GB2398309A

GB2398309A - Subsea wellhead with a sliding sleeve

Info

Publication number: GB2398309A
Application number: GB0303448A
Authority: GB
Inventors: Graeme Collie
Original assignee: FMC TECHNOLOGIES; FMC Technologies Inc
Current assignee: FMC TECHNOLOGIES; FMC Technologies Inc
Priority date: 2003-02-14
Filing date: 2003-02-14
Publication date: 2004-08-18
Anticipated expiration: 2023-02-14
Also published as: GB2398309B; GB0303448D0

Abstract

A subsea wellhead (10) enables monitoring or bleed down of casing annuli (28, 30) by means of ports (32, 34) which extend completely though a side wall of the wellhead (10), each port (32, 34) having an interior end in pressure communication with a well annulus (28, 30). The wellhead (10) has an external sliding sleeve (50) for selectively opening and closing the ports (32, 34).

Description

SUBSEA WELLHEAD WITH SLIDING SLEEVE

Background of the Invention

The present invention relates generally a system for controlling annulus pressure in a subsea wellhead. More specifically, the invention relates to a subsea wellhead comprising monitoring and/or bleed down annulus ports extending completely through a side wall of the wellhead and having an interior end connected to a well annulus.

When drilling subsea wells for the production of oil and gas it is usual to drill a first section of the hole and install a large diameter pipe known as a conductor with a housing fixed at the upper end. The housing will be located approximately at the sea floor. The operator then drills within the conductor to a depth below the bottom of this pipe and installs a first string of smaller diameter casing within this hole. An internal or high-pressure wellhead housing is located at the upper end of the first string of casing. This first string of casing wild be cemented in the well, with cement returns flowing up around the casing, through the conductor pipe and out flow ports located in the conductor housing. These flow ports remain open adorer cementing.

Ihe operator retrieves the running tool for the internal wellhead housing and connects a drilling riser and blowout preventer (BOI') to the internal wellhead housing. The operator will linen drill the well to greater depths and will nonnally install at least two more strings of casing. Each string of casing has a casing hanger at its upper end that will land and seal in the internal wellhead housing.

Some wells, especially wells with high pressure and/or high temperature production fluid generate a requirement to bleed down casing shying annul) , to prevent thermal pressure loads from damaging the completion casing program. Thermal expansion of trapped fluid in the casing annul) could otherwise lead to excessive pressure build up causing damage to or failure of the casing completion system.

Annulus bleed down can be readily achieved on surface wellhead applications, as the wellhead housing can be provided with annulus outlets. Subsea wellheads ordinarily do not have annulus outlets. Usually, no provision is made for communication between each casing string annulus and the wellhead exterior. Even assuming that it were possible to extract annu]us fluid as and when required, there is the further problem of disposing the bleed off fluid in an environmentally acceptable way. With the introduction of IIPl!IT (high pressure, s high temperature) completions, there is a need for subsea wellheads that can facilitate annulus bleed downs.

Ul: published patent application no. 2,358,204 discloses a subsea wellhead with monitoring and/or bleed down ports enabling annu]us pressure to be monitored and controlled. It lo comprises a bolt on valve block incorporating isolation valves, pressure monitoring equipment and an electro/fluidic interface.

The bolt on valve block is heavy, relatively cumbersome and cannot be deployed with the wellhead housing, thereby requiring tools to fix the block to the wellhead housing after deployment of the wellhead housing.

. . . .

Summary of 1ne Invenllon

According to the invention, a subsea wellhead comprises a monitoring and/or bleed down annulus port extending completely through a side wall of the wellhead and having an interior 2( end in pressure communication with a we]] annulus, the wellhead comprising an external sleeve with a bore for selectively opening and closing said annulus port.

The sleeve is operated by a permenantly installed, remotely operated hydraulic tool comprising a reaction ring and one or more actuators. By operating the actuators the sliding 2s sleeve can be shifted between a position allowing the ports in the sleeve to align with those in the wellhead or to isolate the wellhead ports.

Further preferred features and advantages of the invention are in the dependent claims or will be apparent from the following description of an illustrative embodiment, made with reference to the drawings.

Brief description of the Drawings

Fig. I is a vertical section showing the sleeve in its nonnal (open) position, Fig. 2 is a vertical section showing the sleeve in its closed position and before installation of the inner casing strings.

