 
     In one embodiment, an internal blowout preventer (IBOP) for use in drilling operations includes a housing having first and second openings at opposite first and second ends of the housing, and having a flow passage between the openings. The IBOP also includes first and second valves located in the flow passage in the housing. Each valve is movable between an open position in which the flow passage is open and a closed position in which the flow passage is closed. The IBOP also includes an actuator assembly coupled to the housing for independently operating the first or second valve. The first and second valves are received into the housing through the first opening. 
     In another embodiment, a top drive drilling system includes a top drive with an output shaft. The top drive is configured to rotate the output shaft. The system also includes a dual internal blowout preventer (IBOP) coupled to the output shaft of the top drive. The IBOP includes a housing having a mud flow passage, and first and second ball valves located in series in the mud flow passage. Each ball valve is rotatable between open and closed positions to open or close the mud flow passage. The IBOP also includes first and second internal crank mechanisms coupled to the respective first and second ball valves, an actuator coupled to the housing and movable with respect to the housing, and first and second external cranks coupled between the actuator and the respective first and second internal crank mechanisms. Movement of the first or second external crank by the actuator causes rotation of the respective first or second ball valve between the open and closed positions. 
     In another embodiment, a method for operating an internal blowout preventer in a top drive drilling system includes providing an internal blowout preventer with a housing having first and second openings at opposite first and second ends of the housing. The method includes loading first and second valves into the housing through the first opening, mounting an actuator sleeve to the housing and coupling the actuator sleeve to the first valve, configuring the actuator sleeve to operate the first valve, and translating the actuator sleeve to operate the first valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial section and schematic view of an arrangement of a drilling rig for drilling boreholes into the earth according to an embodiment of the invention. 
         FIG. 2  is a partial side and partial cross-sectional view of a top drive drilling system illustrating the arrangement of a dual upper internal blowout preventer, and its placement on the drilling rig, according to an embodiment of the invention. 
         FIG. 3  is another partial section view showing in greater detail the arrangement of selected components of the top drive drilling rig of  FIG. 2  and in particular one arrangement of the dual upper internal blowout preventer. 
         FIG. 4  is a partial cross-sectional view of a dual ball upper internal blowout preventer according to an embodiment of the invention. 
         FIG. 5  is cross-sectional view of a dual ball upper internal blowout preventer with a quick change crank mechanism in another embodiment of the invention. 
         FIG. 6  is a front view of a dual upper internal blowout preventer with actuator assembly, according to an embodiment of the invention. 
         FIG. 6A  is a front and side view of a plate for use with a dual upper internal blowout preventer, according to an embodiment of the invention. 
         FIG. 7  is an upper perspective view of a dual upper internal blowout preventer with actuator assembly, according to an embodiment of the invention. 
         FIG. 8  is an upper perspective view of a dual upper internal blowout preventer with actuator assembly, connected to a lower internal blowout preventer valve, according to an embodiment of the invention. 
         FIG. 9  is a partial side view of a dual upper internal blowout preventer with crank assembly, according to an embodiment of the invention. 
         FIG. 10  is an exploded cross-sectional view of a crank actuator assembly for a dual ball upper internal blowout preventer according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a drill string  2  suspended by a derrick  4  for drilling a borehole  6  into the earth for minerals exploration and recovery, and in particular the recovery of petroleum or natural gas. A bottom-hole assembly (BHA)  8  is located at the bottom of the borehole  6  and comprises a drill bit  10 . In directional drilling, the BHA  8  may have a downhole steerable drilling system  9 . 
     As the drill bit  10  rotates down hole, it cuts into the earth allowing the drill string  2  to advance, forming the borehole  6 . For the purpose of understanding how these systems may be operated, for the type of steerable drilling system  9  illustrated in  FIG. 1 , the drill bit  10  may be one of numerous types well known to those skilled in the oil and gas exploration business. This is just one of many types and configurations of bottom hole assemblies  8 , however, and is shown only for illustration. There are numerous downhole arrangements and rig and equipment configurations possible for use for drilling boreholes into the earth with top drive systems  12 , and the present disclosure is not limited to the particular configurations as detailed herein. 
