Abstract:
A connection for oilfield use is disclosed. It features male and female components held together by dogs actuable through one of the members and into the other. Different configurations of the connections envision a built-in preload to the connection when made-up. This is accomplished by a cantilevered component at the extremity of one of the components of the connection. Alternatively, the preload feature can be incorporated into the dog or other locking assembly that holds the components of the connection together. The connection is particularly useful in subsea chokes which have a removable insert which can be mounted to or removed from the choke body which is located subsea.

Description:
FIELD OF THE INVENTION  
         [0001]    The field of this invention relates to connectors which hold two components together with a preload and more particularly a subsea choke using such a connection for a removable insert.  
         BACKGROUND OF THE INVENTION  
         [0002]    Oilfield applications involve high pressures as well as fluctuating flows and pressures. Thus, when connections need to be made, they need to be able to withstand a variety of different conditions. In the past, various designs incorporating preload into connections have been used. Generally speaking, these connections would involve a tapered ring powered by a hydraulic cylinder or cylinders which would be pulled down on collets having a tapered exterior so as to force the collets against the two pieces being joined. The two pieces would have flanges which would be held together by an internal groove in the collets. Typical of such designs are the model 70 and the high-capacity (HC) collet connectors offered by Cooper Cameron. The high-capacity connector would allow for a preload of 7 million lbs. for 18¾″ connections having a 15,000 psi working pressure. One of the drawbacks of such connectors is that they are expensive to construct and their large size makes their assembly in the field more cumbersome. Additionally, such designs require the use of tapered locking surfaces which depend on friction to remain locked. Lubricating components which can appear on the taper of the lock ring or on the outer surface of the collet segments can act to undermine the connection, causing a potential for leakage.  
           [0003]    Other designs involving preload in a connection in oilfield use are illustrated in U.S. Pat. Nos. 5,066,048 and 5,247,996. Other connections for subsea use involving the use of dogs in grooves are shown in U.S. Pat. Nos. 5,273,117; 5,163,514; and 4,712,621.  
           [0004]    Subsea chokes have been designed with retrievable inserts. The choke body is generally mounted to the Christmas tree or manifold and the insert is a unitized trim cartridge and actuator assembly which can be retrieved to the surface, leaving the choke body subsea. A crown-type connector has been used in such subsea chokes. This design involves a single-piece cylindrical collet with slots machined to form locking fingers. The insert would be pushed into a receptacle and the collet fingers would then move outwardly into an internal groove in the choke body. The operating principle for obtaining the preload in these subsea chokes was similar to the principles relied upon in U.S. Pat. No. 5,066,048. However, the drawback of this design for a retrievable subsea choke was that it was very expensive to manufacture and its large size made it difficult to manipulate it into position in the choke body which remained subsea.  
           [0005]    What is desirable is a connection which could provide the requisite preload in subsea choke while being small and cheaper to manufacture. The preload requirement functionally eliminated in the past the use of dog-in-window or groove-type designs, split rings or other types of connectors that didn&#39;t have a tapered fit between a locking piston and a locking element.  
           [0006]    What was desired and is an objective of the present invention is to provide a simple connection which can give the necessary amount of preload, while combining that design into a compact assembly which would significantly reduce costs compared to previous designs and greatly facilitate installation. Thus, the compactness of the design becomes significant in some instances where room for the connector and actuator for a removable choke insert assembly is in limited supply. Additionally, a more lightweight connector can be more easily manipulated subsea for connection or removal. Another objective was to mount the moving components of the connection on the actuator assembly so that such components do not remain subsea when the connection is undone and the choke insert is removed. While the various configurations of connections are illustrated in this application specifically for a choke with a removable insert, those skilled in the art will appreciate that the objective of the present invention is to provide a connection which can be used in well operations or other applications in the oil and gas industry. Those and other objectives of the present invention will become apparent to those skilled in the art from a review of the description of the preferred embodiment below.  
         SUMMARY OF THE INVENTION  
         [0007]    A connection for oilfield use is disclosed. It features male and female components held together by dogs actuable through one of the members and into the other. Different configurations of the connections envision a built-in preload to the connection when made-up. This is accomplished by a cantilevered component at the extremity of one of the components of the connection. Alternatively, the preload feature can be incorporated into the dog or other locking assembly that holds the components of the connection together. The connection is particularly useful in subsea chokes which have a removable insert which can be fixedly or removably mounted to the choke body which is located subsea.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a sectional elevational view of one form of the connection in assembled form.  
