Method for improved barrier setting

Abstract

A method for placing a barrier in a wellbore The method provides first accessing, cleaning and cementing a first annulus of a wellbore and then accessing, cleaning and cementing a second annulus of a wellbore. The method provides a 2-stage barrier setting method.

Description

INTRODUCTION The disclosure relates to methods for placing a barrier in a wellbore. Methods for ablation of a control line in an annulus and for verification of ablation of control line in an annulus are also disclosed. BACKGROUND Cementing in hydrocarbon wells have been performed for a long time. In some scenarios, the well shall be abandoned and must be permanently plugged. This is done in a plug and abandonment operation (P&A). In other scenarios, an operator plugs a well such that a sidetrack well can be drilled above the plug. The well bore and well annulus / annuli are filled with a plugging material, typically cement forming the plug. Current plug and P&A operations require a large rig on the surface. There may also be challenges with performing these operations due to small tubings and limited flow rates downhole in the well. Another challenge is ensuring ablation of any control lines in the interval of the well to be plugged, as a control line present in a cemented annulus represents a potential inner leak path in the plug. There is also a need for a cost efficient and safe method for placing a rock-to-rock barrier in a well. SUMMARY OF THE INVENTION In first aspect, the invention provides a method for placing a barrier in a wellbore, the method comprising arranging a fluidized barrier material in the first annulus; and ablating a control line in the first annulus. The method may further comprise perforating a tubular of the first annulus before arranging a fluidized barrier material in the first annulus. Verifying ablation of the control line may be performed by injecting a fluid into at least one ablation point on the tubular. Verifying ablation of the control line may be performed by logging. The method may further comprise arranging a sealing material inside the control line. Arranging a sealing material inside the control line may be performed with a cup tool or straddle packer. The method may further comprise perforating a second tubular through the first annulus. After perforating the second tubular a fluidized barrier material may be arranged in the second annulus, in and around the ablated control line of the first annulus and in the main bore of the wellbore. Arranging a fluidized barrier material in the second annulus, in and around the ablated control line of the first annulus and in the main bore of the wellbore may be performed by using a cupless tool or a tool with cups. The method may further include after perforating a tubular of the first annulus, circulating the first annulus clean. The first annulus may be washed after perforating a tubular of the first annulus. Circulating the first annulus clean and arranging a fluidized barrier material in the first annulus may be performed by using a cup tool or straddle packer. Washing the first annulus and arranging a fluidized barrier material in the first annulus may be performed by using a cup tool or cupless tool. In a further aspect, the invention provides a method for placing a barrier in a wellbore, the method comprising: arranging a fluidized barrier material in a first annulus; and perforating a second annulus through the first annulus. The method may further comprise perforating a tubular of the first annulus before arranging a fluidized barrier material in the first annulus. The method may further comprise after perforating the second annulus, arranging a fluidized barrier material in the second annulus through the first annulus. Arranging a fluidized barrier material in the second annulus may be performed by using a cupless tool or a tool with cups. The method may further comprise after perforating a tubular of a first annulus, circulating the first annulus clean. Circulating the first annulus clean and arranging the fluidized barrier material in the first annulus may be performed with a cup tool or straddle packer. The method may further comprise after perforating a tubular of a first annulus, washing the first annulus. Washing the first annulus and arranging the fluidized barrier material in the first annulus may be performed with a cup tool or cupless tool. In an even further aspect, the invention provides a method for ablation of a control line in an annulus of a wellbore, the method comprising arranging a fluidized barrier material in the annulus and ablating the control line in the annulus. The method may further comprise arranging a sealing material inside the control line. Arranging a sealing material inside the control line may be performed by using a cup tool or straddle packer. In an even further aspect, the invention provides a method for verification of ablation of a control line in an annulus of a wellbore, wherein the control line before ablation is fixed in a fluidized barrier material in the annulus, the method comprising injecting a fluid into at least one ablation point of the annulus. The method may further comprise detecting at least one pressure in a further ablation point above the at least one ablation point. In an even further aspect, the