       FIGS. 2 and 3  are side views of components of a drilling rig top drive system  12  according to an embodiment of the present invention. A dual ball upper internal blowout preventer (IBOP)  20  according to an embodiment of the present invention is mounted to the rig along with other components of the top drive drilling rig, including a yoke  17 , a pipe handler frame  15 , and a hydraulic cylinder  13  ( FIG. 2 ). The dual ball upper IBOP  20  includes two ball valves  22 ,  24  inside a single housing. The first upper IBOP valve  22  and the second upper IBOP valve  24  are both adapted for controlling well pressure and drilling mud flow.  FIG. 2  shows the relative location of the upper IBOP valves  22 ,  24  with respect to the other drilling rig components. A single valve lower IBOP  300  with single ball valve  301  is connected below the dual upper IBOP  20 . Below the lower IBOP  300  is a bell-mouth  302  which receives the top end of a pipe segment or pipe stand. 
     As shown in  FIG. 3 , the dual ball upper IBOP  20  is connected to the main output shaft  26  of the top drive system  12 , and is exemplary of one manner in which this dual ball upper IBOP  20  may be implemented on a drill rig with a top drive system  12 . In one embodiment the IBOP  20  is threaded directly to the output shaft  26 . The output shaft  26  is rotated by the top drive  12 . The dual ball upper IBOP  20  is not limited only to these types of drilling systems. The dual ball upper IBOP  20  with first and second valves  22 ,  24  is connected to the top drive system  12  and forms a part of the drill string, as indicated in  FIGS. 2 and 3 . 
     Turning to  FIG. 4 , a detailed view of a dual upper IBOP  20  is shown according to an embodiment of the invention. The dual upper IBOP  20  includes two separate valve assemblies  22 ,  24  and is referred to as a “dual” upper IBOP. The dual upper IBOP  20  includes a mud flow passage  28  through the center of the IBOP, along the central longitudinal axis of the IBOP. Each valve assembly  22 ,  24  can be rotated through  90  degrees to open or close the valve to allow or block mud flow through the IBOP  20 . The dual upper IBOP  20  may replace an existing single upper IBOP valve in a typical drill rig. Further details of the dual upper IBOP  20  are described below, including the arrangement of the valves  22 ,  24 , the actuating mechanism, the single-end loading capability, and the compact length. 
     In one embodiment, the dual upper IBOP valve assembly  20  consists of two substantially independent valve assemblies  22 ,  24  inside a single IBOP housing  23 . In one embodiment, the two IBOP valve assemblies  22 ,  24  each include a ball valve  30 ,  32 , and the IBOP may be referred to as a dual ball upper IBOP. In other embodiments, the valves  22 ,  24  could be plug valves or other suitable valves. The first valve  22  may be located at the top, above the second valve, and the second valve  24  may be located at the bottom, or vise versa. When the dual upper IBOP  20  is installed, one valve is identified as the primary valve, and the other valve as the back-up valve. Either valve may function as the primary valve. In one embodiment, the first valve  22  is the primary functioning IBOP valve, and the second valve  24  is the back-up IBOP valve. 
     As mentioned, the valves  22 ,  24  may be ball valves  30 ,  32 , as shown in  FIG. 4 . In one embodiment, each ball valve  30 ,  32  is similar to a ball valve in a single upper IBOP valve. In other embodiments, the valves  22 ,  24  may have other designs, depending on system requirements and interchangeability. In one embodiment, the dual upper IBOP assembly  20  occupies the same space in the drill string as an existing single upper IBOP valve. Thus, an existing drilling rig with a single upper IBOP valve can be retrofitted with a dual upper IBOP  20  by simply removing the single upper IBOP valve and replacing it with the dual upper IBOP  20 , without adding any additional length or width to the drill string. 
