Patent Application
20080023204
Referring to
In this example, a tubing spool 19 is secured to the upper end of high pressure wellhead housing 13 by a conventional connector 21, typically hydraulically actuated. Tubing spool 19 comprises a tubular member having a load shoulder therein for supporting a tubing hanger 23. Tubing hanger 23 has a single passage 25 extending through it, the passage 25 being in communication with a string of tubing 26 extending into the well. Well fluid will flow up tubing 26 and through passage 25 of tubing hanger 23.
During completion and certain workover operations, access must be provided to a tubing annulus that surrounds tubing 26. In this example, access is provided by a lower tubing annulus passage 27 that leads from the bore of tubing spool 19 to the exterior. An optional upper tubing annulus passage 29 leads from the exterior back into the bore of tubing spool 19. Lower and upper tubing annulus passages 27, 29 are located, respectively, below and above the seal for sealing tubing hanger 23 to tubing spool 19. Tubing annulus passages 27, 29 have valves for opening and closing either passage 27, 29, and are connected to each other by an external line containing one or more valves 31. A conduit leads from valve 31 to other subsea equipment, such as a production cross-over line (not shown). Upper tubing annulus passage 29 facilitates the use of a monobore riser (not shown) for completion and workover operations. However, it could be omitted if desired. Also, alternatively, tubing hanger 23 could be landed within high pressure wellhead housing 13 rather than utilizing a tubing spool 19.
Referring to
A mounting plate 45 is mounted to lower tree module 33. In this example, mounting plate 45 is mounted to the upper end of tree block 35 and lower end of mandrel 43 perpendicular to the axis of passage 37. Mounting plate 45 extends laterally outward and supports a production line connector 47. Production line connector 47 is secured to a conduit 49 that preferably leads downward to a flowline connector (not shown) that connects to a flowline extending along the sea floor. Production line connector 47 has a stab interface 51, which in this embodiment comprises an upward facing receptacle. The axis of receptacle 51 is parallel to and offset from the axis of production passage 37.
An upper tree module 53 lands on top of lower tree module 33. Upper tree module 53 has a conventional connector 55, which may be of the same type as connectors 34 and 21, for connection to mandrel 43. Upper tree module 53 includes an upper tree member 57, which has a vertical, large diameter monobore production passage 58 extending through it. Upper tree member 57 is preferably a cylindrical tube and stabs into a receptacle in mandrel 43. Preferably, the inner diameter of passage 58 is the same as the inner diameter of production passage 37 and also the inner diameter of tubing 26. Seals 59 on the lower end of upper tree member 57 seal in the receptacle within mandrel 43.
One or more flow interface devices 61 is mounted to upper tree module 53 in communication with the well fluid flowing upward through production passage 58. The flow interface devices may include a multi-phase flow meter as well as pressure and temperature sensors. Also, one of the flow interface devices preferably comprises a choke assembly 63. Choke assembly 63 is a conventional device that allows the operator to vary the orifice size through which the production flow passes, thereby creating a desired back pressure and controlling the fluid flow rate.
Upper tree module 53 also includes a passage 65 that leads from choke assembly 63 to an optional buffer chamber 67 for buffering the fluid flow. A production line sub 69 is connected to buffer chamber 67. Production line sub 69 is a pipe that extends downward alongside and generally parallel to upper tree tubular member 57. The lower end of production line sub 69 comprises a stab interface 71. In this embodiment, stab interface 71 comprises a stinger having seals 73 for sealing into receptacle 51 of flowline connector 47. Stab interface 71 is located at an elevation approximately at the lower end of upper tree tubular member 57 so that it will stab into sealing engagement with receptacle 51 during the same operation that the lower end of upper tree tubular member 57 stabs into mandrel 43. Preferably, upper tree module 53 is lowered on a lift line and has a hook or pad eye 75 on its upper end for connection to a lift line.
In operation, the operator will drill and complete the well by running tubing 26 in a conventional manner. The operator then lowers lower tree module 33 onto tubing spool 19 and connects it to tubing spool 19 with connector 34. Stinger 39 will simultaneously stab sealingly into bore 25 of tubing hanger 23. The operator will connect the main flowline connector, which is not shown but is located at the lower end of conduit 49, to a flow line.
If weight permits, the operator may connect upper tree module 53 to lower tree module 33 while at the surface and lower the two tree modules together on a lift line connected to pad eye 75. Otherwise, the operator will lower upper tree module 53 onto lower tree module 33 and connect connector 55 to mandrel 43 after lower tree module 33 has been previously installed on tubing spool 19. During this operation, upper tree member 57 will stab sealingly into mandrel 43, and stab interface 71 will stab sealingly into receptacle 51.
The operator opens valves 41, which allows well fluid to flow up tubing 26 through passages 37 and 58. The well fluid flows through choke 63, buffer chamber 67, down production line sub 69, and out conduit 49. Flow interface devices 61 will monitor the well flow, such as determining the pressure, temperature and flow rate, and choke 63, also a flow interface device, will control the flow rate.
The hydraulic and electrical controls (not shown) for controlling the various valves 31, 41, connectors 21, 34, and 53, and flow interface devices 61 and choke 63, are preferably located in a separately retrievable unit or units that may be mounted to either upper tree module 53, lower tree module 33, or both. Alternately, the controls may be integrated in upper tree module 53 but retrievable only with upper tree module 53 rather than separately. If a failure occurs in connection with one of the flow interface devices 61, 63, the operator may close valves 41 and pull upper tree module 53 to the surface.
The invention has significant advantages. The upper tree and lower tree modules have large bores because space doesn't need to be provided for a tubing annulus through-bore. Placing a stab interface in separate subs alongside and adjacent the tree members enables the tree member to have large diameter through-bores.
While the invention has been shown in only one 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.
