Abstract:
A well tubing hanger designed for severe service applications includes an annular seal formed about the tubing hanger exterior that is not energized during normal well operations. The annular seal is energized by lowering the tubing hanger downward within the tubing head until the annular seal subsequently contacts in a fluid-tight manner both the tubing hanger and the tubing head. The tubing hanger is lowered relative to the tubing head by rotative disengagement of a treaded mandrel operatively connected between the tubing hanger and the tubing head. The annular seal is energized prior to installation or removal of well flow control equipment located above the tubing hanger and tubing head, preferably after well fluid flow through the well has been secured.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an improved well tubular hanger having a seal system suitable for operation when subjected to wide variations in temperature. Such temperature variations may be experienced, for example, during production in Alaska (-75° F. to 250° F.) and in steam injection applications (up to 1000° F.). 
     2. Description of the Prior Art 
     As discussed in U.S. Pat. No. 4,190,270 issued Feb. 26, 1980 to Vanderford, entitled &#34;Tubing Hanger for Temperature Variations and Extremes&#34;, a tubing system is disclosed wherein the pressure seal is maintained by a metal seal ring. As shown in FIG. 3 of this patent, a sleeve is used to force the metal seal ring downwardly within an annular space defined between the head and body of the apparatus. The location of the seal ring provides an additional pressure boundary between pressurized annulus fluids and wellhead components located above the seal ring. Operation of the seal ring, however, requires actuation of a pin 128 to force sleeve 124 downward. The opening required for pin 128 through the head 100 creates a potential leak spot through the head. 
     A seal apparatus therefore needs to be developed that minimizes the amount of potential leak sources from the head of a well. Such a system should provide a positive pressure seal when it is desired to isolate a potentially pressurized annulus from wellhead components located above the tubing hanger. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a moveable tubing hanger located within a tubing head, the tubing hanger having a seal defined in an annular manner about its exterior. The seal is not energized in a fluid-tight manner during the normal producing or injection condition of the well. The seal is only used to provide a pressure boundary between the tubing hanger and the tubing head when it is desired to install or remove well components located above the tubing head of the well. Since the seal is not &#34;energized&#34; during normal well operations (not subject to compressive set or other problems associated with seal compression during thermal cycling), the seal retains its fluid sealing properties even after being subjected to high temperatures such as would be encountered in a steam injection well. The seal is only actuated after the injection or production operation has been terminated. 
     To actuate the seal the tubing hanger is moved downward within the tubing head. 
     In a preferred embodiment, a seal flange located above the tubing head and the moveable tubing hanger has a threaded coupling formed common to both flange and hanger such that by rotation of the seal flange the tubing hanger is lowered downward within the tubing head. Such downward movement causes the seal to engage between the tubing hanger and the tubing head. The weight of the tubing suspended from the tubing head assists in insuring that the seal engages in a fluid-tight manner between the hanger and the tubing head. 
     An object of the present invention, therefore, is to provide an improved hanger sealing system which can form pressure-tight seal after being subjected to temperature cycling and extremes of temperature. 
     Another object is to provide an improved tubing hanger having a seal which withstands extreme temperature variations yet still maintains a seal between the hanger and the tubing head during the installation and/or removal of well equipment located above the tubing head. 
     It is a feature of the present invention to provide a moveable tubing hanger capble of axial movement relative to the tubing head. It is another feature of the present invention to provide axial movement means operatively connected between the moveable tubing hanger and the tubing head to axially move the tubing hanger relative to the tubing head, so as to engage a seal in a fluid-tight manner between the tubing head and the moveable tubing hanger, and to disengage the seal from the fluid-tight engagement between the tubing head and the moveable tubing hanger. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of the present invention are hereinafter set forth and explained with reference to the drawings wherein: 
     FIG. 1 shows a schematic representation in partial cross-section of a well tubing hanger apparatus of the preferred embodiment of the present invention. 
     FIG. 2 shows a schematic representation and partial cross-section of the well tubing hanger apparatus shown in more detail, the seal means not forming a pressure tight boundary between the tubing hanger and the tubing head. 
     FIG. 3 shows a schematic representation in partial cross-section of the well tubing hanger apparatus, showing the seal means engaged in a fluid-tight manner between the movable tubing hanger and the tubing head. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1 the well 10 having a wellhead 11 casing 12 and tubing string 13 is shown controlling the flow of well fluids 15 to or from a typical formation 16, as is well known to the art. The well 10 may be a production well, or a steam injection well, or any other well known to the art. Well 10 may also include for example wellhead valve apparatus 18 which may for example incorporate the use of valves 19A, 19B. It should be well recognized that wellhead valve apparatus 18 may take many forms, dependent upon the desired well operation to be conducted, such as a typical production tree well known to the art, or for example blowout prevention equipment that may be used during the workover or completion of a well. 
