This invention relates generally to offshore drilling operations.
Offshore drilling operations may be implemented with a variety of different platforms which may be secured to the seabed floor. These platforms may be effective at shallower depths. At greater depths, such as depths greater than 5000 feet, it is generally desirable to use ships or semi-submersible rigs to conduct such deep water drilling operations.
These ships or rigs may be precisely positioned at a desired location so that the drilling equipment may be operated to precisely drill wells at desired locations. The ship or rig may be maintained in position under dynamic positioning even in extreme seas. As used herein, a “ship” is a floating platform capable of propulsion on its own or by being pushed, pulled or towed. It includes semi-submersible rigs and self-propelled vessels.
As a result, a number of exploration wells may be drilled, one after the other, in a deepwater offshore environment, such as the outer continental shelf of the United States, Africa, Asia, or Western Europe. However, the large number of operations that must be performed when successively drilling a number of exploration wells, even in the same area, may be extremely time consuming because of the complexity of deep water operations.
Conventionally, tubulars must be made up, lowered through extensive sea depths to the seabed floor, used to drill the seabed floor, and then withdrawn to be replaced by other tubulars. As used herein, “tubulars” refers to piping, conduits, conductors, casing, drill strings, and risers. In addition, marine risers must extend ultimately from the ship to the seabed floor and blowout preventers may ultimately be run and installed on the seabed floor for well control reasons. Assembling, positioning, and removing these disparate tubulars generally involve operations that take extensive time periods. The time needed to extend a tubular through 5000 or greater feet of water results in some delay. The time needed to make up tubulars results in additional delay.
With a conventional ship having a single drilling platform, it is impossible to perform multiple operations in parallel. Thus, the time periods needed to complete each well may be relatively long. Since, generally, these drilling ships are operated on a rental basis, the longer that it takes to drill the well, the more expensive is the resulting well.
So called dual activity drilling ships are known. In these ships, a pair of derricks may be provided on the ship which provide a structural support for underlying drilling tubulars. The dual derricks may be operated in some degree in parallel. For example, while one operation is occurring on one derrick, other operations may be implemented on another derrick. While such approaches may result in some time savings, there are still some deficiencies in such dual activity approaches.
Thus, there is a need for even faster ways to drill deep water wells.
Referring to
Prior to arriving on the drilling site, tubulars may be readied. For example, a blow out preventer and riser may be assembled, skidded, and tested prior to arrival. Likewise, the 20 inch casing may be assembled prior to arrival as well.
Initially, as the ship comes on a drilling site, operations are implemented to precisely orient the ship with respect to the seabed floor. Global positioning satellites and other technology may be utilized for this purpose. Some amount of time is needed, prior to initiation of drilling operations, to precisely position the ship at the desired location. During this time, some drilling preparation activities may be accomplished in accordance with some embodiments of the present invention. Tubulars may be made up and readied for use. For example, a 30 inch conductor may be made up and stowed in appropriate tubular holding facilities prior to being actually run into the sea. Likewise, the blow out preventer and riser may be run during the dynamic positioning.
In some embodiments, a main drilling center 14 and a secondary drilling center 12 may be provided. In some embodiments, the secondary drilling center is adapted for handling lighter tubulars, while the main drilling center is adapted to handle heavier tubulars and drilling the well. In one embodiment, the main and secondary drilling centers may be implemented by hydraulic RAM devices 11 and 15. In other embodiments, derricks or superstructures may be provided. Such derricks or superstructures may provide structural support for the tubulars hung from such derricks.
In contrast, with a hydraulic RAM system, the tubulars may be supported directly on the ship's deck. This avoids the need for expensive, heavy derricks to support the tubulars. However, in some embodiments, even using a hydraulic system, masts or guides may be provided to guide the tubulars when they are in their uphauled positions.
Thus, depending on the nature of the centers 12 and 14, different tubular storage facilities may be utilized. For example, when a derrick system is utilized, the derricks are of sufficient strength that tubulars may be stored by simply leaning them against the insides of the derricks. In other cases, tubular and storage systems, setbacks envelopes, and racks may be provided to hold the assembled or partially assembled tubulars.
Conventional equipment may be used for advancing, running, withdrawing, lifting, or rotating the tubulars to the seabed and ultimately into the seabed floor. In this regard, hoists, top drives, sheaves, draw works, rotary tables, traveling blocks, motion compensators, hydraulic RAMS, or any other known equipment may be utilized. The hydraulic RAM may support tubulars on the deck, but derricks support tubulars from above the deck. The present invention is in no way limited to any particular equipment.
