Patent Publication Number: US-7216699-B2

Title: Sub mudline abandonment connector

Description:
RELATED APPLICATIONS 
   This patent application claims the benefit of co-pending, provisional patent application U.S. Ser. No. 60/433,672, filed on Dec. 16, 2002, which is hereby incorporated by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to subsea wellhead assemblies, more specifically assemblies having a conuit with an upper portion capable of disconnecting from a lower portion that has been cemented into the well. 
   2. Background of the Prior Art 
   Subsea wells typically have a low pressure wellhead housing with a string of conductor casing suspended therefrom. A high pressure wellhead housing lands with in the low pressure wellhead housing and supports another string of casing suspended into the well. Additional intermediate hangers and strings of casing are supported within the high pressure wellhead housing which extend to deeper depths within the subsea well. In a typical subsea well, the outer casing suspended from the low pressure wellhead housing is embedded into the seafloor to a predetermined depth below the mudline. 
   When the well is abandoned after completing the exploratory drilling, many laws and regulations require that there cannot be any structure protruding above the seafloor. Several of the intermediate strings of casing are cut below the mudline to allow removal of the upper portion of those strings. The conductor casing suspended from the low pressure wellhead housing must also be cut to remove the low pressure wellhead housing. Cutting the conductor casing can be time consuming and does not allow for the conductor casing above the cut to be reused. 
   SUMMARY OF THE INVENTION 
   In this invention, a subsea wellhead assembly has an outer tubular member suspended below a low pressure wellhead housing. A grooved profile is formed in the bore of the outer tubular member. The outer tubular member receives an inner tubular member that is adapted to be joined to a sting of conductor casing extending upward to the low pressure wellhead housing. The inner tubular member carries a locking member that moves between a locked and unlocked position. In the locked position, the locking member engages the grooved profile on the outer tubular member. The inner tubular member is connected to the outer tubular member when the locking member engages the grooved profile. 
   The inner tubular member also carries an axially moveable locking sleeve. The locking sleeve is hydraulically actuated. The locking member slidingly engages the locking member for selectively camming the locking member between the locked and unlocked positions. A remote operated vehicle (ROV) port extends from the locking sleeve to the exterior of a portion of conductor casing joined to the inner tubular member. An ROV supplies hydraulic fluid through the ROV port to actuate the locking sleeve, and thereby the locking member. The ROV port can consist of a plurality of ports with some supplying hydraulic fluid below the locking sleeve to actuate the sleeve upward, and some for supplying hydraulic fluid above the locking sleeve to actuate the sleeve downward. 
   Typically, the outer tubular member has an upper end that is located below the mudline of the seafloor. Therefore, the ROV port extends through a portion of the casing joined to the inner tubular member, to an elevation above the seafloor terminating at a port for ROV or other means of hydraulic actuation. With the locking member in the unlocked position, and not engaging the grooved profile, the inner tubular member and portion of the conductor casing extending upwards therefrom can be lifted from within the outer tubular member located below the mudline. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view of a sub mudline abandonment connector in a outer tubular member of a subsea wellhead assembly constructed in accordance with this invention, with the connector in its locked position. 
       FIG. 2  is a cross-sectional view of the connector and outer tubular member shown in  FIG. 1  in its unlocked and unlatched position. 
       FIG. 3  is an enlarged cross-sectional view of a portion of the one side of the connector and outer tubular member shown in  FIG. 1  in its locked position. 
       FIG. 4  is an enlarged cross-sectional view of one side of the connector and outer tubular member shown in  FIG. 2  in its unlocked and unlatched position. 
       FIG. 5  is a cross-sectional view of the connector and outer tubular member shown in  FIG. 1  in its latched but unlocked position. 
       FIG. 6  is an enlarged cross-sectional view of a portion of the one side of the connector and outer tubular member shown in  FIG. 5  in its latched but unlocked position. 
       FIG. 7  is an enlarged perspective view of a portion of a locking sleeve of the connector housing shown in  FIG. 1 . 
