Patent Application
20080264643
1. Field of the Invention
The present invention is generally directed to the field of subsea oil and gas production, and, more particularly, to a lightweight device for remote subsea wireline intervention.
2. Description of the Related Art
Offshore oil and gas wells may generally be divided into two groups—surface piercing wells and subsea wells. Surface piercing wells are wells that are located on an artificial surface above sea level that is supported by a fixed structure, e.g., a platform, or a floating structure, e.g., a spar, a semi-submersible, a tension leg platform, a vessel, etc. Subsea wells reside on the sea floor, including their wellhead structure and valving control (subsea Christmas tree).
Often during the life of a well, intervention into the well bore may be required for a variety of reasons. For example, an intervention may be required to diagnose a problem, correct a problem, stimulate production and/or repair equipment within the well bore. Performing intervention operations on surface piercing wells is very straightforward as surface piercing wells are easily accessed through the top of the Christmas tree (located on the artificial surface) using traditional means developed for land-based wells, e.g., a lubricator, pressure containment assembly (wireline rams), and one or more lifting devices. Such operations can be performed at a relatively low cost due to the ready accessibility to the top of the Christmas tree on such surface piercing wells and the equipment used in performing such interventions.
However, intervention on subsea wells is much more difficult and expensive. Intervention of a subsea well frequently requires the rental and use of a surface vessel, a completion/workover riser, and both surface and subsea pressure containment assemblies (a surface tree that mimics a surface piercing Christmas tree—so that workover hardware can be attached, and a Lower Workover Riser Package (LWRP) 5—e.g. a lower riser package (LRP 5A) with actuated pressure containment rams, and an emergency disconnect package (EDP) for well control to gain surface access to the subsea Christmas tree. Equipment used in such subsea intervention projects may not be readily available and they are much more expensive than their land-based counterparts. Moreover, intervention on a subsea well is much more complex and involved as compared to intervention projects on surface piercing wells. Thus, intervention on subsea wells may be delayed or not performed at all, or the subsea wells may simply be allowed to operate inefficiently.
So-called lightweight intervention was initially introduced in the North Sea in an effort to increase accessibility and reduce the costs associated with intervention of a subsea well. Generally, as shown in
When performing an intervention in a hydrocarbon well it is necessary to isolate the well from the environment. When performing intervention operations on a subsea well 10 using wireline techniques (braided wire, composite cable or slickline), pressure in the well during operations must be contained and structures must be employed to prevent or reduce hydrocarbons from escaping into the surrounding environment. To achieve these objectives, intervention operations involve the use of an isolation control device (lower riser package—LRP) 5A, a pressure control head (PCH) 5C and a lubricator 5B. The PCH 5C provides a dynamic seal between the cable 9 and the wellbore enclosures to maintain pressure control and prevent wellbore fluids from leaking into the environment. The lubricator 5B is a length of pipe that is used to hold a tool during insertion and withdrawal from the well 10, and the isolation control device (LRP) 5A controls the environment between the lubricator 5B and the rest of the well.
At the start of such a process, the LRP 5A and the lubricator 5B are lowered to the well 10 and retrieved therefrom by wire rope (not shown) or by drill pipe. Guidance and alignment of equipment may be done with the use of one or more guidelines (not shown) that are well known to those skilled in the art. After the LRP 5A and subsea lubricator 5B are secured to the subsea Christmas tree 4, a wireline deployed tool (not shown) may be employed to enter the well 10 via a simple wireline 9 intervention. During such a process, the tool is lowered to the well 10 and retrieved therefrom by the same wire 9 that will eventually lower the wireline tool up and down inside the well. The ROV 15 may provide added assistance (in addition to the guidelines) to align the wireline tool with the topmost entry point of the lubricator 5B. Once the tool is safely inside the lubricator cavity, a stuffing box, or pressure control head (PCH) is lowered by a separate wire rope or drill pipe until the PCH 5C reaches the entry point of the lubricator 5B. Then, the PCH's connector is remotely locked and provides a pressure-tight seal over the entry to the lubricator 5B. After connection, the lubricator 5B and stuffing box assembly may be pressure tested to assure proper connection and well control containment. This is followed by opening the valves in the subsea Christmas tree 4 to allow the wireline tool access into the well under a pressure controlled condition. The PCH 5C assembly contains a packing arrangement containing one or more seals which allows the wireline 9 to pass therethrough and the wireline tool is raised or lowered into the well. After the well intervention is completed, the tool is pulled up via the wireline 9 back into the lubricator cavity and the tree and LRP valves are closed. This is followed by evacuating any residual well fluids trapped in the lubricator 5B and replacing them with sea water and the pressure equalized to ambient conditions using a plurality of hydraulic line conduits (leading to the control umbilical) to circulate fluids in and out of the lubricator cavity. Afterwards, the PCH 5C is unlocked from the end of the lubricator 5B and the PCH 5C is hoisted back to the surface vessel.
