GB2559071A

GB2559071A - Control cable removal

Info

Publication number: GB2559071A
Application number: GB1807229.8A
Authority: GB
Inventors: Viggo Hemmingsen Pål; Grimsbo Gjermund; Fathi Marcus
Original assignee: Statoil Petroleum ASA
Current assignee: Equinor Energy AS
Priority date: 2014-02-17
Filing date: 2014-02-17
Publication date: 2018-07-25
Anticipated expiration: 2034-02-17
Also published as: GB201807229D0; GB2559071B

Abstract

A method of preparing a well for subsequent plugging, the well comprising a casing 53, a tubular 55 provided within the casing, and a cable 56 provided between the casing and the tubular, wherein an annulus is provided between the tubular and the casing, the method comprising filling the annulus with an insulating material 57 for protecting the casing or a further tubular provided between the tubular and the casing, removing at least part of the tubular and the cable in the portion of the tubular where insulating material is provided by thermal energy, whilst leaving the casing or further tubular substantially undamaged.

Description

(56) Documents Cited:

GB 2524905 A WO 2016/069305 A1

WO 2016/118525 A1 US 20160130903 A1 (62) Divided from Application No

1718843.4 under section 15(9)ofthe Patents Act 1977 (58) Field of Search:

INT CL E21B

Other: Online: WPI, EPODOC (71) Applicant(s):

Statoil Petroleum AS (Incorporated in Norway)

Statoil Petroleum AS, Stavanger, N-4035, Norway (72) Inventor(s):

Pal Viggo Hemmingsen Gjermund Grimsbo Marcus Fathi (74) Agent and/or Address for Service:

Marks & Clerk LLP

Fletcher House (2nd Floor), Heatley Road,

The Oxford Science Park, OXFORD, OX4 4GE, United Kingdom (54) Title of the Invention: Control cable removal

Abstract Title: Control cable removal using thermal means (57) A method of preparing a well for subsequent plugging, the well comprising a casing 53, a tubular 55 provided within the casing, and a cable 56 provided between the casing and the tubular, wherein an annulus is provided between the tubular and the casing, the method comprising filling the annulus with an insulating material 57 for protecting the casing or a further tubular provided between the tubular and the casing, removing at least part of the tubular and the cable in the portion of the tubular where insulating material is provided by thermal energy, whilst leaving the casing or further tubular substantially undamaged.

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Fig. 6

Control cable removal

Background

The integrity of a well in drilling and well operation, including placement of a plug and abandonment of a well, may be compromised by the presence of control cables. Control cables may create vertical leak paths through a well barrier. The problem lies specifically with the insulation material of the electrical or hydraulic control cables, which may degrade in contact with hydrocarbons or which may be damaged during placement of a barrier, creating void space between the plug material and the metal cable. Degradation of the cable material could also happen during manufacturing of the cable, running the cable in the well and by downhole conditions. Another problem is hydraulic cables, which are hollow and therefore cannot be a part of permanent barrier because the hollow cable may provide a path for a fluid leak after abandonment. If the location for a permanent barrier contains control cables, the practice today is to remove these by pulling out the whole production or injection tubing which the cables and cables are attached to. This requires a drill rig onsite, for example a floating drill rig. A problem with this is high time demands and cost, and sometimes safety issues.

Statement of invention

According to an aspect of the invention there is provided a method of preparing a well for subsequent plugging, the well comprising a casing, a tubular provided within the casing, and said cable provided between the casing and the tubular, wherein an annulus is provided between the tubular and the casing; the method comprising: filling the annulus with an insulating material for protecting the casing or a further tubular provided between the tubular and the casing; removing at least part of the tubular and the cable in the portion of the tubular where insulating material is provided by thermal energy, whilst leaving the casing or further tubular substantially undamaged.

The thermal energy may be provided by igniting thermite. The insulating material is provided in the entire annulus in the region where the tubular is removed. The insulating material may be one of resin and plastics. One or more holes may be formed in the tubular wall before placing the insulating material.

The method may further comprise forming a plug in the region where the control cables have been severed. The method may be repeated several times along the tubular

Drawings

Some embodiments of the invention will now be described by way of example only and with reference to the accompanying figures, in which:

Fig. 1 illustrates schematically a tubular with a helical cut.