invention provides a method for verification of ablation of a control line in an annulus of a wellbore, wherein the control line before ablation is fixed in a fluidized barrier material in the annulus, the method comprising injecting a fluid into the control line after ablation. In an even further aspect, the invention provides a method for placing a barrier in a wellbore, the method comprising arranging a fluidized barrier material in a first annulus; and arranging a fluidized barrier material in a second annulus through the first annulus. The method may further comprise ablating a control line in the first annulus and verifying ablation of the control line by injecting a fluid into the ablated control line. The method may further comprise arranging a sealing material on the inside of the control line. The fluidized barrier material may be cement. The sealing material may be e.g. a resin, an engineered sealing material or cement. Ablation of control lines may be performed by explosives, jetting or mechanical ablation. In an even further aspect, the invention provides use of the methods according to above in a plug and abandonment operation. By first accessing, cleaning and cementing the first annulus and then accessing, cleaning and cementing the second annulus, this enables to effectively control the hydraulic operation for each annulus and ensure proper clean up and cement placement for a competent rock-to-rock barrier. If a control line is present outside the first tubular, then the control line will be cemented inside the first annulus before being ablated. Ablation inside cement is easier to achieve and control as less energy is required to create the perforation channel and ablate the control line with cement around versus having the annulus filled with fluid. Also, the control line will be cut cleaner as no parts of the control line will be pushed outwards and deformed by the explosive jet when cutting. This solution also allows to create 360° cuts of the inner tubular without the risk of disconnecting the upper and lower portion of the tubular and subsequently risk of not accessing the lower portion as it is dislocated (shifted horizontally and vertically) versus the upper portion thus not allowing to run drill pipe, coil tubing or wireline through to the lower portion. The method provides first accessing, cleaning and cementing a first annulus of a wellbore and then access, clean and cement a second annulus of a wellbore. The disclosed method provides a 2-stage barrier setting method. The method enables to effectively control the hydraulic operation for each annulus and ensure proper clean up and cement placement for a competent rock-to-rock barrier. The invention enables placing a rock-to-rock barrier in casing or through tubing with a single or dual annulus scenario. The invention enables working through smaller tubulars (possibly with restrictions) with limited available flow rates and enables to direct the flow and the hydraulic energy effectively into the annuli. The invention also provides effective ablation of control line, its verification and proper sealing of potential inner leak path. If a control line is present outside the first tubular, then the control line is cemented inside the first annulus before being ablated. The control line is fixed in the cement. Ablation inside cement is easier to achieve and control as less energy is required to create the perforation channel and ablate the control line with cement around versus having the annulus filled with fluid. Also, the control line will be cut cleaner as no parts of the control line will be pushed outwards and deformed by the explosive jet when cutting. The method enables cementing inside the control line to seal the leak path as an option after confirming ablation by injection and circulation through control line. Cementing inside the control line may be performed by use of a cup tool or straddle packer. This solution also allows to create 360° cuts of the inner tubular without the risk of disconnecting the upper and lower portion of the tubular and subsequently risk of not accessing the lower portion as it is dislocated (shifted horizontally and vertically) versus the upper portion thus not allowing to run drill pipe, coil tubing or wireline through to the lower portion. The disclosed method does not need to perform pulling or milling the tubulars to create a window. The disclosed method does not require a big rig on the surface, as the tubing does not need to be cut through. The disclosed method can be used for a single annulus scenario with the same steps as in a dual annulus scenario, except that there is no second tubular and hence no perforation of the second tubular and no second PW (perforate, wash) operation. In a single annulus scenario, there is cement placement inside control lines and inside tubular after the washing operation of the first annulus. In a dual annulus there are either two tubulars and open hole on the outside or three tubular strings with two annuli between tubulars or open hole on the outside. Single annulus have one or two tubulars or open hole on the outside of first tubular. The disclosed method may be performed in a single run or in multiple runs. BRIEF DESCRIPTION OF DRAWINGS Example embodiments are described with reference to the following