Patent Publication Number: US-2021189822-A1

Title: Wellhead assembly and test sealing architecture

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to, and the benefit of the earlier filing date of U.S. Provisional Application No. 62/951,158, titled “Testable Ring Gasket,” filed Dec. 20, 2019, the entirety of which is hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. As a result, over the years, well architecture has become more sophisticated where appropriate in order to help enhance access to underground hydrocarbon reserves. For example, in addition to land-based oilfields accommodating wells of limited depth, it is not uncommon to find both on and offshore oilfields with wells exceeding tens of thousands of feet in depth. Furthermore, today&#39;s hydrocarbon wells often include a host of lateral legs and fractures which stem from the main wellbore of the well toward a hydrocarbon reservoir in the formation. 
     In addition to the complexities of the field itself, ongoing management and periodic interventions may be particularly sophisticated undertakings. For example, it is not uncommon for a variety of different wells at a given field to require a variety of different applications and servicing at the same time and throughout production. This may include the simple opening and closing of different valves or a more rigorous undertaking such as the installation of monitoring equipment or the conducting of a cleanout application, just to name a few examples. 
     In addition to merely producing well fluids from a given well, there may be a substantial amount of monitoring, management and periodic interventions that may take place over time. This means that a variety of different mechanisms and sophisticated architectural features should be maintained and ensured to be operational over the course of the life of the well. For example, a variety of different valves and sealing devices should remain functional throughout the life of the well. Given the level of complexity and sophistication in modern wells, the overall expense of modern well completion and maintenance is often dramatically greater than for well of prior generations. Thus, ensuring even the most basic well components remain safeguarded and operational may be of greater importance, from a dollar standpoint, for more modern wells. 
     Along these lines, regardless of the level of well architecture and sophistication, one constant in terms of ensuring functional well components involves sealing, such as at the wellhead seal. That is, whether the well is onshore, offshore, of extensive depth, simple or extremely complex architecture, the governing interface to the well, the wellhead, will be landed and sealed at a base entry to the well. The wellhead interface may support a Christmas tree and/or other architectural features that are used to govern production, guide interventions and facilitate other well operations. Thus, ensuring a properly set wellhead seal for isolation of the wellbore is necessary for the ongoing success of well operations. 
     Presently, as a part of well installation and completions operations, a wellhead seal may be installed and set along with surrounding architecture. Given the importance of the seal in continued functionality of the well, it is generally tested prior to further installations and use of the well. Pressure testing the wellhead seal is currently a simple but time consuming process. Specifically, the wellbore may be plugged below the seal location. Pressure is then applied to the wellbore above the plug. So, for example, where the seal is properly set, an effort to introduce 10,000 PSI of fluid pressure to the wellbore above the plug over the course of several hours should result in the surface detection of 10,000 PSI of pressure. However, where the effort to drive up pressure fails, for example, regardless of the pumping of fluid into the wellbore, it may be due to a leak at the wellhead seal, calling for further inspection and redress where necessary. 
     Of course, the described manner of testing the wellhead seal is time consuming which doesn&#39;t just result in delays, but also in the added expense of plugging and unplugging the main bore. Furthermore, since it is the main bore that is used to test the seal, other aspects of installation are generally halted. Everything regarding the well completion is halted while the time consuming and laborious undertaking of wellhead seal testing takes place. Unfortunately, as a practical matter, there is presently no reliable manner of testing the wellhead seal in some manner other than through the time consuming process of shutting down and relying on the central wellbore. 
     SUMMARY 
     A wellhead assembly is disclosed. The assembly includes a primary seal at an interface of the assembly. The primary seal has an outer face and an interior face with the outer face sealingly isolating fluids of a wellbore and defined by a wellhead on a base at the interface. A test port is located at an exterior location of the wellhead with a leak path running therefrom to the primary seal for pressure testing of the outer face. A secondary seal at the interface is located adjacent the primary seal and opposite the leak path to back up the interior face of the primary seal to facilitate the pressure testing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side cross-sectional view of an embodiment of a wellhead assembly with an exterior test port for a primary seal at a wellhead interface. 
         FIG. 2  is an enlarged view of the test port and wellhead interface taken from  2 - 2  of  FIG. 1 . 
         FIG. 3  is an overview schematic representation of an oilfield accommodating the wellhead assembly of  FIG. 1  at a well. 
         FIG. 4  is an enlarged view of the primary seal and an adjacent secondary seal taken from  4 - 4  of  FIG. 2 . 
         FIG. 5  is a side and partial cross-sectional view of an alternate embodiment of a wellhead assembly with an exterior test port. 
         FIG. 6  is a flow-chart summarizing an embodiment of testing a primary seal at an interface of a wellhead with an exterior test port. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous details are set forth to provide an understanding of the present disclosure. However, it will be understood by those skilled in the art that the embodiments described may be practiced without these particular details. Further, numerous variations or modifications may be employed which remain contemplated by the embodiments as specifically described. 
