Sting, punch tool, and method for perforating and plugging a downhole tubular

Abstract

A sting is proposed for use in a punch tool, for perforating and plugging of a downhole tubular with an insert. The sting has a sting base, which has a cylindrical sting body extending about a longitudinal punch axis. The base at a proximal end thereof is adapted for cooperation with a press device, to move the sting in a direction along the longitudinal punch axis toward the wall of the downhole tubular. The insert, also having a cylindrical body extending about the longitudinal punch axis, abuts the cylindrical sting body at an interface, and is secured to the cylindrical sting body by an external body that surrounds the interface. The external body is slidable onto the cylindrical sting body by application of a force along the longitudinal punch axis directed from the insert to the sting base. The sting can be used in a method of perforating and plugging.

Description

[0001] STING, PUNCH TOOL, AND METHOD FOR PERFORATING AND PLUGGING A DOWNHOLE TUBULAR

[0002] FIELD OF THE INVENTION

[0003] In one aspect the invention relates to a sting for perforating and plugging of a downhole tubular with an insert. In another aspect, the invention relates to a method of perforating and plugging a downhole tubular with an insert. In yet another aspect, the invention relates to a punch tool comprising a sting for perforating and plugging of a downhole tubular with an insert.

[0004] BACKGROUND TO THE INVENTION

[0005] Oil and gas wells are normally provided with various ty pes of downhole tubulars. Oil and gas wells typically comprise various sections of casing and the wells are often completed with a production tubing and / or provided with other types of liners. During the lifecycle of such a well, it may be desired to retrofit one or more of the downhole tubulars with a functional insert of some sort. For example, WO 2024 / 110292 Al describes punching a sensor unit (or other type of functional plug) into the wall of a wellbore tubular that is installed in the well, by running a punch tool and perforating the wall of the wellbore tubular with the sensor unit. Subsequently, the punch tool is removed from the wellbore, while leaving the sensor unit behind in the wall. The sensor unit (or other type of functional plug) are held by shear pins, which are designed to break upon pulling the punch tool back to the surface. Unfortunately, these shear pins could break prematurely, when then sensor unit has been pushed only over a part of its available length, but not fully, into the wellbore tubular wall. In such a case, a part of the sensor unit (or other type of functional plug) will remain sticking out into the bore of the w ellbore tubular, thus causing internal restriction of the open passage.

[0006] SUMMARY OF THE INVENTION

[0007] In accordance with a first aspect of the present invention, there is provided a sting for perforating and plugging of a downhole tubular with an insert, said sting comprising:

[0008] - a sting base having a cylindrical sting body extending about a longitudinal punch axis, said sting base at a proximal end adapted for cooperation with a press device to move the sting in a direction along the longitudinal punch axis; - an insert having a cylindrical insert body extending about the longitudinal punch axis; wherein the insert abuts the cylindrical sting body at an interface, and is secured to the cylindrical sting body by a an external body that snuggly surrounds the interface, whereby the external body is slidable onto the cylindrical sting body by application of a force along the longitudinal punch axis directed from the insert to the sting base which overcomes a static longitudinal frictional force between the external body and the sting by which the external body is held in place.

[0009] In accordance with another aspect of the invention, there is provided a method of perforating and plugging a downhole tubular with an insert, the method comprising:

[0010] - providing a punch tool comprising a sting according to any one of the preceding claims on a press device of the punch tool, said sting comprising the insert abutting the cylindrical sting body and held in place by an external body that snuggly surrounds an interface between the abutting insert and the cylindrical sting body;

[0011] - running the punch tool into a bore of the downhole tubular to a desired depth;

[0012] - activating the press device whereby punching the insert into a wall of the dow nhole tubular perforating the downhole tubular with the insert until the external body has been pushed completely on the cylindrical sting body by the wall of the downhole tubular; and

[0013] - subsequently removing the punch tool from the bore while leaving the insert unit behind in the wall.