drawings, where: Fig. 1 is a flow chart for an exemplary method for barrier setting in a dual annulus wellbore scenario with or without control line. Although a dual annulus scenario is illustrated in the flow chart, the flow chart also illustrates a single annulus with control line scenario expect that there is no perforation of the casing and a perforate, wash, cement operation is not required as there is not second annulus. Fig.2 is a schematic illustration of an exemplary cross section of a dual annulus section of a wellbore with a tubing, a first casing and a second casing and a first and a second annulus. A control line is arranged inside the first annulus attached to the tubing by clamps. Fig.3 is a schematic illustration of an exemplary cross section of the dual annulus section of the wellbore where the tubing has been perforated in an upper and lower section of a planned barrier interval. Fig.4 is a schematic illustration of an exemplary cross section of the dual annulus section of the wellbore where the first annulus is circulated clean of particles by establishing a circulation path from the lower perforated section to the upper perforated section of the tubing. Fig.5 is a schematic illustration of an exemplary cross section of the dual annulus section of the wellbore where the first annulus is cemented by squeezing cement into the first annulus through the lower perforation interval by a cup tool or straddle packer. Fig.6 is a schematic illustration of an exemplary cross section of the dual annulus section of the wellbore where the first annulus has been cemented and the control lines are embedded and fixed in the cement. Ablation of the control line creating slots in the cement has been performed (e.g.by use of explosives) in intervals along the tubing between the lower perforations and the upper perforations. Fig.7 is a schematic illustration of an exemplary cross section of the dual annulus section of the wellbore where the verification of the ablation of the control lines are illustrated performed with logging (ultrasound) or performed by injecting a fluid over the ablations by use of a cup tool or straddle packer. Fig.8 is a schematic illustration of an exemplary cross section of the dual annulus section of the wellbore illustrating perforation of the casing. The perforations go through the tubing and through the cement in the first annulus and through the first casing and into the second annulus. The perforations are arranged in interval(s) along the tubing between the lower perforations and the upper perforations. Fig.9 is a schematic illustration of an exemplary cross section of the dual annulus section of the wellbore illustrating washing of the second annulus by a cup tool or cupless tool. A circulation path is set up from the lower perforations to the upper perforations. Fig. 10 is a schematic illustration of an exemplary cross section of the dual annulus section of the wellbore illustrating cementing the second annulus and inside control lines and first annulus perforations and inside the main wellbore. The illustrated cup or cupless tool is shown positioned in the upper perforations after the wellbore has been filled with cement in the interval to be plugged. Fig. 11 is a schematic illustration of an exemplary cross section of a dual annulus section of the wellbore where the control line has been cemented in the first annulus and ablated creating a 360° cut (e.g. by mechanical, milling, jetting or explosives). Fig. 12 is a schematic illustration of an exemplary cross section of a dual annulus section of the wellbore where the control line is ablated with 360° milled windows of varying sizes. Fig. 13 is a schematic illustration of an exemplary cross section of a dual annulus section of the wellbore where the ablation is verified by injecting with a cup tool or straddle packer over ablations and / or by confirming ablation with logging (e.g. ultrasonic or visual). Fig. 14 is a schematic illustration of an exemplary cross section of a dual annulus section of the wellbore where the ablation is verified with logging (e.g. ultrasonic, camera or visual etc.). Fig. 15 is a schematic illustration of an exemplary cross section of a dual annulus section of the wellbore where the ablation is verified with injectivity testing. DETAILED DESCRIPTION Example embodiments will be described with reference to the drawings. The same reference numerals are used for the same or similar features in all the drawings and throughout the description. The example embodiments are examples only and not limiting for the invention. The drawings may not be to scale. In the example embodiments cement is used as an example of a fluidized barrier material. The example embodiments are not limited to cement. Cement is an example only and the example also covers use of fluidized barrier materials suitable for forming a barrier in the wellbore. A wellbore with a control line 18 is illustrated in Fig.2. In Fig.6 a fluidized barrier material 24 has been placed in the first annulus 15. The fluidized barrier material is arranged in a planned barrier section of the wellbore. The control line 18 in the first annulus is ablated 25, e.g. by use of explosives, jetting or mechanical ablation. After ablation of the control line, the ablation of the control line is verified. Verifying of