CROSS-REFERENCE TO RELATED APPLICATION
The present document is based on and claims priority to U.S. Provisional Application Ser. No. 60/908,101, tiled Mar. 26, 2007.
The retrieval of desired fluids, such as hydrocarbon based fluids, is pursued in subsea environments. Production and transfer of fluids from subsea wells relies on subsea installations, subsea flow lines and other equipment. Additionally, preparation and servicing of the subsea well relies on the ability to conduct subsea intervention work. Subsea intervention work involves numerous challenges not normally faced when working on land wells or fixed offshore platforms.
Intervention in subsea wells often is performed from a floating platform or ship, and access to the subsea well is achieved by a variety of techniques. In many applications, the intervention operation is performed with wireline, slickline or other cable-type conveyance methods. For example, tools can be conveyed from a surface vessel to a subsea installation through open water. With this technique, the tools are conveyed into a subsea lubricator with a dynamic seal at the top of the lubricator. Such operations are sometimes called “open water” or “riserless” operations and require that the equipment be moved through the open sea water. Additionally, these types of open water operations cannot be performed with coiled tubing while maintaining a coiled tubing injector at the surface.
In another technique, tools are conveyed through a tubular riser or guide system connecting a surface intervention vessel with the subsea installation. However, the tubular system can provide technical constraints, such as a limited internal diameter. The technical restraints are problematic in moving certain types of intervention tools to the subsea installation. For example, movement of large diameter tools through the tubular system to the subsea installation can be difficult or impossible.
In general, the present invention, provides a technique for subsea intervention operations which utilizes a Y-tool mounted at a subsurface facility. The Y-tool comprises a guide branch and an open water branch to enable movement of intervention tools to the subsea installation along two different paths. For example, a tubular guide member can be coupled to the guide branch to enable movement of equipment down through the tubular guide member and into the Y-tool. Other equipment can be moved down through the open water and into the Y-tool through the open water branch. The availability of two different paths greatly enhances the ability to carry out a wide variety of intervention operations at a subsea well.
BRIEF DESCRIPTION OF THE DRAWINGS
Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:
FIG. 1 is a schematic front elevation view of a subsea intervention system, according to an embodiment of the present invention;
FIG. 2 is a schematic front elevation view similar to that of FIG. 1 but showing another example of an intervention operation, according to an embodiment of the present invention; and
FIG. 3 is a schematic front elevation view similar to that of FIG. 1 but showing another example of an intervention operation, according to an embodiment of the present invention.
In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.
The present invention generally relates to a technique for performing intervention operations. The technique utilizes a side entry tool or Y-tool deployed proximate a subsea installation to facilitate a wide range of intervention procedures. The Y-tool comprises a base branch that is mounted to the subsea installation to direct intervention equipment into the subsea installation and the subsea well. At its upper end, the Y-tool comprises a plurality of branches through which tools can be directed into the Y-tool and subsequently down into the subsea installation and subsea well. In many applications, the Y-tool comprises a pair of upper branches that can be referred to as a guide branch and an open water branch designed to receive and direct various types of intervention equipment.
The side entry tool is referred to as a Y-tool because of the divergent upper branches that can be used to direct equipment downwardly to the base branch and subsequently into the subsea installation and well. However, the Y-tool can be constructed in a variety of configurations, shapes and sizes. The various branches can be of different lengths and/or diameters, and two or more upper branches can serve as guides to the lower branch. Use of the Y-tool at the subsea installation enables use of a greater variety of intervention procedures than otherwise afforded by conventional intervention equipment. In some applications, for example, a tubular guide member is connected to the guide branch of the Y-tool, and the other, divergent, branch extends to the open water.
The Y-tool allows an operator to select whether equipment is deployed to the subsea well through the tubular guide member or through the open water. Often the intervention operations can be facilitated by deploying some equipment through a tubular guide member and other equipment through the open water. The ability to utilize different access points to the well helps optimize deployment of tools into the subsea installation, particularly when intervention operations are conducted with different conveyances, e.g. wireline, slickline and coiled tubing. The Y-tool also enables deployment of intervention tools, e.g. tool strings, that, are too large for movement through the tubular guide member. In this latter example, the intervention tool can simply be deployed through the open water, moved into the Y-tool via the open water branch, and positioned within a lubricator that is either part of the Y-tool or positioned below the Y-tool. A coiled tubing conveyance or other conveyance is routed down through the guide branch of the Y-tool and connected to the intervention tool within the enclosed, pressure protected Y-tool/lubricator. In other applications, the subsea Y-tool enables both the efficient removal of crown plugs from horizontal Christmas trees and the transfer of those plugs through open water.
