Glass plugged tie back stem

Abstract

The present invention relates inter alia to a device for deployment in a wellbore, comprising a tubular element (1) adapted for cementing the annular space around the tubular element (1) in a wellbore, and a plug (200) arranged inside the tubular element (1), wherein the plug (200) is frangible and also a method for cementing a wellbore, comprising the steps of providing a device (502), inserting the device into a wellbore (504), providing cement into the device (508), cementing the annular space around the device and breaking the frangible plug of the device (512).

Description

[0001] GLASS PLUGGED TIE BACK STEM Field of the invention

[0002] The present invention generally relates to a device for deployment in a wellbore, in particular a stem to facilitate tie back operations in a wellbore, e.g. for workover operations. Background

[0003] In the field of wellbore workover operations, a critical aspect is in the maintenance, restoration, and enhancement of oil well production. Workover operations are essential for the continued productivity and longevity of e.g. oil wells and involve various interventions to repair or optimize oil wells that have been drilled and are in production or temporarily abandoned. Among the array of tools utilized in these operations, the Tie Back Stem has emerged as a conventional and indispensable component. For workover operations on existing wells, it is commonly used in a combination with a previously seated mechanical barrier, e.g. a bridge plug.

[0004] In such operations, a mechanical barrier is crucial to prevent the downward movement of cement in the hole and to ensure a proper path through the annulus space. The current state of the art in the oil and gas industry presents several types of barriers, each with its own set of advantages and limitations.

[0005] Among the commonly used barriers are the bridge plug (BP), balanced cement plug, and the combination of an annular casing packer (ACP) with a stage tool. However, each solution has distinct challenges. For instance, the use of a bridge plug necessitates a dedicated trip prior to the cementing, since it needs to be installed beforehand. Postcementing, the bridge plug also needs to be drilled and pushed to total depth when used in a 6-inch open hole. This approach is not feasible for wells that have Open Hole (OH) lower completion already installed. The balanced cement plug, another prevalent solution, also requires a dedicated trip. This method often proves inefficient and costly, especially in scenarios involving fluid losses, leading to repeated cement operations and prolonged non-productive days.

[0006] Another solution in the market involves using an annular casing packer combined with a stage tool. However, these tools do not allow for cementing below the packer. Another drawback is that this solution is not recommended for gas or gas lift flowback technology (GLFT) wells.

[0007] The existing solutions in the field of cemented tie back operations thus present significant operational challenges, including limitations in tool suitability, efficiency issues, and applicability for specific well types. This invention aims to introduce an innovative approach that addresses these challenges, offering a more efficient, cost-effective, and versatile solution for cemented tie back jobs in the oil and gas industry. The proposed invention seeks to fill the gaps in the current state of the art, streamlining operations and reducing non-productive time in well workover and completion processes by providing a tie back stem with a frangible plug. The invention thus combines these two critical components into a single, cohesive unit. This integration is enhancing the effectiveness of workover operations, reduce operational downtime, and improve safety measures, thereby making a significant contribution to the field of oil wellbore maintenance and restoration.

[0008] As a state of the art, the publication US 9,260,926 B2 describes a sealing apparatus that features a mandrel composed of at least two distinct sections. The first section includes a seal ring positioned on its exterior surface, while the second section does not have a seal ring on its exterior. In one variation, the seal ring encircles the first section of the mandrel. Additionally, in another embodiment, both the first and second sections of the mandrel have comparable levels of burst and collapse integrity.

[0009] In publication US 10316616 B2 a dissolvable bridge plug is disclosed, engineered for effective use in high-pressure environments, specifically within the range of 8,000 to 10,000 psi. This plug is designed to ensure both anchoring stability and structural integrity in cased wells. Notably, it features components that can substantially dissolve, facilitating easier removal post-application. Additionally, this plug can be expediently drilled out, approximately within a 30-minute timeframe, even when situated in complex sections of the well, such as lateral legs.