the control line 18 may be performed by injecting 29 a fluid into the control line as illustrated in Fig.7. The fluid is injected in over the ablations, preferably by a cup tool 22 or straddle packer 22. Circulation of the fluid through the ablated hollow control line ensure the control line is ablated. Optionally a sealing material may be placed inside the control line. This seals a potential leek path through the hollow control line. Arranging a sealing material inside the control line may be performed with a cup tool 22 or straddle packer 22. Verifying ablation of the control line may also be performed by logging. A second tubular is perforated through the first annulus as illustrated in Fig.8. The perforations 27 go through the barrier material 24 in the first annulus. After perforating the second tubular a fluidized barrier material is placed 30 in the second annulus. The fluidized barrier material is placed in and around the ablated control line of the first annulus and in the main bore 31 of the wellbore. This may be performed by using a cupless tool or a tool with cups 22. The method provides first accessing and cementing a first annulus of a wellbore and then accessing and cementing a second annulus of a wellbore. The method provides a 2-stage barrier setting method. Fig. 1 is a flow chart for an exemplary method for barrier setting in a dual annulus wellbore scenario with or without control line in an annulus. The method provides a two-stage annulus barrier setting. In the flow chart in Fig. 1, the second annulus is filled with barite. The second annulus may also be cemented. First it is decided whether the first annulus is free (Answer=Yes) or filled i.e. with mud settlings or cement (Answer=No). If the annulus is free (Yes) then the next step is to perform a squeeze operation in the first annulus and follow the sequence on the left side of the flow chart in Fig. 1. If the first annulus is filled i.e. with mud settlings, settled barite or cement (Answer=No), then the next step is to perform a perforate-wash-cement (PWC) operation in the first annulus and follow the sequence on the right side of the flow chart in Fig. 1. The two alternatives (first annulus free or filled) are explained below. Annulus is free (Yes) The following sequence is performed. 1. The first tubular is perforated below and on top of the planned barrier. If required, a cement base is installed below the bottom perforations. 5       2. The first annulus is circulated free. 3. Cement is squeezed in the first annulus. 4. The control lines are ablated. Ablation of control lines after cementing the first annulus, increases the chance of a clean ablation and fixes the control lines in place avoiding movement / deformation during ablation. Fixing the io          control lines in the cement allows full cuts (360°) of the tubular. A cemented first annulus enables the option to do full cuts of tubular without disconnecting and dislocating openings and thus keeping access to the lower tubular portion. 5. Verify Ablation. This is performed either by wireline (WL) Logging by visual is          confirmation that the control lines are ablated, by use of acoustics (e.g. imaging)) or by an injectivity test I interval testing between ablation points injectivity test. The control lines are ablated while in cement. The control lines are hollow and those parts of the control lines that have not been ablated are fixed in position in the cement. Ablation may be verified by the 20          injectivity test; injecting a fluid into the ablations. Pressure may be detected above the ablation to verify whether the control lines are completely cut off and destroyed in the ablated area. 6. (Optional) If confirmation of ablation has been performed by injectivity test / interval testing, the inside of the control line may be filled with a sealing 25          material to seal the leak path. 7. Perforate second tubular through first annulus cement. The next step after verifying the ablation and possibly sealing of the inside of the control line, is to perform a perforate-wash-cement operation in the second annulus. The second tubular is perforated over the entire interval for the perforate-wash- 30         cement operation. 8. Wash the second annulus. The washing of the second annulus is performed from the main bore and through the cemented and ablated first annulus and perforated casing. 9. Cement the second annulus and in and around the control lines in the first annulus and in the main well bore. 10. Test and verify the barrier. Annulus is filled (i.e. with mud settlings, settled barite or cement) (No). 1. Perforate an entire interval of the first tubing for a perforate-wash-cement (PWC) operation in the first annulus. A cement base is optionally installed below the interval if required. 2. Wash the first annulus. 3. Cement the first annulus. 4. Ablate the control line in the first annulus. 5. Drill out cement in the first annulus. 