[0014] In still another aspect of the invention, there is provided a punch tool comprising a sting according to the first aspect, for perforating and plugging of a downhole tubular with an insert, comprising:

[0015] - a tool housing extending along a longitudinal tool axis;

[0016] - the sting according to the first aspect extending about a longitudinal punch axis which is perpendicular to the longitudinal tool axis; said sting comprising a sting base comprising a cylindrical sting body extending about a longitudinal punch axis, and an insert having a cylindrical insert body extending about the longitudinal punch axis mounted on a distal end of the cylindrical sting body; and

[0017] - a press device cooperating with a proximal end of the sting base, configured to move the sting in a direction along the longitudinal punch axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawing figures depict one or more implementations in accordance with the present teachings, by way of example only, not by way of limitation. In the figures, like reference numerals refer to the same or similar elements.

[0019] Fig. 1 shows a schematic cross-sectional view of a punch tool for punching an insert in a wall of a downhole tubular, the punch tool in a position about to be run in the downhole tubular;

[0020] Fig. 2 shows a schematic cross-sectional view' of the punch tool of Fig. 1 w ith stings in expanded position;

[0021] Fig. 3 shows a schematic cross-sectional view of the punch tool of Fig. 1 as it is being retrieved to surface;

[0022] Fig. 4 shows a schematic cross-sectional view' of a sting for use w ith the punch tool of Fig. 1 prior to the insert being punched into the wall of the downhole tubular;

[0023] Fig. 5 shows a schematic cross-sectional view of the sting of Fig. 4 as the insert is being punched into the wall;

[0024] Fig. 6 shows a schematic cross-sectional view of the sting of Fig. 4 immediately prior to release of the insert;

[0025] Fig. 7 shows a schematic cross-sectional view of the sting of Fig. 4 after the base of the sting has been released from the insert;

[0026] Fig. 8 shows a perspective view of a sting with a clamp for use with the punch tool of Fig. 1;

[0027] Fig. 9 shows a schematic cross-sectional view of the sting of Fig. 8 as the insert is being punched into the wall of a downhole tubular;

[0028] Fig. 10 shows a schematic cross-sectional view' of the sting of Fig. 8 immediately prior to release of the insert;

[0029] Fig. 11 show s a schematic cross-sectional view of the sting of Fig. 8 after the base of the sting has been released from the insert; and

[0030] Figs. 12 and 13 show example installations of a sting of the present invention.

[0031] DETAILED DESCRIPTION OF THE INVENTION

[0032] The person skilled in the art will readily understand that, while the detailed description of the invention will be illustrated making reference to one or more embodiments, each having specific combinations of features and measures, many of those features and measures can be equally or similarly applied independently in other embodiments or combinations.

[0033] The present disclosure provides a sting comprising a sting base and an insert mounted on a cylindrical sting body at a distal end of the sting base. The insert comprises a substantially cylindrical insert body extending around a longitudinal punch axis. The insert can be punched in a direction along the longitudinal punch axis through the tubular wall, by means of a punch tool. The insert can be punch-fitted into the wall of a downhole tubular. The downhole tubular may be a w ellbore tubular.

[0034] The insert abuts the cylindrical sting body at an interface and is secured to the cylindrical sting body by an external body that snuggly surrounds the interface. The external body is slidable onto the cylindrical sting body by application of a force along the longitudinal punch axis directed from the insert to the sting base, which overcomes a static longitudinal frictional force between the external body and the sting by which the external body is held in place. Once the external body has been moved far enough onto the cylindrical sting body, the interface becomes exposed, and the insert is then readily releasable from the cylindrical sting body. I.e. at this stage, the external body no longer contributes to securing the insert in place on the cylindrical sting body.

[0035] The insert may be a blind plug, or a functional plug. A functional plug ty pically comprises elements that provide specific functionality. Examples of such elements include a sensor or a circulation device. Circulation devices may include one or more of an orifice, a strainer, a valve, a check valve, a flow' rate limited valve for gas lift, and a filter. Sensors may include one or more of a pressure sensor, a temperature sensor, and a chemical sensor.

