Patent Publication Number: US-11396785-B2

Title: Low pressure starter wellhead system for oil and gas applications with potential thermal growth

Description:
TECHNICAL FIELD 
     This disclosure relates to low pressure starter wellhead systems capable of accommodating thermal expansion and related methods of installing such a wellhead system at a pipe assembly within a wellbore. 
     BACKGROUND 
     Drilling activities performed at a well within a surface formation can sometimes cause the surface formation to detrimentally leak fluids to the environment through tubing assemblies installed in the well. A starter wellhead may be installed to a casing assembly at the surface of the well. However, such wellheads are prone to failure with respect to sealing a surface formation to prevent fluid leakage and cannot accommodate thermal expansion of the tubing assembly. 
     SUMMARY 
     This disclosure relates to a low pressure starter wellhead system for casings of first and second sizes and a method of installing the wellhead system at a pipe assembly including such casings. The wellhead system appropriately seals a surrounding surface formation without restricting thermal-related expansion of the first and second casings and is designed to be installed beneath a primary casing. The wellhead system includes a first starter wellhead associated with the first size and a second starter wellhead associated with the second size that are arranged in a vertically stacked configuration. 
     In one aspect, a wellhead system includes a housing defining an axial bore, an outer pipe secured to the housing and extending axially from the housing, an inner pipe passing through the axial bore and through the outer pipe and having an outer diameter that is smaller than an inner diameter of the outer pipe, and a sealing device positioned along an inner surface of the housing and sealed to the inner pipe to seal an annular region defined between the inner and outer pipes. 
     Embodiments may provide one or more of the following features. 
     In some embodiments, the wellhead system further includes a lock ring that secures the sealing device to the inner surface of the housing. 
     In some embodiments, the sealing device includes an outer interference fit sealing element that seals to the outer pipe. 
     In some embodiments, the sealing device includes an inner interference fit sealing element that seals to the inner pipe. 
     In some embodiments, the sealing device is configured to accommodate thermal expansion of the inner pipe while maintaining a seal integrity against the inner pipe. 
     In some embodiments, the sealing device includes a test port for testing an integrity of the seal. 
     In some embodiments, the sealing device is configured to be reenergized following a reduction in sealing performance. 
     In some embodiments, the sealing device includes an injection port for injecting a substance to reenergize the sealing device. 
     In some embodiments, the outer pipe includes an outer pipe wall and a landing ring that protrudes radially inward from the outer pipe wall. 
     In some embodiments, the inner pipe includes an inner pipe wall and an abutment ring that protrudes radially outward from the inner pipe wall. 
     In some embodiments, the inner pipe is configured such that the abutment ring can land on the landing ring, and the outer pipe is configured to support a load of the inner pipe. 
     In some embodiments, the landing ring is a first landing ring, and the inner pipe includes a second inner landing ring that protrudes radially inward from the inner pipe wall. 
     In some embodiments, the wellhead system further includes a base plate positioned atop the housing. 
     In some embodiments, the housing defines an exterior quick connect profile for attachment to an accessory component. 
     In some embodiments, the wellhead system further includes a valve carried on the housing for relieving a pressure within the annular region. 
     In some embodiments, the housing is a first housing, the sealing device is a first sealing device, the inner pipe is a first inner pipe, and the wellhead system further includes a second housing positioned above the first housing and secured to the first inner pipe such that the first inner pipe extends axially from the second housing, a second inner pipe passing through an axial bore of the second housing and through the first inner pipe and having an outer diameter that is smaller than an inner diameter of the first inner pipe, and a second sealing device positioned along an inner surface of the second housing and sealed to the second inner pipe to seal a second annular region defined between the first and second inner pipes. 
     In some embodiments, the second sealing device is configured to accommodate thermal expansion of the second inner pipe while maintaining a seal integrity against the second inner pipe. 
     In some embodiments, the lock ring is a first lock ring, and the wellhead system further includes a second lock ring that secures the second sealing device to the second housing. 
     In another aspect, a method of installing a wellhead system at a pipe assembly includes securing an outer pipe to a pipe segment of the pipe assembly, the outer pipe secured to and extending axially from a housing defining an axial bore, landing an outer abutment ring of an inner pipe on an inner landing ring of the outer pipe such that the inner pipe passes through the axial bore of the housing and through the outer pipe, the inner pipe having an outer diameter that is smaller than an inner diameter of the outer pipe, installing a sealing device to an inner surface of the housing, and contacting the sealing device with the inner pipe to seal an annular region defined between the inner and outer pipes. 
