FIELD OF THE INVENTION
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The present invention relates generally to offshore facilities used in connection with the exploration and production of oil and gas, and in a particular though non-limiting embodiment, to a docking and drilling vessel system suitable for deploying self-standing risers and conducting oil and gas drilling, production and storage operations.
BACKGROUND OF THE INVENTION
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Offshore drilling is quickly becoming the prevalent method of exploring and producing oil and gas, especially in Western countries where land operations are frequently inhibited by environmental concerns. There is, however, a serious shortfall of offshore drilling units called Mobile Offshore Drilling Units, or MODUs. The relative unavailability of MODUs has resulted in significant delays in many drilling projects. Consequently, the cost of obtaining either a new or existing MODU for an exploration and production operation has dramatically increased over the past decade.
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As will be readily appreciated by those of skill in the art, MODUs are utilized during the early testing phase required to evaluate oil, gas, and other hydrocarbon discoveries. However, due to the lack of floating production facilities and the high cost of MODUs, early testing is seldom accomplished, which often results in unnecessary delays and inaccurate predictions of economic assessments, project development schedules, etc. Moreover, procurement of offshore production and storage facilities required to operate offshore projects in a timely manner can be quite difficult. In extreme circumstances or in especially remote regions, the lag time between hydrocarbon discovery and the production phase can reach 10 years or more.
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Meanwhile, self-standing riser assemblies supported by buoy devices are becoming a more common method of performing oil and gas exploration and production related activities. Compared to the large scale riser assemblies typically serviced by MODUs, the self-standing riser provides for lighter and less expensive riser tubulars (e.g., drilling pipe, stack casing, etc.). Self-standing risers also admit to the use of lighter blowout preventers, such as those used by land drilling rigs.
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Moreover, the top buoy of a self-standing riser system can be positioned near the surface of the water in which it is disposed (for example, less than around 100 ft. below surface level), allowing for efficient drilling in even shallow waters. Furthermore, where riser systems are tensioned and controlled with associated buoyancy chambers, buoy-based systems can be used successfully in much deeper waters.
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However, as those of skill in the art have learned in the field, buoy-based systems utilizing general purpose vessels for riser and buoyancy chamber deployment are deficient in that large-scale operations (e.g., deployment in very deep or turbulent waters, or projects involving multiple combinations of riser strings and buoyancy chambers, etc.) are very difficult to control, and thus installation, operation and maintenance of the resulting system is significantly impaired.
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There is, therefore, a need for a custom vessel that admits to efficient deployment of large-scale riser systems in a manner similar to the manner of a MODU even when a MODU is not available.
SUMMARY OF THE INVENTION
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A sea vessel exploration and production system is provided, wherein the system includes a drilling station formed from at least one section of a first sea vessel hull; and a docking station, which is also formed from at least one section of a second sea vessel hull. A mooring system suitable for connecting the drilling station to the docking station is also provided. Means for anchoring the vessels to the seafloor, and for attaching them to turret buoys, are also considered. Various exploration and production packages, as well as equipment required to deploy and control a self-standing riser system in either deep or shallow waters, are also described.
BRIEF DESCRIPTION OF THE DRAWINGS
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FIG. 1A is an overhead view of a docking and drilling station moored end-to-end, according to example embodiments.
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FIG. 1B is a side view of a docking and drilling station moored end-to-end, according to example embodiments.
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FIG. 2 is a schematic diagram of an anchored drilling station and docking station operating a self-standing riser assembly, according to example embodiments.
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FIG. 3 illustrates a sequence of steps for mooring a docking station and a drilling station using an end-to-end method, according to example embodiments.
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FIG. 4 illustrates a sequence of steps for mooring a docking station and a drilling station using a side-by-side method, according to example embodiments.
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FIG. 5 illustrates a sequence of steps for mooring a docking station and a drilling station to a turret buoy anchoring assembly, according to example embodiments.
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FIG. 6 is a schematic diagram of an alternative docking station with side-by-side docking to a docking station, according to example embodiments.
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FIG. 7 is a schematic diagram of alternative docking station mooring schemes for varying current conditions, according to example embodiments.