[0010] In view of the foregoing, there is a need for improved tie back stems. It is thus an object of the present invention to overcome some or all the deficiencies of the prior art. It is in particular an object to provide an improved tie back stem, which allows cementing workover operations without the need for a dedicated trip to install a plug in the wellbore. Other objects which may be overcome with the present invention are more efficient wellbore workover operations, by reducing or eliminating all difficult and cumbersome steps in the process, and relieving the operators e.g., from the step of setting a bridge plug, later drilling the same and then pushing it to the total depth (TD) of the well and thus decreasing the daily rig cost. Summary

[0011] The above-mentioned objects are at least partially achieved by the subject-matter of independent claim 1. Such a combination of a tieback stem with a breakable plug offers potentially significant improvements in workover operations, particularly in scenarios where a bottom plug that can be easily drilled through or broken is required for operational efficiency or safety purposes. Preferred embodiments are subject of the dependent claims, and the skilled person finds hints for other suitable aspects of the present invention through the overall disclosure of the present application.

[0012] An aspect of the invention relates to a device designed for use in a wellbore in oil and gas extraction processes. The device comprises two main components: a tubular element and a plug. The tubular element is specifically designed to be cemented in the annular space of a wellbore. This means it is intended to fit into the circular space between the wellbore's walls and the tubular element, with cement used to secure it in place. The cementing process is critical in wellbore operations as it helps in stabilizing the wellbore, preventing fluid migration between different geological formations, and isolating high-pressure zones. The plug is situated inside the tubular element. A key characteristic of this plug is that it is 'frangible', which means it is designed to break or shatter easily. In the context of wellbore operations, the use of a frangible plug has specific advantages. For example, this type of plug can be used to temporarily block the wellbore or specific sections of it during certain operations, such as cementing. Once these operations are completed, the plug can be easily broken or shattered, allowing for the resumption of normal wellbore activities without the need for complex removal processes. Since the plug is disintegrated into a number of smaller pieces, the same can easily be removed from the borehole. The breakability of the plug is advantageous in ensuring efficiency and safety in operations, as it allows for easy transition between different stages of wellbore exploitation, such as drilling, cementing, and extraction.

[0013] In a preferred embodiment the plug is made of a material that is capable to break into pieces, for example glass.

[0014] The advantage of glass is that it by itself tends to be a frangible material when arranged in a specific manner. Such materials are intentionally chosen for their ability to fracture or shatter when subjected to specific conditions or stress. In this particular embodiment, the use of materials with these characteristics further enhances the plug's frangibility. The advantage of using these types of materials like glass lies in their predictability and consistency in breaking into pieces, ensuring a dependable performance within the wellbore context.

[0015] In another preferred embodiment the plug is sealing off a first section of the tubular element.

[0016] This configuration involves placing the frangible plug within the tubular element in such a way that it creates a barrier, effectively partitioning the interior of the tubular element into different sections. This partitioning action is carried out by the frangible plug, which is designed to form a secure seal, preventing the passage of fluids or materials between the two separated sections. This partitioning function can have various applications in wellbore operations: For instance, it can be utilized to isolate specific zones within the wellbore, control fluid flow, or facilitate pressure testing in a controlled manner. This versatility enhances the adaptability of the device to various wellbore requirements. Thus, the advantage of this configuration lies in its ability to provide precise and controlled isolation within the tubular element, contributing to operational safety and efficiency during wellbore activities.

[0017] In another preferred embodiment the plug is constructed from a range of materials, including glass (preferably not tempered), composites, polymers, metals, or combinations thereof.

[0018] These materials provide various advantageous features. The frangible plug may be constructed from glass, which can be tempered or nontempered, depending on the demands on the plug. The plug can also be made from polymer materials, which are synthetic substances known for their versatility and durability, which can be adapted w.r.t. the durability, rigidity, or other mechanical features of the plug. They can also be readily adapted to provide the necessary resistance to the demanding harsh mechanical and chemical environment inside a borehole. Metal materials can also be used for constructing the frangible plug. Metals are valued for their strength and resilience but can also be adapted be frangible. Alternatively, the frangible plug can be made from composite materials. Composites are materials formed by combining two or more distinct materials to create a new material with specific properties which can be tuned to specific characteristics of the plug. The frangible plug can be made from a combination of the mentioned materials. This combination approach allows for tailoring the plug's properties to meet specific wellbore requirements. The materials can be adapted to include mechanical properties such as strength, durability, elasticity and plasticity, and fatigue resistance. They also can have specific chemical properties like corrosion resistance and chemical stability. Thermal characteristics might be important as well, including thermal stability and thermal expansion. Environmental resistance can also be crucial, encompassing abrasion resistance and UV resistance. In terms of manufacturability and maintenance, aspects like machinability and maintainability are considered. Economic factors play a role, with cost-effectiveness and availability being some of the considerations to be considered. Additionally, health, safety, and environmental factors can be critical, focusing on non-toxicity and environmental compatibility.