     The ball valves  30 ,  32  each include a generally spherical ball  36 ,  37 . Each ball is seated between a fixed seat  34 ,  35  and a floating seat  42 ,  43  with proper sealing arrangements. The fixed and floating seats provide arcuate surfaces that rest against the balls  36 ,  37  to trap the balls inside the IBOP housing  23 . The fixed seats  34 ,  35  are fixed to the IBOP housing  23  such as by threads or other mechanical fasteners. The floating seats  42 ,  43  are biased against other components to apply a force to the respective ball  36 ,  37  to hold the ball in place between the two seats. In one embodiment, one or more springs  38 , such as a wavy circular spring or other type of spring, urges against the floating seats  42 ,  43 , forcing the seat against the respective spherical ball  36 ,  37 . The spring and floating seat thereby urge the ball against the fixed seat  34 ,  35  on the other side of the ball. In the event that the ball valve is closed against pressure from the wellbore, the pressure from the wellbore lifts the ball  36 ,  37  from the respective fixed seat  34 ,  35  and presses the ball against the respective floating seat  42 ,  43 . The contact of the ball against the arcuate surface of the floating seat creates a pressure seal along the contact area between the ball and the floating seat, to contain pressure from the well. In the event of pressure from above, such as the comparatively low pressure from the mud pump, the floating seat  42 ,  43  urges the ball  36 ,  37  against the fixed seat  34 ,  35  below the ball to create a positive seal. 
     A mud flow passage  28  through the center of the IBOP continues through the ball and seat components. Each ball  36 ,  37  includes a bore  40  through the ball, and the bore can be aligned with the mud flow passage  28  through the IBOP to allow mud flow. The ball can be rotated through 90 degrees to move a solid side of the ball into the mud flow passage  28 , blocking further passage of mud or other fluid through the IBOP  20  (shown in  FIG. 5 ). 
     Each ball  36 ,  37  is connected to two internal crank assemblies, one on each side of the ball, identified as  41 A and  41 B respectively. It should be noted that in other embodiments, each ball may be connected to only one crank assembly. These internal crank assemblies  41 A,  41 B are located within the housing  23 . Each assembly  41 A,  41 B includes an internal crank  51  connected to a universal coupling  53 . The coupling  53  fits into a slot in the side of each ball. Each crank  51  has a hexagonal opening  50  on the outer side, facing away from the ball, for engagement with an external crank assembly which is used to rotate the ball between open and closed positions, as described in more detail below. In other embodiments, the opening  50  can take other suitable shapes other than hexagonal, such as the shape of a square, triangle, or star. 
     As mentioned above, in one embodiment, the dual upper IBOP  20  includes two valves  22 ,  24  inside a single housing  23 . The single housing  23  reduces the number of external connections or couplings that would otherwise be needed to connect two separate valve assemblies together. The housing  23  includes an upper end  46  and a lower end  47 . The upper end  47  is toward the top drive system  12 , and the lower end  47  is toward the borehole  6 . 
     Both valve assemblies  22 ,  24  (including the valve and associated seats, springs, seals, and other components) can be loaded into the housing  23  from the same end, in one embodiment the upper end  46 . That is, the dual upper IBOP valve assembly  20  has the capability of being assembled from one end of the housing  23 , and as such be characterized as a “single end loading” dual upper IBOP valve. This capability is shown in  FIG. 4 , where both valves  22 ,  24  are loaded into the housing  23  through the upper end  46 . The upper and lower ends  46 ,  47  each have an opening  46 A,  47 A that communicates with the mud flow passage  28  through the IBOP. Each opening may have internal threads  46 B,  47 B. The opening  46 A and the mud flow passage  28  through the upper end  46  are wide enough in diameter to receive the valves  22 ,  24 . The valve  24  can be received into the IBOP housing  23  through the opening  46 A, arranged between seats  35  and  43 , and subsequently the other valve  22  can be loaded into the IBOP and seated above the lower valve  24 . A retainer ring  71  is provided above the valve  22 , capturing the spring  38  between the ring  71  and the floating seat  42 . The diameter of the opening  46 A is selected to be wide enough to receive these valves and seats and corresponding components into the housing  23 . It should be noted that the IBOP can be designed to provide single-end loading from either the upper end  46  or the lower end  47 . The embodiment of  FIG. 4  provides loading from the upper end  46 . In either case, the two valves are both loaded from the same end, and are functionally configured in the same way (as described in more detail below). 