Although specific examples of intervention systems utilizing a Y-tool are described below, it should be noted that many configurations and methodologies related to the intervention operations and use of the Y-tool are possible. Furthermore, the subsea intervention operations can be performed in conjunction with a variety of subsea installations, including subsea wells, subsea flowlines and other subsea systems.
Additionally, the subsea installation and subsea Y-tool are designed to prevent pressurized fluids from escaping the subsea installation during the intervention operation. Accordingly, the subsea installation and the Y-tool have appropriate sets of seals and valves that can be selectively actuated to maintain a pressure tight envelope that prevents the escape of pressurized borehole fluids. A wide variety of such pressure control valves, seals and other devices can be used to contain the pressurized environment within the subsea installation and Y-tool.
The system and methodology described herein enable the use of open water and tubular guide member deployment techniques according to a variety of flexible procedures. Thus, a service company can switch from one technique to another without major hardware changes. Also, the techniques can be used individually or in combination during interventions performed on a subsea installation to optimize operational efficiency and to reduce the occurrences of hardware deployment and hardware retrieval between the surface facility, e,g. surface intervention vessel, and the seabed.
By way of example, the use of a Y-tool intervention system enables wireline, slickline and coiled tubing operations to be performed with the same deployed hardware. The system also enables open water wireline and slickline operations without disconnection of the tubular guide member. Coiled tubing conveyance systems also can be used with large tools that can not be moved through the guide member. The need for subsea wet connection of wireline and slickline big diameter took is eliminated, because such tools can be conveyed through the open water. Similarly, the need for an open water wireline or slickline kill line can be eliminated, because the tubular guide member can be used for this purpose. Horizontal Christmas tree plugs can be removed to the open water with a wireline or slickline while allowing immediate access with coiled tubing, via the tubular guide member, without deploying any additional hardware. Similarly, no additional hardware need be deployed or retrieved to switch between wireline/slickline open water operations and coiled tubing operations. The methodology also facilitates the flushing of the lubricator for open water wireline operations, because the coiled tubing/tubular guide member can be used rather than providing an additional service Also, a coiled tubing conveyance can be provided as a contingency for wireline or slickline operations without requiring additional deployment or retrieval of hardware. In each of these applications, the efficiency of the intervention operation is improved and the risk of exposure to hazards related to the subsea intervention is reduced due to the reduced number of activities required to perform the intervention procedures.
Referring generally to FIG. 1, one example of an intervention system 20 is illustrated according to an embodiment of the present invention. In this embodiment, system 20 comprises a subsea Y-tool 22 proximate a subsea installation 24. By way of example, subsea installation 24 may comprise a wellhead, a flowline, a Christmas tree, or another type of subsea installation that is subjected to intervention procedures. The subsea Y-tool may be mounted above subsea installation 24 to direct intervention equipment into the subsea installation. In the example illustrated, subsea Y-tool comprises a base branch 26 mounted to subsea installation 24. The Y-tool further comprises at least two upper branches, such as an open water branch 28 and a guide branch 30.
A tubular guide member 32 is coupled between subsea installation 24 and a surface facility 34, such as an intervention vessel. The tubular guide member 32 may be in the form of a riser system comprising, for example, a rigid, flexible or compliant riser that connects the surface facility 34 to the subsea installation 24 via the Y-tool. The tubular guide member 32 also may comprise a compliant guide such as a spoolable compliant guide having a hollow interior along which equipment may be guided into subsea installation 24. The lower end of tubular guide member 32 is connected to guide branch 30 of subsea Y-tool 22.
Subsea installation 24 also may comprise a lubricator 36 which allows deployment of an intervention tool string into a pressurized installation that prevents escape of pressurized fluids. The lubricator 36 may he formed as an integral part of subsea Y-tool 22, or the lubricator 36 may be a separate component positioned beneath the Y-tool 22. Depending on the specific application, the lubricator can be installed at a variety of positions in the Y-tool, below the Y-tool, or above the Y-tool. The pressurized installation can be achieved by a variety of valves and seals positioned in various arrangements. For example, a plurality of subsea valves 42 can be positioned in the subsea installation 24 beneath the Y-tool 22. Additionally, a subsea valve 44 and a dynamic seal 46 can be positioned in the open water branch 28 proximate the net to the open water branch. Similarly, a subsea valve 48 can be positioned in guide branch 30 of Y-tool 22. A dynamic seal 50 also is positioned to cooperate with guide branch 30 and can be located in a variety of positions in guide branch 30 or along tubular guide member 32. In the illustrated embodiment, dynamic seal 50 is positioned generally at a lower end of the tubular guide member 32 proximate an emergency disconnect 52.