[0019] In a preferred embodiment the plug is adapted to disintegrate and / or collapse into pieces.

[0020] In other words, the plug is intentionally engineered to undergo a controlled disintegration process or collapse into smaller components when subjected to certain conditions or stress. This adaptation is a critical feature because it enhances the versatility and precision of the device within wellbore operations. When the frangible plug is required to break or disintegrate during the wellbore operation, it does so in a controlled and predictable manner. This controlled disintegration or collapse can serve various purposes, such as facilitating fluid flow, pressure release, or the initiation of specific processes within the wellbore.

[0021] In a preferred embodiment the plug comprises one or more predetermined breaking points, allowing a controlled disintegration into a number of smaller pieces.

[0022] The predetermined breaking points can be placed strategically within its structure. These breaking points are intended to remain intact under normal conditions but can be triggered to break when necessary. When activated, they facilitate the controlled disintegration of the plug into smaller pieces. This feature offers precise control over the plug's behavior during wellbore operations, enhancing safety and operational efficiency. The placement and number of breaking points can be customized as needed, providing flexibility in various wellbore applications.

[0023] In another embodiment the tubular element comprises at least two discrete tubular sections attached together, preferably detachably attached.

[0024] The tubular element is composed of at least two distinct tubular sections that are connected together. Importantly, these sections are designed to be detachably attached, allowing for easy separation when necessary. This modular design offers flexibility in wellbore operations, enabling operators to adjust the device's length as needed. The preference for detachable attachment simplifies deployment and retrieval, enhancing operational efficiency.

[0025] The discrete tubular sections may have the same outer and / or inner diameter at their ends.

[0026] These separate tubular sections designed so that they have the same outer and / or inner diameter at their ends when connected. This uniformity ensures a smooth and consistent tubular structure, optimizing fluid flow and structural integrity in wellbore operations.

[0027] In a preferred embodiment, these discrete tubular sections are attached together by a means of connection, where the means of connection is preferably a sleeve.

[0028] In practical terms, the means of connection could be a sleeve, which is a cylindrical component, which can be utilized to secure and join the discrete tubular sections. The sleeve serves as a connecting element that holds the sections together. This sleeve serves as a reliable and efficient way to connect and disconnect the tubular sections, simplifying the device's assembly and disassembly for wellbore operations.

[0029] In a preferred embodiment, the sleeve and at least one discrete tubular section are equipped with threads, preferably in the form of a stub ACME connection.

[0030] These threaded connections enhance the device's reliability and efficiency during assembly and disassembly in wellbore operations and are a standard means of connection in the oil and gas industry. Any connection can be used, but the stub ACME connection has been found to be the most appropriate so far.

[0031] In a preferred embodiment, at least one of the discrete tubular sections comprises at least one region with a decreased inner diameter compared to the inner diameter at the respective ends of the discrete tubular section. This design feature can serve various purposes within wellbore operations. For instance, it may be strategically implemented to create a flow restriction or to control fluid dynamics in specific sections of the tubular element. It can also be used for specialized tools or instruments that require a change in inner diameter to perform specific tasks, e. g. as a float collar for a cementing plug. The float collar, also referred to as orifice float collar is usually located above the plug.

[0032] In a preferred embodiment, the plug is arranged in a first discrete tubular section and port holes for cementing are arranged in a second discrete tubular section, and both discrete tubular sections are directly neighboring each other.

[0033] The advantage of this design lies in the clear separation of functions, enhancing the device's efficiency in executing cementing tasks in the wellbore while maintaining operational flexibility.

[0034] In another preferred embodiment the tubular element comprises a guide for facilitating insertion of the device into a polished bore receptable.

[0035] A polished bore receptable is a component commonly used in well completions. It typically has a smooth and polished inner surface to facilitate the insertion of tools or devices like the one described in this invention. The addition of a guide within the tubular element of the device serves to streamline and facilitate the insertion process into the PBR. This guide ensures that the device aligns correctly and smoothly with the PBR, reducing the risk of misalignment or damage during insertion.

[0036] In a preferred embodiment the tubular element comprises at least one or more outer sealings, to allow a sealing between the tubular element and inner walls of a bore hole.

