Abstract:
A well production assembly includes a production tree which has a lateral production passage extending laterally from a vertical bore of the tree. A tubing hanger, also having a lateral production passage, lands in the tree, with the lateral passages registering with each other. The junction of the lateral passages has flat, tapered sealed areas which mate with one another. An annulus passage extends vertically through the tubing hanger offset from and parallel to the tubing hanger vertical production passage. The annulus passage also has a lateral passage which registers with the lateral passage formed in the tree. The annulus lateral passages have a flat seal area at their junction. The tubing hanger has a downward facing hydraulic connector which registers with an upward facing hydraulic connector located on a shoulder formed in the bore. Once mated, the connectors provide hydraulic or other auxiliary fluid communication to downhole equipment.

Description:
This application is a Continuation of Ser. No. 08/968,392 filed Nov. 12, 1997 now U.S. Pat. No. 6,062,314, which claims benefit to Provisional 60/030,807 filed Nov. 14, 1996. 
    
    
     TECHNICAL FIELD 
     This invention relates in general to wellhead equipment, and in particular to a production tree having a tubing hanger therein, the tubing hanger and production tree having lateral production passages. 
     BACKGROUND ART 
     A conventional subsea wellhead assembly includes a wellhead housing which supports one or more casing hangers located at upper ends of strings of casing extending into the well. A tubing hanger lands in the wellhead housing above the casing hanger and supports a string of production tubing that extends through the smallest diameter casing. The tubing hanger has a production bore which is offset slightly from the longitudinal axis. An annulus bore also extends through the tubing hanger, parallel to and offset from the axis, for communicating the tubing annulus to above the tubing hanger. The annulus bore is needed during installation of the tubing hanger and tubing to establish circulation down the tubing and back up the annulus. After the well has been completed, a removable plug is installed in the annulus bore, then a production tree is mounted to the wellhead housing. Access through the production tree to the tubing may be made for various workover operations that are needed. 
     In the last few years, operators have begun installing a different type of wellhead assembly, referred to generally as a horizontal tree. In a horizontal tree, the tubing hanger lands in the tree, not in the wellhead housing located below the tree. The tubing hanger has a lateral flow passage extending from its vertical flow passage. The lateral flow passage registers with a lateral flow passage extending through a sidewall of the tree. Gallery seals are employed to seal the junction between the lateral production passages. The gallery seals comprise seal rings which are coaxial with the vertical axis, with one of the seals located above the lateral passage and the other located below. The lower seal necessarily will be of a smaller diameter than the upper seal in order to provide clearances for installation. 
     With the horizontal tree, a tubing hanger can be pulled through the horizontal tree without removing the tree. This cannot be done with a conventional tree. While this is an advantage, one disadvantage is the horizontal tree tubing hanger has inadequate room to utilize a vertical annulus passage extending through the a tubing hanger as with a conventional tubing hanger. as Instead, tubing annulus communication is accomplished generally by utilizing a bypass passage through the tree from below the tubing hanger and back into the tree above the tubing hanger. While a bypass passage is workable, it relies on a valve on the exterior for closing the annulus. Some operators believe that a removable plug installed within an annulus passage in a tubing hanger is safer than a valve. 
     Another disadvantage of a typical horizontal tree tubing hanger has to do with the need to communicate auxiliary fluid to downhole equipment. For example, downhole safety valves are used in a tubing string at some distance below the surface. A safety valve remains open so long as it is supplied with hydraulic fluid pressure. In the absence of fluid pressure, it will close. Consequently, if the production wellhead assembly is severely damaged, the well would be held under control through the safety valve. In conventional tree tubing hangers, passages are drilled through the tubing hanger from the upper end to the lower end. The upper ends of the hydraulic passages have connectors which mate with connectors on the tree to supply hydraulic fluid. In the horizontal tree, however, this cannot occur because the tubing hanger lands within the tree, not in the wellhead housing below. 
     Some manufacturers have drilled ports through the sidewall of the tree to communicate with hydraulic passages drilled within the tubing hanger. These manufacturers have employed gallery type seals to seal the junctions of the ports. This again requires a reduction in inner diameter of the bore of the tree. There may be several ports for auxiliary fluid passages, requiring several sets of gallery seals. U.S. Pat. Nos. 5,465,794 and 5,555,935 show ports on the exterior of a tubing hanger that do not requires gallery seals. These ports locate on a spherical surface formed on the tubing hanger and in the bore of the tree. 
     SUMMARY OF THE INVENTION 
     In this invention, the tree is of a horizontal type, having a lateral production passage. A tubing hanger, also having a lateral production passage, lands in the tree. The tree has a seal area that surrounds the inlet of the lateral production passages which is flat and inclined relative to the axis. The tubing hanger also has a seal area which is flat and inclined and mates with the tree seal area. The mating flat surfaces obviate the need for gallery seals, allowing a larger bore at that area than in the prior art gallery seal type. 