[0036] An advantage of punch fitting is that it can be applied to retrofit a downhole tubular that is already installed downhole in an existing wellbore, without removing the downhole tubular from the well. Moreover, punch fitting requires only one tool run and a single combined operation to fit the insert in a perforation in the downhole tubular which perforation is created by the insert that is to be fitted into the tubular. No separate perforation run is required. Moreover, no pre-provided landing rims or landing nipples are required for seating the tool, so that the inserts can be retrofitted at any desired depth or location as long as it is within reach of the punching tool. Once it has been retrofitted, the insert remains in the tubular wall permanently (i.e.. with no intention of removing or recovering while the tubular remains operative). Also, the insert can be punched substantially flush with the inside w all of the downhole tubular, thereby minimizing any flow restriction in the downhole tubular and retaining full accessibility for other access to lower parts of the borehole e g. for running other tools.

[0037] Figs. 1 to 3 show a sequence of steps generally illustrating punch fitting of an insert 17 in the wall of a downhole tubular 11.

[0038] | In Fig. 1 a view of a punch tool 1 is shown, prior to running the punch tool 1 into the downhole tubular 11. The downhole tubular 11 extends in a borehole 20 in an earth formation 10. The downhole tubular 11 may typically have a bore having a certain inside diameter (ID). The dow nhole tubular 11 may be any ty pe of wellbore tubular, such as a production tubing, or any other type of tubing such as casing or a liner. The downhole tubular 11 may be surrounded by an open annulus, or it may be cemented. The punch tool 1 comprises a tool housing 3, which extends along a longitudinal tool axis 2. The punch tool 1 is intended to be lowered into the bore of the dow nhole tubular 11, in a direction parallel to the longitudinal tool axis 2.

[0039] The punch tool 1 further comprises a sting 6 arranged within the tool housing 3. A major part of the sting 6 extends along a longitudinal punch axis 8. The longitudinal punch axis 8 is substantially perpendicular to the longitudinal tool axis 2 and extends radially outw ard therefrom. Each sting 6 comprises a sting base and one insert 17 which is mounted on a cylindrical sting body 7 at a distal end of the sting base.

[0040] A press device is provided to move the sting 6 along a trajectory in an outward direction from the tool housing 3, in a punch direction along the longitudinal punch axis 8, from a retracted position to an expanded position. As depicted in Fig. 1, the sting 6 is in its retracted position. Any suitable press device may be employed. As a generic example, in the schematic of Fig. 1, the press device comprises a cylinder piston within a pressure chamber 9 which can be filled with a pressurized fluid to exert an outward directed force on the sting 6. Other press devices have been proposed in the art, such as devices that include a wedge to mechanically push the sting 6 outward. The present invention is not restricted to any particular press device.

[0041] Turning now to Fig. 2, the punch tool 1 has been lowered inside the bore of the dowTihole tubular 11 in the direction of the longitudinal tool axis 2. The press device has been activated and the sting(s) 6 is / are now in expanded position(s). The sting(s) 6 have been moved in an outward direction from the tool housing 3 in each respective trajectory in the punch direction away from the longitudinal tool axis 2. As each sting 6 transitions from the retracted position to the expanded position, the sting base moves the insert 17 towards the wall of the downhole tubular 11. The insert 17 is thus forced to penetrate into the wall of the downhole tubular 11 thereby perforating the wall. At the same time, the insert 17 plugs the perforated hole created by the insert 17 itself. This combined action is referred to as punch fitting.

[0042] Referring now to Fig. 3. the punch tool 1 is being retrieved to surface by pulling the tool housing 3 up through the bore of the downhole tubular 11. The insert 17 has been released from the cylindrical sting body 7, and preferably it is flush with the inner surface of the wall of the downhole tubular 11. After release, the remaining part of the cylindrical sting body 7 may be recovered to its retracted position to facilitate the retrieval to surface.