Intervention operations can be performed in a variety of subsea installations 24, and with a variety of configurations of additional equipment connected on top of the subsea installation. In the embodiment illustrated in FIG. 1, the subsea installation 24 comprises a subsea wellhead 54 that may include a Christmas tree and other components positioned above a subsea well 56. The other components may include subsea valves 42 and related devices, such as a subsea lubricating seal and a blowout preventer having one or more cut-and-seal rams able to cut through the interior of the subsea installation and seal off the subsea installation during an emergency disconnect. The subsea installation 24 also may comprise additional blowout preventers as well as a subsea stripper assembly positioned above the blowout preventers. The number and type of devices mounted on a given subsea installation can vary from one subsea application to another.
In FIG. 1, an example of one use of the Y-tool to facilitate an intervention operation is illustrated. In this example, an intervention operation is performed through the open water branch 28 of Y-tool 22. An intervention tool 58, such as a tool string or other well equipment, is lowered through the open water by a conveyance, such as a cable-type conveyance 60. By way of example, conveyance 60 may be a wireline, slickline or other cable-type conveyance deployed and retrieved via a crane 62 mounted on surface facility 34.
The intervention tool 58 is connected to conveyance 60, lowered through the open water and into open water branch 28 of Y-tool 22. The intervention tool 58 continues to travel down through the base branch 26, through a tool holder 62, and through subsea installation 24 until entering the borehole of subsea well 56. One or more dynamic seals provide a pressure barrier around the cable-type conveyance 60 as it moves up and down in subsea well 56. The dynamic sealing can be formed by dynamic seal 46 in open water branch 28 or by dynamic seals incorporated at subsea valves 42. During this type of intervention operation, guide branch 30 can be left open in some applications or sealed off to prevent movement of fluids from the subsea installation 24 into tubular guide member 32. By way of example, guide branch 30 can be sealed by closing subsea valve 48. It should be noted, the open water branch 28 also can be used to provide a pathway for the removal of crown plugs from horizontal Christmas trees before an intervention operation and to reinstall the crown plugs at the end of the intervention operation.
Another intervention operation is illustrated in FIG. 2. In this example, intervention tool 58 is deployed along the interior of tubular guide member 32 by a conveyance 64. By way of example, conveyance 64 may comprise wireline, slickline or coiled tubing depending on the particular type a intervention operation being performed. In some applications wireline or slickline can be used to deploy intervention tool 58, e.g. a tool string, through the tubular guide member, provided the intervention tool string has an outer diameter small enough to pass through the guide member. If conveyance 64 comprises coiled tubing, the coiled tubing can be coupled to intervention tool 58 by an appropriate connector 66.
In many coiled tubing intervention operations, the intervention tool 58, e.g. tool string, has a configuration that is difficult or impossible to move through tubular guide member 32. In these applications, intervention tool 58 can be lowered through the open water and into open water branch 22 by the cable-type conveyance 60. The intervention tool 58 is continually lowered into the lubricator 36 and held by tool holder 62, as illustrated in FIG. 3. The cable-type conveyance 60 is then disconnected from the intervention tool, e.g. tool string, and coiled tubing conveyance 64 is lowered toward the intervention tool 58 through tubular guide member 32. The coiled tubing conveyance 64 is engaged with intervention tool 58 via connector 66 which may be in the form of a subsea tool wet connector. Once connected, tool holder 62 is released to enable the lowering of intervention tool 58 through subsea installation 24 and into subsea well 56 via coiled tubing conveyance 64.
The examples described above are just a few examples of the many ways in which Y-tool 22 can be utilized to facilitate a variety of intervention operations. Additionally, the Y-tool 22 is amenable to use with a wide variety of methodologies and cooperating devices. For example, the dynamic seals 46, 50 that are used in cooperation with the open water branch 28 and guide branch 30, respectively, can be retrievable dynamic seals. Alternatively, the dynamic seals can be non-retrievable seals which are temporarily opened to full bore for passage of intervention tools and then closed on the conveyance to establish a pressure tight barrier.
The open water branch 28 also can be sealed of by a variety of pressure barriers, including valves and plugs. Additionally, guide branch 30 can include or work in cooperation with emergency disconnect 52 which enables release of tubular guide member 32 from Y-tool 22 in the event of an operational emergency where the surface intervention vessel must disconnect from the subsea installation 24. Valves can he placed above, below, and/or above and below the emergency disconnect 52 to prevent the escape of fluids into the sea water. Numerous additional and alternate devices can be utilized in cooperation with the Y-tool to facilitate a great range of intervention operations. The relative orientation of the guide branch and the open water branch as well as the relative size of the branches also can vary. For example, the open water branch may have a larger diameter than the guide branch for some applications. The length of the Y-tool branches also can vary to accommodate many types of intervention tools.
Although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Accordingly, such modifications are intended to be included within the scope of this invention as defined in the claims.