Abstract:
A high pressure seal adapter for a conductor housing of a wellhead, and a method of completing a well having a conductor housing attached thereto, are disclosed. The high pressure seal adapter has a unitary body including a first circular bore extending through the unitary body. The first circular bore has a circular perimeter extending beyond a centerline of the unitary body. The unitary body further includes a second circular bore adjacent the first circular bore and extending through the unitary body. The seal adapter is configured to be installed in the conductor housing. The method includes providing such a high pressure seal adapter and installing the high pressure seal adapter in the conductor housing.

Description:
FIELD OF INVENTION 
     Embodiments of the present invention provide a high pressure seal adapter that connects a splitter conductor housing to a wellhead of a well. 
     BACKGROUND 
     In the drilling industry, the term well completion is often used to denote the operations that prepare a well bore for producing oil or gas from the reservoir. It may similarly refer to a completed wellhead assembly. The goal of these operations is to install a wellhead and other connections to optimize the flow of the reservoir fluids into the well bore, up through the producing string, and into the surface collection system. 
     To begin a drilling operation a conductor pipe may be driven into the ground to prevent the loose surface soil from caving into the hole as the upper portion of the borehole is being drilled. Various components are then attached to the conductor pipe. A single conductor for 2 or more well completions is often used as it provides benefits such as smaller platform sizes and reduced installation time. Each well completion requires one wellhead to be installed before oil/gas production can commence. Thus 2 or more separate wellheads may be provided in a single conductor. 
       FIG. 1  shows a cross-sectional view of one example of a prior art conductor pipe assembly, designated generally as reference numeral  10 .  FIG. 1A  illustrates a close-up cross-sectional view of the circled portion “A” of  FIG. 1 .  FIG. 2  illustrates a cross-sectional view of the assembly  10  of  FIG. 1  with two wellheads attached.  FIG. 3  illustrates a top perspective view of the conductor housing of  FIGS. 1 and 2 . 
     With continuing reference to  FIGS. 1-3 , the assembly  10  includes a conductor  12  and a conductor housing  20  mounted to a top  14  of the conductor  12 . The conductor housing  20  includes two cylindrical holes  24   a ,  24   b  separated by a central section  26  that extends longitudinally into the central bore of the conductor  12 . The two cylindrical holes  24   a ,  24   b  of the assembly  10  facilitate the drilling of 2 separate wells  6 ,  8  (represented graphically as the centerlines of the holes  24   a ,  24   b ) within the conductor  12 . Typically, the following steps are required to complete the connection between the conductor housing  20  and each wellhead  30   a ,  30   b  ( FIG. 2 ). Usually, only one well ( 6  or  8 ) is worked on and the other well  6 ,  8  is covered with a debris cap  16 . 
     For example as shown in  FIG. 1 , during the installation phase, a riser  40  that is used to protect the well fluids from the environment is required to be installed before any drilling operations. In this example, the riser  40  is installed above well  6 . One or more seals  42  are located at the bottom of the riser  40  between an outside surface  44  of the riser  40  and an inside surface  22  of the conductor housing  20 . In this prior art assembly, the seals  42  directly contact the conductor housing  20 . 
     A separate debris cap  16  is installed on the conductor housing  20  to protect well  8 . As best shown in  FIG. 1A , the debris cap  16  includes one or more seals  17  between the debris cap  16  and the inside surface  22  of the central portion  26  of hole  24   a  in the conductor housing  20 . In this prior art wellhead, the riser  40  seals directly onto the conductor housing  20 . The “Sealing Thickness”, shown as T s , must be sufficient to hold pressure regardless of whether the riser  40  is installed in either of the cylindrical holes  24   a ,  24   b  above the well bores  6 ,  8 . The thickness of the riser  40  is shown as T r . The total available thickness for well drilling operations is shown as T total . The portion marked T w  is “Wasted Thickness” which is there to provide for the riser  40  to be installed when drilling operations are switched to the other bore. When no drilling operations go through that bore, the area is dead space and is considered wasted. This wasted thickness T w  is undesirable. 
     After the well  6  is drilled through, a casing hanger  50  ( FIG. 2 ) is installed, and a casing  55  is inserted into the well  6 . The riser  40  is then dismantled. Subsequently, the wellhead  30   a  is installed onto the conductor housing  20 . One or more seals  32  may be installed on an inside surface  34  of the wellhead  30   a  to provide a leak-proof connection to an outside surface  52  of the casing hanger  50 . 