6. Verify Ablation. This is performed either by wireline (WL) Logging by visual confirmation that the control lines are ablated, by use of acoustics (e.g. imaging)) or by an injectivity test / interval testing between ablation points. The control lines are ablated while in cement. The control lines are hollow and those parts of the control lines that have not been ablated are fixed in position in the cement. Ablation may be verified by injecting a fluid into the ablations. Pressure is detected above the ablation to verify whether the control lines are completely cut off and gone in the ablated area. 7. (Optional) If confirmation of ablation has been performed by injectivity test / interval testing, the inside of the control line may be filled with a sealing material to seal the leak path. Perforate second tubular through first annulus cement. The next step after verifying the ablation, and possibly sealing of the inside of the control line, is to perform a perforate-washcement operation in the second annulus. The second tubular is perforated over the entire interval for the perforate-wash-cement operation. 8. Wash the second annulus. The washing of the second annulus is performed from the main bore and through the cemented and ablated first annulus and perforated casing. 9. Cement the second annulus and in and around the control lines in the first annulus and in the main well bore. 10. Test and verify the barrier. The dual annulus scenario illustrated in the flow chart in Fig. 1 may also be used to illustrate a dual annulus with no control line present scenario. If no control line is present, then there is no need of any ablation and ablation verification. The steps of ablating control lines and verify ablation (WL logging or injectivity test) are thus skipped. The dual annulus with no control line present provides a sequential operation by first determining whether the first annulus is free or filled and then perforate, clean and cement the first annulus in either a squeeze operation or a PWC operation. Then, a PWC operation is performed on the second annulus through from the main wellbore, through the tubing and the cement in the first wellbore and through the casing. Although a dual annulus scenario is illustrated in the flow chart, the flow chart may also illustrate a single annulus with control line scenario. In a single annulus with control line scenario there is however no perforation of the casing and a perforate-wash-cement operation of the second tubular / second casing is not required as there is not a second annulus. The exemplary methods explained above may be performed in a single run or in multiple runs. Example sequence single annulus with control line 1. If the first annulus is free: Perforate and Squeeze the first Annulus: a) Perforate tubing at top and bottom of planned barrier section, b) Circulate annulus clean in planned barrier section using straddle packer type of tool / cup tool. c) Squeeze cement in the first annulus (no drill out required vs if using standard PWC (Perforate-Wash-Cement) for first annulus). 2. If the first annulus is filled i.e. with mud settlings or cement, then Perforate-Wash-Cement the first Annulus: a) Perforate entire interval between the bottom perforation and the top perforation. b) Wash and cement the first annulus with cup or cupless tool. 3. Ablate control lines in the first annulus by e.g. use of explosives, jetting or mechanical ablation. 4. Ablation verification a) WL logging to confirm ablation (optional). b) Verify ablation through interval testing (optional). 5. (Optional) If confirmation of ablation has been performed by interval test, the inside of the control line may be filled with a sealing material. The inside of the control line represents a leak path through the barrier which is then sealed off. Use of cup tool or straddle packer. 6. Cement in first annulus in and around control lines using cup or cupless tool. 7. Verify barrier (pressure test and or acoustics) Example sequence dual annulus without control line 1. If the first annulus is free: Perforate and Squeeze the first Annulus: a) Perforate tubing at top and bottom of planned barrier section. b) Circulate annulus clean in planned barrier section using straddle packer type of tool / cup tool. c) Squeeze cement in the first annulus (no drill out required vs if using standard PWC (Perforate-Wash-Cement) for first annulus). 2. If the first annulus is filled i.e. with mud settlings or cement, then Perforate-Wash-Cement the first Annulus: a) Perforate entire interval between the bottom perforation and the top perforation. b) Wash and cement the first annulus with cup or cupless tool. 3. Perforate casing through first annulus cement. 4. Wash the second annulus using cup or cupless tool (optional: verify produced amount of particles using acoustics). 5. Cement the second annulus, in the perforations of the first annulus and in the main wellbore using a cup or a cupless tool. 6. Verify barrier (pressure test and or acoustics). Example sequence dual annulus with control line in first annulus 1. If the first annulus is free: Perforate and Squeeze the first Annulus: a) Perforate tubing at top and bottom of planned barrier section. b) Circulate annulus clean in planned barrier section using straddle packer type of tool / cup tool. c) Squeeze cement in the first annulus (no drill out required vs if using standard PWC (Perforate-Wash-Cement) for first annulus). 2. If the first annulus is filled i.e. with mud settlings or cement, then Perforate-Wash-Cement the first Annulus: a) Perforate entire interval between the bottom perforation and the top perforation. b) Wash and cement the first annulus with a cup or cupless tool. 3. Ablate control lines in the first annulus by e.g. use of explosives, jetting or mechanical ablation. 