       FIG. 8  is an enlarged perspective view of a portion of a dog of the connector housing shown in  FIG. 1 . 
       FIG. 9  is an enlarged cross-sectional of an alternative embodiment of the portion of connector and outer tubular member shown in  FIGS. 3 ,  4 , and  6  in its locked position. 
       FIG. 10  is a sectional view of a subsea wellhead assembly with the submudline connector shown in  FIG. 1  below the low pressure wellhead housing. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 10 , a subsea wellhead assembly  111  is shown at the seafloor. A low pressure wellhead housing  113  is located above the mudline of the seafloor, with a string of conductor casing  116  extending from its lower end into the well. Low pressure wellhead housing  113  receives a high pressure wellhead housing  115 , which has a string of intermediate casing  117  extending from its lower end into the well. A sub mudline abandonment connector, or connector  119  is shown as part of conductor casing  116  below low pressure wellhead housing  113 . String of casing  117  extends through the inner bore of connector  119 . Conductor casing  116  includes an upper conductor casing  16  extending between the upper end of connector  119  and lower pressure wellhead housing  113 . Conductor casing  116  also includes a lower conductor casing extending from the lower end of connector  119  further into the well. 
   Referring to  FIG. 1 , subsea mudline abandonment connector, or connector  119  is shown positioned with an outer tubular member  13  enclosing connector  119 . Outer tubular member  13  has a string of conductor casing  14  extending from the lower portion. Outer tubular member  13  is typically located below the mudline of the sea floor, after it has been cemented into place in a manner known in the art. Connector  119  preferably includes an inner tubular member  11  that is typically designed to interface with outer tubular members  13  having either 30-inch or 36-inch diameter string of conductor casing extend into the well. Inner tubular member  11  lands and sealingly engages the bore of outer tubular member  13 . Inner tubular member  11  preferably has an inner tubular member or connector casing  15  that is joined to a lower end of a upper conductor casing  16  extending to low pressure wellhead housing  113 . 
   Inner tubular member  11  also preferably has an inner sleeve  17  that comprises the bore of inner tubular member  11 . A locking sleeve  19  is located between connector casing  15  and inner sleeve  17 . A landing sleeve  21  is preferably located with a portion below locking sleeve  19  and between connector casing  15  and inner sleeve  17 . Landing sleeve  21  has an inclined surface  23  extending below connector casing  15  that lands on an upwardly facing shoulder  25  of outer tubular member  13 . Landing sleeve  21  has an inner leg  27  located below and radially inward of inclined surface  23 . Inner leg  27  extends axially below shoulder  25  when inclined surface  23  lands on shoulder  25 . A seal  29 , located around the outer surface of inner leg  27 , sealingly engages an inner surface of outer tubular member  13  below shoulder  25 . 
   A threaded fastener preferably a screw  31  extends through landing sleeve  27  and engages connector casing  15  and inner sleeve  17  to prevent movement of landing sleeve  27  relative to connector casing  15  and inner sleeve  17 . Screw  31  is located axially below locking sleeve  19 . In the preferred embodiment, screw  31  engages a ring  33  that matingly fits into a groove  35  located on the inner surface of connector casing  15 . In the preferred embodiment, ring  33  is a C-Ring that is biased radially inward. The screw  31  expands ring  33  outward to lock ring  33  in groove  35 . Preferably, landing sleeve  27  can be removed from between connector casing  15  and inner sleeve  17  when a predetermined force is applied. 
   A plurality of landing sleeve seals  37 ,  38  are preferably located above and below screw  31  and engage the inner surface of connector casing  15 . An upper tubular member  39  defines an upper portion of landing sleeve  27 . Landing sleeve seals  37 , which are above screw  31 , are preferably located on the outer surface of upper tubular member  39 . Upper tubular member  39  has a larger inner diameter than the remaining portion of landing sleeve  27 , and does not engage inner sleeve  17 . 