     The well tubing hanger apparatus 20 of the present invention can be seen to include a tubing head 22, a seal flange 23 which forms a portion of axial movement means 24, a moveable tubing hanger 25 having the other portion of the axial movement means 24, and seal means 26 which in a preferred embodiment comprises elastomeric seals well known to the art. As can be seen from FIG. 1, the elements of the well tubing hanger apparatus 20 in a preferred embodiment are arranged in a concentric manner around a common central longitudinal axis 28 defined through the center of each element 22, 23, 24, 25, and 26. It should be well recognized, of course, that in the case of a dual completion well a plurality of apparatus 20 may be used. 
     Referring now to FIG. 2 the well tubing hanger apparatus 20 may be described in more detail. The tubing head 22 can be seen to have a tubing head central opening 29 defined upwardly therethrough. The moveable tubing hanger 25 is centrally positioned within the tubing head central opening 29 and in a preferred embodiment has a tubing hanger central opening 30 defined upwardly therethrough, the moveable tubing hanger 25 being axially moveable relative to the tubing head 22 along the central longitudinal axis 28. The well tubing hanger apparatus 20 also includes seal means 26 as mentioned earlier located in a preferred embodiment between tubing head 22 and the tubing hanger 25, the seal means 26 being engageable in a fluid-tight manner between the tubing head 22 and the tubing hanger 25. 
     In a preferred embodiment the axial movement means 24 are operatively connected between the moveable tubing hanger 25 and the tubing head 22 to axially move the tubing hanger 25 relative to the tubing head 22 along the central longitudinal axis 28, so as to engage the seal means 26 in a fluid-tight manner between the tubing head 22 and the moveable tubing hanger 25, and thereafter to disengage the seal means 26 from the fluid-tight engagement between the tubing head 22 and the moveable tubing hanger 25, dependent of course upon the direction of axial movement of the hanger 25 relative to the tubing head 22. 
     It shall be well recognized that the seal means 26 may be located in other positions relative to the hanger 25 and tubing head 22 depending upon the design and configuration of the cooperating surfaces formed between the head 22 and the hanger 25. 
     The axial movement means 24 in a preferred embodiment further include the seal flange 23 operatively carried in a fluid-tight manner by the upper surface 32 of the tubing head 22 and located above the moveable tubing hanger 25, the seal flange 23 having a central longitudinal axis common with the central longitudinal axis 28 of the tubing head 22 and having a seal flange central opening 33 defined upwardly therethrough. The axial movement means 24 can also be seen to include threaded engagement means 34 operatively connected between the seal flange 23 and the moveable tubing hanger 25. The threaded engagement means in a preferred embodiment have a first portion and a second portion both portions having cooperating threads 35 being rotatably engaged with one another. In a preferred embodiment, rotation of the seal flange 23 about central longitudinal axis 28 and thereby rotation of the threaded engagement means 34 between the seal flange 23 and the tubing hanger 25 causes the moveable tubing hanger 25 to move axially relative to the tubing head 22. One of the threaded engagement means portions is operatively formed adjacent at least a portion of the seal flange central opening 33 and another of the threaded engagement means 34 portions is operatively formed adjacent a portion of the tubing hanger central opening 30. 
     In a preferred embodiment the first portion of the threaded engagement means 34 comprises a threaded receptacle 37 formed radially within a portion of the seal flange central opening 33, and the second portion of the threaded engagement means 34 comprises a threaded mandrel 38 operatively connected to the moveable tubing hanger 25 and extending upwardly from the tubing hanger 25 into threaded engagement with the cooperating threads 35 formed by the threaded receptacle 37. 
     It should be well recognized, of course, that any threaded system may be employed between the seal flange 23 and moveable tubing hanger 25 to move the hanger 25 relative to the seal flange 23. 
     Any other device may also be used to accomplish the same mechanical result. The tubing hanger 25 may initially for example be set upon a wedge device that may be retracted from beneath the tubing hanger 25 by actuation of pins extendable through the tubing head, when it is desired to lower the tubing hanger 25 downwardly within the tubing head 22. Hydraulic actuators may also be connected to the tubing hanger to accomplish the same mechanical result. 