         [0009]    [0009]FIG. 2 is a sectional elevational view of another form of the connection, illustrating an embodiment with the dog mechanism removable with the actuator.  
         [0010]    [0010]FIG. 3 is a sectional elevational view of an alternative embodiment illustrating the preload feature in the dogs in the run-in position.  
         [0011]    [0011]FIG. 4 shows the view of FIG. 3 with the dogs aligned with opposing grooves.  
         [0012]    [0012]FIG. 5 is the view of FIG. 4 with the dogs cammed into the opposing grooves to complete the joint.  
         [0013]    [0013]FIG. 6 is a plan view of the dog-actuating mechanism of FIGS.  1  or  2  with the dogs retracted.  
         [0014]    [0014]FIG. 7 is the view of FIG. 6 with the dogs extended for securing the connection.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    Referring to FIG. 1, a choke body  10  which is usable in subsea applications is illustrated. The choke body  10  accepts an insert  12 . Inside of insert  12  is bore  14  which communicates through openings  16  to the inlet  18  of the choke body  10 . Bore  14  communicates to outlet  20  of the choke body  10 . An actuator  22  moves plug  24  between the two positions shown in the split view of FIG. 1. In the upper position, the openings  16  are exposed, allowing the choke to operate to reduce pressure between inlet  18  and outlet  20 . In the lower position shown at the top of FIG. 1, the plug  24  covers the opening  16  and there is no flow from inlet  18  to outlet  20  in the choke body  10 .  
         [0016]    In the embodiment of FIG. 1, the choke body  10  further comprises a dog-operating mechanism  26 , which is also shown in FIGS. 6 and 7. A series of dogs  28  extend through openings in a sleeve  30  and are retained by a tab  32  to keep them from being pushed all the way in through sleeve  30 . A cam  34  has teeth  36  which mesh with teeth  38  which are, in turn, rotatable by rotation of shaft  40 . Shaft  40  is configured so that it can be gripped by a remotely operated vehicle (ROV) for actuation subsea. Those skilled in the art will appreciate that rotation of shaft  40  rotates cam  34  from the position shown in FIG. 6 to the position shown in FIG. 7 and vice versa. By virtue of profiles  42 , the dogs  28  are pushed inwardly, as shown in FIG. 7, or allowed to be pushed back to the position shown in FIG. 6 for disconnection of the connection C.  
         [0017]    The connection C as shown in FIG. 1 has a male component  44  which is insertable into female component  46 . Male component  44  has a tapered or sloping shoulder  48 . Dogs  28  have a sloping shoulder  50  matching the orientation of shoulder  48 . FIG. 1 shows the male component  44  fully inserted into the female component  46 , with the dogs  28  extended so that sloping shoulders  48  and  50  are in contact. The female component  46  has an internal shoulder  52 . The male component  44  has a cantilevered component  54 , shown schematically in FIG. 1. In actuality, the cantilevered component  54  bottoms on internal shoulder  52 . The cantilevered component extends obliquely with respect to the longitudinal axis  56  of the choke body  10 . In the preferred embodiment, the orientation of the cantilevered component  54  is within a range of substantially perpendicular to axis  56  to an offset of approximately 75° from axis  56 . The cantilevered component has the appearance of a U-shape in cross-section as shown in FIG. 1. When the male component  44  is fully inserted into the female component  46  and the dogs  28  are extended, the cantilevered component  54  bottoms on shoulder  52 , thus bringing it closer to or even in contact with surface  58  under certain conditions. Those skilled in the art will appreciate that the cantilevered component  54 , when bottomed on shoulder  52 , gives preload to the connection C. Thus, uncertainties about the amount of extension radially toward axis  56  of dogs  28  becomes irrelevant since sufficient extension of dogs  28  radially inwardly towards axis  56  will cause the sloping shoulders  48  and  50  to contact sufficiently to force the cantilevered component  54  against the internal shoulder  52 , while at the same time locking the connection C together so as to prevent the male component  44  from being blown out of the female component  46 .  