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FIG. 8 is a schematic diagram of a docking station or a drilling station attached to a turret buoy, according to example embodiments.
DETAILED DESCRIPTION
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The description that follows includes exemplary systems, methods, and techniques that embody various aspects of the presently inventive subject matter. However, it will be readily understood by those of skill in the art that the disclosed embodiments may be practiced without one or more of these specific details. In other instances, well-known manufacturing equipment, protocols, structures and techniques have not been shown in detail in order to avoid obfuscation in the description.
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Referring now to the example embodiment illustrated in FIG. 1A, an overhead view of a docking station 6 and a drilling station 8 are depicted as being moored together in an end-to-end manner. The embodiment of the drilling station 8 shown in FIG. 1B comprises crew quarters and an operations office; a drilling rig; a void space designed for housing and deploying various buoyancy devices 14; a helipad; a moon pool 12; a plurality of anchor lines used to anchor the system to an associated seabed; and mooring lines configured to moor said drilling station 8 and said docking station 6 together. The example embodiment of the docking station 6 further comprises modular production, testing and injection facilities 10; a plurality of anchor lines; and mooring lines configured to mate with the mooring assembly of the drilling station. A self-standing riser disposed in mechanical communication with one or more buoyancy devices 14 is also provided.
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In the embodiment depicted in FIG. 1A, the docking station 6 and drilling station 8 are moored together using mooring lines in such a manner that both portions of the combined vessel are able to properly perform offshore drilling operations. In alternative embodiments, various other devices can be used to secure the mooring system, for example, clamps, rods, latches, locks and other mechanical devices; strong magnets and electrical control systems; vacuum systems, etc.
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Although not illustrated in FIG. 1, typical embodiments of the docking and drilling stations further comprise a plurality of oil and gas related drilling, production and exploration equipment. For example, a modified land or platform drilling rig installed on the drilling station can be used to operate a self standing riser while maintaining functional stability and efficient operational continuity. Similar equipment disposed within or upon the drilling station 8 enables storage, deployment, lifting, and retrieval operations, as well as storage of additional risers, such as stress joints 16, and one more buoyancy devices 14 should they be required during drilling operations.
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In further embodiments, hydrocarbons such as oil, gas, liquid natural gas, etc., encountered during the drilling process are separated, treated and stored either onboard or within docking station 6. In still further embodiments, docking station 6 further comprises modular production facilities 10 and storage space that can be used for testing operations or as a facility to separate oil, gas, water, etc. Other embodiments of the docking station 6 comprise one or more of a flare boom used to bleed off gas and fluid pressure; oil, water and gas separators; and storage facilities used to store crude and previously treated oil and gas. In further embodiments still, water and gas injection equipment used to re-inject wells and the mechanical equipment required to facilitate such operations are also included.
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Since the drilling station does not necessarily have to support deployment of conventional riser and buoyancy chamber systems, it can utilize a typical land or platform drilling rig modified to endure extreme sea and weather conditions. The embodiment depicted in FIG. 2, for example, illustrates an anchored drilling station and docking station operating in tandem to support and control a self-standing riser system equipped with an associated buoyancy device 14. The drilling station of FIG. 2 further comprises a void space suitable for the storage and handling of buoyancy devices 14, as well as a hoisting system and retractable guide rails that assist in guiding the buoyancy devices 14 below the hull of drilling station.
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In various other embodiments, the drilling station depicted in FIG. 2 allows the drilling rig to hoist, lower and otherwise handle self standing riser, casing, drilling pipe, etc., passed through the moon pool 12. One specific example embodiment permits self standing riser tubulars to be lowered into the water until a desired length is obtained and the required quantity of buoyancy devices 12 are in place. Although not depicted, those of skill in the art will appreciate that further embodiments of the drilling station are equipped to deploy, store and handle most other types of routine or custom fit offshore drilling equipment, such as shear rams, ball valves, blowout preventers and hoists therefor.