Description of the Preferred Embodiment

Referring to Fig. 1, a wellhead housing 10 is shown mounted on a first casing string 18.

Wellhead housing 10 has an internal bore 11 and an upper end 21 with a profile for connecting to a blowout preventer (BOP). Wellhead housing 10 has a thickened portion 38 lo defining an upward facing shoulder 39 (Fig. 2) that can act as a stop. Wellhead housing 10 also has a groove 35 arranged around the outer circumference -for the attachment of a reaction ring 60 to be described later.

A first casing hanger 12 is landed and secured in the Wellhead housing internal bore 11 with a casing string 20 suspended therefrom and extending into the well. A second casing hanger 14 is also landed and secured in wellhead housing internal bore With a casing string 22 suspended therefrom and extending info iDe well.

A first annular space 3(), usually called the "C" annulus, is defined between the casing string 2() and the first casing string 18. A second annular space 28, usually called the "B" annulus, is Reined between casing strings 22 and 20.

The first casing hanger 12 has passages 13 for communication between the annulus 3() and a ring groove or port 29 foamed in the exterior of the casing hanger 12. The second casing 2s hanger likewise has passages]5 for communication between the annulus 28 and a ring groove or port 27 conned in the exterior of the casing hanger 14.

Wellhead housing 10 has a first port 32 extending through its wall, with its inner opening in communication with ring groove 29 and hence in communication with passage 13 and annulus 30. A second port 34, which is located above first port 32, is formed extending through the wall of the wellllead housing 10, having an inner opening in communication with ring groove 27 and hence with passage 15 and annulus 28.

A sleeve, generally designated by 50, is shown located concentrically around the wellhead housing. The sleeve is at its upper end attached to the reaction ring 60 and has a lower face 37 (Fig. 2) abutting against the wellhead stop shoulder 39 so that it is arranged for limited axial movement along the external wall of the wellhead housing 10. The sleeve includes an upper horizontal bore 51 and a lower horizontal bore 53, both bores extending radially through the wall of the housing. An upper blind bore 52 and lower blind bore 54 are located below the bores 52 and 53 respectively. Elastomer seals 55 and 56 are located above and below lower blind bore 54 and elastomer seals 57 and 58 are located above and below upper 0 blind bore 53. Metallic lipseals 41 and 43 are located at the lower and upper end of the sleeve 50, sealing between the sleeve and the wellhead housing 10. In addition, a metallic lipseal 42 is preferably located between bores 52 and 53, sealing between the two ports.

As shown in lFig. 2, the reaction ring 60 has a rib 61 or similar feature that is complementary ]5 to the groove 35 on the wellhead housing. An hydraulic actuator is provided between the reaction ring 60 and sleeve 50 with cylinders 69 being attached to reaction ring 60 and piston rods 70 attached to r'ne sleeve 5(). The reaction ring 60 is inienueu to pr-OviL'ie a reaction pond for the actuator when it is operated for axial movement of the sleeve. Lines 71, 72 are shown, for supplying/draining hydraulic Quid to/from the actuators. 2()

tipper bore 51 has a reducing flange 44 boiled OTltO the exterior of the sleeve 50 and connected to a line 45 that is its communication with an umbilical. Lower bore 53 is likewise equipped with a reducing flange 46 bolted onto the exterior of the sleeve and connected to a line 47 that is connected to the umbilical.

Alternatively, the lines 45 and 47 can he connected to the production control system or to the flow line.

Pressure sensors (not shown) are located in the annul) to monitor the pressure situation there.

The signals are conveyed to the production or workover controls system (not shown) as appropriate.

To prepare the apparatus for use, the sleeve 50 is installed over the wellhead housing. The reaction ring and piston assembly is likewise attached to the outer past of the wellhead housing and locked in place in the groove 35. The sleeve will now be free to move up and down between its lowermost position when its 1oNver end 37 abuts against the stop shoulder 39, and an upper position. During installation, drilling and cementing the sleeve is maintained its uppermost position as shown in fig. 2, where the blind bores 52, 54 are in alignment with the wellhead housing Potts 32, 34. The communication between the annul) and the outside of the well is now closed.