   Locking sleeve  19  has a lower tubular member  41  located towards the lower portion of locking sleeve  19 . Lower tubular member  41  has an outer diameter that is less than the inner diameter of upper tubular member  39  on landing sleeve  27 . The outer surface of lower tubular member  41  slidingly engages the inner surface of upper tubular member  39 . At least one seal  43 , preferably a pair of seal rings extending around the outer circumference of lower tubular member  41 , engages the inner surface of upper tubular member  39  on landing sleeve  27 . 
   A piston  45  is formed on the outer surface of locking sleeve  19 . Piston  45  protrudes radially outward from a portion of locking sleeve  19  and slidingly engages the inner surface of connector casing  15 . At least one piston seal  47  extends around the outer circumference of piston  45  to sealingly engage the inner surface of connector casing. Piston  45  is preferably located axially above upper tubular member  39 . A lower annular chamber  49  is defined between piston  45 , upper tubular member  39 , and the outer surface of lower tubular member  41  of locking sleeve  19 . Annular clamber  49  receives a hydraulic fluid to actuate locking sleeve  19  from a locked position shown in  FIG. 1  to a latched but unlocked position shown in  FIG. 5 , and then to an unlocked and unlatched position shown in  FIG. 2 . Seals  37 ,  43 ,  47  help to prevent the hydraulic fluid from escaping lower annular chamber  49  when hydraulic fluid is injected into lower annular chamber  49 . A hydraulic port  51  formed in the inner surface of connector casing  15  at substantially the same axial position as the upper portion of upper tubular member  39 , communicates the hydraulic fluid into lower annular chamber  49  to actuate locking sleeve  19 . Annular chamber  49  increases in sizes as piston  45  moves from the locked position shown in  FIG. 1  to the unlocked and unlatched position shown in  FIG. 2 . 
   A piston shoulder  53  is formed toward the upper portion of piston  45 . A downward facing lip  55  formed on the inner surface of connector casing  15  prevents piston  45  from sliding axially upward along connector casing  15  after piston shoulder  53  engages lip  55 . The portion of connector casing axially below lip  55  has a larger inner diameter than the portion of connector casing above lip  55 . An upper annular chamber  56  is defined between piston shoulder  53  and lip  55 . As shown in  FIG. 2 , locking sleeve  19  is in its unlocked and unlatched position when piston shoulder  53  engages lip  55 , thereby preventing further upward motion of locking sleeve  19 . A medial portion  57  of locking sleeve  19  located above piston  45  slidingly engages the inner surface of the portion of connector casing  15  located above lip  55 . At least one seal  59 , preferably a pair of seal rings extending around the outer surface of the medial portion  57  of locking member  19 , sealing engages the inner surface of the portion of connector casing  15  located above lip  55 . 
   Referring to  FIGS. 3 and 4 , at least one lock  61  is located above medial portion  57  of locking sleeve  19 . Lock  61  comprises a lock cam  63 , a locking dog  65  and a locking slot  67 , and a lock ring  69 . Lock cam  63  is formed above medial portion  57  with a lower portion  63   a  of lock cam  63  connected to medial portion  57  of locking sleeve  19 . Lock cam  63  has substantially the same outer circumference as medial portion  57  of locking sleeve  19 . As shown in  FIG. 7 , locking cam  63  is formed adjacent a portion of locking slot  67 . In the preferred embodiment, locking slot  67  passes through locking sleeve  19 , locking cam  63  is formed along the sides of locking slot  67 . Lock cam  63  preferably also comprises an upper portion  63   b  and an inclined or middle portion  63   c . Lock cam upper portion  63   b  connects to an upper portion  70  of locking sleeve  19 , which extends axially upward from lock cam  63 . Lock cam upper portion  63   b  has a larger inner diameter than lock cam lower portion  63   a , so that upper portion  63   b  is thinner than lower portion  63   a . Lock cam inclined portion  63   b  is inclined along the inner surface to connect the radially inward inner surface of lower portion  63   a  with the radially outward inner surface of upper portion  63   b.    