         [0018]    The configuration and location of the cantilevered component  54  can vary without departing from the spirit of the invention. The orientation of the cantilevered component  54  can also vary without departing from the spirit of the invention. The compliant portion of one of the male  44  or female  46  components can be anywhere on its length as long as it is energized by bringing the components together and holding them together with a locking assembly, such as dogs  28 . As long as at least one of the male and female components has a compliant segment that elastically deforms when the components are brought together, the benefits of the present invention are achieved. The compliant segment can be on both components of the connection C.  
         [0019]    In the embodiment shown in FIG. 1, the dog-operating mechanism  26  is a part of the choke body  10  and, thus, remains subsea, even if the actuator  22  is removed with insert  12  after the dogs  28  are retracted by an ROV or a diver.  
         [0020]    An alternative preferred design allowing the dog-operating mechanism  26  to be removed from the choke body  10  is illustrated in FIG. 2. The principle of operation is the same as in FIG. 1, except that the compliant cantilevered component  54  is now part of the choke body  10 . In the embodiment of FIG. 1, the choke body  10  had an internal shoulder  52 . In FIG. 2, the internal shoulder on the choke body is eliminated, and the cantilevered component  54  represents the end of the choke body  10 . The difference is that the dog-operating mechanism  26  is now a portion of the female component  46  which is connected to the actuator  22 . In the FIG. 1 embodiment, the male component  44  was connected to the actuator  22 . In essence, this reversal of orientations between FIGS. 1 and 2 operates functionally the same, the difference being that when the actuator  22  is removed with the insert  12 , the dog-operating mechanism  26  comes away from the choke body  10  with the insert  12 . In either case of FIGS.  1  or  2 , the flexing or compliance of the cantilevered or preload component  54  allows the preload to be built into the assembled connection C locked together by dogs  28 . As a clear juxtaposition to prior art designs which involved tapered cones pushing on collets where the amount of movement of the tapered cone plus reliance on residual frictional forces were required to hold the connection together, the connection C of the present invention is far simpler and cheaper to build and takes up less space. It is also not dependent on residual friction forces to hold the connection together. The connection stays together with preload as desired as long as sufficient radial inward movement of the dogs  28  occurs to prevent the male and female components  44  and  46 , respectively, from coming apart. Accordingly, there&#39;s no continuing wedging action required to maintain the preload on the connection. The preload occurs because of sufficient extension of the dogs  28  which, in turn, flexes or moves the preload or cantilevered component  54  sufficiently against an opposing member of the connection or internally within one component of the connection so as to retain a preload force when required. It should be noted that the preload is generally necessary when conditions of high flow and low pressure occur which could create chattering in the connection due to clearances inherent in dog-type closures. Additionally, in view of the fact that radial seals  60  are shown in the embodiments of FIGS. 1 and 2, there is less of a requirement of a longitudinal closing force on the connection to activate the seals. Thus, it is the fit between the insert  12  and the passage in the choke body  10  which provides the necessary configuration to retain differential pressures across the seals  60 . The dogs  28  acting on shoulders  48  are for the purpose of holding the connection together and providing preload as opposed to loading up these particular types of seals. However, other types of seals (Le., face seals) can be used with this type of a connection without departing from the spirit of the invention.  
         [0021]    The compliant component  54  need not be cantilevered; it can be a segment of the male  44  and/or female  46  components which can bend, fold, crumple or otherwise deform elastically under load created by actuating the closure, one type of which can be dogs  28 .  