     Due to the single end loading capability, the opening  47 A at the lower end  47  of the IBOP is not limited by the size of the valves  22 ,  24 . Because both valves  22 ,  24  are inserted through the opening  46 A at the upper end, the diameter of the opening  47 A at the lower end is not constrained by a minimum size to receive the valves. Instead, the diameter of the lower opening  47 A is free to be smaller than the valves  22 ,  24 . This freedom of design allows the lower opening  47 A to be sized for a desired component below the IBOP  20 . For example, in one embodiment, a lower single IBOP assembly  300  (shown in  FIG. 8 ) may be attached to the lower end  47  of the dual upper IBOP  20 , between the IBOP  20  and the drill string. The lower IBOP valve  300  provides the required regulatory redundancy for safety. In one scenario, the lower IBOP  300  may be smaller in diameter than the dual upper IBOP  20  and may be sized to fit within the drill string or casing string in the wellbore, so that it can be detached from the upper IBOP  20  and deployed into the wellbore as needed. The single-end loading capability of the upper IBOP  20  enables this flexibility in sizing of the lower IBOP  300 . 
     The single-end loading capability of the dual upper IBOP  20  also provides flexibility with other design features at the lower end  47  of the IBOP. For example, in the embodiment shown in  FIG. 4 , an internal shoulder or step  64  is provided between the threads  47 B and the second valve  24 . The lower fixed seat  35  rests against this step  64 . The diameter of the opening through the step  64  may be smaller than the diameter of the valves  22 ,  24  and the opening  46 A. 
     The single-end loading capability of the IBOP  20  also enables the two ball valves  30 ,  32  to have the same configuration with respect to the borehole. Each ball valve  30 ,  32  includes a ball  36 ,  37  trapped between two seats, as described above. When the valve is assembled, the fixed seat  34 ,  35  is inserted first, followed by the ball  36 ,  37 , followed by the floating seat  42 ,  43 . Thus, the floating seat is oriented toward the opening through which the valve was inserted, between that opening and the ball. If the two valves  30 ,  32  were inserted through different openings, for example the upper valve through an upper opening and the lower valve through a lower opening, then the two floating seats would face away from each other, toward the respective openings, and the two fixed seats would face toward each other. Such a configuration would result in one valve having a fixed seat toward the wellbore, and the other valve having a floating seat toward the wellbore. 
     By contrast, valves  30 ,  32  of the single-end loading IBOP  20  in  FIG. 4  are both inserted through the upper opening  46 A, and therefore both floating seats are toward the top, and both fixed seats toward the bottom. Both valves  30 ,  32  have the same orientation with respect to the borehole. In  FIG. 4 , both valves  30 ,  32  include a fixed seat toward the borehole (toward the lower end  47  of the IBOP) and a floating seat toward the top drive (toward the upper end  46  of the IBOP). If the valve is needed to control a pressure kick, the pressure will originate from the borehole side, lifting the ball  36 ,  37  off of the fixed seat  34 ,  35  and pressing it against the floating seat  42 ,  43 . In both cases, the ball is pressed against its respective floating seat, since both floating seats are toward the top end  46 . Therefore, the single-end loading capability of the IBOP  20  enables both of the dual valves  22 ,  24  to have the same configuration (the orientation of the fixed and floating seats) with respect to the high-pressure side, which simplifies design and testing of the valves. 
     In one embodiment, the single-end loaded dual upper IBOP  20  includes nesting components, which reduce the overall length of the IBOP  20 . For example, as shown in  FIG. 4 , the floating seat  43  for the valve  24  and the fixed seat  34  for the valve  22  are nested, with the seats overlapping each other as noted at area A. The seats  43 ,  34  each have a stepped shape, with the floating seat  43  fitting within the fixed seat  34 . The spring  38  is placed between the two seats, to urge the floating seat  43  toward the lower ball  37 . This nested, overlapping configuration reduces the overall axial length of the IBOP  20 . Because both valves  22 ,  24  are loaded into the housing  23  from the same opening, the seats  43 ,  34  of the two valves can be configured to nest together. Similarly, the upper floating seat  42  and the retainer ring  71  have a nested configuration, overlapping as noted at area B. In one embodiment, the overall length of the IBOP  20  as shown in  FIG. 4  is about 24-30 inches. 
     The upper end  46  of the IBOP  20  includes internal threads  46 B, which in one embodiment are configured to mate with the output shaft  26  of the top drive  12 . The lower end  47  includes internal threads  47 B, which in one embodiment are configured to mate with the drill string, or with a lower IBOP valve such as the lower single IBOP  300  ( FIG. 8 ). 
