WELL CONSTRUCTION AND COMPLETION
A well sealing system includes a tailipipe set in a wellbore casing, the annular space between the tailpipe and the casing being sealed by a packer comprising at least two annular seals, and the internal diameter of the tailpipe being sealed by at least two internal seals. Disclosed are also an apparatus and a method for providing a casing in a bore hole for a well an offshore location, comprising the steps of: a) fabricating a casing in a location remote from the offshore well location; b) floating the casing to the location; c) orienting the casing to a substantially vertical position; d) lowering in a drilling assembly; e) operating a drill bit included in the drilling assembly to drill a borehole; f) lowering the casing into the bore hole as required.
This invention is a new method of constructing a well in deepwater without the use of a rig
Setting up a rig when drilling a subsea well is an expensive and time-consuming exercise. Casing sections are transported to an offshore rig, and as the bore hole is extended a new casing section is lowered onto the top of the previous casing and secured to it to extend the casing string. The object of the present invention is to provide a new method of constructing an offshore well without the use of a rig.
According to the present invention, there is provided a well sealing system including a tailipipe set in a wellbore casing, the annular space between the tailpipe and the casing being sealed by a packer comprising at least two annular seals, and the internal diameter of the tailpipe being sealed by at least two internal seals, so that the wellbore above the tailpipe and the wellbore below the tailpipe are separated by two layers of seals.
According to another aspect of the present invention, there is provided a length of casing for installation in a wellbore, the casing including a dynamic seal which seals the annulus between the outer diameter of the length of casing and the inner diameter of any previously installed conductor or casing lengths.
According to a further aspect of the present invention, there is provided a method of providing a casing a bore hole for a well an offshore location, comprising the steps of
- a) fabricating a casing in a location remote from the offshore well location
- b) floating the casing to the location
- c) orienting the casing to a substantially vertical position
- d) lowering in a drilling assembly
- e) operating a drill bit included in the drilling assembly to drill a borehole
- f) lowering the casing into the bore hole as required.
According to another aspect of the present invention, there is provided a casing installation system comprising a casing supported by flotation means, and a first ship for towing the casing, and an orientation means for orienting the casing vertically.
This method of deployment allows the use of a length of casing which may be very much longer than the sections of casing currently employed. This entirely obviates having to short sections of casing together on a rig to produce a casing string.
Other key benefits are;
The casing is manufactured and quality assured in a controlled environment. Independent of drilling process and time line.
Significantly lower cost vessel used to deploy casing, drill and complete the well.
Umbilical supports the casing and supplies the drilling fluid
When cementing casing, umbilical is retracted to deactivate circulation ports used in the drilling process.
The following figures describe one embodiment of the invention
Referring to
Ideally, two vessels are involved in the deployment of the casing string—a towing vessel which tows the casing string to the drill site, and a deployment vessel which takes the casing string from the towing vessel and manoeuvres the casing string to the seabed. The two vessels may support the casing together while the casing string is being oriented. Alternatively, a single vessel may both tow the casing to the drill site, and orient and deploy the casing string.
The casing may be fabricated on-shore so that it is already fully prepared for deploying into the well, or final procedures for readying the casing may be carried out immediately before the casing is deployed. Referring to
Referring to
When the casing has reached its maximum depth, collets 42 in uppermost end of the casing locate and support the weight of the casing in a profile 43 of the previous casing or conductor section. The collets also include a sealing surface to seal the casing against the inner surface of the previously installed casing. A ball may be allowed to fall through the tubing to activate the release of both the upper and lower casing termination 32 and 33. Also, cessation of fluid pumping causes the expandable bit to retract to its minimum diameter, so that the inner assembly and bit may then be conveyed back to surface on the inner tube 11.