     The details of one or more embodiments are set forth in the accompanying drawings and description. Other features, aspects, and advantages of the embodiments will become apparent from the description, drawings, and claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional cutaway view of a wellhead system. 
         FIG. 2  is an enlarged cross-sectional view of a first set of sealing devices of the wellhead system of  FIG. 1 . 
         FIG. 3  is an enlarged cross-sectional view of a second set of sealing devices of the wellhead system of  FIG. 1 . 
         FIGS. 4-8  sequentially illustrate a method of installing the wellhead system of  FIG. 1  at a pipe assembly within a surface formation. 
         FIG. 9  is a flow chart illustrating an example method of installing the wellhead system of  FIG. 1  at a pipe assembly. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a wellhead system  1000  installed to a pipe assembly  101  within a wellbore  105  at a surface formation  103 . The pipe assembly  101  includes an inner production pipe  121  that produces reservoir fluids from the wellbore  105  and an outer pipe  113  that surrounds the production pipe  121 . The wellhead system  1000  is a starter wellhead that provides wellhead sealing integrity for the surface formation  103  in order to prevent the surface formation  103  from releasing fluids through the pipe assembly  101  to the environment during a lifecycle of operations performed at the wellbore  105 . The wellhead system  1000  includes a first wellhead assembly  100  of a first size and a second wellhead assembly  200  of a second size that is larger than the first size. The first wellhead assembly  100  is disposed above the second wellhead assembly  200  and is also disposed beneath a reference wellhead assembly  107  (for example, a primary wellhead assembly) of a reference size that is smaller than the first size. 
     The reference wellhead assembly  107  includes a generally cylindrical housing  109  that defines a recessed profile  111  (for example, an inner, inverted circumferential seat) at which the outer pipe  113  is mated to the housing  109  at a lower end. The reference size of the reference wellhead assembly  107  is defined by an outer diameter of the outer pipe  113  that the recessed profile  111  is sized to securely accommodate. Accordingly, an inner diameter of the recessed profile  111  is sized to securely and snuggly accommodate the outer diameter of the outer pipe  113 . In some embodiments, the reference size is about 24 inches (in) (for example, about 0.61 meters (m)). The outer pipe  113  is defined by a cylindrical pipe wall  119  and an outer abutment ring  117  that protrudes radially outward from the pipe wall  119 . The outer abutment ring  117  can be landed on a surrounding pipe of the first wellhead assembly  100 , as will be discussed in more detail below. 
     The first wellhead assembly  100  supports the reference wellhead assembly  107  and defines an axial bore  160  that surrounds the outer pipe  113  of the pipe assembly  101 . The first wellhead assembly  100  includes a generally cylindrical base plate  106  that is positioned beneath the housing  109  of the reference wellhead assembly  107  and a generally cylindrical housing  108  that is located beneath the base plate  106 . An inner diameter of the base plate  106  is about equal to the inner diameter of the recessed profile  111  of the housing  109  such that the outer pipe  113  passes through the base plate  106 . 
     Referring to  FIGS. 1 and 2 , the housing  108  defines an upper recessed profile  112  (for example, an inner circumferential seat) and a lower recessed profile  114  (for example, an inner inverted circumferential seat). The housing  108  is equipped with an elastomeric, circumferential sealing device  118  (for example, a packoff) that is seated against the upper recessed profile  112  and a lock ring  116  that secures (for example, locks) the sealing device  118  in place against the upper recessed profile  112 . The sealing device  118  and the lock ring  116  have an inner diameter that is about equal to the inner diameter of the base plate  106 , thereby allowing passage of and contact with the outer pipe  113  of the pipe assembly  101 . The sealing device  118  includes two inner interference fit sealing elements  126  that seal against the outer pipe  113  of the pipe assembly  101 , multiple outer interference fit sealing elements  130  that seal against the upper recessed profile  112  of the housing  108 , a seal body  120  that supports the sealing elements  126 , a test fitting  122  for testing a performance of the sealing device  118 , and two injection ports  104 . In the event that the sealing device  118  begins to perform poorly, the sealing device  118  can be re-energized to improve the sealing performance by injecting plastic into the injection ports  104 . 