     In such a conductor splitter application, the wells  6 ,  8  have to be located close to each other, constrained by the internal diameter of the conductor  12 , and the thickness T total  of the central section  26  of the conductor housing  20 . Furthermore, the center to center distance  18  between well  6  and well  8  is constrained to allow two separate vertical bores to pass through the conductor housing  20  through cylindrical holes  24   b ,  24   a , respectively. As the riser  40  and subsequently the wellhead  30   a ,  30   b  must be fitted within the boundary of each bore for well isolation, the wall thickness of the riser  40  is also constrained. The internal diameter of the riser  40  is also constrained by the minimum allowed diameter based on industry standards. Similarly, as the bottom of the riser  40  seals directly on the conductor housing  20 , the central section  26  must be sufficiently thick to withstand the well pressure and allow sealing on either side of the bore. These constraints limit the amount of pressure under which the wells  6 ,  8  may operate. For example, in typical well completions as shown in  FIGS. 1 and 2 , each well may be constrained to operate at a pressure of 3000 psi (20.6 MPascal) or less. 
     One solution to increase the available pressure in the wellhead is to use a smaller drill bit that would allow for a thicker riser wall. However, using a smaller drill bit also results in a smaller casing size for the well. While the operating pressure of the resulting well may be increased, the overall volume is less than what would be produced using the larger drill bit at the higher pressure. This is often unacceptable to the operator of the well. An alternate solution is to provide a larger conductor, thus increasing the center to center distance between the wells, so that the original drill bit may be used, and appropriate high-pressure wellheads installed. This option may greatly increase the cost of the required wellhead equipment. 
     Yet another solution is to use an underreamer which is able to pass through the riser and subsequently expand the cutter arms to enlarge the borehole. However, this solution increases both the time required and the costs associated with the drilling operation. 
     SUMMARY 
     One aspect of the present invention provides a high pressure seal adapter for a conductor housing of a wellhead, the high pressure seal adapter having a unitary body comprising: a first circular bore extending through said unitary body; and a second circular bore adjacent said first circular bore and extending through said unitary body; wherein said seal adapter is capable of being installed in said conductor housing. 
     In alternate embodiments, the high pressure seal adapter may further include at least one seal extending around a perimeter of said unitary body, said at least one seal contacting said conductor housing. The adapter may receive a high pressure riser in said first circular bore when said seal adapter is installed in said conductor housing, said high pressure riser having a lower surface that contacts said flange and at least one seal extending around an outside perimeter of said riser, said at least one seal contacting said side wall to facilitate well drilling operations through said high pressure riser and said first bore for a first well. 
     In further embodiments, the high pressure seal adapter may further include an upper and lower planar surface, wherein said lower planar surface rests on a flange of said conductor housing and said upper planar surface is substantially co-planar with an upper surface of said conductor housing when said seal adapter is installed in said conductor housing. The seal adapter may be rotated 180 degrees and installed in said conductor housing to facilitate well drilling operations for a second well. The high pressure seal adapter may be capable of operating at well pressures up to 34.5 Mega Pascals. 
     An alternate aspect of the present invention provides a method of facilitating high pressure drilling and extraction operations for a well, the well comprising a conductor having a conductor housing attached thereto, the method comprising the steps of: providing high pressure seal adapter having a unitary body comprising: a first circular bore extending through said unitary body; and a second circular bore adjacent said first circular bore and extending through said unitary body; and installing said seal adapter in said conductor housing. 
     In alternate embodiments, the method may further include connecting a high pressure riser to said conductor housing, said high pressure riser having a lower surface that extends into said first circular bore and contacts said flange, and at least one seal extending around an outside perimeter of said riser, said at least one seal contacting said side wall to facilitate well drilling operations through said high pressure riser and said first bore for a first well. 