     Another embodiment of a dual upper IBOP  20 ′ is shown in  FIG. 5 . The IBOP  20 ′ includes two valves  22 ,  24  within a single housing  23 . In the embodiment shown, the valves  22 ,  24  are ball valves. The first valve  22  is shown in the open position, while the second valve  24  is closed. The closed valve  24  has been rotated to move a solid side of the ball  37 A into the mud flow path  28 , blocking the path. Each valve can be rotated through 90 degrees between the open and closed positions.  FIG. 5  also shows an external actuator assembly  166  that is used to operate the valves, to open or close them. As shown in  FIG. 5 , the actuator assembly  166  includes an actuator shell or sleeve  68  mounted around the housing  23 , externally of the two valves  22 ,  24 , and two external crank assemblies  44 A,  44 B (one on the left side of the figure and one on the right) associated with each valve. The external crank assemblies  44 A,  44 B for each valve are coupled on one end to the respective internal crank assembly  41 A,  41 B and at the other end to the actuator sleeve  68 . The actuator sleeve  68  moves up and down with respect to the housing  23 , to operate the crank assemblies to rotate the valves between the open and closed positions. This is just one of many types and configurations of actuators, however, and other arrangements and configurations of actuators may be used with the dual upper IBOP. Further details of the actuator assembly are described below. 
       FIGS. 6-7  show a dual upper IBOP  20 ″ with an actuator assembly  66 , according to an embodiment of the invention. The actuator assembly  66  is used to operate the valves  22 ,  24  within the dual upper IBOP  20 ″. Both valves can be operated by a single actuator assembly. The actuator assembly  66  controls both valves. Because the IBOP  20 ″ is a dual valve assembly with two valves, rather than a single IBOP with only one valve, the actuator assembly  66  is used to perform two functions—to hold one of the two valves in a fixed (typically open) position, and to operate the other valve to open or close it. For example, the first valve  22  may be acting as the primary valve, and the second valve  24  may be the back-up valve. Initially, the actuator assembly holds both valves open, allowing mud or other fluid flow through the IBOP. In the event of a pressure kick, a test event, or a mud-saver function, the actuator assembly  66  can be operated to close the first (primary) valve while continuing to hold the second valve open. Thus the actuator assembly  66  is designed to operate either valve while maintaining the other valve locked in the open position. In an emergency event, both valves can be closed. 
     As shown in  FIG. 6 , the actuator assembly  66  includes an actuator sleeve  68  that is mounted externally of the IBOP housing  23  and that is slidable with respect to the housing  23 . To operate the valves, the actuator sleeve  68  engages four external cranks  54 A,  54 B,  55 A,  55 B coupled to the two valves  22 ,  24 , respectively. Two of the cranks  54 A and  55 A are visible from the view in  FIG. 6 , and the other two are on the opposite side of the dual upper IBOP  20 ″. The description below refers to the visible cranks  54 A and  55 A in  FIG. 6 , and it should be understood that the same operations are taking place on the opposite side with cranks  54 B and  55 B. 
     When the sleeve  68  is translated between the upper and lower ends of the IBOP  20 ″, the sleeve rotates one of the two cranks  54 A,  55 A to open or close one of the valves, while retaining the other crank in a fixed position. The cranks  54 A,  55 A are shown in  FIG. 6  with their arms  57  pointed downwardly and to the right (in the orientation of the figure). In this position, both valves  22 ,  24  are open. To close one of the valves, the crank is rotated through 90 degrees in the counter-clockwise direction, until the crank arm is pointed upwardly and to the right. 
     The cranks  54 A,  55 A extend externally of the housing  23  to engage the actuator sleeve  68 . The cranks  54 A,  55 A include a projection such as an internal arm  59  (shown in  FIG. 5 ) that engages the hexagonal hole  50  of the internal crank assemblies  41 A,  41 B (shown in  FIG. 4 ). As a result, rotation of the external cranks  54 A,  55 A is transmitted to the internal crank assemblies  41 A,  41 B. The internal crank assemblies  41 A,  41 B fit into a slot in the outer surface of the balls, as described above, and thus rotation of the internal cranks causes a corresponding rotation of the balls, thus rotating the balls into the open or closed position. The external cranks  54 A,  55 A pass through a slot  73  in the actuator sleeve  68  to engage the valves  22 ,  24 . 
