Wells – Submerged well – Submerged – buoyant wellhead or riser
Reexamination Certificate
1999-05-26
2001-04-10
Tsay, Frank (Department: 3673)
Wells
Submerged well
Submerged, buoyant wellhead or riser
C166S366000
Reexamination Certificate
active
06213215
ABSTRACT:
FIELD OF INVENTION
This invention relates to a system for offshore production of oil or gas, comprising a surface vessel having means for maintaining a desired position and orientation, a bottom installation at the seabed, for at least two production wells, and risers for connecting the bottom installation to the vessel. Moreover, in the following specification there is described a method of producing oil or gas with the system, whereby the method initially comprises deployment of the bottom installation at the seabed and the vessel in position at the sea surface above the bottom installation.
BACKGROUND OF THE INVENTION
When developing oil or gas fields at sea the time factor is very significant. The time taken from the drilling of the first well being able to produce, until this well and other wells in association therewith are completed and in full production, should be as short as possible. This has to do, inter alia, with the large investments being made in the form of expensive drilling and production equipment. Also this comprehensive equipment as such should be designed and built aiming at the lowest possible total costs.
BRIEF SUMMARY OF THE INVENTION
One aspect of the present invention is a system for offshore production of oil or gas. The system includes a surface vessel which has an apparatus for maintaining a desired position and orientation, a bottom installation at a seabed for at least two production wells, and at least one riser for connecting the bottom installation to the vessel. The vessel is provided with drilling equipment for wells at the seabed and with process equipment for produced oil or gas. The bottom installation comprises a template having a foundation at the seabed. The bottom installation has a manifold unit. The bottom installation is designed with at least two wellhead sections adapted for installation of associated Christmas trees. The system also includes a drill string adapted to extend from the drilling equipment at the vessel, and a movable operation module adapted to be installed on the bottom installation and to be connected to the lower end of the drill string. The at least one riser includes a product riser adapted to connect the operation module to the process equipment on the vessel.
The system may also include a swivel unit having a vertical axis, in association with the riser. The swivel unit may be located on the vessel, and may be incorporated in the operation module. The swivel unit may be motor driven under control by the apparatus for maintaining the vessel at a desired position and orientation. The swivel unit may have a through-going axial hole for the drill string, and may be underneath a blowout preventer which is also incorporated in the operation module.
The product riser may extend upwards through the water for connection at the vessel at a point at a distance from equipment, abaft on the vessel. The product riser may extend up through the water in an approximate S-shape with an upwardly curved, elevated middle portion of the product riser. The product riser may be attached along a drilling riser for the drill string.
The vessel may be provided with a means for dynamic positioning/orientation.
According to another aspect of the present invention a vessel is provided with drilling equipment for wells at a seabed and with process equipment for produced oil and gas. The vessel includes an apparatus for maintaining a desired position and orientation at the sea surface, and an apparatus for controlling a swivel unit in association with the means for maintaining the desired position and orientation, being based on dynamic positioning and orientation.
The vessel may be equipped with a swivel unit for the upper end of a product riser. The drilling equipment may include an associated work opening, and be located generally midship, and may also have an associated coupling for the product riser. The process equipment may be located abaft.
According to yet another aspect of the present invention a bottom installation includes a template and movable operation module. The template has a foundation at a seabed, and is provided with a manifold unit. The template is designed with at least two wellhead sections adapted for installation of associated christmas trees. The movable operation module is adapted to establish a rotatable connection to a riser extending to a surface vessel.
The movable operation module may include a swivel unit which is motor-driven, and may have a through-going axial hole for a drill string. The swivel unit may be located underneath or over a blowout preventer which may be also incorporated in the operation module.
The operation module may have at a lower portion an interface of the same type as christmas trees intended for being landed and connected to the wellhead sections. The operation module may be provided with a guide yoke adapted to hold product risers extending laterally and at an inclination upwards, with a clearance in relation to remaining components and equipment of the template.
According to yet another aspect of the present invention, a system for offshore production of oil or gas is provided which includes a surface vessel equipped with an apparatus for maintaining a desired position and orientation, a bottom installation at a seabed for at least two production wells, and risers for connecting the bottom installation to the vessel. The vessel is provided with drilling equipment for wells at the seabed and with process equipment for produced oil or gas. The bottom installation comprises a template having a foundation at the seabed. The bottom installation is provided with a manifold unit. The bottom installation is designed with at least two wellhead sections adapted for installation of associated christmas trees. The system further comprises a drill string adapted to extend from the drilling equipment on the vessel to a blowout preventer on the bottom installation. The risers include a product riser adapted to connect one or more production wells on the bottom installation to the process equipment on the vessel.
According to yet another aspect of the present invention, a method of producing oil or gas with a system including a surface vessel, a bottom installation for at least two production wells and provided with a manifold unit and a plurality of wellhead sections, and at least one riser for connecting the bottom installation to the vessel is provided. According to the method the bottom installation is deployed at a seabed, and the vessel is positioned at the sea surface above the bottom installation. A first well is drilled and completed at one of the plurality of wellhead sections. A second well is initially drilled at a second one of the plurality of wellhead sections. The operation module and riser are set down for landing and connection at the second one of the plurality of wellhead sections and the second well is additionally drilled and completed. Production is established for the first well through the manifold and the operation module at the second one of the plurality of wellhead sections, simultaneously with the additional drilling of the second well. A corresponding third well is drilled from a third one of the plurality of wellhead sections and production is subsequently established through the operation module from the third well.
The initially drilling of the second well may include installing both conductor and casing tubes for the second well.
Additional new wellheads may be drilled according to the method. If additional new wells are drilled the operation module may be disconnected and removed from the new wellhead sections after drilling, completing and putting into production a desired number of wells. If additional new wells are drilled, the operation module may also be finally located at a dedicated section of the bottom installation separated from the new well head sections.
It is an object of this invention to provide a system and a method as well as associated components, in particular in the form of a bottom installation and a special vessel, that in an optimal man
Breivik Kare
Ingebrigtsen Atle
Den Norske Stats Oljeselskap A. S
Foley & Lardner
Tsay Frank
LandOfFree
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