Patent Application
20120291684
This relates generally to drilling oil and gas wells in artic regions.
Oil and gas deposits have been located in regions which would be generally covered by ice throughout the year. In order to drill in such areas, a drilling ship must be led through the ice by an ice breaker. In addition, a second drilling ship maybe desirable on site in order to drill a relief well if a blowout or other failure occurs. Commonly, the second drilling ship maybe accompanied by its own separate ice breaker. Thus, a convoy of four ships may be needed.
Such a convoy is highly expensive since each of the drilling ships demands extremely high hourly rates and is very expensive to operate. Moreover, the second drilling ship may never even be needed and simply is on site in a standby mode in case of emergency.
In accordance with some embodiments of the present invention, a single drilling vessel may be capable of both ice breaking and drilling a relief well. This means that only two ships may be needed on site in an ice covered artic drilling regions such as Alaska and the Canadian Beaufort Sea through West and East Greenland to the Barents Sea and then on into the Russian seas. In some embodiments, substantial cost saving may result.
By the use of the term “drilling vessel”, it is intended to refer to any vessel that is capable of drilling for oil or gas, including drilling ships with dynamic sufficient and capability, drilling platforms or any other floating device that is capable of drilling for a well for oil or gas.
In some embodiments, the drilling vessel has a stowable mast. The term “stowable mast” is intended to refer to any structure for use in supporting crown blocks and/or drillstrings from a drilling vessel, including a mast or a derrick to mention two examples. The term “stowable” is intended to refer to a mast that is positionable in at least two positions, one of which is a vertical operating position and the other is a position of reduced height, for example to enable ice breaking operations without unduly stressing the mast during ice collisions.
In some embodiments, the mast may be stowed during ice breaking or operations other than drilling. Thus, when the vessel is used for breaking ice, the high moment arm caused by the crown block and extended drilling mast may not be applied to the drilling vessel. As a result, the drilling vessel may be manufactured more economically for lower stress. Moreover, the vessel may be quicker and more maneuverable with the mast in the stowed position. Then, if drilling operations are necessary, the mast may be raised and drilling may be conducted.
Referring to
Within the hull 12 are basic drilling accessories including a drilling package 14, a 1000 meters of riser 18 in one embodiment, drilling tubulars 20, and relief well material 22. The drilling package may include items such as a blowout preventer and the relief well materials may include things such as a well head and casing required for a relief well.
The deck 28 may be punctuated by a crane 24. A stowable mast 26 may be recessed below deck within the hull such that its upper surface, when stowed, is substantially co-planar with the deck surface 28. It may be covered in some embodiments with the deck material such that the deck is fully usable with the mast 26 in the stowed position shown in
A hinge 31 secures the pivoting part 25 of the mast 26 to a stationary part 32. The bottom surface of the pivoting part 26 may be angled as may be the upper surface of the non-pivoting part 32. Thus, when the pivoting part 25 rotates 90 degrees clockwise to the position shown in
The pivoting part 25, may itself include two telescoping sections 36 and 38. The section 36 can be telescoped out of the section 38 as indicated by arrow B.
The source of pivoting force applied to the mast 26 may in one embodiment be a reciprocating hydraulic cylinder 35 with a bar 33 that connects to the moveable portion. When the bar 33 is pulled forward the mast may be erected. In some embodiments, the bar 33 and the hydraulic cylinder 35 may be recessed within the deck.
In some embodiments, a hinged cover (not shown) may be provided over the stowed mast 26 and the hydraulic cylinder 35 and bar 33. This hinged cover may pivot away when the mast is raised. Once the mast is raised, the hinged cover can be closed back to provide usable deck space and to cover the empty storage slot 40 for the stowable mast. As a result, the deck is substantially entirely usable whether the mast is stowed or in use.
A pilot house 15 may be formed on the deck 28 in some embodiments.
Suitable means for righting the stowed mast 26 are varied and may include hydraulic cylinders, cable systems, and rack and pinion systems. In the embodiment shown in
Once upright, in the position shown in
Furthermore, as shown in
Once the mast is fully extended to the position shown in
In some embodiments, advantageously, only one drilling vessel and an ice breaker combined drilling vessel may be needed on site in the remote artic areas covered with ice. The ice breaker may function to break ice for the accompanying drilling vessel and, if needed, may be also capable of drilling a relief well. Because the mast may be collapsed or stowed, the ship may effectively function as an ice breaker in that the mast may not be subject to extreme loading during ice breaking operations. Moreover, the ice breaker may proceed with greater speed in some embodiments without the upright mast in place.
In some embodiments, only the minimum amount of drilling equipment may be provided, sufficient to drill only a relief well. For example, only a 1000 meters of riser may be carried in one embodiment. Reducing the drilling equipment reduces the overall vessel weight.
In accordance with another embodiment of the present invention shown in
In some embodiments, the arrangement shown in
Other arrangements may be also considered. For example instead of collapsing the mast to a position in alignment with the deck, the mast may be folded 180 degrees so that it extends vertically into the hull. When raised to the intermediate position (corresponding to
References throughout this specification to “one embodiment” or “an embodiment” mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation encompassed within the present invention. Thus, appearances of the phrase “one embodiment” or “in an embodiment” are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be instituted in other suitable forms other than the particular embodiment illustrated and all such forms may be encompassed within the claims of the present application.
While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.
