The present disclosure belongs to the field of plugging & abandoning a well. More precisely, the present disclosure refers to a method to plug a well in a through tubing plug and abandonment operation.

BACKGROUND OF THE DISCLOSURE

When a well connected to an oil or gas reservoir is abandoned, it may be necessary to plug the well in order to prevent fluid migration from the reservoir to the environment.

Plugging a well typically comprises filling parts of the well with an adapted material such as cement, thus creating a barrier between the reservoir and the environment.

One of the main challenges when plugging a well may be the presence of control lines present in the well, for example between tubing and casing. Control lines (which may comprise plastic material) may deteriorate over time and create a leak path through the cement barrier between the reservoir and the environment. Thus, it may not be possible to let the control lines in place and encapsulate them with cement. Standard well abandonment techniques comprise removing parts of the control lines, the tubing or even the casing from the well before filling the well with cement. Such techniques may be complex and expensive since they may involve the use of a rig.

Leaving the control lines, the tubing and the casing in place would be an attractive solution as it may save time and as it may be done without using a rig.

However, in the prior art, there is no technique that can mitigate the presence of control lines for such plugging. Accordingly, a need exists for a simple and cost-effective method to plug a well.

SUMMARY OF THE DISCLOSURE

The present disclosure provides a method to plug a well. The well may comprise a tubing, a casing, and an assembly comprising at least one control line located between the tubing and the casing. The method may comprise the following steps:

/a/ detecting azimuthal positional characteristics of the assembly;

Ibl creating a plurality of apertures in the tubing based on the azimuthal positional characteristics of the assembly to simultaneously sever the assembly;

Id filling a space between the tubing and the casing with a filling material enclosing at least a part of the severed assembly.

Control lines may be electrical or optical or hydraulic lines used to operate equipment in the well, to control and measure for example pressure or temperature, or to provide chemical products.

“Simultaneously” may refer to the fact that the tubing and the assembly may be severed in one step, for example with only one charge of a perforating tool.

The azimuthal positional characteristics of the assembly may comprise an angular width and a central angular position of the assembly, or angular values defining “left” and “right” angular positions of the assembly.

When plugging a well, the assembly may deteriorate over time and create a leak path through a barrier between a reservoir connected to the well and an environment. The claimed method allows creating a rock-to-rock plug, i.e. shutting and permanently sealing the well by creating a permanent well barrier and without removing the assembly from the well. This may comprise filling a space between the tubing and the casing, but even other parts of the well, such as the tubing for example, with a filling material.

Thus, the objective of the method may be that the created apertures “cover” the angular width of the assembly. For example, for given left, right and central angular positions of the assembly, left and right angular positions of the apertures may both have a greater distance to the central angular position of the assembly than left and right angular positions of the assembly. This may allow totally severing the assembly at the positions of the apertures.

In one embodiment, azimuthal positional characteristics of each of the plurality of apertures to be created in the tubing may be determined based on the azimuthal positional characteristics of the assembly and a predetermined margin value.

For instance, said predetermined margin value may be a constant angular value that respects any permanent inaccuracy or uncertainty of the method, mainly related to a detection tool and/or a perforating tool involved in the detection of the assembly and the creation of the plurality of apertures.

In one embodiment, azimuthal positional characteristics of each of the plurality of apertures to be created in the tubing may be determined based on the azimuthal positional characteristics of the assembly and an uncertainty value, the uncertainty value being determined based on the azimuthal positional characteristics of the assembly.

The uncertainty value may be a variable value and depend on the azimuthal positional characteristics of the assembly or a quality of any signal of the detection tool and/or the perforating tool.

Thus, the variable uncertainty value may differ from the constant predetermined margin value.

The use of the constant margin value and the variable uncertainty value may ensure that the created apertures “cover” the angular width of the assembly and that the assembly is severed, thus avoiding any possible leak path. It further allows avoiding waste of resources such as explosive materials that may be used to create the apertures by precisely determining the properties of the plurality of apertures to be created.

In one embodiment, a distance in an axial direction of the tubing between two consecutives apertures may lie in a range from 10 cm to 50 cm.

This allows creating pieces of the assembly with dimensions that may be small enough to fall in the space between tubing and casing, mainly driven by gravity. Thus, the severed assembly pieces do not constitute a leak path in a permanent well barrier.