     In other embodiments, when said well drilling operations are completed for said first well, the method may further include: removing said high pressure riser; removing said seal adapter; rotating said seal adapter 180 degrees; reinstalling said seal adapter in said conductor housing; connecting a first casing hanger through said second bore to the conductor housing; and connecting said high pressure riser to said conductor housing, said high pressure riser having a lower surface that extends into said first circular bore and contacts said flange, and at least one seal extending around an outside perimeter of said riser, said at least one seal contacting said side wall to facilitate well drilling operations through said high pressure riser and said first bore for a second well. When said well drilling operations are completed for said second well, the method may further include: removing said high pressure riser; connecting a second casing hanger through said first bore to the conductor housing; installing first and second casings in said first and second well, respectively; attaching a first wellhead to said conductor housing above said first well; and attaching a second wellhead to said conductor housing above said second well. 
     In alternate embodiments, the seal adapter may further include an upper and lower planar surface; and said step of installing said seal adapter may further include seating said lower planar surface on a flange of said conductor housing such that said upper planar surface is substantially co-planar with an upper surface of said conductor housing. The high pressure drilling and extraction operations may be conducted at well pressures up to 34.5 Mega Pascals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will be better understood and readily apparent to one of ordinary skill in the art from the following written description, by way of example only, and in conjunction with the drawings, in which: 
         FIG. 1  illustrates a cross-sectional view of one example of a prior art conductor pipe assembly; 
         FIG. 1A  illustrates a close-up cross-sectional view of the circled portion “A” of  FIG. 1 ; 
         FIG. 2  illustrates a cross-sectional view of the assembly of  FIG. 1  with two wellheads attached; 
         FIG. 3  illustrates a top perspective view of the conductor housing of the assembly of  FIGS. 1 and 2 . 
         FIG. 4  illustrates a perspective view of one embodiment of a high pressure seal adapter according to the present invention; 
         FIG. 5  illustrates a top view of the high pressure seal adapter of  FIG. 4 ; 
         FIG. 6  illustrates a cross-sectional side view of the high pressure seal adapter of  FIGS. 4 and 5 ; 
         FIG. 7  illustrates a perspective view of one embodiment of a modified conductor housing that may be used with the seal adapter of  FIGS. 4-6 ; 
         FIG. 7A  illustrates a cross-sectional side view of the high pressure seal adapter of  FIGS. 4-6  installed in the modified conductor housing of  FIG. 7 ; 
         FIG. 8  illustrates a cross-sectional side view of a riser installed on the high pressure seal adapter of  FIG. 7 ; 
         FIG. 9  is a top perspective view of the riser and seal adapter of  FIG. 8 ; 
         FIG. 10  illustrates a cross-sectional side view of a riser installed on the high pressure seal adapter of  FIG. 7 , which has been installed on the conductor housing in a reversed position; 
         FIG. 10A  illustrates a close-up cross-sectional view of the circled portion “A” of  FIG. 10 ; and 
         FIG. 11  illustrates a cross-sectional side view of two completed wellheads installed on the high pressure seal adapter of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention provide a separate seal adapter that may be installed in a modified conductor housing. The seal adapter and modified conductor housing facilitate the drilling of well bores using standard sized drill bits, and allow for high pressure operation of the resulting wells. The example embodiment of the present invention will be discussed in an application using a standard 36 inch (0.9144 meter) conductor having two bore holes. However, it is understood that appropriately configured embodiments of the present invention may be used with conductors of any size and having two or more bore holes. 
       FIG. 4  illustrates a perspective view of one embodiment of a high pressure seal adapter  100  according to the present invention.  FIG. 5  illustrates a top view of the high pressure seal adapter  100  of  FIG. 4 .  FIG. 6  illustrates a side view of the high pressure seal adapter  100  of  FIGS. 4 and 5 . 
     The seal adapter  100  includes a first bore  110  and a second bore  120  that allow equipment access through the seal adapter  100  and conductor housing  150  ( FIG. 7 ) to the underlying conductor  12 . The first bore  110  and second bore  120  are separated by a central section  112 . As best shown in  FIG. 5 , a circular perimeter  113  of the first bore  110  extends slightly beyond a centerline  107  of the seal adapter  100 . The seal adapter  100  may include one or more seals  102   a ,  102   b  located in corresponding grooves  104   a ,  104   b  respectively around an outside perimeter  106  of the seal adapter  100 . In the embodiment illustrated in  FIGS. 4-6 , the first bore  110  may include a circular flange  108  extending partially into the bore  110  around an inside surface  109 . The flange  108  may have a downward taper that helps to prevent the accumulation of debris which may occur with a flat shoulder, and which also assists in guiding tools going into the bore  110  before the riser is installed. The bore  120  includes a substantially vertical inside surface  121 . This will be discussed in more detail below. The seal adapter  100  may have a planar upper surface  117   a , and a planar lower surface  117   b.    