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Following installation of the self standing riser, the drilling station can commence drilling, completion, testing and workover operations, etc. As operations continue, some portions of the system can be removed so that the drilling station can be utilized in other types of operations. In further embodiments, the drilling station is utilized to drill a hole in a seabed so as to permit installation of a wellhead and associated casing. In still further embodiments, the drilling station is used to remove and store the riser assemblies, such as stress joints 16, as well as attendant buoyancy devices 14 and other offshore drilling equipment.
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In some example embodiments, the described installation and removal process is applied to wellheads created by others and abandoned. Such projects would typically utilize cranes, hoists, winches, etc., operating in mechanical communication with the drilling station in order to perform installation and removal of existing riser assemblies, wellheads, production trees and blowout preventers.
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In some embodiments, the void space formed to store and handle buoyancy devices 14 further comprises a moveable floor, tracks, a gantry, etc., that transports buoyancy devices to a desired location (e.g., near the moon pool) to be joined with a self standing riser assembly stack. Various embodiments of the moon pool 12 further comprise retractable guide rails that assist in guiding and delivering the buoyancy devices 14 down below the hull to a deployment station.
End-to-End and Side-to-Side Mooring of the Docking and Drilling Stations
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FIGS. 3 and 4 depict an embodiment of the docking station 6 and the drilling station 8 moored together using end-to-end and side-to-side mooring methods, respectively. In the example embodiment illustrated in Step 1 of both FIGS. 3 and 4, docking station is towed by a towing vessel toward anchor lines preinstalled by workboats, anchor handling vessels, etc. Towing of the docking and drilling stations can of course be facilitated by any vessel capable of towing another vessel of appropriate size, such as a work boat, a tug, etc.
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Step 2 depicts various transportation vessels (e.g., workboats, towing vessels, etc.) transporting a plurality of anchor lines to fastening members disposed in communication with the docking station 6. Some embodiments of the fastening members assist in adding tension to the anchor lines, and slowly moving the docking station toward desired site coordinates.
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In the end-to-end embodiment shown in FIG. 3, the anchor lines are affixed to fastening members positioned on all sides of the docking station 6. Note, however, that the anchor lines would typically be affixed to fastening members on a particular side of the docking station 6 in the side-to-side method depicted in Step 2 of FIG. 4. Such embodiments of side-to-side mooring help maintain proper lateral spacing and controlled efficient movement as the drilling station 8 and docking station 6 are joined. In further embodiments, the drilling station 8 is transported to within a close proximity of the docking station 6 during Step 2, and a plurality of anchor lines are thereafter affixed to fastening members of the drilling station in order to secure the system in a desired dynamic equilibrium.
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Step 3 illustrates the drilling station as disposed in stable operative communication with the docking station 6. Various known attachment means, such as mooring lines, as well as any new or custom designed fasteners or the like can be used to facilitate stable and reliable operations. In the embodiment depicted in FIG. 3, the drilling station 8 and the docking station 6 are mutually joined and operated in a back-to-back or end-to-end manner, whereas in the embodiment illustrated in FIG. 4, the drilling station 8 and the docking station 6 are joined in a side-to-side manner. Either manner will, if configured correctly, permit the drilling station 8 to drill, deploy casing, deploy self standing riser tubulars, etc. In some embodiments, the drilling station 8 is configured to position itself over an existing self standing riser system in order to perform workover operations, well completions, and other common drilling operations.
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In the embodiment illustrated in Step 4 of FIGS. 3 and 4, the drilling station 8 is disconnected from the docking station 6 and towed away. In a typical example embodiment, anchoring lines previously used to anchor the drilling station 8 in place are attached to the remaining docking station 6, thereby resulting in a spread mooring configuration suitable for receiving a new vessel. In some embodiments, the docking station is then used as a testing or production vessel to process and separate oil, gas and water, etc. In further embodiments, the docking station provide facilities to inject water and gas back into well(s), power to operate electric submersible pumps, or lifting support to aid with other production methods.
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Step 5 depicts an embodiment of the mooring sequence in which an oil tanker is joined in communication with the docking station 6. As previously discussed, example embodiments may comprise a wide variety of attachment methods and means, such as mooring, docking, fastening, etc. In one example embodiment, the docking station 6 then utilizes pipes, tubulars, hoses, etc., to transfer oil, gas or other stored fluids to and from the tanker.