Normally, the lubricator consists of a number of pipes that are made up together permanently on the vessel to the desired length. The PCH 5C is releasably connected to the top of the lubricator. In normal operations, a BOP is first lowered from the vessel and connected to the top of the Christmas tree 4. The lubricator 5B is lowered and connected to the BOP.
The cable or wireline 9 is inserted through the PCH 5C and then the tool is attached to the cable end. The PCH 5C is arranged so that the cable or wireline 9 can slide through the PCH 5C while the PCH 5C maintains a seal around the cable or wireline 9, as is well known in the art. Now the whole assembly can be lowered towards the well by paying out the cable or wireline from the drum 13 on the vessel. As the assembly reaches the lubricator stack on the seabed, the tool enters into the lubricator 5B. Further lowering of the assembly brings the PCH 5C into contact with the top of the lubricator 5B. A mechanical connector (not shown) is used to releasably lock the PCH 5C and the lubricator 5B together. The tool is now inside the lubricator. To lower the tool into the well, the valves in the BOP are opened and additional cable 9 is played out so that the tool is lowered into the well. The PCH 5C seals around the cable 9 during the operation, thus acting as a barrier against the well pressure.
If multiple wireline interventions are required on the wireline, the wireline tool is redressed or exchanged with another tool at the surface and the tool is redeployed to the subsea lubricator 5B; followed by redeployment/connection of the PCH 5A. If the job is complete, the LRP 5A and lubricator 5B are separately retrieved from the well 10, using wire rope (not shown) or drill pipe.
The use of all of these hoisting wire ropes, guidelines, etc. is envisioned as becoming more difficult as water depth increases. Such an operation with multiple guidelines, equipment and wire rope can be cumbersome. More specifically, handling the wire rope and the multiple guidelines results in fouling problems that the crew of the workover vessel must deal with, to a point where operations become inefficient or more difficult to perform.
The lubricator 5B will behave as a vertical column and be affected by forces of current and other producing bending stresses. The length of the lubricator 5B is limited by tower or crane lifting height restrictions. The length of the lubricator 5B should therefore be as short as possible but must necessarily be longer than the tool to be able to hold the tool before going in or after coming out of the well. This is a limitation that limits the use of riserless well intervention to tools shorter than about 20 meters. However, some operations may require a longer tool than normal tools and today the practice is to use standard riser for operations requiring longer tools. Examples of such tools are perforating guns and straddle packers that may be up to 40 meters long. Since operations involving risers are far more costly than riserless techniques it is desirable to find means of extending the scope of wireline operations. As shown therein, a subsea lubricator stack is depicted as the tool 430 is lowered onto the stack prior to insertion into the well.
The present invention is directed to various devices and methods for solving, or at least reducing the effects of, some or all of the aforementioned problems.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.
In one illustrative embodiment, the present invention is directed to a device adapted to be positioned adjacent an end of a tool housing of a subsea lubricator, wherein the device comprises a structural member that is adapted to be positioned adjacent an end of the tool housing, a body coupled to the structural member and a sealing device that is adapted to sealingly engage a wireline extending through the sealing device. In some embodiments, the body may be comprised of a non-metallic material or a material having a density less than that of steel or other similar materials. In some cases, the sealing device may comprise a stuffing box design or a grease injection system.
In another illustrative embodiment, a method is disclosed which comprises lowering an assembly toward a tool housing of a subsea lubricator positioned subsea using a wireline for the tool to support a weight of the assembly, wherein the assembly comprises a wireline tool and a device comprising a structural member that is adapted to be positioned adjacent the end of a tool housing, a body coupled to the structural member, and a sealing device that is adapted to sealingly engage a wireline extending through the sealing device.