0 When preparing the well for production, the reducing flanges 44, 46 with attached hoses 45, 47 are bolted on to the sleeve 50, for example with the aid of an ROV. Fluid is supplied to the actuators and the sleeve is moved to its lower position where communication is established between the annul) and the outside of the well. During operations the pressure in the annul) is constantly monitored. When the pressure reading frown one of the downhole sensors exceeds a critical value, excess pressure can be relieved by allowing annulus fluid to be vented or bled, either to a dedicated return line in the production or workover umbilical, the prouuciion conir,i system or k' ine Bowline.

Many variations and/or modifications can be made to the system without diverting from the scope of the invention as defined in the claims. The actuator can for example be a manually operated actuator, being operated by diver or ROV and based on the well know gear and tooth system. Alternatively, the sleeve and reaction ring can be made as one piece, Witil the actuator integrated into the sleeve and having an annular cylinder and ring piston that operates to move the sleeve. The reaction r ing can he welded onto the wellhead or be in two halves that are clamped in place.

The pressure sensors (where present) may be situated in the casing annul) as described above, for example with signal lines passing through the casing hangers and into a Christmas tree mounted on the wellhead housing. Alternatively, the pressure sensors may be situated in the casing hangers or ananged in the wellhead housing to sense the pressure in the ports 32, 34, or situated in or on the sleeve to sense the pressure in the blind bores 52, 54. Yet a further alternative is to sense the pressure in the lines 45, 47.

The sleeve can he actuated for rotation about the wel]head housing s vertical axis instead of for linear movement along that axis. Such rotation can be used for example to bring annulus potty extending completely through the side wall of the wellhead housing into and out of s circumferential alignment with corresponding ports in the sleeve.

Claims

CLAIMS: l. A subsea wellhead comprising a monitoring and/or bleed down

annu]us port extending comp]ete]y through a side wall of the wellhead and having an interior end in pressure communication with a well annulus, the wellhead comprising an external sleeve with a bore for selectively opening and closing said annulus post.

2. A subsea wellhead as defined in claim I comprising a pressure sensor.

lo 3. A wellhead as defined in claim I or 2 comprising an actuator for moving the sleeve.

4. A we]]head as defined in claim 3 wherein the actuator is connected between the sleeve and a reaction ring attached to the wel]head.

5. A we]]head as defined in any preceding claim wherein the bore in the sleeve is connected to an external Bowline.

6. A wellhead as defined in any preceding claim wherein the sleeve is sealed to the wellhead by an annular sealing element 7. A wellhead as defined in claim 6 wherein the annular sealing element is a metallic lipseal.

8. A wellhead as defined in claim tS or 7 in which a pair of said annular sealing elements are positioned on the sleeve with one above and the other below the bore.

9. A wellhead as defined in any preceding claim comprising a pair of said annulus ports and a corresponding pair of said bores in the sleeve, for selective pressure communication with a corresponding pair of well annul).

l 0. A subsea wellhead comprising a monitoring and/or bleed down annulus port, substantially as described with reference to or as shown in the drawings.

Amendments to the claims have been filed as follows CLAIMS: 1. A subsea wellhead comprising a monitoring and/or bleed down annulus port extending completely through a side wall of the wellhead and having an interior end in pressure communication with a well annulus, the wellhead comprising an external sleeve with a bore for selectively opening and closing said annulus port.
2. A subsea wellhead as defined in claim I comprising a pressure sensor.
3. A subsea wellhead as defined in claim 1 or 2 comprising an actuator for moving the lo sleeve.
4. A subsea wellhead as defined in claim 3 wherein the actuator is connected between the sleeve and a reaction ring attached to the wellhead.
5. A subsea wellhead as defined in any preceding claim wherein the bore in the sleeve is connected to an external Bowline.
6. A subsea wellhead as defined in any preceding claim wherein the sleeve is sealed to the wellhead by an annular sealing element
7. A subsea wellhead as defined in claim 6 wherein the annular sealing element is a metallic lipseal.
8. A subsea wellhead as defined in claim 6 or 7 in which a pair of said annular sealing elements are positioned on the sleeve with one above and the other below the bore.
9. A subsea wellhead as defined in any preceding claim comprising a pair of said annulus ports and a corresponding pair of said bores in the sleeve, for selective pressure communication with a corresponding pair of well annul). so
10. A subsca wellhead comprising a monitoring and/or bleed down annulus port, substantially as described with reference to or as shown in the drawings.