     Preferably the tubing hanger has an annulus flow passage that is offset from and parallel to the vertical production passage in the tubing hanger. The vertical annulus passage may be accessed from above and will receive a removable plug after completion. Preferably a lateral passage extends laterally from the vertical annulus passage of the tubing hanger and registers with a lateral annulus passage formed in the tree. The mating openings of the tree annulus passage are on flat and inclined sealed areas formed on the tubing hanger and in the bore of the tree. The lateral annulus passage allows access to the annulus through a valve as an option. 
     The tree also has an auxiliary passage which extends through a sidewall of the tree and has an auxiliary connector which is located on an upward facing shoulder forming the bore of the tree. The tubing hanger has a downward facing hydraulic connector which telescopingly mates with the connector in the tree bore. The auxiliary passages lead to a downhole safety valve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A and 1B comprise a vertical sectional view of a wellhead assembly constructed in accordance with this invention. 
     FIG. 2 is an enlarged partial sectional view of a portion of the wellhead assembly of FIGS. 1A,  1 B. 
     FIG. 3 is a sectional view of a portion of the wellhead assembly of FIGS. 1A,  1 B, taken along the line  3 — 3  of FIG. 2, with the left side showing an installation step and the right side showing the assembly after installation has been completed. 
     FIG. 4 is a sectional view of the wellhead assembly of FIGS. 1A,  1 B, taken along the line  4 - 4  of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1B, a subsea wellhead is shown, including a tubular low pressure housing  11  that lands in a guide base  13  supported on the sea floor. Housing  11  is connected to a large diameter conductor extending into the well to a first depth. A high pressure housing  15  lands in the low pressure housing  11 . High pressure housing  15  is also a tubular member, and it is secured to a string of casing  17  which extends into the well to a second depth. A lower casing hanger  19  lands in wellhead a housing  15  and supports a string of casing  21  which extends into the well to a third depth. An upper casing hanger  23  lands on top of lower casing hanger  19  and supports a string of casing  25  which extends to the bottom of the well in the embodiment shown. Both casing hangers  19 ,  23  are conventionally sealed to the bore of high pressure housing  15 . 
     A lower tubing hanger  27  lands in the bowl of the upper casing hanger  23 . Lower tubing hanger  27  is secured to a string of production tubing  29  which extends into the well for providing a conduit for the flow of production fluid. Lower tubing hanger  27  has a vertical production passage  31  which is coaxial with tubing  29 . An annulus passage  33  is also axial or vertical, and extends alongside production passage  31 . Annulus passage  33  is in communication with an annulus space surrounding tubing  29 . 
     Lower tubing hanger  27  is secured conventionally in upper casing hanger  23  by means of a cam sleeve  35 , lock ring  37 , and actuating sleeve  39 . Actuating sleeve  39  extends upward above the upper end of lower tubing hanger  27 , as shown in FIG. 1B, and can be shifted by a running tool between an upper released position and a lower locked position. A downhole safety valve  38  is located in tubing  29  some distance below wellhead housing  11 . Safety valve  38  is connected to a hydraulic line  40  which extends upward to lower tubing hanger  27 . Hydraulic pressure in line  40  maintains safety valve  38  in an open position. The absence of hydraulic pressure in line  40  causes safety valve  38  to close. 
     Referring also to FIG. 1A, a Christmas tree  41  lands on top of wellhead housing  15 . A conventional hydraulic connector  43  carried by tree  41  connects tree  41  to a grooved profile  45  formed on housing  15  near its upper end. Tree  41  is a large tubular member that has a grooved profile  47  on its upper end that is identical to wellhead profile  45 . Tree  41  has a production passage  49  that is horizontal, perpendicular to the longitudinal axis, and extends from its bore  48  to the exterior. A production master valve  51  controls the flow of production fluid out tree horizontal passage  49 . Tree  41  also has an annulus passage  53  that is horizontal and perpendicular to the vertical axis. In the embodiment shown, it is located 180 degrees from and is coaxial with horizontal passage  49 . Tree annulus passage  53  also extends from the tree bore  48  to the exterior. An annulus valve  55  can be controlled from the surface for opening and closing annulus passage  53 . 