In one example, a single wireline is employed to hoist and lower the combination of a wireline tool and a sealing device that will be operatively coupled to the subsea lubricator. Such an assembly may be lowered to the sea floor using guidelineless techniques well known to those skilled in the art. An ROV may provide additional assistance to align the wireline tool with the topmost entry point of the subsea lubricator. Once the tool is safely inside the lubricator cavity, the assembly is lowered further until the sealing device reaches the entry point of the subsea lubricator. Then, an ROV may be employed to activate a connector assembly which locks the sealing device to the subsea lubricator and provides a pressure-tight seal over the lubricator entry. After connection, the lubricator and sealing device assembly may be pressure tested to assure proper connection and well control containment. This is followed by opening the valves of the subsea Christmas tree to allow the wireline tool access into the well under a pressure controlled condition. The sealing device may contain a packing arrangement containing one or more seals which allows the wireline to pass therethrough. After the well intervention is completed, the wireline tool is retrieved, via the wireline, back into the lubricator cavity and the tree and the LRP valves are closed. This is followed by evacuating any residual well fluids trapped in the lubricator and replacing them with sea water and the pressure equalized to ambient conditions using a plurality of hydraulic line conduits (leading to the control umbilical) to circulate fluids in and out of the lubricator cavity. Afterwards, the sealing device may be unlocked from the end of the lubricator and the combination of the wireline tool and the sealing device may be hoisted back to the surface vessel using the single wireline.
If multiple wireline interventions are required, the wireline tool may be redressed or exchanged with another tool at the surface and both the tool and sealing device may be re-deployed to the subsea lubricator using the same technique as described above. If the job is complete, the LIP may be separately retrieved from the well, using wire rope (not shown) or drill pipe. This approach described herein may save time and reduce the number of lines in the water by eliminating the separate deployment and recovery of the sealing device.
The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The present invention will now be described with reference to the attached figures. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.
Additionally, it should be understood that
As shown in
In accordance with one aspect of the present invention, the lubricator housing 120 may be coupled to the LIP 116 at the surface and installed above the subsea Christmas tree 118 using a lift rope (not shown) or drill pipe (not shown) that is of sufficient strength to support the combined weight of the LIP 116 and the lubricator housing 120. For example, the combined weight of the LIP 116 and the lubricator housing 120 may range from approximately 150,000-200,000 pounds, depending upon the particular application. Additionally, in another aspect of the present invention, the fluid connections 170 between the lubricator housing 120 and the rest of the LIP 116 may be established at the surface as the lubricator housing 120 and the LIP 116 may be configured together prior to the combination of the lubricator housing and the LIP 116 being lowered toward the well 110.
The lubricator housing 120 may be permanently or removably coupled to the LIP 116 depending upon the particular application and the need to simplify surface handling of the LIP 116. For example, the lubricator housing 120 may be assembled as an integral part of one or more components that comprise the LIP 116. If desired, the lubricator housing 120 may be removably coupled to the LIP 116 by a bolted or clamped connection. Additionally, it should be understood that an intermediate structure, such as a spool, may be positioned between the LIP 116 and the actual lubricator housing 120. Nevertheless, in such an arrangement, it will be understood that the lubricator housing 120 is operatively coupled to the LIP 116.
The lubricator housing 120 may be of traditional size, configuration and construction, e.g., it may be made of steel or other metals. Of course, the particular details of construction and dimensions of the lubricator housing 120 may vary depending upon the particular application. As will be understood by those skilled in the art after a complete reading of the present application, the lubricator housing 120 has a cavity that is adapted to receive the wireline tool 150. The wireline tool 150 may be any type of tool or device that may be employed in performing an intervention in the well 110. For example, the wireline tool 150 may be a pressure/temperature sensor, a plug installation/retrieval tool, a caliper measurement tool, a downhole camera, a whipstock diverter, a side pocket kickover tool, etc. A wireline 140 may also be employed with the present invention to lower or retrieve the tool 150 and other downhole devices (not shown) such as a gas lift valve, a tubing plug, storm choke, as a combined unit. The device described herein may also be employed with a so-called downhole “tractor,” a locomotive mechanism that can drive the wireline tool 150 further into the well 110, especially in instances where the well's inclination goes from near vertical to near horizontal. All these configurations will dictate the cavity diameter and overall length of the lubricator housing 120.