         [0022]    An alternative embodiment is illustrated in FIGS.  3 - 5 . In the embodiment illustrated in these figures, the concept of a preload on the connection and the dogs which hold the connection together or allow it to be taken apart are combined. Referring to FIG. 3, a choke insert  61  is attached to an actuator  62 . The running tool  88  has as a part thereof sleeve  94  and skirt  64 . Shoulder  65  on skirt  64  lands on choke body  64  as long as pin  68  is in a retracted position (not shown). Thus, pin  68  retains the running tool  88  to choke body  66  when it extends into groove  70 . The choke body  66  is partially shown in FIG. 3. Pin  68  can be mechanically or hydraulically actuated. Choke body  66  has peripheral internal groove  72  and a series of alignment holes  74  which accept alignment pins  76 . Alignment pins  76  extend from actuator  62 . Actuator  62  has a series of peripheral openings  78 , in each of which is located a generally U-shaped dog  80 . Behind each of the dogs  80  is a sleeve  82 , which has a taper  84 . A split ring  86  holds the sleeve  82  to the actuator body  62  during run-in. Run-in is accomplished using a running tool  88  which engages a groove  90  using a schematically illustrated pin  92 , which can be mechanically or hydraulically operated. The running tool  88  has an extension sleeve  94  such that pin  92  cannot be retracted out of groove  90  until it is in alignment with opening  96  of sleeve  94 , as shown in FIG. 5. This prevents inadvertent release subsea of the actuator  62  and insert  61 . The actuator  62  enters choke body  66  with pins  76  guiding the advancement as they move into openings  74 . Eventually, the actuator  62  bottoms in choke body  66  as shown in FIG. 4. At that point, sufficient setdown weight moves split ring  86  into groove  98  of sleeve  82 , thus allowing sleeve  82  to continue moving downwardly, thereby camming the dogs  80  radially outwardly into groove  72  due to the action of tapered surface  84 .  
         [0023]    This final position is shown in FIG. 5. Depending on the configuration of the dogs  80  and the groove  72 , the amount of movement of legs  100  and  102  determines how much preload is on the connection between the actuator  62  and the choke body  66 . It is within the scope of the invention to allow the legs  100  and  102  to touch during normal operations. Thus, for example, when high internal pressures are developed in the choke body  64 , the legs  100  and  102  will likely touch each other. However, when there is high flow and low pressure, the legs will be apart as a preload force is applied. Optionally, within the recess defined between legs  100  and  102 , small projections can be used on each or at least one of the legs  100  and  102  which will limit the amount of movement of the legs  100  and  102  toward each other during operation of the choke. These projections  104  are illustrated in FIG. 5.  
         [0024]    It should also be noted that when the sleeve  82  reaches its full downward movement as the split ring  86  is forced into groove  98 , the pin  92  comes into alignment with opening  96  in sleeve  94 . Thus, with the pin  92  no longer in groove  90 , the running tool  88  can be retrieved.  
         [0025]    Those skilled in the art will appreciate that the drawings of FIGS.  3 - 5  illustrate one possible way of configuring the connection for application of a predetermined amount of preload. However, the actual construction of the actuator  62  insofar as how it operates the insert  60  is not a portion of the invention and is a design known in the art. The significant feature of the embodiment shown in FIGS.  3 - 5  is that preload is applied to a connection where the preload function and the locking function of the connection are combined in a single element.  
         [0026]    Another feature of the invention illustrated in FIGS.  3 - 5  is the elimination of tapered cones acting on collets which left uncertainties as to the solidity of the connection in that reliance on residual friction forces was required. In the embodiment of FIGS.  3 - 5 , sufficient sleeve movement to cam the dogs  80  outwardly into a groove  72  of predetermined configuration ensures the locking of the connection together with the desired preload. It should be noted that groove  72  has a cross-sectional shape in general conformance with the tapered surfaces  106  and  108  on legs  102  and  100 , respectively. While a U-shaped cross-section is shown for the dogs  80 , other configurations for the dogs can be used without departing from the spirit of the invention. The dog or dogs  80  can have some other shape as long as they also have a compliant component (i.e., that bends, folds, crushes, or otherwise changes in dimension) that elastically deforms while at the same time serving to lock the connection components together. While the orientation of the long axis of the dogs  110  is perpendicular to the axis  112 , different orientations of the dogs  80  can be used without departing from the spirit of the invention. As long as the dogs  80  can effect a straddle between the actuator  82  and the receptacle  66  so as to hold the connection together, while at the same time changing its configuration elastically so as to provide a preload, the physical embodiment of how those features are executed are all within the purview of the invention.  
         [0027]    By integrating the compliant component  54  into a male  44  and/or female  46  portion of the joint, the installation and removal is simpler and faster as compared to using a separate element to achieve the preload which is independent of the constituent parts.  
         [0028]    Those skilled in the art will appreciate that connections for services other than for subsea chokes with removable inserts are envisioned for the present invention and that the limits are well beyond chokes or even subsea equipment or even oilfield equipment in general.  
         [0029]    The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.