Fig. 2 is a flow diagram of a first method disclosed herein.

Fig. 3 illustrates schematically a tubular with a cut-out window.

Fig. 4 is a flow diagram of a second method disclosed herein Fig. 5 illustrates schematically a method of severing control.

Fig. 6 is a flow diagram of a third method disclosed herein.

Specific description

A hydrocarbon well considered herein includes at least one tubular extending downhole and a casing which lines the formation. The casing protects the formation and strengthens the walls of the well. One or more control cables extend downhole for providing electricity or hydraulic power to downhole tools, or for carrying an optical signal or to send and receive control signals or measurements. The control cables are provided outside the tubular to avoid obstructions to fluid flow inside the tubular and to protect the control cables during use. If a well is permanently abandoned, a plug may be formed which seals the portion of the well below the plug from the portion of the well above the plug and thereby prevents hydrocarbons from escaping the abandoned well. The presence of control cables extending through a plug may cause a leak to the plug. The leak may be caused by deterioration of the material of the control cables over time or by hollow cables providing a path for a fluid leak or a leak path may be caused during manufacturing.

The control cables are provided outside the tubular, but within the casing. The control cables may be attached to the outside wall of the tubular by clamps or other fasteners.

The inventors have appreciated that the control cables need to be severed in at least a portion of the well region in which a plug is to be formed. The absence of control cables in at least a portion of the plug enables the formation of an effective plug whereby leaks are avoided. Besides the formation of plugs for abandonment of a well, plugs may be used when the well is extended sideways above the plug into a new part of the formation.

In an example provided by way of background, the cable is severed by providing within the tubular a means for cutting the tubular and the cable and by cutting the tubular and the cable with said means along a helical path on the wall of the tubular. The step of cutting may be achieved by rotating the means for cutting around the longitudinal axis of the tubular and simultaneously moving the means for cutting along the longitudinal direction of the tubular. The cutting means is provided within the tubular and the control cable is present outside the tubular. An advantage of this method of cutting is that the exact location of the cable does not need to be known given that after the cutting means has rotated around the longitudinal axis of the tubular by more than 360 degrees, the control cables will necessarily have been cut, provided that the cutting depth is sufficient.

The cutting means may be a wireline tool, thereby avoiding the need of a drill rig. The cutting means may be an abrasive tool such as a drill or milling tool. Other means for cutting include thermal means such as thermite or by any energetic material, such as explosives, chemical means and mechanical means.

The helical cutting path may include a plurality of windings such that the control cables are cut in a plurality of locations. An advantage of cutting a helical path through the tubular wall is that the tubular itself is not severed and a lower portion of the tubular below the cut region will not drop down into the well.

Figure 1 illustrates a well with a casing 1, a tubular 2 extending within the casing and a control cable 3 provided between the tubular and the casing. An annular space is provided between the casing and the tubular. A wireline 4 is used to lower a tool 5 within the tubular 2. The tool 5 includes a cutting means for cutting a helical opening 6 into the tubular wall. A helical opening 6 may be formed at more than one location along the tubular. The cutting depth is chosen such that the cable 3 is cut at a plurality of locations 7, without damaging the casing 1. After severing the control cable, a plug is placed in the portion of the well where the helical opening 6 has been made.

Figure 2 is a flow diagram illustrating the steps of providing a means for cutting (S1) and making a helical cut in the tubular (S2) for severing the control cable.

The cable may be connected to the pipe wall by way of clamps and the clamps may automatically release after the cable has been severed. In a specific example, the spacing between the clamps is typically 10 to 12 meters and the helical cut may be made over a 1 meter interval on either side of a clamp or in between two clamps.

An example provided by way of background includes the method steps of providing within the tubular a means for cutting the tubular and the cable, cutting a window in the tubular wall using said means, accessing the cable through the window with a tool and attaching the cable to the tool and moving the cable through the window into the tubular. Before or after moving the cable through the window, the cable may be cut at one or more locations. The cut portion of the cable can be removed from the portion of the tubular with the window by lifting the cut portion towards the surface using the tool.

The cutting means may be a wireline tool. For example, the tool may be a computer numerical control, CNC, tool which is able to carry out multiple functions of cutting, grabbing and pulling. The tool may be a tool such as the one described in WO 2010/066276. A locating device may be used to locate the cable before cutting the window in the tubular wall.