In one embodiment, the method further may comprise reiterating steps /a/ and Ibl until a predetermined criterion is met.

The predetermined criterion may require that a possible leak path in a permanent well barrier between the reservoir and the environment is at least partially avoided.

In one embodiment, the criterion may be met if a predetermined portion of the assembly is severed.

If a predetermined percentage of the assembly is severed and if the resulting assembly pieces fall in the space between tubing and casing, the risk that the assembly represents a possible leak path in a permanent well barrier is minimized.

In one embodiment, the criterion may be tested by measuring magnetic, electrical or optical properties at positions defined by the detected azimuthal positional characteristics of the assembly.

Since the assembly may comprise different materials such as metal and plastic which differ in their magnetic, electrical and optical properties, it may be possible to determine which parts of the assembly are not severed and still present in the space between tubing and casing.

In one embodiment, the method may further comprise reiterating steps lal and Ibl at a plurality of axial positions of the tubing. This allows creating a plurality of apertures in the tubing at different axial positions of the tubing and severing the assembly at the corresponding positions into pieces. This allows avoiding a possible leak path at these positions.

In one embodiment, step /a/ may comprise detecting azimuthal positional characteristics of the assembly with a detection tool using ultrasound imaging, magnetic resonance imaging or X-ray imaging.

The detection tool may be inserted in the tubing to obtain information about the assembly through the surface of the tubing, such as a three-dimensional image and/or information about its positional characteristics.

In one embodiment, the detection tool may be connected to at least one wireline and may be movable along an axial direction of the tubing.

Cables and connections used for the acquisition of subsurface data, such as petrophysical and geophysical data, are referred to as wireline. The use of wirelines represents an easy and inexpensive way to insert and control devices in the tubing or other parts of the well. This allows detecting the azimuthal positional characteristics of the assembly at different axial positions of the tubing.

In one embodiment, step /b / may comprise creating a plurality of apertures in the tubing based on the azimuthal positional characteristics of the assembly to simultaneously sever the assembly using a perforating tool comprising a perforating gun, a laser, a cutter or a blowtorch.

“Simultaneously” refers to the fact that the tubing and the assembly may be severed in one step, for example with one gun charge.

A plurality of holes may be created in one step, i.e. by using one charge of the perforating tool.

Different perforating tools have different advantages with respect to parameters such as their dimensions, perforation precision etc. Thus, the assembly may be severed without damaging other parts of the well such as the casing. This allows permanently plugging the well without creating any possible leak path in the barrier.

In one embodiment, the perforating tool may be connected to at least one wireline and may be movable along an axial direction of the tubing.

This allows creating apertures in the tubing and simultaneously severing the assembly at different axial positions, which allows avoiding a possible leak path at all these positions.

In one embodiment, the filling material may comprise cement.

Cement has advantageous material characteristics for permanently and safely plugging the well by creating a permanent well barrier. Cement is stable and does not deteriorate over time.

In one embodiment, the assembly may comprise a flatpack.

A flatpack comprises one or more control lines, typically encapsulated in a plastic housing. This allows efficient installation, operation and maintenance of control lines in the well.

Another aspect of the disclosure may comprise a system to plug a well. The well may comprise a tubing, a casing, and an assembly comprising at least one control line located between the tubing and the casing. The system may comprise:

- a detection tool configured to detect azimuthal positional characteristics of the assembly;

- a perforating tool configured to create a plurality of apertures in the tubing based on the azimuthal positional characteristics of the assembly to simultaneously sever the assembly;

- a filling material configured to fill a space between the tubing and the casing and to enclose at least a part of the severed assembly.

This system allows plugging a well by creating a permanent well barrier without removing the assembly from the well. Figs. 1 - 6 show parts of a well and the system to plug the well. Another aspect of the disclosure may comprise a non-transitory computer readable storage medium, having stored thereon a computer program comprising program instructions, the computer program being loadable into a data-processing unit and adapted to cause the data-processing unit to carry out a method to plug a well. The well may comprise a tubing, a casing, and an assembly comprising at least one control line located between the tubing and the casing. The method may comprise the following steps:

/a/ detecting azimuthal positional characteristics of the assembly;

Ibl creating a plurality of apertures in the tubing based on the azimuthal positional characteristics of the assembly to simultaneously sever the assembly;

Id filling a space between the tubing and the casing with a filling material enclosing at least a part of the severed assembly.