[0043] The insert 17 stays behind in the wall of the downhole tubular 11 and plugs the perforation. Optionally, when there is more than one sting 6 in the punch tool 1, one which may be used to install a first insert of one type, while another may be employed to punch fit a second insert, which may be of the same type or a different type of insert having a different specified functionality than the first insert.

[0044] Fig. 4 illustrates a ty pical embodiment of a sting 6 for use in such a punch tool and / or in a method of punching and plugging. The sting 6 comprises a cylindrical sting body 7 on a distal end of a sting base. The cylindrical sting body 7 extends about the longitudinal punch axis 8. A proximal end 4, the sting base is adapted for cooperation with a press device (e.g. as shown in Figs 1-3) to move the sting 6 in punch direction 16 along the longitudinal punch axis 8. The sting 6 further comprises an insert 17. The insert 17 has a cylindrical insert body, also extending about the longitudinal punch axis 8 when the insert 17 is mounted on the cylindrical sting body 7. The insert 17 abuts the cylindrical sting body 7 at an interface 5. The cylindrical sting body, measured from the interface 5, has a length H.

[0045] The sting 6 further comprises an external body 19. The external body 19 fits tightly (snugly) around the circumference of the cylindrical sting body and the cylindrical insert body. The external body 19 may have a cylindrical bore, with an inner diameter that matches the outer diameter OD of the cylindrical sting body so that it can snugly be fitted on the cylindrical sting body 7. The insert 17 is secured to the cylindrical sting body 7 by the external body 19, when the external body 19 surrounds the interface 5 and thus overlaps parts of both the cylindrical insert body and the cylindrical sing body. As shown in Fig. 4, the external body 19 overlaps the insert 17 over a distance I measured parallel to the longitudinal punch axis 8. The external body 19 has a body length L as schematically indicated in Fig. 4. This means, that seen in the direction of the longitudinal punch axis 8, the external body 19 takes up a space of L. Accordingly, the external body 19 overlaps the cylindrical sting body 7 by a distance of L - I ( / . minus / ).

[0046] The external body 19 is slidable (in a sliding direction that is parallel to the longitudinal punch axis 8) onto the cylindrical body 7 of the sting base, by overcoming a static longitudinal frictional force between the external body and the sting by which the external body is held in place. Generally, static friction force between an object and another body must be overcome by an applied force before an object can move in sliding contact vxi th the other body. The maximum value of static friction, when motion is impending, is sometimes referred to as limiting friction.

[0047] The length H should be equal to or greater than L, to ensure the external body 19 can entirely be accommodated within the length of the cylindrical sting body. This ensures that the abutting interface 5 between the insert 17 and the cylindrical sting body 7 can become fully exposed such that the insert 17 can easily be freed from the cylindrical sting body 7.

[0048] As depicted in Fig. 4, the sting 6 is moved in the punch direction 16 to the inside wall of a downhole tubular 11. The movement may be actuated from a suitable punch tool (not show n in Fig. 4) w hich has been lowered into the bore of the downhole tubular 11. Fig. 5 illustrates a stage of the perforation operation, where the insert 17 has perforated the downhole tubular 11 and the external body 19 is just in contact with the inside of the wall of the downhole tubular 11. As the external body 19 exceeds the OD of the cylindrical insert body, it will not fit in the perforation that has been created by the insert 17. When the push device continues to push the sting 6 through the perforation, the wall of the downhole tubular 11 will exert a force along the longitudinal punch axis 8 in the direction from the insert 17 to the sting base (i.e. opposite to the punch direction 1 ). This force may exceed the static frictional force by which the external body 19 is held in place on the sting 6. This results in the external body 19 sliding onto the cylindrical sting body 7.

[0049] As shown in Fig. 5, there is enough distance h available on the cylindrical sting body 7 of the sting base, to accommodate a sliding movement by the external body 19 over the distance I. Fig. 6 shows the situation where external body 19 has slid distance I over the cylindrical sting body 7. The interface 5 is now fully exposed to release the insert 17 from the cylindrical sting body 7.