The sealing device 130 comprises a means for sealing around the wireline 140 to prevent or limit the amount of well fluids (including hydrocarbons) from escaping to the environment from the point where the wireline 140 exits the lubricator housing 120 when intervention operations are performed. As described more fully below, the sealing device 130 may be of any structure that is capable of performing this function. For example, the sealing device 130 may comprise a stuffing box or a grease injection assembly to provide the necessary seal around the wireline 140 during operations. Of course, it should be understood that through use of the term sealing device, applicant does not mean to imply that the seal established between the wireline 140 and the sealing device is absolutely liquid tight (although it may be in some cases). Rather, the sealing device 130 described herein provides at least an appropriate level of sealing as is commonly accepted using traditional devices or arrangements such as a stuffing box or a grease injection device to seal around wirelines that are employed in well intervention operations. An illustrative grease injection system may be employed as the sealing device 130 to help seal around an irregular wireline surface, most notably the “wire rope” braided exterior of a braided wireline cable. In such a system, the grease is injected into the crevices and voids between the wire strands to assist in sealing between the cable body and the seal elements. However, when the wireline 140 has a smooth exterior surface of a traditional “slickline” or composite cable 140 shown in
One illustrative embodiment of the wireline 140 that may be employed with the present invention is shown in
The small weight per linear foot makes the wireline 140 nearly neutrally buoyant in water and wellbore fluids. This characteristics reduces or eliminates increasing drum tension load associated with a steel slickline and a braided cable which add its weight to the overall tension as more wireline is paid out. Using the composite cable 140 disclosed herein, drum tension capacity may be kept to a minimum regardless of water depth or well depth.
In accordance with one aspect of the present invention, portions of the sealing device 130 are of lightweight construction. For example, portions of the device 130 may be made of a material that has a density less than that of steel (approximately 0.283 lb/in3). In some cases, portions of the sealing device 130 may be comprised of a material having a density that is significantly less, e.g., 10-40% less than that of steel or other like materials. For example, portions of the sealing device 130 may be made of a variety of non-metallic materials, high density molecular weight plastics composites, or other materials having a higher strength-to-weight ratio as compared to carbon steel. Using such a construction along with smaller bore packaging may greatly reduce the weight of the sealing device 130 to less than approximately 5,000 pounds as compared to prior art configurations weighing as much as 20,000-25,000 pounds. Due to the lightweight nature of the sealing device 130 disclosed herein, the sealing device 130 has a degree of buoyancy which reduces its effective weight in water, and more importantly, it may be lowered and retrieved in combination with the wireline tool 150 by the same wireline 140 that is employed in deploying the wireline tool 150, without exceeding the structural tensile strength of the wireline 140. This is particularly true if the wireline 140 has a composite structure similar to that shown in
The sealing device 130 comprises a body 302, a plurality of latch pins 304, and a plurality of latch pin release handles 306 that are coupled to rods 335.
Also depicted are elongated structures 314, an ROV handle 315, an inner body 380, a nose end cap 324 and lines 344a, 344b (for purposes of drawing a vacuum or conveying hydraulic fluid). A sleeve 200 (shown in dashed lines) may be provided at the end of the inner body 380. Such a sleeve 200, if provided, may act as a stab to assist in the landing of the sealing device 130 on the end 122 of the lubricator housing 120. The sleeve 200 may also provide protection for the schematically depicted tool 150.
In operation, the sealing device 130 is seated and latched in place (latch keys 304 extended and engaged into a recessed external groove 123 in the upper end 122 of the lubricator housing 120), as shown in
In the illustrative embodiment depicted herein, the sealing device 130 also encases an isolation valve 346, e.g., a needle valve, connected between the inner body 380 through a set of lines. When opened, the isolation valve 346 allows passage of sea water or other fluids trapped between the inner body 380 and the bore of the lubricator housing 120, thereby preventing any chance of hydraulic lock. This porting may be employed to generate additional downward force from the sea water's hydrostatic head to push down on the sealing device 130 and seat it on the end 122 of the lubricator housing 120. Once the inner body 380 is fully landed and sealed in the bore of the lubricator housing 120 (as shown in
Conversely, during unlocking and removal of the sealing device 130, a small amount of injected pressure from the ROV into the line 344b moves the piston 399 up, allowing the expanding ring to collapse and free the inner body 380 from up and out of the bore of the lubricator housing 120. The sealing device 130 may be mechanically released by upward mechanical force on the upper handle 315. The sealing device 130 and inner body 380 may also be hydraulically pushed up and out of the lubricator housing 120 by opening the isolation valve 346 and allowing sea water to be pumped in through porting to create the necessary upward force. In the depicted embodiment, the body 302 essentially surrounds the structural member 308 and inner body 380. However, if desired, the body 302 could be formed as separate segments, e.g., four ninety degree segments, or other configurations.