4. Ablation verification. a) WL logging to confirm ablation (optional). b) Verify ablation through interval testing (optional). 5. (Optional) If confirmation of ablation has been performed by interval test, the inside of the control line may be filled with a sealing material. The inside of the control line represents a leak path through the barrier which is then sealed off. Use of cup tool or straddle packer. 6. Perforate casing through first annulus cement. 7. Wash the second annulus using cup or cupless tool (optional: verify produced amount of particles using acoustics). 8. Cement the second annulus and around control lines using a cup or cupless tool. 9. Verify barrier (pressure test and or acoustics). In the following the different operations in the method exemplified in the flow chart is illustrated and explained in further detail. The different operations may be performed in multiple runs. A single run may be possible. Some of the operations may be performed standalone. A cross section of a dual annulus section with a tubing 12, a casing 13 and a casing 14, a first annulus 15 and a second annulus 16 is illustrated in Fig.2. A control line 18 is arranged inside the first annulus 15 attached to the tubing by clamps 18. In Fig.3 the tubing 12 from Fig.2 has been perforated below 21 and on top 20 of a planned barrier in the well to create a lower perforation interval 21 and an upper perforation interval 20. The upper perforation interval is arranged above the upper clamp illustrated in Fig.3. The perforations may be made by e.g. a mechanical perforator tool or explosives. In Fig.4 the first annulus 15 is circulated free of particles by establishing a circulation path 19 inside the first annulus from the lower perforation interval 21 to the upper perforation interval 20 of the tubing 12. A cup tool or straddle packer 22 is arranged over the lower perforation interval. The cup tool or the straddle packer seals off on each side of the lower perforated interval of the tubing. The washing fluid being pumped down the washing tool 22 is forced into the annulus through the lower perforations. The first annulus 15 is circulated clean. In Fig.5 the first annulus 15 is cemented by squeezing cement into the first annulus through the lower perforation interval 21 by a cup tool or straddle packer 22. The first annulus is washed by the cup tool or straddle packer 22 arranged in the main bore 11 over the lower perforation area 21 of the tubular. The flow path 23 for the cement (dotted line with arrow) is from the lower perforation interval and upwards towards the upper perforation interval. After the squeezing operation, the control line 18 is embedded in the cement 24 in the planned plugging interval of the first annulus. In Fig.6 the first annulus has been cemented and the control line 18 is embedded in and fixed in the cement 24 (hatched lines). The control line is ablated 25 (e.g.by use of explosives) in intervals along the tubing between the lower perforations and the upper perforations creating slots in the cement. Ablation of control line after cementing the first annulus increases the chance of clean ablation and fix the control line in place avoiding movement / deformation during ablation. In the ablation process, as much as possible of the control line should be destroyed. The control line is cut into many parts in the ablation process. When the control line is fixed in cement, the parts of the ablated control line not destroyed in the ablation process will remain fixed in the cement. Use of a perforation gun represents a risk of shooting through a second casing. Cementing the first annulus and then ablating the control line by use of explosives enables a more directed and controlled explosion with considerably reduced risk of perforating the second casing and makes use of explosives easier. Cementing the control line in the cement also allows full cuts of the tubular (360°) without disconnecting and dislocating openings, and thus enabling to keep access to the lower tubular portion. In Fig.7 the ablation of the control line is verified with logging 26 (ultrasound) or by injecting a fluid 29 over the ablations by use of a cup tool or straddle packer 22. Further details of verification of ablation of the control line are provided in Fig. 1314. In Fig.8 the casing is perforated 27 in intervals along the planned plugging interval. The perforations go through the tubular 12, the cement 24 in the first annulus and through the first casing 13 and into the second annulus 15. In Fig.9 second annulus 16 is washed by a cup tool or cupless tool 22 arranged in the main bore over the lower perforation area of the tubular. The washing sets up a circulation path 28 (the dotted lines with arrow) from the lower perforations 21 towards the upper perforations 20. In Fig. 10 the second annulus 16 is cemented 30, the perforations of the first annulus 15 are cemented in and around the control line 18 inside the first annulus, and the wellbore 11 is cemented. A barrier in the form of a cement plug is created in the two annuli 15,16 and in the main bore 11. Fig. 11 illustrates an example of ablation 32 of a control line 18 in the first annulus 15 in a dual annulus well. The first annulus 