     In a preferred embodiment the tubing head 22 can be seen to have an upwardly facing tapered surface 39 defined circumferentially about the interior of the tubing head 22. The moveable tubing hanger 25 in a preferred embodiment can also be seen to include the downwardly facing tapered surface 40 defined circumferentially about the exterior of the moveable tubing hanger 25. Both surfaces 39, 40 are capable of cooperative engagement with one another so as to support the weight of the moveable tubing hanger 25 when the tubing hanger 25 is lowered downward into contact with the tubing head 22. 
     In a preferred embodiment the seal means 26 can be seen to further include at least one seal ring, such as seal rings 42, 42A shown in FIG. 2, each ring 42, 42A carried in a cooperating annular recess 43, 43A, respectively formed about the exterior of the moveable tubing head 25, each seal ring 42, 42A engageable in a fluid-tight manner with the interior of the tubing head 22 and the exterior of the moveable tubing hanger 25 when the moveable tubing hanger 25 is moved downward within the tubing head 22. Each seal ring 42, 42A, in a preferred embodiment, may form a fluid-tight seal between the tubing hanger 25 and the tubing head 22 prior to the downwardly facing tapered surfce 40 of the tubing hanger 25 coming into contact in a weight supporting manner with the upwardly facing tapered surface of the tubing head 22. 
     It should also be recognized in an alternative embodiment that the seal means 26 may be carried by the tubing head 22 whereupon annular recesses are formed within the interior surface of the tubing head 22. 
     Each seal ring 42, 42A is typically formed from an elastomeric material, such as butyl rubber, well known to the art, the material being selected to properly survive in differing operating environments encountered by the well tubing hanger apparatus 20. 
     It should be recognized of course that in an alternative embodiment, the seal means 26 may comprise metal gaskets well known to the art used instead of gaskets formed from elastomeric material. 
     The seal flange 23 in a preferred embodiment is operatively carried in a fluid-tight manner by the tubing head upper surface 32 by use of at least one seal flange seal ring 45 positioned between the tubing head 22 and the seal flange 23. The seal flange 23 may be securely fastened to the tubing head 22 by use of fastener means 46 such as an array of bolts 47 and nuts 48, in a manner well known to the art. The seal flange seal ring 45 may be retained in cooperating annular recesses 49, 49A formed in the seal flange 23 and the tubing head 22, respectively. 
     It should be well recognized that the seal flange 23 in an alternative embodiment may be securely fastened in a fluid-tight manner to the tubing head 22 by means of a threaded connection existing between the seal flange 23 and the tubing head 22. 
     In a preferred embodiment of the present invention, a standard &#34;F&#34; tubing head housing manufactured by Cameron Iron Works, P. O. Box 4716, Ventura, Calif. 93304, is used for the tubing head 22. The tubing head 22 is welded to the casing 12. The tubing hanger 25 is directly connected to the seal flange 23 by a 5-inch API casing thread and may comprise a &#34;double box bushing&#34; type hanger assembly. A back pressure valve preparation is supplied in the tubing hanger 25. An internal 31/2&#34; EUE thread 50 may be cut in the upper portion of the tubing hanger central openings 30 to allow makeup of a handling joint 61 (FIG. 3) used during installation and removal of the tubing hanger 25. 
     The seal flange 23 threaded receptacle 37 has 5&#34; API casing threads 35 formed thereon. These 5&#34; casing threads 35 in a preferred embodiment are designed so that at full makeup the tubing hanger 25 would not be in contact with the tubing head 22 upwardly facing tapered surface 39, when the seal flange 23 is landed on the seal flange seal ring 45 carried by the tubing head 22. Therefore the tubing hanger 25 is ineffective during production or steaming operations of the well 10 to provide a pressure seal across the annular passage 51 above and below the tubing hanger 25. 
     In a preferred embodiment after the moveable tubing hanger 25 is lowered downwardly into contact with the tubing head 22, the length of the threads 35 is selected such that during rotation of the seal flange 23 about the threaded mandrel 38 at least two rotations of the seal flange 23 can be made before the seal flange 23 contacts the seal flange seal ring 45 located in annular recess 49A, the seal ring 45 typically consisting of a type &#34;RX&#34; seal ring. 
     In a preferred embodiment 4&#34;×11/4&#34; bar openings 56 (FIG. 3) may be defined in the side of the seal flange 23 so that four foot torque bars can be inserted in these openings 56 and by manpower or workover rig tugger the seal flange 23 can be rotatably engaged to the threaded mandrel 38 in accordance with API torque specifications. 