     The actuator assembly  66  is configured to operate the first, primary valve between the open and closed positions while maintaining the second, back-up valve in the open position. To rotate one crank but not both cranks, the actuator sleeve  68  is provided with a plate  70  bolted to the sleeve. The plate includes a recess  72  that receives an end of the arm  57  of the first crank  54 A, and a stop or wall  74  that contacts an end of the arm  57  of the second crank  55 A. When the actuator sleeve  68  is moved toward the upper end  46  of the IBOP, the plate  70  moves with the sleeve, and the wall  74  slides along the second crank  55 A, preventing the arm  57  of the crank from rotating counter-clockwise. The wall  74  thus prevents the crank  55 A from rotating the second valve  24  into the closed position. The wall  74  retains the second valve  24  in the open position. At the same time, as the sleeve  68  and plate  70  move upwardly, the recess  72  and its side edges or arms  72 A engage the arm of the first crank  54 A and rotate it counter-clockwise. The recess  72  is deep enough to allow the crank to rotate through its arc. This in turn rotates the first valve  22  into the closed position. Thus, the first valve is closed while the second valve is held open. The sleeve  68  can be translated back down toward the second end  47  to open the first valve, while still holding the second valve open. 
     The plate  70  can be removed from the sleeve  68  by removing the screws  75 . With the plate removed, either crank  54 A,  55 A can be rotated to the desired position, opening or closing the valves  22 ,  24 . When the cranks and valves are in the desired position, the plate  70  is replaced. The plate can be attached to the sleeve  68  in either of two orientations—with the recess  72  engaging the upper crank  54 A or engaging the lower crank  55 A. Thus, the plate  70  can operate either crank while holding the other crank in a fixed position, and the fixed position can be chosen to be either open or closed. Typically the fixed position will be open so that the back-up valve is held open while the primary valve is operated. 
     The actuator sleeve  68  includes a groove or channel  76 , which can be located at any convenient position along the sleeve. The groove  76  could alternatively be provided as a space between two rims or flanges  78 . The groove  76  receives a yoke  17  (see  FIG. 9 ) which is in turn connected to a hydraulic cylinder or other actuator. The cylinder and yoke move the sleeve  68  up and down with respect to the housing  23 , to operate the crank that is engaged with the recess  72 . The groove  76  and yoke  17  are provided to accommodate the rotation of the IBOP  20 ″, as the IBOP is rotated along with the top drive output shaft  26  and the drill string. The yoke  17  does not rotate with the IBOP. The groove  76  and rims  78  allow translational force from the yoke  17  to be transmitted to the sleeve  68  while isolating the yoke  17  from rotation of the IBOP. The cylinder can be controlled remotely, such that operation of the cylinder, actuator sleeve, and valves can be controlled from a remote location. A controller may be provided to send signals between a remote control station and the cylinder. 
     As an alternative to the two cranks  54 A and  55 A shown in  FIG. 6 , the non-operational crank (the crank held in a fixed position by the wall  74 ) can be replaced by a plate such as the plate  81  shown in  FIG. 6A . The plate  81  includes a protrusion such as a male hexagonal arm  83  that engages the female hexagonal (or other shaped) hole  50  in the internal crank assembly of one of the two valves (see  FIG. 4 ). The plate  81  is bolted to the housing  23  with the male hexagonal arm  83  engaging the female hexagonal hole  50 , to fix the position of the valve and prevent the valve from rotating. The actuator  66  can be used to operate the other crank, to rotate the other valve between the open and closed positions. The plate  81  provides a secure way to fix the position of the back-up valve, such as to lock it into the open position. In this instance, the wall or stop  74  is not needed, as the plate  81  replaces the non-operating crank  55 A. To operate the back-up valve, the plate  81  is removed and replaced with the crank (such as crank  55 A), which can then be operated by the actuator sleeve  68  to rotate the valve. 
     The IBOP  20 ″ with actuator assembly  66  is also shown in  FIG. 7 . This figure shows the dual crank assemblies provided on each side of the IBOP, and indicates the location of the four cranks  54 A,B and  55 A,B. In this embodiment, each valve includes two crank mechanisms, one on each side of the valve. Also shown in  FIG. 7  is a cover plate  80  attached to the sleeve  68  to cover the cranks, the plate  70 , and the screws  75 . This cover plate  80  is provided to protect these components and to prevent loose components from falling to the rig floor. The cover plate  80  may include one or more windows  82  to view the position of the cranks. 