In operation, the combination of the light weight sealing device 130 and the wireline tool 150 are lowered toward the well 110 by a single wireline 140. By use of an ROV, a diver and/or a guideline (not shown), the sealing device 130 is landed on the upper end 122 of the lubricator housing 120. An ROV may then be employed to grasp and rotate the handles 306 to thereby engage the latch pins 304 with the profile 123 in the outer surface of the upper end 122 of the lubricator housing 120. In turn, this causes the ends 122 and 124 to sealingly engage one another. Subsequent operation of the upper handle 315 and/or line 344a engages the inner body 380 for a higher pressure/structural connection to the interior of the upper end 122 of the lubricator housing 120. The latch pins 304, when locked into the external groove 123 of the upper end of the lubricator body 122, provides the necessary mechanical resistance to oppose the insertion force when sealingly engaging the inner body 380 down into the interior of the lubricator housing 120.
As indicated above, the exact structure of the sealing device 130 may vary depending upon the particular application. As shown in
Additional components or features may be combined with or used with the illustrative sealing device 130 disclosed herein. For example,
A third component or feature may be added for more precise positioning or applying additional locomotive force to the wireline 140 to assist with the movement of the wireline tool 150 and wireline 140 as they perform intervention operations in the well. For example,
A fourth component or feature may be added to sealing device assembly which mechanically retains the wireline tool 150 in place while lowering or retrieving the tool and sealing device 130 to or from the lubricator housing 120, then selectively releases the tool so that it can be lowered into the well. This feature is know in the art as a “tool catcher” 210. An illustrative wireline tool 150 is depicted as being positioned within the body of the combined assembly, just below the stuffing box sealing element(s) in the sealing device 130. The tool catcher mechanism 210 features a locking device, such as latch pins, keys, cantilevered locking segments or other locking devices (not shown) that passively connect to a profile on the wireline tool's body that can independently supports and suspends its weight. Conversely, the locking mechanism can be intentionally retracted to allow passage of the wireline tool 150 into the well. In conjunction with the shearing device 180, when actuated, the shearing mechanism will sever the wireline 140 allowing the wireline tool 150 to free fall back down into the well. The tool catcher 210 prevents this free fall from occurring should the shearing operation take place. In an embodiment of the tool catcher 210, the catcher may be configured with a thin elongated body 212 which concentrically fits inside the bore of the lubricator housing 120. In this way the catcher body 212, much like the sleeve 200, provides easier alignment for the tool as the tool and sealing assembly are lowered and aligned with the top of the lubricator housing 120 and provides an element of structural protection around the wireline tool 150 as the entire assembly is lowered down to the subsea assembly 100 or retrieved back to the surface.
Another aspect of the disclosed subject matter will now be discussed with references to
If the intervention operation demands a wireline tool 440 that is longer than the lubricator 120, the present invention proposes the use of an extension pipe 432 to be connected to the lubricator 120, as illustrated in
Alternatively, more than one extension pipe 432 may be in the system. This enables the basic lubricator 120 to be as short as possible and only for use with the smallest tools. This may be the situation when the plugs are pulled from the Christmas tree 116 to enable access to the well. Then, for normal operations, depending upon the length of the tool, the lubricator 120 may only be employed, or one or more extension pipes 432 may be employed as necessary. For example, if it becomes necessary to perform operations using even longer tools, a third extension pipe 432 can be added. However, the length of the lubricator 120 and lubricator extension may become structurally unstable if built too long and subsequently exposed to adverse ocean current conditions. Added tension from wires 442 suspended from the vessel 1 above or some form of buoyancy may be added to improve structural stability to the lubricator 120 and extension pipe 432.
The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order or the various components stacked and assembled in different configurations. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.
| Number | Date | Country | Kind |
|---|---|---|---|
| NO 20072118 | Apr 2007 | NO | national |