[0050] Fig. 7 shows how the insert 17 can stay behind in the downhole tubular 11, while the cylindrical sting body 7, preferably with the external body 19 still on it, is moved away from the insert 17. The insert 17 is substantially aligned flush with the inside of the wall of the downhole tubular 11.

[0051] The external body 19 is preferably sufficiently tight around the sting 6 to keep the insert 17 in place during the initial phases of the operation of running the punching tool into the downhole tubular and initiating the outward movement of the sting 6 in the punch direction 16 along the longitudinal punch axis 8. Optionally, the static friction can be enhanced by application of e.g. an adhesive between the external body 19 and the sting 6.

[0052] Optionally , additional means, such as for example an optional layer of adhesive, may be employed on the abutting interface 5, to keep the insert 17 secured on the cylindrical sting body 7 before the external body 19 is brought in place. This might for example facilitate the initial preparation and assembly of the sting 6, prior to the external body 19 being applied to the sting 6. Additional fixing means should however be kept to a minimum to facilitate ease of release of the insert 17 after punching in.

[0053] A stop body may be provided, which moves with the sting 6 in the punch direction 1 until the stop body engages with the inside of the tubular wall. Herewith a fixed predetermined maximum penetration depth of the insert 17 relative to the tubular wall is guaranteed. Optionally, the stop body may comprise a shoulder 21 provided on the sting base between the cylindrical sting body and the proximal end 4. The optional shoulder 21 is wider than the cylindrical sting body (laterally with respect to the longitudinal punch axis 8). The shoulder serves as the stop body, when the external body 19 lands on the shoulder 21. If the distance H equals then the rim 22 of the external body 19 aligns with the distal face of the cylindrical sting body 7. As a result, the insert 17 is released when the interface 5 is automatically aligned flush with the inside of the downhole tubular wall at the end of the stroke. The cylindrical sting body is then obstructed from penetrating into the perforation made by the insert 17.

[0054] A small taper 18 (sometimes referred to as “chamfer” or “bevel”) may be applied to part of the cylindrical side wall of the insert body to provide a frustoconical shape. The effect of this is that a slightly smaller hole is punched out of the tubular 11 wall and that a slightly oversized part of the housing is then forced in the smaller hole to secure the cylindrical insert body more rigidly in the tubular 11 side wall. The chamfer 18 may be optimized to enhance push-back resistance of the insert 17 left behind in the wall of the tubular 11. The front face of the insert 17 is preferably substantially flat, so that the punch pressure is distributed over a significant area available on the insert 17 thereby allowing the tubular 11 wall material to shear at the edges of the flat surface.

[0055] The outer diameter OD of the cylindrical insert body may be as small as 20 mm. The maximum diameter of the cylindrical insert body is practically limited by the maximum force that the punch tool 1 is capable of delivering. Preferably, the maximum diameter is 30 mm, more preferably 25 mm. The minimum diameter of the cylindrical insert body may be limited by the maximum compressive strength of the insert 17. The axial length of the insert 17 can be selected in relation to the wall thickness of the tubular 11 side wall. However, there are also other functional requirements which need to be accounted for. as the insert 17 needs to provide enough internal space to accommodate any parts (mechanical and / or electrical) that are needed to achieve the intended functionality.

[0056] The force required to slide the external body 19 onto the cylindrical sting body 7 is lower, preferably lower by at least a factor of 100, more preferably lower by at least factor of 1000. than the perforation force that is required to perforate the downhole tubular wall by punching the insert 17 in. In one example, a punching tool may have a maximum punching force of 100 metric ton (mt), corresponding to 105kgf or 9.8 kN. Depending on the materials properties of the tube wall material and the diameter and shape of the insert, the force required to punch the insert through the wall may t pically be in a range of from 20 mt to 80 mt. In production tubing, the range is typically from 20 mt to 40 mt. Only one or a few kgf of static friction would suffice to keep the external body 19 and the insert 17 in place until the insert has been punched into the wall. This is negligible in comparison with the push force available in the punching tool.