   A lock ring recess  71  is formed on the outer surface of connector casing  15  axially above medial portion  57  of locking sleeve  19 . Lock ring  69  extends around the circumference of connector casing  15  and rests in lock ring recess  71 . In the preferred embodiment, lock ring  69  is a C-Ring that is biased radially outward. Lock ring recess  71  engages the upper and lower ends of lock ring  69 , thereby holding lock ring  69  axially relative to connector casing  15 . In the preferred embodiment, a plurality teeth  75  extend circumferentially around the outer circumference of lock ring  71 . Each tooth  75  has an axially upward facing lip  76  and an angled leading edge  77  located below each lip  76 . A plurality of grooves  78  are formed on the inner surface of outer tubular member  13 . Grooves  78  are preferably formed around the inner circumference of outer tubular member  13  so that when inclined surface  23  of landing sleeve  21  engages shoulder  25  of outer tubular member, grooves  78  are at substantially the same axial elevation as teeth  75 . Each groove  78  has an axially downward facing lip  79  and an angled trailing edge  80  located above each lip  79 . Leading edges  77  of teeth  75  slide along trailing edges  80  of grooves  78  and allow lock ring  69  to travel axially downward relative to grooves  78  and outer tubular member  13 . Lock ring  69  and connector casing  15  cannot move axially upward relative to outer tubular member  13  when upward facing lips  76  engage downward facing lips  79 . 
   A passage  73  is formed in connector casing  15  and extends between lock ring recess  71  and lock cam  63 . Preferably, locking dog  65  is located within passage  73 . Locking dog  65  has an outer end  81  that engages lock ring  69 , and a dog head or inner end  83  that engages lock cam  63 . Lock ring  69  is preferably biased radially outward for teeth  75  to engage grooves  78 . Locking dog  65  preferably has a threaded fastener or screw  85  located between its inner and outer ends  83 ,  81  so that locking dog  65  supplies a radially inward force against lock ring  69 . As shown in  FIG. 8 , the dog head  83  has inclined surfaces that matingly engage lock cam  63  as dog  65  is actuated along the surfaces of cam portions  63   a ,  63   b ,  63   c .  FIG. 8  also shows a barrel  65   a , which is the portion of dog  65  that extends above dog head  83 . Barrel  65   a  also passes through locking slot  67  and passageway  73  in connector housing  15 . A flat  65   b  is located toward the interface of barrel  65   a  and dog head  83 . In the preferred embodiment, there are a pair of flats  65   b  on opposite portions of barrel  65   a  where barrel  65   a  connects to dog head  83 . Referring to  FIG. 7 , a slot  67  includes a reduced area portion, or reduced area slot  63   d  located adjacent upper cam portion  63   b . Slot  67  has a large enough area for barrel  65   a  to pass through slot  67  as dog head  83  actuates along cam portions  63   a  and  63   c . The area of slot  67  is smaller that the area of barrel  65   a  in reduced area slot  63   d . The portion of cam  63  in reduced area slot  63   d  engages flats  65   b  as dog head  83  actuates from cam portion  63   c  to  63   b . Reduced area slot acts as a physical barrier to prevent ring  69  and dog  65  from moving radially inward relative to slot  67  when reduced slot area  63   d  engages flats  65 , thereby locking lock  61 . 
   In the preferred embodiment, lock dog  65  extends through locking slot  67  so that inner end or head of dog  65  is radially inward of lock cam  63 . The head of dog  65  slidingly engages the inner surface of lock cam  63 . Dog  65  is forced radially inward as it slides from lock cam upper portion  63   b  to lock cam lower portion  63   a . Dog  65  pulls its outer end  81  radially inward, which in turn pulls the lock ring  69  radially inward. Dog  65  is moved radially inward as cam lock  63  is actuated by piston  45  between its locked position shown in  FIG. 3 , its latched but unlocked position shown in  FIG. 6 , and its unlocked and unlatched position shown in  FIG. 4 . As shown in  FIG. 4 , in the unlocked and unlatched position, dog  65  pulls its outer end  81  radially inward enough so that teeth  75  do not engage grooves  78 , thereby allowing connector casing  15  to move axially upward relative to outer tubular member  13 . 