End-to-End Mooring Using a Turret Buoy
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FIG. 5 depicts an embodiment of a turret mooring buoy 18 that allows the drilling station and the docking station to cooperate in a synchronized manner even in very poor weather conditions, such as strong winds, rough currents, etc. In the embodiment illustrated in Step 1 of FIG. 5, conventional mooring lines and anchors are affixed to a turret mooring buoy 18 as known in the art. Embodiments of the drilling station 8 are subsequently towed to the turret mooring buoy 18, as illustrated in Step 2. In the embodiment depicted in Step 3, a plurality of towing vessels position the drilling station in relatively close proximity to the turret mooring buoy 18, where the drilling station 8 and the turret mooring buoy 18 are mutually joined. In Steps 4 and 5, the docking station is similarly joined to the system in accord with the principles previously discussed above. In one specific embodiment, the drilling station is also capable of performing a multitude of other offshore drilling functions, including deployment and operation of drilling equipment; the drilling of holes on the seabed and installation of casing; deployment and operation of self-standing riser, etc.
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In the embodiments illustrated in Step 5 and Step 6, the docking station 6 is moved to a location and attached in communication with turret mooring buoy 18 after completion of operations by the drilling station 8. In further embodiments, the drilling station is then removed from turret mooring buoy 18 to allow for attachment of the docking station 6 so that testing and production can commence.
Side-by-Side Mooring Using a Spread Mooring System
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Referring now to the example embodiment depicted in FIG. 6, the docking station 6 and drilling station 8 are joined using a side-by-side mooring system. Various embodiments of the drilling station 8 are affixed to the docking station using a system of attachment mechanisms, such as mooring, docking, fastening devices, etc., which lend support and provide rigid separation in the lateral direction while still allowing mutual vertical movement. In one embodiment, conventional mooring with anchor lines can secure the drilling station 8 and docking station 6 in proximity of a self-standing riser.
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Several embodiments of side-by-side mooring utilize hydraulically compensated cylinders to maintain constant lateral distance and compensate for wave and swell actions. For example, embodiments using a hydraulically compensated cylinder can maintain separation forces while dampening related transient forces caused by wave and swell movement.
End-to-End and Side-by-Side Mooring of the Drilling Station and Docking Station Using the Turret Moored Buoy
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Referring now to the example embodiment in FIG. 7, side-by-side and end-to-end mooring configurations of the drilling station 8 and docking station 6 attached in communication with a turret mooring buoy 18 is illustrated. In some embodiments, the turret buoy is utilized for situations where a particular area of the water has significantly varying or conflicting currents. In further embodiments, turret mooring buoy 18 is designed to be attached to a self-standing riser, while relative positioning of the drilling station 8 and docking station 6 is maintained. According to still further embodiments, the design of the turret mooring buoy 18 varies depending on the dimensions of the docking or drilling stations, or in conformity with the dimensions of the moon pool 12.
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In some embodiments, the drilling station 8 and the docking station 8 attach to the turret mooring buoy 18 using mechanical or hydraulic couplers or other fastening devices known in the art. In the embodiment illustrated in FIG. 8, the turret mooring buoy 18 allows for a 360 degree rotation of the particular station with which it is disposed. For example, the docking station 6 can rotate 360 degrees once it is attached to the turret mooring buoy 18.
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In some example embodiments utilizing a turret mooring buoy 18, the drilling station 8 is moored first, and used to perform one or more of drilling, deployment, workover, completion, testing, etc., operations. In other embodiments, the docking station 6 is moored to the drilling station 6, and used to conduct one or more of the aforementioned operations, as depicted in FIG. 8. Once the work of drilling station is concluded, it is detached from the turret buoy while the docking station 8 remains behind for continued operations.
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The foregoing specification is provided for illustrative purposes only, and is not intended to describe all possible aspects of the present invention. Moreover, while the invention has been shown and described in detail with respect to several exemplary embodiments, those of ordinary skill in the art will appreciate that minor changes to the description, and various other modifications, omissions and additions may also be made without departing from the spirit or scope thereof.