Figure 8 shows and describes the non-transitory computer readable storage medium configured to implement the method of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the disclosure and to enable a person skilled in the pertinent art to make and use the disclosure. In the drawings, like reference characters indicate identical or functionally similar elements.

- Fig. 1 is a three-dimensional schematic view of a well comprising a tubing, a casing and a flatpack located in an annulus between the tubing and the casing.

- Fig. 2 is a three-dimensional schematic view of the well with a perforating gun inside the tubing.

- Fig. 3 is a three-dimensional view of the well, wherein the flatpack is partially severed and resulting flatpack pieces pile up in the annulus. - Fig. 4 is a three-dimensional schematic view of a flatpack that comprises three control lines.

- Fig. 5 is a top view of the well to illustrate the process of determining azimuthal positional characteristics of the flatpack in the annulus. - Fig. 6 illustrates the perf and wash technique used to fill the annulus with cement.

- Fig. 7 shows a flow chart of a method to plug a well.

- Fig. 8 shows a non-transitory computer readable storage medium configured to implement a method to plug a well.

DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 is three-dimensional schematic view of a well, also referred to as wellbore or borehole. A well may be a narrow shaft bored in the ground, typically in a direction vertical to the ground surface. A well may be constructed for the extraction of fluids such as petroleum or gases off-shore or on-shore. Therefore, the well may be connected to a subsurface reservoir.

The well may comprise a tubing 201 and a casing 202. A tubing 201 may be a tube inside the well through which production fluid such as petroleum may stream. A casing 202 may be a tube with a diameter larger than the tubing 201 and often in contact with the surrounding environmental material, such as earth, sands or rock. The casing 202 may surround the tubing 201 , wherein the space between tubing 201 and casing 202 may be referred to as annulus 203. The well further comprises an assembly comprising one or more control lines 401 , 402, typically located in the annulus 203. Control lines 401 , 402 may be electrical or hydraulic lines used to operate equipment in the well, to control and measure for example pressure or temperature, or to provide chemical products. The assembly may be attached to an outer surface of the tubing 201 and be oriented along the axial direction of the tubing 201 .

The assembly may comprise a flatpack 204 which assembles several control lines 401 , 402 by encapsulating them, for example in a plastic housing.

In the following, the example of a flatpack is considered, even though the disclosure is not limited to the use of a flatpack.

The well may further comprise clamps 205. The clamps 205 may be ring- shaped plates configured to fix the flatpack 204 to the outer surface of the tubing 201 when tightened. Thus, the flatpack 204 may be partially loose in the annulus 203, i.e. the flatpack 204 may be attached to the tubing 201 at several positions along the axial direction of the tubing 201 using the clamps 205. The clamps 205 may be located at joints of different tubing elements. Since the length of tubing elements may be typically 12 meters, an axial distance between consecutive clamps 205 may be 12 meters as well.

The present disclosure is not limited to a well with the above-mentioned characteristics. A well may comprise more than one tubing 201 , more than one casing 202 and even more than one flatpack 204 or any other type of assembly.

Fig. 2 shows a three-dimensional view of the well of Fig. 1 , wherein a perforating gun 206 may be now located inside the tubing 201 .

The perforating gun 206 may be located on an axis of the tubing 201 and may be connected to one or more wirelines. Wirelines may be cables and connections used for the acquisition of subsurface data, such as petrophysical and geophysical data. Wirelines may be used to suspend and control devices such as the perforating gun 206 in the tubing.

The perforating gun 206 may be configured to create apertures 207 in the tubing 201 , wherein the positions and dimensions of the apertures 207 may be based on the azimuthal positional characteristics of the flatpack 204. The apertures 207 may be created at different axial positions.

The azimuthal positional characteristics of the flatpack 204 may be detected by using a detection tool 502. The detection tool 502 may use ultrasound imaging or any other ultrasound detection method, magnetic resonance imaging or X-ray imaging to locate the flatpack. The detection tool 502 may be connected to one or more wirelines.