     Embodiments are described with reference to certain land-based oilfield operations. For example, operations in which an onshore well is being installed, completed and tested is illustrated. In the embodiment shown, the wellhead assembly for the well is manually accessible along with an exterior test port for testing of the wellhead seal which is a ring gasket at the interface of the wellhead and base. However, a variety of different well types may take advantage of an exterior test port in this manner. For example, even subsea wells may take advantage of such wellhead architecture. Indeed, so long as the wellhead assembly includes an exterior test port for testing of an internal primary seal in combination with a secondary seal to facilitate the testing, appreciable benefit may be realized. 
     Referring now to  FIG. 1 , a side cross-sectional view of an embodiment of a wellhead assembly  101  is illustrated with an exterior test port  100 . The assembly  101  includes a wellhead  130  that is mounted to a base  140  which together define a wellbore  180  and provide a platform from which other well devices may be used to mange the wellbore  180 . The wellhead  130  and base  140  meet at an interface  120  which is sealed by a primary seal  125  to prevent leakage of wellbore fluids through the potential leak path of the interface  120 . In the embodiment shown, other coupling features such as a collar device  190  and guide pins  175  are provided to facilitate the mating of the wellhead  130  as described. 
     The noted exterior test port  100  is for the primary seal  125  at the interface  120 . More specifically, the test port  100  is fluidly coupled to the seal  125  at the interface  120  by way of an intentional leak path  110 . This allows for the introduction of pressure to the seal  125  to test and confirm functionality thereof. For example, as detailed further below, a portable pump  301  may be coupled to the port  100  to direct 10,000 PSI or more of pressure through the leak path  110  in order to confirm that the seal  125  is in proper working order. This is particularly beneficial because it allows for a way to test the seal  125  from an exterior location of the assembly  101  without requiring that the wellbore  180  be plugged and the more substantial undertaking of pressurizing the entire wellbore  180  above the plug. 
     Confirmation of the functionality of the primary seal  125  at the interface  120  means that concern over leakage of wellbore fluids from the wellbore  180  via the interface  120  during subsequent well operations may be assuaged. However, due to the configuration of the primary seal  125  and the fact that the pressure testing is directed at the seal  125  from an external location, an additional architectural feature is provided. Specifically, a secondary seal  150  is provided interior of the primary seal  125  and also at the interface  120 . 
     With added reference to  FIG. 2 , as detailed below, because of the manner in which the primary seal  125  functions, this backup secondary seal  150  allows for an accurate read of the functionality of the primary seal  125  from the described pressure test. Namely, the use of the secondary seal  150  means that both an interior face  250  and an outer face  275  of the seal  150  are tested. Without the secondary seal  150 , the pressure testing may falsely indicate seal failure of a functional seal  125  due to lack of sealing at the interior face  250  which is not determinative of seal functionality. 
     Referring now to  FIG. 2 , an enlarged view of the test port  100  and wellhead interface  120  is shown, taken from  2 - 2  of  FIG. 1 . In this depiction, the wellbore  180 , defined by the wellhead  130  and base  140  is apparent, immediately adjacent the interface  120 . Thus, concern over potential wellbore pressures directed at the interface  120  is apparent. It is along these lines that the primary seal  125  has been installed and set as illustrated. Setting aside the port  100 , leak path  110  and secondary seal  150  for the moment, the primary seal  125  is wedged into a primary groove  450  that is defined by the interfacing wellhead  130  and base  140  (see  FIG. 4 ). In the embodiment illustrated, it is the outer face  275  of this seal  125 , sealing against the wellhead  130  and base  140  structures that provide the sealing at the interface  120  relative the wellbore  180 . 
     Returning to the test port  100 , it is possible that the application of test pressure through the leak path  110  in the wellhead  130  to the primary seal  125  would overcome the interior face  250  of the seal  125  even for a functionally set seal  125 . Thus, to ensure that the outer face  275  sealing is the feature tested by the application of the port pressure, the secondary seal  150  is provided. So, for example, in circumstances where fluid pressure from the test port  100  overcomes the interior face  250 , the presence of the secondary seal  150  assures that the pressure will merely be routed back to the outer face  275  of the primary seal  125 . Thus, so long as the outer face  275  is in sealing engagement with the wellhead  130  and base  140 , pressuring up to a predetermined level via the test port  100  is possible and the primary seal  125  will test as functional. Of course, if pressure is unable to build to the predetermined level, even with the backstop of the secondary seal  150  in place, it may mean that the outer face  275  is not maintaining the intended sealing and the primary seal  125  has not passed the pressure test. 
     It is worth noting that for the testing scenario described above, the pressure applied through the port  100  for testing is “predetermined”. So, by way of example, where the potential pressure expected in the wellbore  180  following completion is to be over about 5,000 PSI but below about 10,000 PSI, the predetermined pressure test may be to a level of 10,000 PSI. Thus, a primary seal  125  passing the test may be rated at 10,000 PSI and considered well suited for use in the given well. Of course, wellbore pressures near the interface  120  may be higher. Thus, along these same lines, it may be possible to utilize the exterior port  100  to confirm a rating of 30,000 PSI or more for the primary seal  125 . 