       FIG. 8  shows a dual upper IBOP  200  with actuator assembly  66 . The actuator assembly is shown with the recess  72  of the plate  70  engaging the lower crank  55 A. The dual upper IBOP  200  is attached at its lower end to a single lower IBOP valve  300 , which is provided as required by regulation. The single lower IBOP  300  may be attached to the dual upper IBOP  200  via the lower threads  47 B (see  FIG. 4 ). Optionally, clamps such as the clamps  84  shown in  FIG. 8  may also be provided to secure the connection between the IBOPs  200 ,  300 . 
     Another embodiment of an actuator assembly  66 ′ is shown in  FIG. 9 . In this case, the cranks  54 A,  55 A for the upper and lower valves are offset about the circumference of the IBOP. Two separate plates  70  are provided, one to engage each crank. Each plate  70  includes one side with a wall  74  and an opposite side with a recess  72 . The plate can be removed and reversed to place either the wall or the recess in engagement with the crank. The crank can be positioned in the desired position to open or close the respective valve, and the plate can then be used to either operate the crank or to retain the crank in the desired position. In  FIG. 9 , the recess  72  engages the upper crank  54 A, which is currently in the open position (pointed down), and the wall  74  engages the lower crank  55 A, which is also in the open position (pointed down).  FIG. 9  also shows the yoke  17  with two rollers  19  that fit into the groove  76  to transmit translational movement from the yoke  17  to the sleeve  68  while the sleeve  68  is rotating. 
     Another embodiment of an actuator assembly  166  is shown in  FIG. 10 . This actuator assembly includes a sleeve  68 , internal crank mechanisms  41 A,  41 B, external crank assemblies  44 A,  44 B, and external cranks  54 ,  55  (only one of which,  55 B, is shown in the figure). The external crank  55 B is coupled to the other crank assemblies through several components, and an exploded view is shown in  FIG. 10 . In this embodiment, the engagement of the sleeve  68  and the cranks  54 ,  55  utilizes a rotation of a shaft  60  to rotate each valve  22 ,  24 . 
     Referring now to  FIG. 10 , disclosed, and externally mounted on the housing  23 , are four crank housing actuator assemblies shown generally as  44 A and  44 B (a pair for each valve  22 ,  24 ). Each assembly engages an internal assembly  41 A,  41 B, which includes a crank  51  that is attached to each ball. Each crank  51  engages the ball  36  such that rotation of the crank  51  causes rotation of the ball. Each crank  51  has a hexagonal hole  50  facing outwardly, away from the ball. The external crank assembly  44 A,  44 B includes a hexagonal shaft end  48  that mates with the hexagonal holes  50 . The mating hexagonal shape of the shaft end  48  and the hole  50  causes rotation of the shaft end  48  to be transmitted to the crank  51 , and thereby to the ball. The shaft end  48  is rotated by movement of the shell  68  and crank  54 , as described further below. 
     The vertical motion of the actuator shell  68  is integrated with cam rollers  52 A sliding in a horizontal slot  52 B. Movement of the shell  68  thus causes an angular movement of the crank  55 B. This movement in turn rotates the shaft  60  and the shaft end  48 , causing a rotation of the crank  51  and the attached ball. Thus the angular motion of the crank arm assemblies rotates the balls  36 ,  37  to open and close the valves. The rotation of the crank  55 B of the crank assembly  44 B is passed through a first threaded sleeve  56  through a hex drive  58  and threaded shaft  60 , which then passes through a threaded sleeve  62  to engage the crank assembly  44 B and thus the crank  51  and ball  37 . 
     This crank system assembly ( 44 B,  48 ,  62 ,  60 ,  58 ,  56 ,  52 A,  52 B,  55 B) is installed over the dual ball upper IBOP valve assembly. An actuator arm assembly such as a yoke shaped arm is provided with two cam rollers that fit into a groove in the actuator sleeve  68 , to transmit motion to the sleeve  68  (see  FIG. 9 ). A hydraulic cylinder may be mounted on the rig, for example on a pipe handler frame (see  FIG. 2 ), through a linkage to slide the actuator sleeve vertically up and down. The crank arm assemblies with the cam rollers are captured by a retainer on the crank housing assemblies preventing them from sliding out but allow them the freedom to rotate. The vertical motion of the actuator shell with the crank arm assembly cam rollers sliding horizontally in the slots generates a circular motion applying a torque to rotate the ball valve through 90 degrees either clockwise or counterclockwise directions, to open and close the valve as desired. 