   Locking sleeve  19  also includes an upper member, or sleeve location indicator  89  that connects to upper portion  70 . A threaded fastener  90 , preferably a screw, connects a lower portion of location indicator  89  to upper portion  70 . Location indicator  89  extends axially upward from upper portion  70  to an axial elevation above outer tubular member  13 . Referring to  FIGS. 1 ,  2 , and  5 , an indicator passageway  91  extends through connector casing  15  from its outer surface to its inner surface. Indicator passageway  91  is located toward the upper portion of connector casing  15  so that indicator passageway  91  is above the top of outer tubular member  13  when inclined surface  23  of landing sleeve  21  engages shoulder  25  of outer tubular member. Indicator passageway  91  aligns with an inner opening  93  formed in an radially inward portion of conductor casing  15 . 
   An additional indicator passageway  95  extends through location indicator  89  of locking sleeve  19 . An intermediate opening  97  is also formed above indicator passageway  95  in the outer surface of location indicator  89  of locking sleeve  19 . Indicator passages  91 ,  95  and openings  93 ,  97  are typically only useful to an operator when working on the connector  119  at the surface. Indicator passages  91 ,  95  and openings  93 ,  97  can help an operator determine the position of the lock  61  by monitoring the location of locking sleeve  19 . As shown in  FIG. 1  for example, opening  97  of locking sleeve  19  aligns with indicator passage  91  when connector  119  is in its locked position. An indicator or gage tool (not shown), when inserted into passage  91  and opening  97 , only inserts to a first predetermined length that shows the operator that connector  119  is in its locked position. 
   As shown in  FIG. 2 , passage  91  opens to the outer surface of location indicator  89  of locking sleeve  19 . A gage tool (not shown) only inserts to a second predetermined length that shows that connector  119  is in its unlocked and unlatched position. The second predetermined length is shorter in length than the first predetermined length. As shown in  FIG. 5 , passage  91  opens into passage  95  in location indicator  89  of locking sleeve  19 , which opens into opening  93  of the radially inward portion of outer tubular member  15 . The indicator (not shown) inserts to a third predetermined length showing that connector  119  is in a latched but unlocked position. Typically, connector  119  is only in the latched but unlocked position shown in  FIGS. 5 and 6  while connector casing is at the surface and being worked on. Additionally, in the preferred embodiment, connector  119  is already locked in outer tubular member  13  when outer tubular member  13  is landed at the sea floor. The latched but unlocked position allows the operator to stab or ratchet lock ring  69  to secure inner tubular member  11  axially relative to outer tubular member  13  without the use of hydraulics while at the surface. A pipe plug (not shown) is inserted into indicator passage  91  before connector casing is installed at the sea floor to prevent mud from entering passage  91 . 
   When connector  119  is below the seafloor, hydraulic fluid is used to lock and unlock inner tubular member  11  to outer tubular member  13 . A stab or hydraulic port opening  99  is located toward the upper end of connector casing  15 . A hydraulic passageway  101  connects port opening  99  in fluid communication with hydraulic port  51 . Hydraulic passageway  101  supplies hydraulic fluid to lower annular chamber  49  to actuate piston  45 , moving piston  45  upward, causing lock cam  63  to pull locking dog  65  and teeth  75  away from grooves  78 , therefore unlocking lock  61 . Another hydraulic passage  103  provides communication from a port (not shown) located at the upper portion of connector casing  15  with upper annular chamber  56 . Any fluid in upper chamber  56  vents out hydraulic passage  103  when piston  45  moves upward due to hydraulic fluid injected into lower annular chamber  49 . Any fluid in lower annular chamber  49  vents out hydraulic passage  101  when hydraulic fluid is injected through hydraulic passage  103  into upper annular chamber  56  and pushes piston  45  downward. 