     In a preferred embodiment the seal flange 23 may be formed for example form a standard API 11&#34; flange machined on the bottom with annular recess 49 and drilled and tapped to mate with a 4&#34; API flange on the top surface, in order to connect with either a typical steam injection tree or a rod pump production assembly. 
     After study of the well tubing hanger apparatus 20 major advantages of the system over the prior art become obvious. The well is controlled during blowout prevention equipment installation and removal by the seal system of the present invention, metal to metal or threaded seals are used throughout the tubing system, the wellhead is capable of operating at high temperature and/or pressure conditions without resilient seal problems or concerns, and lastly, the simple design eliminates tubing hanger seal problems during well operation. 
     Referring now to FIG. 3, the apparatus of the present invention can be seen to provide a method of well fluid control. In simplest terms the axial movement means 24 may be actuated, thereby causing the moveable tubing hanger 25 to move relative to the tubing head 22. Such movement, depending upon the design and location or the seal means 26, will subsequently cause the engagement of the seal means 26 between the tubing head 22 and the moveable tubing hanger 25 in a fluid-tight manner thereby preventing fluid flow between the tubing head 22 and the tubing hanger 25. 
     As mentioned earlier, since the axial movement means 24 comprises in a preferred embodiment the seal flange 23 and the threaded engagement means 34 the step of actuation of the axial movement means comprises the step of rotating the seal flange 23 since movement of the seal flange 23 causes corresponding rotative interaction between both portions of the threaded engagement means 24. Movement of seal flange 23 combined with the rotative interaction of the threaded engagement means 34 causes axial movement of the tubing hanger 25 relative to the seal flange 23. 
     More specifically, the method of the present invention may comprise the following steps. 
     Torque generation means 53, such as a manually actuatable bar 54 are provided. A portion of the torque generation means 53 may be formed to be operatively connected to the seal flange 23 by use of torque generation connection means 55, in a preferred embodiment consisting of bar openings 56, 56A defined radialy inward about the exterior of the sealing flange 23, the bar openings 56, 56A formed to operatively engage with another portion of the torque generation connection means 55 defined by the exterior of one end of the bar 54 formed to be insertable within at least one of said bar openings 56, 56A. The torque generation means 53 in a preferred embodiment are capable of generation and application of sufficient torque to the threaded engagement means 34 to rotate the seal flange 23 relative to the moveable tubing hanger 25 so as to move the seal flange 23 toward and away from the tubing hanger 25. 
     It should be well recognized that other devices other than the bar 54 coupled within the bar opening 56 may be used to form the torque generation means 53, in order to accomplish the same mechanical results. Seal flange 23 may be rotated for example by hydraulic and/or pneumatic devices well known to the art. 
     Prior to rotation of the seal flange 23 the fastener means 46 (shown in FIG. 2) that secure the seal flange 23 to the tubing head 22 are unfastened. Well annulus pressure should be reduced to zero prior to unfastening the fastener means 46. 
     Torque generation means 53 are then actuated, and thereby seal flange 23 is rotated so as to move the moveable tubing hanger 25 a preferred distance 58 away from seal flange 23. By proper consideration of whether threaded engagement means 34 comprise &#34;right&#34; or &#34;left&#34; handed threads and the direction of rotation of seal flange 23 about central longitudinal axis 28 the moveable tubing hanger 25 and the seal means 26 may therefore be lowered downwardly within the tubing head 22. 
     Due to the location and inclination of upwardly and downwardly facing tapered surfaced 39, 40 (FIG. 2), such downward movement within the tubing head 22 causes the seal means 26 to engage between the tubing head 22 than the moveable tubing hanger 25, as discussed earlier. 
     It should be well recognized, of course, that in an alternative embodiment the seal means 26 may be carried by the tubing head 22, or may be carried in any other position whereupon movement of the tubing hanger 25 relative to the tubing head 22 causes a seal to be formed by the seal means 26. Seal means 26 may for example be located on the bottom surface of tubing hanger 25 in order to contact and form a seal upon contact with a lower horizontal shoulder formed by a portion of the tubing head 22 (not shown). 