Referring to
Once the cement is set, a new casing string 21 is lowered on a tube 52 into the well with the drilling BHA 22 installed inside it. As for the previous casing string, the casing string 21 has a stepped seal 50 which prevents pressure during the drilling process being exerted on the upper section of open hole. Once the casing reaches the top of the previous casing, the stepped seal 50 disengages from the casing 25 and engages with the top of the previously installed casing 10, supplementing the sealing portions of the previously installing casing's collets 42 as an additional seal. The casing 25 includes a secondary annular seal 51 having a smaller radius, which seals the casing 25 against the inner surface of the previously installed casing 25. Surface pressure control hardware 23 is deployed at the same time and docks onto the wellhead 24. The fluid circulation path is down the central tube 11 and internal circulating tube 30, through the bit, through the tubing ports 14 and up the annulus between internal circulating tube 30 and the casing 21, and back to the surface vessel 3 via the umbilical 26
Alternatively to providing the drilling assembly connected to the end of the casing, a drilling assembly may be deployed separately and inserted through the casing.
Referring to
At some point, it maybe necessary to remove the completion from the well. To do this, two barriers are required to protect the surface from the reservoir. Referring to
Referring to
Referring in particular to
Claims
1. A well sealing system including a tailpipe set in a wellbore casing, the annular space between the tailpipe and the casing being sealed by a packer comprising at least two annular seals, and the internal diameter of the tailpipe being sealed by at least two internal seals, so that the wellbore above the tailpipe and the wellbore below the tailpipe are separated by two layers of seals.
2. A well sealing system according to claim 1 wherein tubing extends from the surface of the wellbore to the tailpipe, and the two internal seals are deployed down this tubing.
3. A well sealing system according to claim 1 wherein the two internal seals engage with a profile in the internal diameter of the tailpipe.
4. A well sealing system according to claim 2, wherein the tubing is disengaged after the internal seals have been deployed.
5. A well sealing system according to claim 1 wherein the internal seals are removable.
6. A length of casing for installation in a wellbore, the casing including a dynamic seal which seals the annulus between the outer diameter of the length of casing and the inner diameter of any previously installed conductor or casing lengths.
7. A length of casing according to claim 6, wherein the dynamic seal includes a disengagable part that can release from the length of casing for installation to engage with the annulus between two previously installed casing lengths.
8. A length of casing according to claim 7, wherein the dynamic seal includes a non-disengagable part that remains on the length of casing being lowered after the disengagable part has been released, the non-disengagable part continuing to seal the annulus between the length of casing being lowered and a previously installed casing length.
9. A method of providing a casing a bore hole for a well an offshore location, comprising the steps of a) fabricating a casing in a location remote from the offshore well location b) floating the casing to the location c) orienting the casing to a substantially vertical position d) lowering in a drilling assembly e) operating a drill bit included in the drilling assembly to drill a borehole f) lowering the casing into the bore hole as required.
10. A method according to claim 9 wherein the drilling assembly is lowered simultaneously with the casing.
11. A method according to claim 9 wherein a bore hole pressure control means is lowered onto the bore hole after the casing is introduced to the bore hole.
12. A method according to claim 9 wherein an umbilical having a flowpath is included in fluid communication with the bore hole.
13. A method according to claim 9 wherein after the casing is lowered in the bore hole to its final position, a cement plug is formed at the bottom of the casing before the drilling assembly is removed from the bore hole.
14. A method according to claim 9 wherein a subsequent casing is provided at the sea bed in the same manner, the subsequent casing having an outer diameter smaller than that of the inner diameter of the previous said casing, the subsequent casing being lowered through the previous casing.
15. A casing installation system comprising a casing supported by flotation means, and a first ship for towing the casing, and an orientation means for orienting the casing vertically.
16. A casing installation system according to claim 15 wherein the casing is supported between a first ship and a second ship during orientation.
17. A casing installation system according to claim 16 wherein a control system including one or more rotatable grips are attached to the casing to hold the casing while it is orientated.
18. A casing installation system according to claim 15 wherein a drilling assembly is provided that is insertable within the casing.
19. A casing installation system according to claim 15 wherein a sealing means is provided for sealing the bore hole from the surrounding environment.
Type: Application
Filed: Sep 10, 2007
Publication Date: Nov 19, 2009
Inventor: Phillip Head (Surrey)
Application Number: 12/440,750
International Classification: E21B 7/20 (20060101); E21B 33/12 (20060101); E21B 7/12 (20060101); E21B 23/00 (20060101); E21B 17/00 (20060101); E21B 19/00 (20060101); E21B 43/10 (20060101);