[0037] These outer sealings are designed to create a tight and reliable seal between the device and the surrounding borehole walls. This sealing is crucial in various wellbore operations to prevent unwanted fluid flow or leaks and to maintain the integrity of the wellbore. The outer sealings can be made from materials or designed in such a way as to ensure a robust and dependable seal, even under challenging wellbore conditions. The advantage of this feature lies in its ability to maintain wellbore integrity and prevent fluid or material migrations, enhancing the reliability and safety of wellbore operations.

[0038] In another preferred embodiment the device comprises a cementing plug, wherein the cementing plug is arranged movable in the axial direction of the tubular element, to push cement through the tubular element.

[0039] This plug's ability to move along the tubular element's length is essential for pushing cement through the tubular element during wellbore operations, ensuring effective cementing.

[0040] In a preferred embodiment the plug has essentially the form of a round cylinder.

[0041] This shape is chosen for its practicality and versatility in wellbore applications, as a round cylindrical shape can be arranged in a versatile manner inside a tube since its shape corresponds to the tube’s axial symmetry.

[0042] In another preferred embodiment, the wall portion of the tubular element around the plug is reinforced compared to the wall portions where the plug is not arranged.

[0043] This reinforcement refers to strengthening the wall in this specific area compared to the wall portions where the plug is not present. The purpose of this reinforcement is to provide additional structural integrity and support to the tubular element in the vicinity of the plug. Since the plug may undergo movements, impacts, or forces during wellbore operations, reinforcing the adjacent wall portions helps ensure the overall stability and robustness of the device. The reinforcement can take various forms, such as thicker materials, additional layers, or specific design enhancements tailored to withstand the operational demands. In a further preferred embodiment, the tubular element comprises port holes for cementing.

[0044] In wellbore workover, cementing is a crucial process used to seal and secure the annular space around the tubular element. These port holes within the tubular element serve as access points for injecting cement into the desired locations within the wellbore. The size, placement, and number of these port holes can be customized to suit the specific requirements of the cementing operation. The advantage of this feature lies in its ability to streamline and optimize the cementing process, ensuring that cement is accurately placed where needed to maintain wellbore integrity.

[0045] Further preferred is an embodiment where, when the device is in use inside a borehole, the plug is arranged in a downhole position relative to the port holes.

[0046] That means that during deployment in a wellbore, the plug will be positioned below these port holes. This arrangement ensures that during cementing operation, no cement will be flowing below the plug within the wellbore.

[0047] Preferably the tubular element comprises fixation means to hold the plug in its position.

[0048] These fixation means serve the purpose of securely holding the plug in its designated position within the device. The primary function of these fixation means is to prevent the plug from moving or shifting unintentionally during wellbore operations. This ensures that the plug remains precisely where it needs to be. These fixation means can take various forms, such as mechanical locks, clamps, or other mechanisms designed to secure the plug in place. The advantage of this feature is its ability to provide stability and reliability in maintaining the plug's position. The plug could be manufactured as an integral part of the device or as a separate part. It can for example be placed in a metal recess with dedicated seals and supported by other part connected to metal body by threaded and pinned connection, that form the necessary fixation means. In a preferred embodiment, the plug is able to disintegrate and / or collapse upon breaking into at least 15 pieces, more preferably 20 pieces, even more preferably 30 pieces and most preferably at least 50 pieces.

[0049] This feature offers adaptability in the disintegration characteristics of the plug. It enables precise control over the plug's behavior, allowing for controlled collapse and or disintegration when required. When the plug disintegrates, the breaking behavior depends on the material that is used for the plug. Nevertheless, all debris can be removed during the process of drilling or breaking the plug by a circulation fluid used during the process, so that the inner diameter of the device remains free from any residuals.

[0050] Preferably the pieces of the plug after disintegration and / or collapse upon breaking comprise a largest piece, wherein the largest piece has a volume of at most 10 cm3, more preferably at most 15 cm3and most preferably at most 30 cm3.

[0051] This feature enhances operational safety and predictability in wellbore activities. By limiting the size of the largest fragment, potential risks associated with large debris are significantly reduced. It ensures a safer and more controlled wellbore environment, safeguarding both personnel and equipment during operations and facilitates the removal of the pieces from the borehole.