     To eliminate unnecessary galling and damage to the material between the seal flange 23 and tubing head 22, such as seal ring 45, in a preferred embodiment tubing hanger lift means 60 comprising a handling joint 61 and other derrick lift equipment well known to the art attached above the handling joint 61 (not shown for clarity), are provided, in order to lift the seal flange 23 off the seal flange seal ring 45 prior to rotation of the seal flange 23. A lower portion 62 of the tubing hanger lift means 60 is formed to be lowered downwardly through the seal flange central opening 33 and be operatively connected by use of hanger lift connection means 63, such as EUE threads 50 (FIG. 2), to the moveable tubing hanger 25. The tubing hanger lift means 60 are capable of lifting at least the moveable tubing hanger 25, the threaded engagement means 34 the seal flange 23 and the seal means 26 a selected distance 65 upward relative to the tubing head 22, so as to avoid contact of the seal flange 23 with the seal ring 45. The tubing hanger lift means 60 may be actuated subsequent to unfastening the fastener means 46 which secure the seal flange 23 to the tubing head 22. 
     Seal flange 23 may then be rotated so as to move the seal flange 23 at least a preferred distance 58 away from the moveable tubing hanger 25. Since the seal flange 23 in its lifted position no longer operatively contacts tubing head 22 the amount of torque applied by the torque generation means 53 may be significantly reduced from the amount of torque necessary to rotate the seal flange 23 if the flange 23 is rotated while still in contact with the tubing head 22. 
     Once the seal flange 23 is located the preferred distance 58 away from the moveable tubing hanger 25 the tubing hanger lift means 60 may be actuated so as to lower the hanger 25 downward within the tubing head 22. In this manner the seal means 26 may be engaged between the tubing head 22 and the moveable tubing hanger 25. 
     The threads 50 of the hanger lift connection means 63 are located on the interior of the moveable tubing hanger 25 adjacent the moveable tubing hanger central opening 30. This threaded portion of the hanger lift connection means 63 is formed to operatively engage in a threaded manner another threaded portion of hanger lift connection means 63 formed about the exterior of the lower end of the tubing hanger lift means 60, the tubing hanger lift means 60 being connectable by engagement of both portions of the hanger lift connection means 63 to the moveable tubing hanger 25. 
     At some point prior to the formation of the seal between the tubing hanger 25 and the tubing head 22 it is desireable in a preferred embodiment to control the flow of well fluid 15 through the tubing string 13. In a preferred embodiment of the present invention, therefore, flow control means 67 are provided which are capable of controlling the flow of well fluids through the tubing hanger central opening 30. The flow control means 67 such as a Type H 21/2&#34; nominal back pressure valve 68 manufactured for example by Cameron Iron Works, Inc., P. O. Box 4716, Ventura, Calif. 93304, may be formed to be lowered downwardly through the seal flange central opening 33 and thereafter operatively connected by use of flow control connection means 69, 69A to the moveable tubing hanger 25. The flow control connection means 69, 69A may be formed by upwardly and downwardly sloping shoulders 70, 71 located on the interior of the moveable tubing hanger 25 adjacent the moveable tubing hanger central opening 30, a portion of the flow control connection means 69, 69A formed to operatively engage with another portion of the flow control connection means 69, 69A formed about the exterior of the flow control means 67. 
     The flow control means 67 are connectable to the moveable tubing hanger 25 by engagement of both portions of the flow control connection means 69, 69A. 
     Prior to the step of lowering the flow control means 67 downwardly through the seal flange central opening 33 additional well fluids 15 may be injected within the well to decrease the pressure of the well fluid 15 at the tubing hanger central opening 30 to ambient pressure. In this manner, the operations required to engage the seal means between the tubing hanger 25 and the tubing head 22 may be done in a safe manner without risk of loss of control of the well. 
     The method of the present invention describes a well operation used to contain the well fluids within a pressurized boundary defined by the seal means 26. During typical well operations, well fluids are injected into the well to effectively &#34;kill&#34; the well and thereafter the flow control means 67 are installed within the tubing hanger 25. Note that the existing wellhead valve apparatus 18 (FIG. 2) may be safely removed from the wellhead 11 prior to engagement of the tubing hanger lift means 60 with the tubing hanger 25. 
     The backpressure valve may be inserted into the tubing hanger central opening by use of a pressure lubricator to control tubing pressure. As in the case of an injection well that uses a packer and expansion joint to confine and control injected steam, (assuming all pressure containing seals are operational), the backpressure valve may be inserted with a lubricator and the bolts common to the seal flange and the tubing head may then be removed with some tubing pressure present. The tubing hanger may then be landed in the tubing head prior to nipple-up of the blow out prevention equipment. 
     Many other variations and modifications may be made in the apparatus and techniques hereinbefore described, by those having experience in this technology, without departing from the concept of the present invention. Accordingly, it should be clearly understood that the apparatus and methods depicted in the accompanying drawings and referred to in the foregoing description are illustrative only and are not intended as limitations on the scope of the invention.