The gun may use severing explosives, propellant or rocket fuel to create the apertures 207 in the tubing. The gun typically may have a cylindrical shape with openings in the cylindrical surface. The openings may be helically arranged on the tubing surface, i.e. they may wind around the axis of the tubing 201. The gun is configured to orient inside the tubing 201 in order to create apertures 207 with the detected azimuthal positional characteristics.

A perforating gun 206 may be configured to cover a distance in an axial direction of 1 to 50 meters, i.e. apertures may be created simultaneously along a distance of 1 to 50 meters. Since a length of the desired permanent well barrier (i.e. cement) in the tubing 201 typically varies between 30 to 100 meters, several “runs” with the perforating gun 206 may be required. This may allow creating apertures 207 at a plurality of axial positions.

In one variant, the perforating gun 206 may comprise a tool configured to create horizontal rectangular slots in a tubing 201. “Horizontal” may refer to any direction perpendicular to an axial direction of the tubing.

Distances between consecutive holes typically lie in a range from 10 to 50 cm.

“Distance” may refer to any mathematical distance, for example to an Euclidean distance between adjacent edges of adjacent apertures 207 or between the geometric centers of adjacent apertures 207. However, any other distance definitions may be possible, such as the Manhattan distance.

The disclosure is not limited to the use of a perforating gun 206. Any other perforating tool adapted to create apertures 207 in the tubing 201 , such as a laser, a cutter or a blowtorch, may be used. Fig. 3 shows a three-dimensional view of the well of Figs. 1 and 2, wherein the flatpack 204 may be partially severed and resulting flatpack pieces 208 pile up inside the annulus 203. The flatpack pieces 208 may be created when creating apertures 207 in the tubing 201 with the perforating gun 206, wherein the flatpack 204 may be severed as well.

The distance between consecutive apertures 207 (for example in a range from

10 to 50 cm) created in the tubing 201 by use of the perforating tool may be chosen such that the severed flatpack pieces 208 may fall in the annulus 203 mainly due to gravity. The smaller the pieces, the higher may be the probability that the pieces fall in the annulus 203.

Fig. 4 is a three-dimensional schematic view of a flatpack 204. The flatpack 204 may comprise electrical, chemical or other types of control lines 401,

402. In the example shown, the flatpack 204 comprises two chemical control lines 401 and one electrical control line 402.

The electrical control line 402 may be used for controlling or operating equipment inside or outside the well and to transmit acquired data, such as pressure or temperature. The chemical control lines 401 may be used for transporting and injecting chemicals in the well.

The flatpack may be oriented along an axial direction in a space between tubing 201 and casing 202. Control lines 401, 402 may have lengths of several tens of meters to kilometers. The housing of a flatpack 204 may be made of plastic (e.g. HDPE), but it may comprise other materials as well.

In one variant, an azimuthal width 501 of the flatpack 204 may be between 3 cm and 4 cm and the thickness 2 cm. “Thickness” may refer to the dimension perpendicular to the tubing surface at the location of the flatpack. Fig. 5 shows a top-view of the well of Figs. 1 to 3 and illustrates the process of detecting the azimuthal positional characteristics of the flatpack in the annulus 203. In the configuration shown, the detection tool 502 may be located in the tubing.

The azimuthal positional characteristics may comprise two values, a first angle a and a second angle b, wherein the flatpack 204 may be azimuthally located between a and b. The azimuthal positional characteristics may also be the first angle a and the angular width b - a.

To totally sever the flatpack 204 in an azimuthal direction, the azimuthal width (i.e. angular width) of the apertures 207 to be created may be chosen to be larger than the azimuthal width 501 of the flatpack 204. Therefore, a constant margin value y may be taken into account that respects any permanent inaccuracy or uncertainty of the method, mainly related to the detection tool 502 and/or the perforating tool. Furthermore, a variable uncertainty value d may be taken into account that may depend on the determined azimuthal positional characteristics of the flatpack or the quality of the determination.