[0052] In a preferred embodiment, the tubular element comprises a mandrel. A mandrel is a bar, shaft or spindle around which other components are arranged or assembled. It adds strength to the overall structure of the device, ensuring that it can withstand the forces and pressures encountered in wellbore operations. Additionally, the mandrel can serve as a guide for various downhole tools and instruments.

[0053] An aspect of the invention relates to a method for cementing a wellbore involves several steps: Firstly, a device is provided, and this device incorporates features described in the preceding embodiments. Next, the device is inserted into the wellbore. Cement is then introduced into the device ensuring accurate delivery to the desired locations within the wellbore. The next step involves cementing the annular space around the device. Finally, the frangible plug within the device is broken intentionally.

[0054] One advantage of the method is that it does not require a dedicated trip to install a bridge plug or something alike, since the dive incorporates already a plug. Thus, the daily rig costs are decreased as well as associated service costs for a dedicated trip for setting a plug. Additionally, the rig time is saved where the drilling of the bridge plug is no longer necessary.

[0055] Preferably, the wellbore has a lower completion.

[0056] The lower completion connects the oil and gas formation with the wellbore and is commonly defined as the completion string that is run in the reservoir zone. It involves the installation of components and equipment necessary to control and facilitate the flow of hydrocarbons or other substances from the reservoir to the surface. The preferred method makes the cementing of a tie back possible even for wells with lower completion, where a bridge plug can not be seated.

[0057] Preferably, the cementing of the wellbore is a workover operation.

[0058] In the context of the method, considering it as part of a workover operation means that it can be used to address various wellbore maintenance or enhancement needs. This might include re-cementing, resealing, or improving the integrity of an existing (cemented) wellbore. The advantage here lies in the method's versatility. By being applicable to workover operations, it provides a solution for addressing and improving the condition of existing wellbores, contributing to their long-term efficiency and performance. In this context, devices with a plug should be used in wells with open hole sections to avoid the hydraulic lock effect when a system is closed and incompressible fluids are injected across the barrier.

[0059] The invention is advantageous in connection with wellbores comprising corroded casings. Corroded casings can compromise wellbore integrity, and this method's tailored approach is specifically designed to mitigate these challenges. The key advantage here is the method's ability to efficiently restore and enhance wellbore integrity in the presence of corroded casings. It ensures that workover operations are effective in mitigating corrosion- related issues, contributing to the longevity and reliability of the wellbore. An objective of using the method according to the invention is to extend the life of the well by curing or protecting the production casing by running the additional casing into the well.

[0060] In this context, it is preferred that the annular space around the device is formed by the outer diameter of the device and the inner diameter of one or more liners.

[0061] By using liners to define the annular space around the device, the method enables precise and stable cementing of the annular space.

[0062] Preferably, the cementing of the annular space around the device is done by pushing a cementing plug through the device until the cementing plug stops at an inner ring formed by a reduced inner diameter of one discrete structural section.

[0063] The key advantage here is the method's ability to optimize cementing operations, ensuring that the cement is precisely positioned for effective wellbore sealing. This level of control enhances the integrity of the cemented annular space. Brief description of the figures

[0064] In the following, preferred embodiments of the disclosure are disclosed by reference to the accompanying figures.

[0065] Fig. 1: illustrates a tie back stem according to the invention in a cross-sectional side view.

[0066] Fig. 2: shows a tie back stem according to the invention with a glass plug in a cross-sectional perspective view.

[0067] Fig. 3: illustrates a tie back stem in accordance with the invention in a half-sectional view. Fig. 4: shows a method of implementing a tie back stem in accordance with the present invention.

[0068] Fig. 5: shows process flow diagram of a method in accordance with the present invention.

[0069] 5. Detailed description of the figures

[0070] Figure 1 illustrates the tie back stem according to the invention in a preferred embodiment in a cross-sectional view. The tie back stem is designed to be inserted into an existing borehole. It comprises two tubular sections 100 which are connected with a sleeve 300 which comprises an ACME stub connection 302. One tubular section 100 comprises two sealings 102 and four port holes 104 wherein the other tubular section 100 comprises a sealing 102 and a reinforcement 106 and a frangible glass plug 200 and a fixation means 108 to hold the glass plug in place. The portholes 104 allow cement to be pushed though for cementing the annular space between the outer wall of the tubular section too and the inner walls of e.g. a borehole in which the sections are inserted. The plug 200 has a round cylindrical shape. In the shown embodiment the ratio of length to diameter of the tubular sections are not to scale. Here, the tubular sections too are not directly adjacent to each other because the sleeve 300 holds them in a small distance from each other and therefore part of the sleeve 300 forms a part of the inner surface of the tubular element. The structural sections comprise an inner and an outer diameter ID and OD. During operation, the left side of the figure points downhole.

