Abstract:
A metal-to-metal sealing system is described for forming a pressure-activated connection between two pieces of equipment under HPHT (high pressure high temperature) conditions which will degrade elastomers. The roughly cylindrical seal comprises four sealing surfaces, two sealing surfaces formed by the circular longitudinal edge, and two sealing surfaces formed by either side of a bulge located halfway along the outer diameter. These surfaces correspond with sealing surfaces on the pieces of equipment to be joined. These pieces of equipment also utilize testing ports in fluid communication with the seal in order to ensure a secure connection.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Application No. 62/338,905, filed 19 May 2016, and entitled “Metal-to-Metal Well Equipment Seal.” The contents of the above-referenced application are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    Embodiments usable within the scope of the present disclosure relate, generally, to a pressure-activated metal-to-metal seal for wellheads and other oil &amp; gas equipment. The metal-to-metal seals are operable in highly corrosive, high-temperature high-pressure (HPHT) conditions. 
       BACKGROUND 
       [0003]    It is increasingly common in the oil &amp; gas industry for exploration operations to take place in harsh, unfriendly environments and well conditions. Therefore, wellhead equipment must be built to withstand high pressure, high temperature (HPHT) environments, as well as to operate efficiently within conditions that include high levels of sulfides, carbon dioxide, and other corrosive gases or compounds. Such conditions often require a “dual” seal, meaning at least two independent barriers. 
         [0004]    Currently, a common procedure is to coat flanged outlets with a non-corrosive metal, such as Inconel, and accomplish a secondary seal using elastomeric rings or gaskets. However, even these options often see high failure rates. Additionally, they often have limited versatility as the metal must be machined for each joint. 
         [0005]    A need exists for a system which is made more reliable by the internal pressure inside the wellhead and which can be independently pressure tested at installation. A need also exists for a system which can be adapted and installed by modification in existing API standard flanges/outlets, along with the standard API ring gaskets or ASME-equivalent ring-type joints to provide an additional corrosion-resistant barrier through a metal-to-metal seal. 
         [0006]    Embodiments of the apparatus described herein meet this and other needs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    In the detailed description of the embodiments, presented below, reference is made to the accompanying drawings: 
           [0008]      FIG. 1A  depicts an overhead view of an embodiment of the seal disclosed herein. 
           [0009]      FIG. 1B  depicts a cross-section of the embodiment of the seal depicted in  FIG. 1A  along section line B-B. 
           [0010]      FIG. 2A  depicts a flange connection to be used with an embodiment of the seal disclosed herein. 
           [0011]      FIG. 2B  depicts a cross-section of the flange connection depicted in  FIG. 2A  along section line B-B. 
           [0012]      FIG. 2C  depicts a magnified cross-section of section C of the flange connection depicted in  FIG. 2B . 
           [0013]      FIG. 3A  depicts a cross-section view of an embodiment of the seal disclosed herein for use in a flange-to-flange connection. 
           [0014]      FIG. 3B  depicts a magnified view of section B of the embodiment depicted in  FIG. 3A . 
           [0015]      FIG. 3C  depicts a cross-section view of an embodiment of the seal disclosed herein for use in a flange-to-flange connection. 
           [0016]      FIG. 3D  depicts a magnified view of section D of the embodiment depicted in  FIG. 3B . 
           [0017]      FIG. 4A  depicts a standard studded wellhead outlet with an embodiment of the seal and test port disclosed herein. 
           [0018]      FIG. 4B  depicts a swivel flanged wellhead outlet with an embodiment of the seal and test port disclosed herein. 
           [0019]      FIG. 4C  depicts a swivel wellhead outlet with an embodiment of the seal and test port disclosed herein. 
           [0020]      FIG. 5A  depicts a zoomed-in view of one embodiment of the seal disclosed herein. 
           [0021]      FIG. 5B  depicts a zoomed-in view of an alternate embodiment of the seal disclosed herein. 
           [0022]      FIG. 6A  depicts a prior art flange connection. 
           [0023]      FIG. 6B  depicts a zoomed-in flange connection having an embodiment of a test port as disclosed herein. 
           [0024]      FIG. 7  shows a perspective/cutaway view of a flange having the seal and test port disclosed herein. 
       
    
    
       [0025]    One or more embodiments are described below with reference to the listed Figures. 
       DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0026]    Before describing selected embodiments of the present disclosure in detail, it is to be understood that the present invention is not limited to the particular embodiments described herein. The disclosure and description herein is illustrative and explanatory of one or more presently preferred embodiments and variations thereof, and it will be appreciated by those skilled in the art that various changes in the design, organization, order of operation, means of operation, equipment structures and location, methodology, and use of mechanical equivalents may be made without departing from the spirit of the invention. 
         [0027]    As well, it should be understood the drawings are intended to illustrate and plainly disclose presently preferred embodiments to one of skill in the art, but are not intended to be manufacturing level drawings or renditions of final products and may include simplified conceptual views as desired for easier and quicker understanding or explanation. As well, the relative size and arrangement of the components may differ from that shown and still operate within the spirit of the invention. 
         [0028]    Moreover, it will be understood that various directions such as “upper,” “lower,” “bottom,” “top,” “left,” “right,” and so forth are made only with respect to explanation in conjunction with the drawings, and that the components may be oriented differently, for instance, during transportation and manufacturing as well as operation. Because many varying and different embodiments may be made within the scope of the concept(s) herein taught, and because many modifications may be made in the embodiments described herein, it is to be understood that the details herein are to be interpreted as illustrative and non-limiting. 
         [0029]    The present invention relates, generally, to a metal-to-metal seal configuration for use in highly corrosive, HPHT environments but has application in other areas as well. This configuration can work in tandem with an existing seal such as a ring-type joint (RTJ) to create a secondary metal-to-metal seal, whereas in existing configurations the secondary seal is usually a standard API ring gasket or single seal combination of metal and elastomer or other easily degraded material. 
         [0030]    Referring now to  FIGS. 1A and 1B , an overhead view of an exemplar seal  10  is shown, in overhead view in  FIG. 1A , as a roughly cylindrical metallic surface surrounding a bore  12  therethrough, and in cross-section along section line B-B in  FIG. 1B . Seal  10  comprises a total of four sealing surfaces  20 ,  22 ,  24 ,  26 , where sealing surfaces  20 ,  22  form a lip on either side of the seal while sealing surfaces  24 ,  26  form the shape of a radial (i.e., semi-circular) bulge extending concentrically around the longitudinal axis of the seal. 
         [0031]    Internally, the seal also features a groove  28  located interior to the two sealing surfaces  24 ,  26 . Groove  28  fulfills two functions: it allows the seal  10  to flex slightly should there be bending, movement, or a change in temperature to the equipment during installation and operation, and it also serves as an extraction groove should the seal  10  become lodged within the equipment. 
         [0032]    In the depicted embodiment, seal  10  comprises a first width W 1  which is defined by the inner diameter of the bore  12  enclosed by the seal  10 , a second width W 2  which is defined by the outer diameter of the seal  10  (i.e., the difference between W 1  and W 2  is a function of seal thickness), and a third width W 3  which represents the maximal width at the apex of the two sealing surfaces  24 ,  26 . 
         [0033]    Referring now to  FIGS. 2A-2C , a standard flange connection  30  is shown comprising a central bore  32  therethrough.  FIG. 2A  depicts the flange connection  30  in side view, while  FIG. 2B  depicts a cross-sectional view along section line B-B.  FIG. 2B  depicts a test port  34  located within the flange connection  30  for monitoring the internal pressure of the flange connection  30 .  FIG. 2C  depicts a magnified view of section C of  FIG. 2B  which includes the fluid connection  36  between the test port  34  and the central bore  30 . Flange connection  30  is also depicted with a negatively angled sealing surface  38  which corresponds to the sealing surface  20  of the seal  10  (both depicted in  FIG. 1B ). 
         [0034]    The central bore  32  of flange connection  30  is also depicted having a series of sealing surfaces corresponding to stepwise changes in radius, shown as R 1 , R 2 , and R 3 . These radii R 1 , R 2 , R 3  correspond to the W 1 , W 2 , W 3  widths (i.e., diameters) shown in  FIG. 1B . (As every diameter implies a radius and vice versa, they are marked as radii solely for clarity.) 