To illustrate said concept, the following example is provided. The flatpack 204 may be detected to be located in a range from a = 28°, referred to as “left azimuthal position”, to b = 53°, referred to as “right azimuthal position”. Thus, the azimuthal width 501 of the flatpack 204 is b - a = 53° - 28° = 25°. A margin value g may be chosen to be y = 5°. For the given properties azimuthal positional characteristics of the flatpack 204, the uncertainty value may be d = 5° as well. However, this value may be dependent on the azimuthal width 501 of the flatpack 204 or the quality of a signal of involved devices such as the detection tool 502 or the perforating tool. A greater azimuthal width 501 may cause a larger uncertainty value. The margin value and the uncertainty value may be considered for both left and right azimuthal positions. Thus, the azimuthal width of apertures 207 to be created in the tubing 201 may be calculated as (b - a) + 2 c g + 2 c d = 25° + 2 x 5° + 2 5° = 45°. As a result of this analysis, the perforating gun 206 may be prepared to create apertures 207 azimuthally located between 18° (28 - 2 x 5°) to 63°(53 + 2 x 5°).

The objective may be that the created apertures 207 “cover” the azimuthal width 501 of the flatpack 204. This means that for given left and right azimuthal positions and a central azimuthal position of the flatpack 204, left and right azimuthal positions of the apertures 207 may both have a greater distance to the central azimuthal position of the flatpack than left and right azimuthal positions of the flatpack to the central azimuthal position of the flatpack.

In one variant, the apertures 207 may be horizontal slots, i.e. the apertures 207 may have their greatest extension in a direction perpendicular to the axis of the tubing 201 .

In one variant, the uncertainty value may be a multiplicative factor of the azimuthal width rather than being added to/subtracted from the determined azimuthal positions of the flatpack as in the above-mentioned example.

In one variant, left and right azimuthal positions may depend on the position z in an axial direction, i.e. a(z ) and /?(z) (indeed, the control lines may turn in the annulus).

Fig. 6 illustrates the “perf and wash technique” to fill the annulus 203 with cement or any other filling material.

When a well connected to an oil or gas reservoir is abandoned, it may be necessary to plug the well in order to prevent fluid migration from the reservoir to the environment.

Therefore, the well may be filled with cement or any other filling material.

Since the annulus 203 may be difficult to access, holes 601 may be created in the annulus 203 along at least a part of the axial length of the annulus 203 in order to place cement in the annulus 203. The holes 601 may typically have circular shape. The holes 601 may be arranged to form a spiral shape winding around the axis of the tubing.

All holes 601 may be created simultaneously over a length in an axial direction of several tens of meters. Through these holes 601 , cement may be pumped and injected in the annulus 203 in order to plug the annulus 203 and enclose the severed flatpack pieces 208.

Furthermore, a permanent well barrier may be created in the tubing 201 , typically at an axial distance at a chosen depth measured from the ground surface, i.e. the most upper part of the well.

Using cement as a filling material may be advantageous since it is stable and does not deteriorate over time.

Fig. 7 shows a flowchart of a method to plug a well. When a well connected to an oil or gas reservoir is abandoned, it may be necessary to plug the well in order to prevent fluid migration from the reservoir to the environment. The method of plugging a well while leaving the tubing 201 in place may be referred to as “through tubing well abandonment”.

The well may comprise a tubing 201 , a casing 202, and an assembly comprising at least one control line 401 , 402 located between the tubing 201 and the casing 202. The assembly may comprise a flatpack 204.

In a first step 701 azimuthal positional characteristics of the assembly may be detected. This detection may be made with a detection tool 502 using ultrasound imaging or other detection methods such as magnetic resonance imaging or X-ray imaging such as disclosed in reference of Figs. 2 and 5.

In a second step 702, a plurality of apertures 207 may be created in the tubing 201 based on the azimuthal positional characteristics of the assembly to simultaneously sever the assembly such as disclosed in reference of Figs. 2, 3 and 5. “Simultaneously” refers to the fact that the tubing and the assembly may be severed in one step.

The apertures may be created using a perforating tool such as a perforating gun 206, a laser, a cutter or a blowtorch. The perforating tool may be inserted in the tubing in order to create the apertures.

The resulting flatpack pieces may have dimensions in a range from 10 cm to 50 cm. This may be ensured by choosing the distance between two consecutive apertures to be in a range from 10 cm to 50 cm.