     Sizes and material formulations of the components of the sealing device  118  are selected such that the outer pipe  113  of the pipe assembly  101  can move axially along the first wellhead assembly  100  when thermal expansion of the outer pipe  113  causes such movement without loss of sealing integrity of the sealing device  118 . The outer pipe  113  has a precisely machined surface and is made of high grade materials for resisting corrosion during the equipment lifecycle. The interference fit sealing elements  126  are made of one or more materials that can provide the required sealing performance and that can withstand frictional forces exerted by the outer pipe  113  during axial movement (for example, upward and downward movement) of the outer pipe  113  due to thermal expansion. The interference fit sealing elements  126  are typically made of one or materials, such as rubber (for example, hydrogenated acrylonitrile butadiene rubber (HNBR)). The outer interference fit sealing elements  130  and the seal body  120  are typically made of one or materials, such as low alloy steel (LAS). 
     The first wellhead assembly  100  also includes a first pipe segment  134  that is securely mated (for example, welded) to the lower recessed profile  114 . The first size of the first wellhead assembly  100  is defined by an outer diameter of the first pipe segment  134 . Accordingly, an inner diameter of the recessed profile  114  is sized to securely and snuggly accommodate the outer diameter of the first pipe segment  134 . In some embodiments, the first size is about 30 in (for example, about 0.76 m). 
     The first pipe segment  134  is defined by a cylindrical pipe wall  102 , an inner landing ring  136  that protrudes radially inward from the pipe wall  102 , and an outer abutment ring  152  that protrudes radially outward from the pipe wall  102 . The outer abutment ring  152  can be landed on a surrounding pipe of the second wellhead assembly  200 , as will be discussed in more detail below. The first pipe segment  134  and the outer pipe  113  of the pipe assembly  101  together define an intermediately located annular region  138  (for example, an annulus). The sealing device  118  is designed to seal off the annular region  138  at an upper end  140  to contain any fluid pressure built up within the annular region  138  and thereby prevent any fluid within the annular region  138  from leaking to the atmosphere. In some embodiments, the pipe wall  102  has a length of up to about 65 in (for example, about 1.65 m) and a thickness that falls in a range of about 2.0 cm to about 1.8 cm. 
     The housing  108  is further equipped with a valve  142  (for example, a gate valve) by which fluid pressure can be relieved from the annular region  138  through an outlet  144 . The outer pipe  113  of the pipe assembly  101  can be further installed to the first wellhead assembly  100  by landing the outer abutment ring  117  of the outer pipe  113  onto the inner landing ring  136  of the first pipe segment  134 . The first pipe segment  134  is strong enough to bear a load of the outer pipe  113  and any components supported thereon without failing throughout drilling operations carried out at the wellbore  105 . 
     The housing  108  is also equipped with a test port  146  by which a fluid (for example, nitrogen gas) can be injected to test the integrity of a welded connection between the first pipe segment  134  and the lower recessed profile  114  of the housing  108 . Near an upper end, the housing  108  defines an exterior, circumferential quick connect profile  150  by which additional equipment can be installed to the first wellhead assembly  100  for facilitating well control (for example, containment of fluid pressure within the wellbore  105  during drilling operations). For example, a diverter system may be installed to the quick connect profile  150  to allow drilling fluid that was used to drill the wellbore  105  or any other formation fluid to be diverted away from the drilling plate form without compromising the well integrity or safety. 
     The second wellhead assembly  200  is a casing hanger that supports the first wellhead assembly  100  and defines an axial bore  260  that surrounds the first pipe segment  134 . The second wellhead assembly  200  includes a generally cylindrical base plate  206  that is positioned beneath the housing  108  of the first wellhead assembly  100  and a generally cylindrical housing  208  that is located beneath the base plate  206 . An inner diameter of the base plate  206  is about equal to the inner diameter of the lower recessed profile  114  of the housing  108  such that the first pipe segment  134  passes through the base plate  206 . 
     Referring to  FIGS. 1 and 3 , the housing  208  defines an upper recessed profile  212  (for example, an inner circumferential seat) and a lower recessed profile  214  (for example, an inner inverted circumferential seat). The housing  208  is equipped with an elastomeric, circumferential sealing device  218  (for example, a packoff) that is seated against the upper recessed profile  212  and a lock ring  216  that secures (for example, locks) the sealing device  218  in place against the upper recessed profile  212 . The sealing device  218  and the lock ring  216  have an inner diameter that is about equal to the inner diameter of the base plate  206 , thereby allowing passage of and contact with the first pipe segment  134  of the first wellhead assembly  100 . The sealing device  218  includes two inner interference fit sealing elements  226  that seal against the first pipe segment  134 , multiple outer interference fit sealing elements  230  that seal against the upper recessed profile  212  of the housing  208 , a seal body  220  the supports the sealing elements  226 , a test fitting  222  for testing a performance of the sealing device  218 , and two injection ports  204 . In the event that the sealing device  218  begins to perform poorly, the sealing device  218  can be re-energized to improve the sealing performance by injecting plastic into the injection ports  204 . 