15 has been cemented 24 and the control line 18 is fixed inside the cement 24. The control line is as illustrated in Fig. 11, ablated 32 in four different positions along the tubing creating a 360° cut 33 through the tubing 12. A 360° cut through the tubing may be performed by e.g. mechanical, milling, jetting or explosives. By cutting by use of e.g. a mechanical tool, milling tool, jetting tool, this type of cut is typically bigger than the slots created by explosive slot charges and can thus be better identified and confirmed by means of logging (e.g. ultrasonic or visual). The size of the cuts can vary from less than an inch to several inch or feet. Fig. 12 illustrates an example of ablation of a control line 18 in the first annulus 15 in a dual annulus well. The first annulus has been cemented 24 (hatched lines) and the control line 18 is fixed inside the cement 24. The control line is as illustrated in Fig. 12, ablated 34 in four different positions along the tubing. The control line is ablated e.g. by milling, creating 360° windows 35 of varying sizes. The windows 35 in the tubing 12 and in cement 24 provides bigger gaps which are easier to see through to get proof of ablation. By cutting by use of e.g. a mechanical tool, milling tool, jetting tool, the cut is typically bigger than the slots created by explosive slot charges. It is then possible to cut windows of varying sizes able to see through the tubular and into the annulus and more easily identify and confirm ablation of the control lines by means of logging (e.g. ultrasonic or visual). The size of the cuts can vary from less than an inch to several inch or feet. Fig. 13 is a schematic illustration of a cross section of a dual annulus section where the ablation is verified by injecting with cup tool or straddle packer over ablations and / or by confirming ablation with logging (e.g. ultrasonic or visual). The first annulus 51 has been cemented 24 (hatched lines) and the control line 18 is fixed inside the cement. Verifying ablation by injecting a fluid through and possibly circulation through the control line may optionally be followed by filling the inside of the control line with a sealing material. The sealing material may e.g. be a resin or an engineered sealing material, e.g. an optimized cement. The inside of the control line represents a leak path through the barrier. Sealing off the inside of the control line seals this leak path in the final barrier. The control line is ablated in several ablation points / positions along the tubular. Filling the inside of the control line with a sealing material may be performed by use of a cup tool or straddle packer. The cup tool or straddle packer is arranged over the ablation points along the tubular to seal off the ablated control line. Fig. 14 is a schematic illustration of a cross section of a dual annulus section where the ablation is verified with logging 36 (e.g. ultrasonic, camera or visual etc.). An image of an irregular cut / window 40 using explosives is illustrated to the upper left in Fig. 14. It can be seen that the cut / window 40 has a rectangular shape but where the surface / boundary itself is irregular. A regular cut / window 41 using a mechanical cutter is illustrated as a rectangle below the image. Small cuts with irregular surface / boundary reduce likelihood of acquiring meaningful data with ultrasonic tool. Typically need minimum of 0.5in or more slot / cut height to get one or more beams from transducer through the opening defined by the cut / window and return reflection to transducer. Irregular cut surface / rugosity causes the beams to scatter. Beam 42 through slot is illustrated above a clear signal 43 and a signal 44 affected by rugosity. The signal 44 affected by rugosity contains more noise and have many peaks that destroys the signal, which makes it difficult to get a clear image of the inside of the first annulus in order to verify whether the control lines is cut or not. Fig. 15 is a schematic illustration of a cross section of a dual annulus section where the ablation of the control line 18 is verified by injectivity testing. A cup tool or straddle packer 22 is arranged over an ablation of the tubular. A fluid is injected with the cup tool or straddle packer over the ablations and into the control line 18. The control lines are fixed in the cement 24. Ablation of the control line 18 should destroy the control line in the annulus 15 on the inside of the cut / window. The parts of the control line which are not ablated are fixed in the cement. The control line is hollow and fluid may flow through the inside of the control line. The inside of the control line is exposed on the overside and underside of the cut / window created by the ablations. To verify the ablation of the control line a fluid is circulated 37 through control line 18 to next ablation or to surface if possible. Pressure may be measured above the injection point 37. A pressure drop through the control line may be calculated. Having described example embodiments of the invention it will be apparent to those skilled in the art that other embodiments incorporating the concepts may be used. These and other examples illustrated above are intended by way of example only and the actual scope of the invention is to be determined from the following 5 claims.