     In this embodiment, the seal adapter  100  has a flattened oval “racetrack” profile as seen from the top ( FIG. 5 ) with substantially straight long edges  103   a ,  103   b  and substantially circular end portions  105   a    105   b . However, it is understood that other profiles may also be used without departing from the scope of the appended claims. For example, in some embodiments, a triangular shaped seal adapter  100  may be used in drilling operations that provide for three well bores in a single conductor. The seal adapter  100  may also include a plurality of mounting holes  111  drilled adjacent the long edges  103   a ,  103   b  that facilitate the connection of the seal adapter  100  to the risers  40   a ,  40   b  and/or the wellheads  30   a ,  30   b . Alternately, the mounting holes  111  may facilitate the connection of the seal adapter  100  to the underlying conductor housing  150 . This will be discussed in more detail below. 
       FIG. 7  illustrates a perspective view of one embodiment of a modified conductor housing  150  that may be used with the seal adapter  100  of  FIGS. 4-6 .  FIG. 7   a  illustrates a cross-sectional side view of the high pressure seal adapter  100  of  FIGS. 4-6  installed in the modified conductor housing  150  of  FIG. 7 .  FIG. 8  illustrates a cross-sectional side view of the riser  40   a  installed on the high pressure seal adapter  100  as mounted on the conductor housing  150 , as shown in  FIG. 7   a .  FIG. 9  is a top perspective view of the riser  40   a  and seal adapter  100  of  FIG. 8 .  FIG. 10  illustrates a cross-sectional side view of the seal adapter  100  in a reversed position on the conductor housing  150 . This facilitates the installation of another riser  40   b  that may be used to facilitate well completion for the well bore  6 . It is understood that riser  40   a  may also be repositioned above well bore  6  for this purpose.  FIG. 10A  illustrates a close-up cross-sectional view of the circled portion “A” of  FIG. 10 . 
     The installation and operation of the seal adapter  100  will now be described with reference to  FIGS. 7-10 . As discussed above, once the conductor  12  has been driven into the ground at the desired drilling location, the conductor housing  150  is installed onto the top  14  of the conductor  12 . This process is known to those of skill in the art, and will not be described in detail here. It is understood that the conductor  12  may also be used in subsea operations. Embodiments of the present invention are thus not limited to surface wells, but may be used in any well drilling operation in which a conductor housing  150  is installed onto a conductor  12 . 
     With reference to  FIG. 7 , once the conductor housing  150  has been installed onto the top  14  of the conductor  12 , the seal adapter  100  may be installed into the top of the conductor housing  150 . In this embodiment, a portion of central section  156  of the conductor housing  150  has been removed to provide a flange  157  to facilitate the connection between the seal adapter  100  and the conductor housing  150 . In this illustration, bore  110  of the seal adapter  100  is positioned above well bore  8  to facilitate well drilling operations ( FIG. 7   a ). 
     When installed in the conductor housing  150 , a portion of the lower surface  117   b  of the seal adapter  100  rests on the corresponding flange  157  in the conductor housing  150 , while the upper surface  117   a  of the seal adapter  100  is substantially flush with a top surface  155  of the conductor housing  150 . The seals  102   a ,  102   b  provide a pressure tight seal between the seal adapter  100  and an inside surface  152  of the conductor housing  150 . A bolt  132  may extend through corresponding holes in the risers  40   a ,  40   b  or wellheads  30   a ,  30   b  into each of the drill holes  111  of the seal adapter  100 . In alternate embodiments, the bolts  132  may extend through each of the drill holes  111  into corresponding holes in the conductor housing  150  to secure the seal adapter  100  to the conductor housing  150 . 