[0071] Figure 2 shows a tie back stem according to the invention in a cross- sectional perspective view in another preferred embodiment. This embodiment shows only one tubular section too. Here the glass plug 200 is secured in place by a fixation means 108 and the surrounding tubular section comprises a reinforced area 106 to maintain the structural integrity of the tubular section in the area of the glass plug. The plug is made of glass and comprises a determined breaking point to fulfil the need for frangibility, so that it can disintegrate into a number of small pieces. The plug is sealing off a section of the tubular element. During operation, the right side of the figure points downhole. Figure 3 illustrates a tie back stem according to the invention in another preferred embodiment in a half-sectional view. Here the tubular element icomprises two tubular sections 100 and a guide 10. The left tubular section comprises three sealings 102 and port holes 104, while the right tubular section comprises one sealing 102 and a plug 200 as well as reinforcement 106 around the plug. The plug is secured in place with a fixation means 108 which comprises threads and is screwed into the tubular section. The two tubular sections are connected with each other with a sleeve 300 which comprises a threaded connection 302. In the shown embodiment the sleeve 300 creates a small distance between the two tubular sections too, thus parts of the sleeve 300 are part of the inner surface of the tubular element 1. On the right end of the right tubular section too a guide 10 is attached with a guide connection 12. This is advantageous to implement the tubular element 1 into a polished bore receptable. In this Figure, the upper side would be pointing in the downhole direction.

[0072] Figure 4 illustrates the use of an embodiment of the invention in three simplified steps. In the first step, a well 400 is shown having various casings 402 and a well head 406. The last part of the well contains a receptacle 404 for holding tools and / or further casings. In the second step, the embodiment according to the invention is shown inserted into the borehole: the tubular element 1 is inserted into the receptacle 404 and thus closes the connection of the well head 406 to the total depth 401 of the well via the seals 102. Cement is introduced through the inside of the tubular element 1 and forced downwards by the cement plug 408. The plug 200 resists the flow of cement so that it flows through the cement ports 104 into the area outside the tubular element 1. In step 3, the cement plug rests on the float collar 410 so that most of the cement is in the area between the tubular element and the casing of the well. This allows the cement to set and form a newly cemented outer wall of the borehole. Afterwards, the plug can be shattered and / or drilled, to give access to the total depth of the wellbore.

[0073] Figure 5 illustrates a method 500 in accordance with embodiments of the present disclosure. The method 500 includes providing a device according to the embodiment which maybe a tie back stem with a glass plug as represented by block 502. Further, the method includes engaging the distal end of a tubular element according to the invention into a well bore, as represented by block 504. Additionally, as represented by block 506 the method includes providing cement into the inner diameter of the tubular device so that the inner part of the tubular device is filled at least partly with cement for a later cementation. Next, as represented by block 508, a cementing plug is provided into the device to push the cement through the inner diameter of the tubular element in the down hole direction so that it's flows through the portholes into the annular space around the tubular element. This is represented by block 510 where the cementing plug is pushed through the device until it reaches a float collar. During that procedure the cement flows through the port holes and afterwards upwards on the outer part of the device into the annular space between the outer walls of the tubular element and the inner walls of the wellbore. Finally, as depicted in a block 512 the frangible plug can be broken after the cementation is completed. This can be done e. g. by a PDC drill (polycrystalline diamond compact bit), so that the access to the total wellbore is restored.

[0074] Reference list:

[0075] 1: tubular element

[0076] 10: guide

[0077] 12: guide connection too: tubular sections 102: sealings 104: port holes 106: reinforcement 108: fixation means 200: plug 300: sleeve 302: connection

[0078] 400: well

[0079] 401: total depth 402: casing 404: receptable 406: well head 408: cement plug 410: orifice float collar 412: cement 500: method

[0080] 502: providing a device according to the embodiment

[0081] 504: engaging the distal end of a tubular element according to the invention into a well bore 506: providing cement into the inner diameter of the tubular device

[0082] 508: provide cement plug into the device 510: push cement plug through the device

[0083] 512: break frangible plug after the cementation is completed

Claims

Claims1. A device for deployment in a wellbore, comprising: a tubular element adapted for cementing the annular space around the tubular element in a wellbore, and a plug arranged inside the tubular element, characterized in that the plug is frangible.