     Referring now to  FIG. 3 , an overview schematic representation of an oilfield  300  accommodating the wellhead assembly  101  of  FIG. 1  at a well  302 . A host of conventional equipment  350  is shown at the wellsite, including a rig  360  to help support various installations. In the embodiment shown, a Christmas tree  355  accommodating various valves and other hookups has been installed at the wellhead  130 . Thus, the importance of ensuring proper internal sealing between the wellhead  130  and the base  140  is brought to mind. 
     In the embodiment shown, the wellbore  180  traverses a formation  375  potentially facing several thousand pounds of pressure in the vicinity of the wellhead  101 . Accordingly, pressure testing as described above may be achieved by use of a handheld, portable external pump  301  that may be hooked up to the external port  100  for testing. By way of comparison, a larger pump  315  and control unit  330  of a mobile equipment truck  310  may be left in place. There is no need to plug the wellbore  180  or pressure up the well  302  internally. Thus, there is also no need to spend 8-10 hours of test time devoted to such measures. Instead, an operator may simply hook up the smaller handheld pump  301  at the test port  100  and ensure that the internal seal (e.g. the primary seal  125  of  FIGS. 1 and 2 ), is properly set. Once confirmed, the tree  355  and other installations may ensue and operations within the well  302  may safely proceed. 
     Referring now to  FIG. 4 , an enlarged view of the primary seal  125  and an adjacent secondary seal  150  is illustrated taken from  4 - 4  of  FIG. 2 . In this view, the intentional leak path  110  is shown intersecting the primary seal  125  in a primary groove  450  defined by the wellhead  130  and base  140  at the interface  120 . It is also apparent that any fluid pressure supplied through the leak path  110  during testing as described above would be directed at both the interior face  250  and the outer face  275  of the seal  125 . As indicated above, sealing by the primary seal  125  may be particular to sealing at the outer face  275 . Therefore, to ensure that leakage past the interior face  250  does not serve as a false indicator of seal failure, the secondary seal  150  is provided at a location interior of the primary seal  125  at the interface  120 . Thus, so long as sealing is maintained at the outer face(s)  275 , pressure may be held and built up within the leak path  110  during testing as described. As a result, leakage through the interior face(s)  250  would not result in a failure designation for the seal  125 . 
     Referring now to  FIG. 5 , a side and partial cross-sectional view of an alternate embodiment of a wellhead assembly  101  is shown, again employing an exterior test port  100 . In this embodiment, a tubular  500  such as a production tubular has been installed within the wellbore. Thus, the potential for a leak path from a failing primary seal  125  continues beyond the horizontal interface  120  and to a vertical interface between the installed tubular  500  and the structure of the wellhead assembly  101  that defines the wellbore  180  (e.g. the wellhead  130  and base  140 ). As a result, backup sealing by a secondary seal may take place at locations of the vertical interface. Namely, as illustrated, backup sealing is achieved by an upper secondary seal  525  above the horizontal interface  120  and a lower secondary seal  550  below this interface  120 . Each secondary seal  525 ,  550  of this embodiment is located at the vertical interface and secured by the tubular  500 . 
     For the embodiment of  FIG. 5 , the secondary seals  525 ,  550  again achieve the function of preventing a false indication of primary seal failure during testing from the exterior port  100  should leakage through the leak path migrate past the interior face  250  even though successful sealing occurs at the outer face  275 . Once more, utilizing the vertical interface for the backup sealing means that the limited space of the horizontal interface  120  is not required. So, for example, where the size and space constraints of the horizontal interface  120  are such that an effective secondary seal may be difficult to manufacture or install, this backup sealing function may be moved to the more available space of the vertical interface. 
     Referring now to  FIG. 6 , a flow-chart is shown summarizing an embodiment of testing a primary seal at an interface of a wellhead with an exterior test port. As indicated at  620 , the wellhead seal is installed at the interface that has the potential to serve as a leak path from the wellbore that is defined by the wellhead assembly. Therefore, in order to test the seal in a manner that does not utilize the wellbore itself, a fluid may be pumped through an external port of the assembly toward the seal (see  640 ). Because the resulting fluid pressure is directed at the seal from an opposite direction of that of the wellbore, a backup or secondary seal may be utilized as indicated at  660 . That is, to prevent a false indication of seal failure, the backup seal may be utilized to prevent leak detection when the leak would be at a face of the seal that is not actually of concern in the real world environment of preventing a wellbore leak. Thus, as indicated at  680 , a true reading of test results based on the ability to pressure up through the exterior test port may be attained. 
     Embodiments described above provide a manner of testing a wellhead seal that avoids the more time consuming conventional techniques that require plugging and subsequent unplugging of the main wellbore. Thus, time, labor and material expenses may all be dramatically reduced. Once more, since the technique is applied externally, other aspects of installation are not impacted by way of closing off of the main bore. Thus, operators may be afforded a greater degree of flexibility in determining whether and when to proceed with other installation steps apart from testing of the wellhead seal. 
     The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle and scope of these embodiments. Furthermore, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.