Figure 3 illustrates a well with a casing 31, a tubular 32 extending within the casing and a control cable 33 provided between the tubular and the casing. The control cable is severed and is illustrated as extending into the tubular through a hole in the wall of the tubular. An annular space is provided between the casing and the tubular. A wireline 34 is used to lower a CNC tool 35 within the tubular 32. The tool 35 includes a cutting means for cutting an opening in the tubular wall, severing the cable, grabbing part of the severed cable and pulling part of the cable through the opening. The cable can be severed at a second place such that a portion of the cable can be lifted out of the well and there is a portion of the annulus

Figure 4 is a flow diagram illustrating the steps of severing the cable at one or more locations (S4.1), providing within the tubular a means for cutting the tubular (S4.2), forming an opening in the tubular was in the vicinity of the cable (S4.3), pulling a portion of the cable through the opening (S4.4).

The step of cutting the tubular and the cable may be carried out using the method of the first example using a helical cutting path.

A method according to an embodiment includes the method steps of placing an insulating material between a portion of the tubular and the casing for protecting the casing and for preventing dispersion of the heat into the annulus, removing at least part of the tubular and the cable in the portion of the tubular where insulating material is provided. Heating means such as thermite or an explosion, or any other means of providing energy could be used to remove the portion of the tubular and control cable. The insulating material will concentrate the heat and potentially protect the casing of the well against the heat and explosive forces. The insulating material is preferably provided around the entire perimeter of the tubular in the region where the tubular is removed. The insulating material is one of resin and plastics. Before the insulating material is placed around the tubular, holes may be formed in the tubular such that the insulating material can be placed from within the tubular.

Figure 5 illustrates a well with a plurality of tubulars 51, 52, 53, 54, 55. In this specific example, the inner tubular 55 is surrounded by another tubular 53, but the inner tubular may also be surrounded by a casing as in the first and second examples discussed before. A cable 56 extends downwards between the outside of tubular 55 and tubular 53. Before forming a plug across the inner diameter of tubular 53, an insulating material is provided which fills the annulus between tubular 53 and tubular 55 for protecting tubular 53. Before placing the insulating material, holes may be punched in tubular 55 to place the material into the annulus from the inside of tubular 55. After placing the insulating material 57, a heating means 58 is lowered with a wireline 59. The heating means may be thermite. The thermite can be ignited once in place and then it will melt a portion of tubular 55 and cable 56, while tubular 53 is protected against the heat by insulator 57. The melted material may become part of the permanent plug. A further advantage of the insulating material is that the heat generated by the heating means is used more efficiently as the insulating material reduces dispersion of the heat. Examples of insulating materials are resin or other plastics. Part of the plastics may also be melted by the heating means while still carrying out its protective function.

Figure 6 is a flow diagram illustrating the steps of placing an insulator in the annulus (S6.1), providing means for heating the inner tubular (S6.2) and severing the control cable and tubular using the heating means (S6.3).

The methods described above for severing a cable and removing part of the tubular may be repeated at a plurality of locations along the length of the tubular. A plurality of plugs can be formed after the cable has been severed.

Claims

CLAIMS:

1. A method of preparing a well for subsequent plugging, the well comprising a casing, a tubular provided within the casing, and said cable provided between the casing and the tubular, wherein an annulus is provided between the tubular and the casing; the method comprising:

filling the annulus with an insulating material for protecting the casing or a further tubular provided between the tubular and the casing;

removing at least part of the tubular and the cable in the portion of the tubular where insulating material is provided by thermal energy, whilst leaving the casing or further tubular substantially undamaged.

2. The method of claim 1, wherein said thermal energy is provided by igniting thermite.

3. The method of claim 1 or 2, wherein said insulating material is provided in the entire annulus in the region where the tubular is removed.

4. The method of any one of claims 1 to 3, wherein said insulating material is one of resin and plastics.

5. The method of any one of claims 1 to 4, further comprising creating one or more holes in the tubular wall before placing the insulating material.

6. The method of any one of the preceding claims, further comprising forming a plug in the region where the control cables have been severed.

7. The method of any one of the preceding claims, comprising repeating said method at a plurality of locations along the tubular.

Application No: GB1807229.8 Examiner: Mr David Hotchkiss