2. A device according to claim i, where the plug is made of a material that is capable to break into pieces, like e.g. glass.

3. A device according to one of the preceding claims, where the plug is sealing off a first section of the tubular element.

4. A device according to one of the preceding claims, where the plug is made of glass, preferably not tempered, a composite, a polymer and / or metal and / or a combination of these.

5. A device according to one of the preceding claims, where the plug is adapted to disintegrate and / or collapse into pieces.

6. A device according to one of the preceding claims, where the plug comprises one or more predetermined breaking points, allowing a controlled disintegration into a number of smaller pieces.

7. A device according to one of the preceding claims, where the tubular element comprises at least two discrete tubular sections attached together, preferably detachably attached.

8. A device according to claim 7, where the discrete tubular sections have the same outer and / or inner diameter at their ends.

9. A device according to claim 7 or 8, where the discrete tubular sections are attached together by a means of connection, where the means of connection is preferably a sleeve.

10. A device according to claim 9, wherein the sleeve and at least one discrete tubular section comprises a thread, which preferably forms a stub ACME connection.

11. A device according to one of claims 7-10, where at least one of the discrete tubular sections comprises at least one region with a decreased inner diameter compared to the inner diameter at the respective ends of the discrete tubular section.

12. A device according to one of claims 7 to 11, where the plug is arranged in a first discrete tubular section and where port holes for cementing are arranged in a second discrete tubular section, and both discrete tubular sections are directly neighboring each other.

13. A device according to any one of the preceding claims, where the tubular element comprises a guide for facilitating insertion of the device into a Polished Bore Receptable.

14. A device according to any one of the preceding claims, where the tubular element comprises at least one or more outer sealings, to allow a sealing between the tubular element and inner walls of a bore hole.

15. A device according to one of the preceding claims, where the device comprises a cementing plug, wherein the cementing plug is arranged movable in the axial direction of the tubular element, to push cement through the tubular element.

16. A device according to one of the preceding claims, wherein the plug has essentially the form of a round cylinder.

17. A device according to one of the preceding claims, wherein the wall portion of the tubular element around the plug is reinforced compared to the wall portions where the plug is not arranged.

18. A device according to any one of the preceding claims, where the tubular element comprises port holes for cementing.

19. A device according to the preceding claim, where, when the device is in use inside a borehole, the plug is arranged in a downhole position relative to the port holes.

20. A device according to any of the preceding claims, where the tubular element comprises fixation means to hold the plug in its position.

21. A device according to one of the preceding claims, where the plug is able to disintegrate and / or collapse upon breaking into at least 15 pieces, more preferably 20 pieces, even more preferably 30 pieces and most preferably at least 50 pieces.

22. A device according to one of the preceding claims, where the pieces of the plug after disintegration and / or collapse upon breaking comprise a largest piece, wherein the largest piece has a volume of at most 10 cm3, more preferably at most 15 cm3and most preferably at most 30 cm3.

23. A device according to one of the preceding claims, where the tubular element comprises a mandrel.

24. A device according to one of the preceding claims, where the device is a tie-back stem and the plug is a bidirectional internal barrier.

25. A device according to one of the preceding claims, where the plug is adapted to withstand the pressure occurring in the wellbore.

26. A method for cementing a wellbore, comprising the steps of:Providing a device according to any of the preceding claims;Inserting the device into a wellbore;Providing cement into the device;Cementing the annular space around the device; and Breaking the frangible plug.o / . A method according to claim 26, where the wellbore has a lower completion.

28. A method according to claim 26 or 27, where the cementing of the wellbore is a workover operation.

29. A method according to any one of the claims 26 to 28, where the wellbore comprises corroded casings.

30. A method according to any one of the claims 26 to 29 where the annular space around the device is formed by the outer diameter of the device and the inner diameter of one or more liners.

31. A method according to any one of the claims 26 to 30, where the cementing of the annular space around the device is done by pushing a cementing plug through the device until the cementing plug stops at an inner ring formed by a reduced inner diameter of one discrete structural section.

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