     As shown in  FIGS. 8 and 9 , the riser  40   a  may then be installed in bore  110  of the seal adapter  100  above wellbore  8 . As is known in the art, the riser  40   a  may be thinner on one side to allow dismantling of the trash cap  16   a  ( FIG. 8 ) while the riser  40   a  is in place. A lower surface  41  of the riser  40   a  may contact the flange  108  in the bore  110  of the seal adapter  100 . The riser  40   a  may then be attached to the conductor housing  150  using a plurality of bolts  46  ( FIG. 9 ). A trash cap  16   a  may also be installed into bore  120  of the seal adapter  100 . The trash cap  16   a  may include one or more seals  17   a ,  17   b  between the inside surface  121  of the bore  120  and an outside surface  18   a  of the trash cap  16   a . The trash cap  16   a  may also include one or more seals  17   b ,  17   b  between the inside surface  152  of the conductor housing  150  and the outside surface  18   a  of the trash cap  16   a.    
     After the riser  40   a  is installed, various tools are run inside the riser  40   a  to test the connection, drill for the next casing depth, wash the bore and to perform other well operations. Once drilling operations are completed, the riser  40   a  and trash cap  16   a  are removed from the conductor housing  150 . 
     With reference to  FIG. 10 , the seal adapter  100  may then be removed, rotated 180 degrees such that the bore  110  is positioned above well bore  6 , and reinstalled into the conductor housing  150  as previously described. A casing hanger  50   a  may then be installed through bore  120  of seal adapter  100 , and connected to the conductor housing  150 . A trash cap  16   b  may then be installed in the bore  120  of the seal adapter  100 , and onto the casing hanger  16   b  to protect the casing hanger  16   b  from debris. The riser  40   b  may then be installed in bore  110  of the seal adapter  100  above wellbore  6 . Drilling and other well operations are then commenced as previously described. 
       FIG. 10   a  illustrates a close-up cross-sectional view of the circled portion “A” of  FIG. 10 . As best shown in  FIG. 10   a , one or more seals  42  are located at the bottom of the riser  40   a  between an outside surface  44  of the riser  40   b  and the inside surface  109  of the seal adapter  100 . Similarly, the trash cap  16   b  may also include one or more seals  17   a  between the inside surface  121  of the bore  120  and the outside surface  18   b  of the trash cap  16   b , as well as one or more seals  17   b  between the inside surface  152  of the conductor housing  150  and the outside surface  18   b  of the trash cap  16   b.    
     By employing the seal adapter  100  in the modified conductor housing  150 , the thickness T r  of the riser  40   b  can be increased, while the total available thickness T total  is approximately the same. This allows for increased pressures in the riser  40   b  using the same conductors of the prior art. 
       FIG. 11  illustrates a cross-sectional side view of two wellheads  30   a ,  30   b  installed on the conductor housing  150  containing the high pressure seal adapter  100  of  FIG. 7 . In this completed well, both of the casing hangers  50  and wellheads  30   a ,  30   b  have been installed onto the conductor housing  150 . The seal adapter  100  is left in the conductor housing  150 . As shown in the illustration, the seal adapter  100  does not interfere with the installation of the wellhead(s)  30   a ,  30   b . The final position and orientation of the seal adapter  100  does not affect well operations. Subsequent operations from the installation of the wellhead  30   a ,  30   b  onwards are per normal well drilling and installation procedures, as know to those of skill in the art. 
     As best shown in  FIGS. 8 ,  10  and  10   a , the seal adapter  100  addresses the problems discussed above by shifting the seal position of the risers  40   a ,  40   b  from the conductor housing  20  of the prior art to the seal adapter  100 . Since the first bore  110  of the seal adapter  100  is slightly larger than what was available in the prior art, a riser  40   a  having thicker walls may be used without reducing the size of the drill bit, or increasing the size of the conductor. The seal adapter  100  can be removed from the conductor housing  150 , rotated 180 degrees, and reinstalled in the conductor housing to facilitate riser installation through bore  110  of the seal adapter  100  to either of the 2 well bores  6 ,  8 . This allows the risers  40   a ,  40   b  to be thicker than the conventional design, and still maintain the same inner diameter for equipment to pass through it. The thicker riser design allows for a higher overall pressure rating for each of the wells. By way of example and not limitation, a well that has been prepared as described above, and configured as shown in  FIGS. 7-11 , may safely operate at pressures of up to 5000 psi (34.5 MPa). It is understood that even higher pressures may be obtained by using non-standard materials for the seal adapter. 
     It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.