         [0035]    Referring now to  FIGS. 3A-3D , two flange connections  30 A,  30 B are shown abutted end-to-end in cross-section with their respective bores aligned to form a single bore  32  therethrough. Seal  10  is aligned within bore  32  and the sealing surfaces  20 ,  22 ,  24 ,  26  of the seal  10  (depicted in  FIG. 1B ) are aligned with the respective sealing surfaces of the flange connections  30 A,  30 B. Test ports  34 A and  34 B are shown fluidly connected to seal  10 , and a test plug  42  may be present during pressure testing. In addition, flange connections  34 A,  34 B may comprise a secondary groove  31 . This secondary groove  31  can accommodate an RTJ gasket  33  illustrated in FIG.  3 D. 
         [0036]    Referring now to  FIGS. 4A-4C , three examples of wellhead connections are depicted, each having a secondary seal  110  and a test port  120 , as well as a standard ring-type joint (RTJ)  130 . The present invention can be retro-fitted to existing “in-field” pieces of equipment (gate valves, wellheads, Christmas tree valves, choke valves, spools) or can be originally present in equipment through manufacturing. As shown, test port  120  can be in communication with the area between RTJ seal  130  and secondary seal  110  in order to determine the efficacy of the secondary seal in isolation. 
         [0037]    Referring to  FIG. 5A , a zoomed-in alternative embodiment of the secondary seal  110 A as depicted in  FIGS. 4A-14C  is shown. The embodiment depicted in  FIG. 5A  comprises a lower sealing bowl  111 A, an upper sealing bowl  112 A, and three sealing areas  115 A,  116 A, and  118 A. In this embodiment, the fluid pressure within a wellbore is in the upward direction from lower sealing bowl  111 A to upper sealing bowl  112 A. Thus, sealing area  115 A seals the lower sealing bowl  111 A against well equipment (e.g., wellheads, gate valves, Christmas tree valves, choke valves, spools, etc.) while sealing area  118 A seals the upper sealing bowl  112 A against the well equipment to be connected. Sealing area  116 A seals lower sealing bowl  111 A against upper sealing bowl  112 A. The angles of sealing areas  115 A,  116 A, and  118 A ensure that fluid pressure works to further activate the seal after initial connection through torqued studs/nuts as shown in  FIGS. 4A-4C . 
         [0038]    Referring to  FIG. 5B , an alternate embodiment of a secondary seal  110 B is depicted which can be used interchangeably and in the same fashion as secondary seal  110 A. As with secondary seal  110 A, secondary seal  110 B comprises a lower sealing bowl  111 B and upper sealing bowl  112 B, and sealing surfaces  115 B and  118 B which function substantially similar to  115 A and  118 A. Secondary seal  110 B additionally can comprise two intermediate sealing areas  116 B and  117 B, which further isolate the connected equipment against HPHT fluids. 
         [0039]    Referring to  FIGS. 6A-6B , a standard prior art flange connection  100  is shown having a groove  131  for accepting a ring-type joint  130  (shown in  FIGS. 4A-4C and 6B ) acting as a primary seal.  FIG. 6B  depicts a modified flange  101  having a testing port  120 , which is in fluid communication through an angled aperture  121  into the space between ring-type joint  130  and secondary seal  110  (shown as the alternate embodiment depicted in  FIG. 5B ). The configuration shown in  FIG. 6B  allows the secondary seal  110  to be monitored and tested independently of ring-type joint  130 . 
         [0040]    Referring to  FIG. 7 , a sectional view of a blind flange  101  having a configuration substantially similar to that shown in  FIG. 3B  is depicted, with flange  101  more clearly showing the testing port  120  and aperture  121  in relation to the groove  130  and ring-type joint  131 , as well as the metal-to-metal seal  110  (shown as the alternate embodiment depicted in  FIG. 2B ) comprising lower sealing bowl  111 , upper sealing bowl  112 , and sealing surfaces  115 ,  116 ,  117 , and  18 . 
         [0041]    The depicted embodiments are capable of maintaining seals at pressures of 5,000 psi in flanged outlets and higher in other end connections (OEC), and temperatures in excess of 250° C.; it can be appreciated that all working pressures and configurations described in API specification  6 A may be designed for utilizing the central design principles shown herein. 
         [0042]    Although several preferred embodiments of the invention have been illustrated in the accompanying drawings and described in the foregoing specification, it will be understood by those of skill in the art that additional embodiments, modifications and alterations may be constructed from the invention principles disclosed herein, while still falling within the scope of the disclosed invention. For instance, while the seal is depicted as a connection between two standard flanges, the same profile may be utilized in other pieces of equipment, e.g., swivel flanges, tubing hangers, clamp hub connections, and OECs.