     Sizes and material formulations of the components of the sealing device  218  are selected such that the first pipe segment  134  of the first wellhead assembly  100  can move axially along the second wellhead assembly  200  when thermal expansion of the first pipe segment  134  causes such movement without loss of sealing integrity of the sealing device  218 . The first pipe segment  134  has a precisely machined surface and is made of high grade materials for resisting corrosion during the equipment lifecycle. The interference fit sealing elements  226  are made of one or more materials that can provide the required sealing performance and that can withstand frictional forces exerted by the first pipe segment  134  during axial movement (for example, upward and downward movement) of the first pipe segment  134  due to thermal expansion. The interference fit sealing elements  226  are typically made of one or materials, such as rubber (for example, HNBR). The outer interference fit sealing elements  230  and the seal body  220  are typically made of one or materials, such as LAS. 
     The second wellhead assembly  200  also includes a second pipe segment  234  that is securely mated (for example, welded) to the lower recessed profile  214 . The second size of the second wellhead assembly  200  is defined by an outer diameter of the second pipe segment  234 . Accordingly, an inner diameter of the recessed profile  214  is sized to securely and snuggly accommodate the outer diameter of the second pipe segment  234 . In some embodiments, the second size is about 36 in (for example, about 0.91 m). 
     The second pipe segment  234  is defined by a cylindrical pipe wall  202  and an inner landing ring  236  that protrudes radially inward from the pipe wall  202 . The second pipe segment  234  and the first pipe segment  134  together define an intermediately located annular region  238  (for example, an annulus). The sealing device  218  is designed to seal off the annular region  238  at an upper end  240  to contain any fluid pressure built up within the annular region  238  and thereby prevent any fluid within the annular region  238  from leaking to the atmosphere. In some embodiments, the pipe wall  202  has a length of up to about 25 in (for example, about 0.635 m) and a thickness that falls in a range of about 1.2 cm to about 1.9 cm. 
     The housing  208  is further equipped with a valve  242  (for example, a gate valve) by which fluid pressure can be relieved from the annular region  236  through an outlet  244 . The first pipe segment  134  of the first wellhead assembly  100  can be further installed to the second wellhead assembly  200  by landing the outer abutment ring  152  of the first pipe segment  134  onto the inner landing ring  236  of the second pipe segment  234 . The second pipe segment  234  is strong enough to bear a load of the first pipe segment  134  and any components supported thereon without failing throughout drilling operations carried out at the wellbore  105 . 
     The housing  208  is also equipped with a test port  246  by which a fluid (for example, nitrogen gas) can be injected to test the integrity of a welded connection between the pipe second pipe segment  234  and the lower recessed profile  214  of the housing. Near an upper end, the housing  208  defines an exterior, circumferential quick connect profile  250  by which additional equipment can be installed to the second wellhead assembly  200  for facilitating well control. For example, a diverter system may be installed to the quick connect profile  250  to allow drilling fluid that was used to drill the wellbore  105  or any other formation fluid to be diverted away from the drilling plate form without compromising the well integrity or safety. 
     The wellhead system  1000  provides several advantages with respect to conventional wellheads. For example, the wellhead system  1000  facilitates efficient equipment installation at a surface formation in that the second pipe segment  234  is pre-welded or otherwise preassembled with the housing  208  of the second wellhead assembly  200  at a shop location that is remote from the field. In contrast, like components of conventional wellheads must be installed to each other at the field, which is associated with relatively higher costs, more installation steps, and accordingly longer operational times. Furthermore, the wellhead system  1000  advantageously provides both sealing integrity and accommodation for thermal growth of interior pipes, which is not provided by conventional wellhead designs. 
     In use at the surface formation  103 , the wellhead system  1000  is installed to the pipe assembly  101  sequentially in stages to carry out multiple operations at the wellbore  105 . Referring to  FIG. 4 , the housing  208  of the wellhead assembly  200 , equipped with the second pipe segment  234  and the valve  242 , is transported to a location of the pipe assembly  101  and welded at the inner landing ring  236  to a pipe segment  115  (for example, a casing stub) of the second size that surrounds the first pipe segment  134  (not shown). A riser adapter (not shown) is built upwards section-by-section (for example, nippled up) and mated to the exterior quick connect profile  250  to establish a connection between the housing  208  and a diverter  115 . The connection will provide a continuous containment of fluid within the pipe assembly  101  until the fluid reaches the diverter  115 . A drilling operation is then performed at the pipe assembly  101 . 