[0057] The surface area of the rim 22 of the external body 19, which comes into contact with the wall of the downhole tubular, should preferably be sufficiently large to avoid that the static friction force would cause the external body 19 to be punched into the wall as well. This will in practice not be a realistic scenario in view of the high punching force that is required. However, in case that the external body 19 is also used as the stop body (in combination with shoulder 21) then the surface area of the rim 22 of the external body 19 should preferably be sufficiently large to avoid that the maximum available punching force would cause the external body 19 to penetrate into the wall of the downhole tubular 11. This can be achieved for example by employing a sleeve with relatively thick mantle, or a sleeve that has an outwardly flanged rim. The surface area of the rim 22 may be curved cylindrically convex to match the concave cylindrical profile of the wall of the downhole tubular.

[0058] So far herein, the external body 19 has been represented by a fitting sleeve, which is positioned as a cylindrical mantle around a part of the sting 6. Fig. 8 shows an embodiment where a clamp is employed as external body 19. This example comprises two clamp halves, brought together with two screws or bolts 24. There are many variations that can be contemplated, including models having only one bolt, and model designs based on pipe clamps, hose clamps, bicycle seat-post clamp. These can be generally ring shaped or rectangular such as shown in the example of Fig. 8. An advantage of clamps is that the static friction is adjustable by adjusting the clamping force. In an advantageous embodiment, the clap includes a clamp bolt with a torque spec, to have a predictable static friction.

[0059] Figs. 9 to 11 illustrate a sequence of perforation events similar to shown in Figs. 5 to 7, employing the sting example of Fig. 8. As can be seen, in this case, the condition L = H is implemented, so that the external body 19 itself when landed on the shoulder 22 functions as a stop for the punching in of the insert into the wall of the dow nhole tubular, resulting in a flush installation of the insert 17 compared to the inside wall surface of the downhole tubular 11.

[0060] The insert 17 can be a blind plug, or a functional plug such as circulation-modifying insert (e.g. an orifice, a strainer, a valve, a check valve, a flow rate limited valve for gas lift, a filter), or a sensor insert, or any other functionality. Sensors in a sensor insert may comprise pressure-sensors, temperature-sensors, chemical-sensors, or combinations thereof. An example of a check-valve that can be punch-fitted is shown in e.g. US Pat. 11 ,851,976. An example of a punch-fittable, flow" rate limited valve for gas lift is provided in e.g. WO 2024 / 013225 Al. An example of a sensor for punch-fitting is disclosed in e.g. WO 2024 / 110292 Al. Different types of inserts could be punched-in simultaneously, or a plurality of inserts of the same type can be punched-in. Figures 1-3 illustrate one example of how inserts 17 can be punched-in simultaneously.

[0061] The stings described above can be applied in a suitable punch tool. A variation of punch tools has been described in literature, which may be, or may be modified to become, suitable for installing inserts. Reference is made to US 2024 / 0052716 Al; US 11,851,976;

[0062] US 2,381,929; and US 2,544,601, which show various non-limiting examples. Other relevant punch tools are described in WO 2023 / 083946 Al and European patent application No. 24186566.6 filed on 4 July 2024. Such tools may be run rigless, for example on a wireline, a slickline, a coiled tubing, or an e-line.

[0063] In one example, the presently proposed sting can be applied in a retrofittable gas lift system. Fig. 12 schematically shows a cross-section view of a production tubing 42 in a typically cased section of a well bore. Inserts comprising a sensor unit 14, an unloading valve 12, or a combination thereof are installed at various depths in the side wall of the production tubing 42. The inserts are substantially flush with the inside wall surface of the production tubing 42, whereby none of the inserts cause any pertinent inner diameter restrictions. This minimizes any restrictions for future tool access through the production tubing 42 to lower parts of the well. Moreover, unnecessary additional pressure drop of the flow of produced fluids 15 in the tubing is thereby avoided as well.