     Tree  41  is installed by lowering it on guidelines attached to guide posts (not shown) of guide base  13  in a conventional manner. As shown in FIG. 2, tree  41  has an orientation sleeve  56  mounted to it that extends around actuating sleeve  39  of lower tubing hanger  27 . A key  58  on the exterior of lower tubing hanger  27  engages a slot in orientation sleeve  56 . Orientation sleeve  39  orients lower tubing hanger  27  if tubing hanger  27  is being installed after tree  41  has already been installed. If lower tubing hanger  27  is installed before tree  41  is installed, it will be oriented by a conventional method using an orientation internal groove on the BOP stack wellhead connector. 
     Referring again to FIG. 1A, an upper tubing hanger  57  is supported in the bore of tree  41 . Upper tubing hanger  57  has a vertical bore  59  that extends through it offset from and parallel to the longitudinal axis of tree  41 . A lateral passage  61  extends horizontally outward from vertical bore  59  perpendicular to the vertical axis. A seat ring  63  is mounted in a counterbore in tree horizontal production passage  49  at the junction with tree bore  48 . Seat ring  63  is sealed to passage  49  and has a hole through it that is the same diameter as passage  49 . Seat ring  63  has an inner face  63   a  that is flat but inclined relative to the axis of tree  41 . The upper edge of inner face  63   a  is farther from the axis of tree  41  than its lower edge Seat ring  63  is sealed to passage  49  but is removable. Upper tubing hanger  57  has a mating seat ring  6 S with a flat inclined outer face that is located at the outer end of lateral passage  61 . Seat ring  65  seals against flat face  63   a  of seat ring  63  in metal-to-metal sealing engagement. 
     Similarly, upper tubing hanger  57  has an annulus vertical bore  67  which extends completely through upper tubing hanger  57  offset from and perpendicular to vertical bore  59 . An annulus passage  69  extends horizontally from vertical bore  67 . A seat ring  71  locates sealingly in a counterbore formed in tree annulus passage  53  at the junction with tree bore  48 . Seat ring  71  is constructed the same as seat ring  63 , except that its hole is smaller because the tree annulus passage  53  is smaller in diameter than the production passage  49 . Upper tubing hanger  57  has a seat ring  72  that sealingly mates with the flat inclined face of seat ring  71 . 
     A crown plug  73  of a conventional wireline retrievable type is installed in upper tubing hanger vertical bore  59 . Crown plug  73  is located above horizontal passages  61 ,  49 . An annulus plug  75 , also wireline retrievable, is located in annulus vertical bore  67 . 
     Referring to FIG. 2, a production isolation sleeve  77  is sealingly secured to the lower end of upper tubing hanger vertical production bore  59 . Sleeve  77  extends sealingly into lower tubing hanger bore  31 . An annulus isolation sleeve  79  secures sealingly to upper tubing hanger annulus bore  67 . Annulus isolation sleeve  79  extends sealingly into lower tubing hanger annulus passage  33 . Upper tubing hanger  57  has an orientation key  81 , shown in FIG. 2, that engages orientation sleeve  56  of tree  41 . This orients upper tubing hanger  57  relative to tree  41 . 
     Referring to FIG. 3; a plurality of hydraulic fittings or connectors  83  are mounted to lower tubing hanger  27  and face upwardly. Hydraulic connectors  83  connect to hydraulic lines  40  (FIG. 1B) for opening and closing downhole safety valves  38  (FIG.  1 B). Female hydraulic fittings or connectors  83  are secured to the lower end of upper tubing hanger  57 . Hydraulic connectors  85  will stab over hydraulic connectors  83  to take up a connection. Belleville springs  87  provide a positive pressure to retain the connection. Similarly, hydraulic connectors  89  are located on an upward facing shoulder  90  in bore  48  of tree  41  outside of where upper tubing hanger  57  will land. Downward facing female hydraulic connectors  91  are mounted to upper tubing hanger  57  to stab onto hydraulic connectors  89  when upper tubing hanger  57  is installed. Hydraulic connectors  89  are connected to passages which lead to a source of hydraulic fluid pressure for opening safety valve  38  (FIG. 1B) or performing other auxiliary functions. Connectors  89  are also shown in FIG. 4 
     Referring to FIG. 3, upper tubing hanger  57  is secured in tree bore  48  by a lock member  93  which is pushed outward by a cam member  95 . The left side of FIG. 3 shows upper tubing hanger  57  prior to insulation while the right side shows upper tubing hanger  57  after it is completely installed. 
     Referring again to FIG. 1A, an internal tree cap  97  locates within tree bore  48  above upper tubing hanger  57 . Internal tree cap  97  has two vertical bores  98 ,  100  which align coaxially with the upper tubing hanger bores  59 ,  67 . Wireline retrievable plugs  99 ,  101  are located within the bores  98 ,  100 . A corrosion cap  103  is installed over the upper end of tree  41  for protection. Referring to FIG. 4, lateral annulus passage  53  leads to a crossover passage  105  which will selectively connect annulus passage  53  with the production passage  49 . is Valves  107  will control opening and closing of crossover passage  105 . 