Claims

1. Method for placing a barrier in a wellbore, the method comprising: - arranging a fluidized barrier material in the first annulus; and- ablating a control line in the first annulus.

2. Method according to claim 1, further comprising perforating a tubular of the first annulus before arranging a fluidized barrier material in the first annulus.

3. Method according to claim 1 or claim 2, further comprising verifying ablation of the control line by injecting a fluid into at least one ablation point on the tubular.

4. Method according to claim 1 or claim 2, further comprising verifying ablation of the control line by logging.

5. Method according to one of claims 1-4, further comprising arranging a sealing material inside the control line.

6. Method according to one of claims 1-4, further comprising arranging a sealing material inside the control line with a cup tool or straddle packer.

7. Method according to one of claims 1-6, further comprising perforating a second tubular through the first annulus.

8. Method according to claim 7, further comprising after perforating the second tubular, arranging a fluidized barrier material in the second annulus, in and around the ablated control line of the first annulus and in the main bore of the wellbore.

9. Method according to claim 8, wherein arranging a fluidized barrier material in the second annulus, in and around the ablated control line of the first annulus and in the main bore of the wellbore is performed by using a cupless tool or a tool with cups.

10. Method according to claim 2, further comprising after perforating a tubular of the first annulus, circulating the first annulus clean.

11. Method according to claim 2, further comprising after perforating a tubular of the first annulus, washing the first annulus.

12. Method according to claim 10, wherein circulating the first annulus clean and arranging a fluidized barrier material in the first annulus is performed by using a cup tool or straddle packer.

13. Method according to claim 11, wherein washing the first annulus and arranging a fluidized barrier material in the first annulus is performed by using a cup tool or cupless tool.

14. Method for placing a barrier in a wellbore, the method comprising: - arranging a fluidized barrier material in a first annulus; and - perforating a second annulus through the first annulus.

15. Method according to claim 14, further comprising perforating a tubular of the first annulus before arranging a fluidized barrier material in the first annulus.

16. Method according to claim 14 or 15, further comprising after perforating the second annulus, arranging a fluidized barrier material in the second annulus through the first annulus.

17. Method according to claim 16, wherein arranging a fluidized barrier material in the second annulus is performed by using a cupless tool or a tool with cups.

18. Method according to claim 14, further comprising after perforating a tubular of a first annulus, circulating the first annulus clean.

19. Method according to claim 18, wherein circulating the first annulus clean and arranging the fluidized barrier material in the first annulus is performed with a cup tool or straddle packer.

20. Method according to claim 15, further comprising after perforating a tubular of a first annulus, washing the first annulus.

21. Method according to claim 20, wherein washing the first annulus and arranging the fluidized barrier material in the first annulus is performed with a cup tool or cupless tool.

22. Method for ablation of a control line in an annulus of a wellbore, the method comprising arranging a fluidized barrier material in the annulus and ablating the control line in the annulus.

23. Method according to claim 22, further comprising arranging a sealing material inside the control line.

24. Method according to claim 22, further comprising arranging a sealing material inside the control line by using a cup tool or straddle packer.

25. Method for verification of ablation of a control line in an annulus of a wellbore, wherein the control line before ablation is fixed in a fluidized barrier material in the annulus, the method comprising injecting a fluid into at least one ablation point of the annulus.

26. Method according to claim 25, further comprising detecting at least one pressure in a further ablation point above the at least one ablation point.

27. Method for verification of ablation of a control line in an annulus of a wellbore, wherein the control line before ablation is fixed in a fluidized barrier material in the annulus, the method comprising injecting a fluid into the control line after ablation.

28. Method for placing a barrier in a wellbore, the method comprising: - arranging a fluidized barrier material in a first annulus; and- arranging a fluidized barrier material in a second annulus through the first annulus.

29. Method according to claim 28, further comprising ablating a control line in 5 the first annulus and verifying ablation of the control line by injecting a fluid into the ablated control line.

30. Method according to claim 29, further comprising arranging a sealing material on the inside of the control line.1031. Method according to one of claims 1 - 30, wherein the fluidized barrier material is cement.

32. Method according to one of claims 1- 30, wherein the sealing material is is e.g. a resin, an engineered sealing material or cement.

33. Use of the method according to one of claims 1-32 in a plug and abandonment operation.

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