[0064] An open annulus may surround the production tubing 42, which is ty pically sealed at the bottom with a packer 47. The bottom of the open annulus, and the packer 47, may be located near a lower end of the production tubing 42. A tubing nipple profile 13, shown at the lower end of the production tubing 42, may not be necessary when the method of the invention is employed.

[0065] In another example illustrated in Fig. 13, an annulus may be betw een two packers 47, or other isolation devices, that separate two different subsurface formations 48, 48’. The invention can also be applied to control or prevent flow betw een such formations (commonly referred to as cross-flow) or prevent flow of undesirable non-hydrocarbon elements such as water or sand by the installation of various types of inserts. In such cases, a w ellbore plug 49 may be installed in the well tubular to ensure flow only travels through a circulation device insert 12.

[0066] The person skilled in the art will understand that the present invention can be carried out in many various ways without departing from the scope of the appended claims.

Claims

CLAIMS1. A sting for perforating and plugging of a dow nhole tubular with an insert, said sting comprising:- a sting base having a cylindrical sting body extending about a longitudinal punch axis, said sting base at a proximal end adapted for cooperation with a press device to move the sting in a direction along the longitudinal punch axis;- an insert having a cylindrical insert body extending about the longitudinal punch axis; wherein the insert abuts the cylindrical sting body at an interface, and is secured to the cylindrical sting body by a an external body that snuggly surrounds the interface, whereby the external body is slidable onto the cylindrical sting body by application of a force along the longitudinal punch axis directed from the insert to the sting base which overcomes a static longitudinal frictional force between the external body and the sting by which the external body is held in place.

2. The sting of claim 1, wherein the external body has a cylindrical bore having an inner diameter that matches an outer diameter of the cylindrical sting body so that external body can snugly be fitted on the cylindrical sting body.

3. The sting of claim 1 or 2, wherein the external body has a body length L measured along the longitudinal punch axis and wherein the cylindrical sting body, measured along the longitudinal punch axis from the interface, has a length H. and wherein H> L.

4. The sting of claim 3, wherein the sting base further comprises a shoulder between the cylindrical sting body and the proximal end, at a distance H from the interface.

5. The sting of claim 4, wherein H = A.

6. The sting of any one of claims 1 to 5, wherein the external body is a pipe clamp.

7. The sting of claim 6, wherein the pipe clamp is secured onto the sting with a clamping force, whereby the clamping force is adjustable.

8. The sting of claim 1, wherein the insert has a frustoconical shape so that a slightly smaller hole can be punched out of a wall of the dowuhole tubular and that a slightly oversized part of the housing can then be forced in the smaller hole to secure the insert in the wall of the downhole tubular.

9. A method of perforating and plugging of a downhole tubular wtith an insert, said method comprising:- providing a punch tool comprising a sting according to any one of the preceding claims on a press device of the punch tool, said sting comprising the insert abutting the cylindrical sting body and held in place by an external body that snuggly surrounds an interface between the abutting insert and the cylindrical sting body;- running the punch tool into a bore of the downhole tubular to a desired depth;- activating the press device whereby punching the insert into a wall of the downhole tubular perforating the downhole tubular with the insert until the external body has been pushed completely on the cylindrical sting body by the wall of the downhole tubular; and- subsequently removing the punch tool from the bore while leaving the insert unit behind in the wall.

10. A punch tool comprising a sting for perforating and plugging of a dow nhole tubular with an insert, comprising:- a tool housing extending along a longitudinal tool axis;- a sting extending about a longitudinal punch axis which is perpendicular to the longitudinal tool axis; said sting comprising a sting base comprising a cylindrical sting body extending about a longitudinal punch axis, and an insert having a cylindrical insert body extending about the longitudinal punch axis mounted on a distal end of the cylindrical sting body;- a press device cooperating with a proximal end of the sting base, configured to move the sting in a direction along the longitudinal punch axis; wherein the sting is according to any one of claims 1 to 8.

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