     Referring to  FIG. 5 , once the drilling operation is completed, the first pipe segment  134  is installed to the second pipe segment  234  by landing the outer abutment ring  152  of the first pipe segment  134  onto the inner landing ring  236  of the second pipe segment  234  and cementing the annular region  238  above the rings  152 ,  236 . The connection between the riser adapter and the quick connect profile  250  is broken, and the first pipe segment  134  is cut to a height appropriate for subsequent installation of the base plate  206  and the housing  108  of the first wellhead assembly  100 . Next, the sealing device  218  is installed to the housing  208  with the lock ring  216  and tested via the test port  222 . If the testing is unsuccessful, then one or more components of the wellhead assembly  200  may be further examined before proceeding with further steps. Otherwise, successful test results indicate that the annular region  238  is fluidically isolated by the sealing device  218 . The base plate  206  is installed to the housing  208 , and the housing  108  of the first wellhead assembly  100  is subsequently installed to the first pipe segment  134  extending through the wellhead assembly  200  atop the base plate  206 . 
     Referring to  FIG. 6 , the riser adapter is built upwards section-by-section and mated to the exterior quick connect profile  150  to establish a connection between the housing  108  and the diverter  115  A drilling operation is then performed at the pipe assembly  101 . 
     Referring to  FIG. 7 , once the drilling operation is completed, the outer pipe  113  of the pipe assembly  101  is installed to the first pipe segment  134  by landing the outer abutment ring  117  of the outer pipe  113  onto the inner landing ring  136  of the first pipe segment  134  and cementing the annular region  138  above the rings  117 ,  136 . The connection between the riser adapter and the quick connect profile  150  is broken, and the outer pipe  113  is cut to a height appropriate for subsequent installation of the base plate  106  and the housing  109  of the reference wellhead assembly  107 . Next, the sealing device  118  is installed to the housing  108  with the lock ring  116  and tested via the test port  122 . If the testing is unsuccessful, then one or more components of the wellhead assembly  100  may be further examined before proceeding with further steps. Otherwise, successful test results indicate that the annular region  138  is fluidically isolated by the sealing device  118 . 
     Referring to  FIG. 8 , the reference wellhead assembly  107  is installed to the outer pipe  113 , and then the base plate  106  is installed on top of housing  108  and below the housing  109  of the reference wellhead assembly  107  to complete installation of the wellhead system  1000 . Upon completion of the installation, the outer pipe  113  of the pipe assembly  101  extends through the wellhead assemblies  100 ,  200 . 
       FIG. 9  is a flow chart illustrating an example method  2000  of installing a wellhead system (for example, the wellhead system  1000 ) at a pipe assembly (for example, the pipe assembly  101 ). In some embodiments, the method  2000  includes a step  2002  of securing an outer pipe (for example, the second pipe segment  234 ) to a pipe segment of the pipe assembly, the outer pipe secured to and extending axially from a housing (for example, the housing  208 ) defining an axial bore (for example, the axial bore  260 ). In some embodiments, the method  2000  includes a step  2004  of landing an outer abutment ring (for example, an outer abutment ring  152 ) of an inner pipe (for example, the first pipe segment  134 ) on an inner landing ring (for example, the inner landing ring  236 ) of the outer pipe such that the inner pipe passes through the axial bore of the housing and through the outer pipe, the inner pipe having an outer diameter that is smaller than an inner diameter of the outer pipe. In some embodiments, the method  2000  includes a step  2006  of installing a sealing device (for example, a sealing device  218 ) to an inner surface of the housing. In some embodiments, the method  2000  includes a step  2008  of contacting the sealing device with the inner pipe to seal an annular region (for example, the annular region  238 ) defined between the inner and outer pipes. 
     While the wellhead system  1000  has been described and illustrated with respect to certain dimensions, sizes, shapes, arrangements, materials, and methods  2000 , in some embodiments, a wellhead system that is otherwise substantially similar in construction and function to the wellhead system  1000  may include one or more different dimensions, sizes, shapes, arrangements, and materials or may be utilized according to different methods. 
     Accordingly, other embodiments are also within the scope of the following claims.