To totally sever the assembly, the azimuthal width of the apertures 207 to be created may be chosen to be larger than the azimuthal width 501 of the assembly. Therefore, a constant margin value may be taken into account that respects any permanent inaccuracy or uncertainty of the process, mainly related to the detection tool 502 and/or the perforating tool. Furthermore, a variable uncertainty value may be taken into account that depends on the determined azimuthal width 501 of the assembly.

The first 701 and the second step 702 may be reiterated at different axial positions of the tubing in order to sever the assembly at different axial positions.

The method may further comprise reiterating the first step 701 and the second step 702 until a predetermined criterion is met. This allows verifying whether the assembly is severed as planned. The criterion may be verified and tested by measuring magnetic, electrical or optical properties at positions defined by the detected azimuthal positional characteristics of the assembly. For example, if at a certain position the tubing and the assembly are entirely severed, an optical reflectivity value may be different from a case where the assembly is not severed. In one variant, this determination may comprise impedance measurements. In another variant, this determination may comprise the detection of ablated or burnt plastic particles. However, even the above-mentioned detection tool 502 may be used for verifying whether the assembly is severed as planned. If it turns out that a certain portion/percentage is severed, the criterion may be considered to be met. In the contrary case, the perforating tool may be again inserted in the tubing in order to sever the tubing and/or the assembly at detected positions.

In a third step 703, a space between the tubing 201 and the casing 202 may be filled with a filling material such as cement enclosing at least a part of the severed assembly as disclosed in reference of Fig. 6.

Both the detection tool 502 and the perforating tool may be connected to at least one wireline. This allows moving these tools along in axial direction of the tubing.

Fig. 8 shows a non-transitory computer readable storage medium 800 configured to implement the method of the present disclosure.

The non-transitory computer readable storage medium 800 may comprise a memory 805 for storing instructions for implementation of at least part of the method, the data received, and temporary data for performing the various steps and operations of the method.

The non-transitory computer readable storage medium 800 further comprises a control circuit 804.

This control circuit can be, for example, a processor or processing unit adapted to interpret instructions in the form of a computer program in a computer language, wherein the processor or the processing unit may comprise, may be associated with or be attached to a memory comprising the instructions. The control circuit can further be the association of a processor / processing unit and a memory, the processor or the processing unit being adapted to interpret instructions in a computer language, the memory comprising said instructions. The control circuit can further be an electronic card whose steps and operations of the method are described in silicon, or a programmable electronic chip such as an FPGA for "Field- Programmable Gate Array", as a SOC for "System On Chip" or as an ASIC for "Application Specific Integrated Circuit".

SOCs or systems-on-chips are embedded systems that integrate all the components of an electronic system into a single chip. An ASIC is a dedicated electronic circuit that brings together custom features for a given application. ASICs are generally configured during their manufacture for performing a dedicated task. The programmable logic circuits of the FPGA type are electronic circuits reconfigurable by the user of the method.

This non-transitory computer readable storage medium 800 comprises an input interface 803 for receiving messages, and an output interface 806 for providing configuration messages controlling any components involved in the implementation of the claimed method.

Depending on the embodiment, the non-transitory computer readable storage medium 800 may be a computer, a computer network, an electronic component, or another device comprising a processor operatively coupled to a memory 805, and, depending on the mode of operation or selected embodiment, a data storage unit, and other associated hardware elements such as a network interface and a media reader for reading a removable storage medium 807 and writing on such a medium not shown in the figure. The removable storage medium may be, for example, a flash disk, a USB stick, etc.

Finally, the computer may include, for allowing interaction with a user, a screen 801 and a keyboard 802.

The memory 805, the data storage unit or the removable storage medium may contain instructions which, when executed by the control circuit 804, may cause this control circuit 804 to performing or controlling the input interfaces, output interface 406, data storage in the memory 805 and / or data processing and method implementation examples described herein.

In addition, the instructions can be implemented in software form, in which case it takes the form of a program executable by a processor, or in hardware form, or "hardware", as an integrated circuit specific application ASIC, a SOC on a microchip, or in the form of a combination of hardware and software elements, for example a software program intended to be loaded and executed on an electronic component described above such as FPGA processor. The non-transitory computer readable storage medium 800 can also use hybrid architectures, for example architectures based on a CPU + FPGA, or an MPPA for "Multi-Purpose Processor Array".