As described above, prior to the point when the ship is precisely positioned, some drilling preparatory activities may be completed. In some embodiments, the tubulars may be in the position shown in
The ship may include a third activity center in the form of a trip saver trolley 16. In one embodiment, the trolley 16 may be a Christmas tree trolley. However, any moveable, tubular supporting surface that can support tubulars may be utilized in some embodiments. Underslung trip saver trolleys mounted on rollers that roll over a rail or track may be utilized, as well as overslung trolleys that ride on top of a rail or track.
In most embodiments, a trolley rail or track allows the trolley to move from a position displaced to the side of the secondary drilling center 12 to a position under or within the secondary drilling center 12. In this way, tubulars already made up and hung from the trolley 16 may be moved in position for use by the secondary drilling center 12. This ability to pre-hang tubulars from the trolley 16 may result in significant time savings since it allows tubulars to be made up prior to the time when drilling operations are actually ready to begin and the ship has been accurately positioned in some embodiments.
Referring to
In some embodiments, the removal of tubulars from one drilling center, such as the drilling center 12, and their securement on the trolley 16 may be done using conventional equipment such as a running tool. In some embodiments, the tubulars may be lifted onto or off of the trolley 16.
In some embodiments, the trolley may have an opening 90 which is sized to mate with components of tubulars such as the casing 18 as shown in
In one embodiment, a split spherical bearing 50, as shown in
At the instance illustrated in
At the same time, in the main drilling center 14, a marine riser 24 may be assembled with the blowout preventer 26 secured to its lowermost end as indicated in
Thus, the blowout preventer 26 has already been skidded, tested, and assembled. Depending on the depth of the sea S, the blowout preventer 26 may be all the way down to a position close to the seabed floor, as shown in
In some embodiments, the blowout preventer 26 may be lowered to the position shown in
Note that at the point in time shown in
While the casing 18 is made up on the secondary drilling center 12, transferred to the trolley 16, and the conductor 22 is made up and lowered from the secondary drilling center 12, the marine riser 24 and blowout preventer 26 may be assembled and may be begun to be run to the seabed S from the main drilling center 14. Thus, it will be appreciated that three different tubulars may be assembled, at least partially in parallel, and partially pre-positioned and preassembled prior to the time that drilling operations can actually begin because the ship is accurately positioned.
Once the ship is accurately positioned, the running of the blow out preventer and riser may be stopped. Then, the 30 inch conductor 22 may be lowered into contact with the seabed floor SB as shown in
After completion of the 30 inch jet in and the 26 inch hole drilling, the 30 inch conductor 22 and its tubulars 20 may be raised from the secondary drilling center 12, disassembled, and stored.
Once the 30 inch conductor is no longer touching the seabed, then the running of the blow out preventer and riser may be resumed.
As soon as the 30 inch conductor 22 is out of the way, the trolley 16 may be rolled to the right to the position shown in
At the times shown in
Thus, operations in the main drilling center 14 with the blowout preventer 26 continue, to the extent necessary and as possible, while other operations are occurring so as to further reduce the overall time of the drilling operation.
In some embodiments, the riser 24 and blowout preventer 26 may be maintained out of contact with the seabed floor at any time when the 20 inch casing 18 is in contact with the seabed floor. Thus, once the 20 inch casing makes contact with the seabed floor, in those embodiments, the blowout preventer 26 is at all times out of contact with the seabed floor and may not be run in some embodiments.
Once the 20 inch casing is in place, the tubulars 18 may be released from the seabed, withdrawn, disassembled, and stored, so that the ship 10 may be repositioned. Particularly, the ship may be repositioned in the direction of the arrows shown in
Once the ship has been positioned accurately, the blowout preventer may be latched on the 20 inch casing already in position. Then, a 17 ½ inch hole is drilled and the 13 ⅜ inch casing may be run and cemented in position. The 13 ⅜ inch casing may be assembled on a pipe racker in some embodiments.
In some embodiments, this results in completion of the well. If subsequent drilling operations are desired, the ship may be repositioned after detaching the riser. For example, in some cases, the ship may be repositioned with the risers still hanging from the ship, as long as the repositioning distance is relatively short. However, in other embodiments, the entire process begins again.
In the case where production is planned, then the ship can be maintained in position and production may begin.
Referring 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.
This application is a continuation of U.S. patent application Ser. No. 11/479,023, filed on Jun. 30, 2006.
Number | Date | Country | |
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Parent | 11479023 | Jun 2006 | US |
Child | 14556412 | US |