   In the preferred embodiment, a port opening  105  extends through a side of upper conductor casing  16  at an elevation above the mudline of the seafloor. A string of tubing  107  extends from port opening  105  through a lower portion of upper conductor casing  16  and stabs into hydraulic port opening  99 . Preferably, tubing  107  stabs into port opening  99  when connector casing  15  attaches to upper conductor casing  16 . The combination of port opening  105 , tubing  107 , port opening  99 , and either hydraulic passage  101  or  103  define an ROV port for either raising or lowering locking sleeve  19 . In the preferred embodiment, there are a plurality of port openings  105 , tubing  107 , and port openings, so that when combined with the other hydraulic passage  101 ,  103  another ROV port is defined for either raising or lowering locking sleeve  19 . 
   Referring to  FIG. 9 , a spring  109  biases lock dog  65  radially outward. Spring  109  helps prevent slippage of lock dogs  65  out of alignment when upper conductor casing  16  and connector  119  are stored at the surface before being lowered to the subsea well. In some situations, horizontal storage causes lock dogs  65  and locking sleeve  19  to slide relative to each other, which misaligns teeth  75  of lock ring  71 , which can later damage teeth  75  when lock ring  71  is actuated outward. Spring  109  helps reduce slippage of locking sleeve  19  and lock dogs  65  during horizontal storage. 
   In operation, inner tubular member  11  is already landed or installed inside outer tubular member  13  at the surface before outer tubular member  13  is lowered to beneath the seafloor. Outer tubular member  13 , with inner tubular member  11  inside, is landed and cemented into place. In the preferred embodiment, piston  45  is in its lower position and lock  61  is therefore in its locked position when outer tubular member  13  is landed and the well is producing well fluids. Inner tubular member  11  and outer tubular member  13  are typically below the mudline. Nothing can protrude above the mudline when the subsea well is abandoned. When the well is to be shut down, inner outer tubular member  11 , upper casing  16 , and low pressure wellhead housing  113  can be removed instead of cutting the portion of conductor casing  116  below the mudline. 
   An ROV stabs into port opening  105  to supply hydraulic fluid into tubing  107 . Alternatively, port opening  105  can also be in fluid communication with a common ROV port, or control module at which an ROV actuates a series of valves for the entire subsea wellhead assembly. At the common module or stab port, the ROV either directly injects or opens valves and causes hydraulic fluid into tubing  107 . Hydraulic fluid is injected through tubing  107  and hydraulic port opening  99  into passageway  101 . The hydraulic fluid communicates through passageway  101  to hydraulic port  51 , where the hydraulic fluid enters lower annular chamber  49 . As more hydraulic fluid enters annular chamber  49 , the pressure increases and causes piston  45  to slide axially upward from the locked position shown in  FIG. 1  to the unlocked position shown in  FIG. 2 . Lock cam  63  moves upward relative to connector casing  15  as piston  45  moves from its position shown in  FIG. 1  to the position shown in  FIG. 2 . Lock cam  63  slides through locking dog  65  so that dog head  77  slides from lock cam upper portion  63   b , over inclined portion  63   c , to lock cam lower portion  63   a , thereby pulling teeth  75  out of engagement with grooves  78 . As shown in  FIGS. 2 and 4 , the operator can lift inner tubular member  11  out of outer tubular member  13  since teeth  75  do not engage grooves  78  in the unlocked position. In order to remove inner tubular member  11  from outer tubular member  13 , a predetermined upward force must be applied for ring  33  to slide out of recess  35 . After inner tubular member  11  has been removed from outer tubular member  13 , the operator can complete the abandonment of the well in a manner known in the art, without having to cut any portion of the wellhead. 
   While the invention has been shown in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For example, rather than positioning the piston  45  below lock  61 , a piston could be placed above the lock cam and locking dogs which would reduce the length of each of the hydraulic passages leading to the upper and lower annular chambers. 
   While the invention has been shown in only some of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.