     In one mode of operation, after the well has been drilled and the casing hangers  19 ,  23  and lower tubing hanger  27  oriented and installed, the operator can run Christmas tree  41  and secure it by connector  43 . The operator then installs upper tubing hanger  57 , which orients by means of its key  81  (FIG. 2) engaging tree orientation sleeve  56 . After testing procedures, the operator installs wireline retrieval plugs  73 ,  75 , internal tree cap  97 , and wireline retrievable plugs  99 ,  101 . The production fluid will flow up production tubing  29  and out horizontal passage  49 . 
     Several workover options are available: In one mode, a drilling riser having a blowout preventer (not shown) will land on tree profile  47  after removing corrosion cap  103 . The internal tree cap  97  is removed through the drilling riser using a recovery string extending through the riser. Closing the downhole safety valves (not shown) allows one to remove the wireline plugs  73 ,  75 . An adapter on the recovery string stabs into the vertical production bore  59  while the annulus vertical bore  67  communicates with the drilling riser annulus around the recovery string and thus with the riser choke and kill lines once the blowout preventer is closed around the recovery string. One conduit leading to the production tubing  29  and one to the annulus space is then established with the workover vessel. 
     Prior to removing tubing  29 , the well ordinarily must be killed. During this procedure, the well production fluid is replaced with a heavier fluid. The operator can kill the well by opening the downhole safety valve, and pumping down the recovery string and production tubing  29 . The fluid flows out a port at the lower end of the production tubing  29 , back up the tubing annulus, upper tubing hanger annulus bore  67 , and up one of the choke and kill lines. 
     After the well is killed, the operator can retrieve production tubing  29  with the recovery string by pulling upper tubing hanger  57 , then pulling tubing hanger  27  along with tubing  29 . After the workover operation, tubing  29  and lower tubing hanger  27  are lowered through tree  41  and re-installed. Lower tubing hanger  27  will orient by engagement of key  58  with orientation sleeve  56  (FIG. 2) during the installation. Alternately, the operator may remove tree  41  without pulling tubing  29 . In this instance, preferably another wireline plug (not shown) will be installed in a grooved profile in lower tubing hanger  27  before removing tree  41 . When tree  41  is pulled upward, upper tubing hanger  57  and isolation sleeve  77  will be pulled with tree  41 , while tubing hanger  27  and tubing  29  remain in place. 
     Further, the well may be killed in other manners than described above. Because of the two vertical bores  59  and  67  in upper tubing hanger  57 , another method of killing involves stabbing a completion riser, which has two strings side by side, into these bores after removal of the internal tree cap  97  and plugs  73 ,  75 . Also, killing of the well can be accomplished by use of the lateral annulus passage  69  and its crossover passage  105  (FIG.  4 ). In this situation, there will be no annulus conduit back to the vessel. Rather, after communication is established between the tubing hanger vertical passage  59  and the vessel, production master valve  51  is closed and annulus valves  55  and  107  (FIG. 4) are opened. Kill fluid is pumped down the production tubing  29 , through a port (not shown) at the lower end and back up the tubing annulus. The return fluid flows out annulus horizontal passage  53 , through crossover passage  105  and out the production line downstream of production master valve  51 . 
     The wireline retrievable plugs  73  and  99  allow various wireline intervention operations without retrieving either tubing hanger  27 ,  57  or internal tree cap  97 . During a wireline intervention when the well is not to be killed, downhole safety valve for tubing  29  will be closed to allow wireline plugs  99 ,  73  to be removed. The wireline tool will be lowered through a wireline riser which will be capable of withstanding the pressure of the well. The wireline riser comprises a wireline BOP stack mounted to tree  41  to control the well pressure. After the wireline tool has been lowered into tubing  29 , the downhole safety valve is opened; allowing the wireline tool to pass through tubing  29 . 
     The invention has significant advantages. Utilizing a flat seal area on the tubing hanger and in the bore of the tree avoids the need for gallery seals around the mating lateral passages. This allows a larger diameter tubing hanger for a particular tree bore than in the prior art, The larger diameter tubing hanger enables a vertical annulus passage to be drilled therein, which may be closed with a removable plug rather than a valve as in the prior art. The hydraulic connectors which mate when the tubing hanger lands also avoids the need for gallery seals. 
     It should be understood that variations to the embodiment may be made. For example, lower tubing hanger  27  may be eliminated. In that instance, upper tubing hanger  57  would connect directly to production tubing  29 . It would not be possible to remove tree  41  without first pulling tubing  29 , but it would be possible to pull tubing  29  without retrieving first the tree  41 .