     The actuator assembly  166  may be used to operate one valve while retaining the other valve open or closed. As described above, the shaft  60 , sleeve  62 , and end  48  can be connected to the hexagonal hole  50  to transmit rotation from the crank  55 B to the ball  37 . However, these components can be disengaged such that movement of the actuator sleeve  68  and rotation of the crank  55 B does not operate the valve, thus allowing the sleeve  68  to move without actuating the back-up valve. The assembly includes the threaded adjustment sleeve  62  running over the threaded drive shaft  60 . A hexagon drive on the end of the drive shaft would screw the threaded adjustment sleeve  62  in and out clockwise and counterclockwise, engaging and disengaging the crank assemblies  44 A,  44 B of the first and second valves, respectively. The engaged first valve becomes the functional valve and the disengaged second valve becomes the nonfunctional, back-up valve which is maintained open. The threaded adjustment sleeves  62  are automatically locked in that position against the hexagonal hole in the crank housing assembly. 
     The threaded adjustment sleeves  62  would have two distinct positions—either screwed in clockwise to a stop to engage or screwed out counter clockwise to a stop to disengage the cranks  44 A,  44 B. The crank that is engaged with the respective crank arm assembly would then either open or close the respective ball valve. The crank arm assembly of the disengaged and locked second valve would continue to go through their angular motions freely similar to the crank arm assemblies of the engaged and operating first valve. However, the disengaged feature of the threaded adjustment sleeves would keep the ball valve from operating and the locked feature would keep the ball valve from accidentally closing. Nylon inserts (not shown) in the threaded adjustment sleeves may provide sufficient friction to prevent inadvertent rotation of the ball when they are in their home positions. 
     It would be apparent to those skilled in the art that many modifications of the dual upper IBOP valve assembly  20  disclosed herein are possible without departing from the teachings of the present invention. For example, alternate components which are equivalent to components already described herein may be used. In addition it may be desirable to modify the disclosed valve assembly so it may have a different number of crank housing assemblies, each connected to an actuator shell and an actuator arm assembly. 
     A method of assembling and disassembling a dual upper IBOP is provided according to another embodiment of the invention. To assemble the valves, break-out the existing single upper IBOP valve from the drill string (as done routinely) and install a new dual upper IBOP valve assembly with the new actuator shell  68 . The new dual upper IBOP is installed by engaging the upper and lower threads  46 B,  47 B with the drill string or top drive and/or by clamping the IBOP to the components of the drill string. Once the dual upper IBOP is installed, the actuator shell  68  is positioned over the dual upper IBOP valve assembly in the neutral position so that the horizontal slots for the crank assemblies are lined up with the center of each valve. 
     Attention must be paid to match the orientation of the hexagonal holes ( 50 ) in the internal cranks with the hexagonal shafts ( 48 ) in the crank housing assemblies. Next, the four crank housing sub-assemblies are installed and secured. One of the two valves is identified as the operational valve and the other valve as the back-up. For actuator assembly  166 , the two threaded adjustment sleeves for the operational valve are screwed in clockwise to their stops. The other two threaded adjustment sleeves, for the non-operational back-up valve, are retracted counter-clockwise to their stops. For actuator assembly  66 , the plates  70  are attached with the recess  72  engaging the crank of the operational valve, and the wall  74  engaging the crank of the non-operational valve (or the plate  81  may be used). 
     When switching from the first valve to the second valve, to reverse functions of the two IBOP valves and utilize the back-up valve, the positions of the threaded adjustment sleeves or plates are reversed. 
     In one embodiment, a method for operating an internal blowout preventer in a top drive drilling system includes providing an internal blowout preventer with a housing having first and second openings at opposite first and second ends of the housing, and loading first and second valves into the housing through the first opening. The actuator sleeve is then attached to the housing and coupled the actuator sleeve to the first and second valves. The method also includes configuring the actuator sleeve to operate the first valve, and configuring the actuator sleeve to maintain the second valve in a fixed position, such as the open position. The actuator sleeve can then be translated along the housing to operate the first valve. 
     The present invention has been described in particular relation to the drawings attached hereto, and it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.