GB2570891A

GB2570891A - Improvements in or relating to well abandonment

Info

Publication number: GB2570891A
Application number: GB1801991.9A
Authority: GB
Inventors: Stewart David; Linklater James
Original assignee: Ardyne Holdings Ltd
Current assignee: Ardyne Holdings Ltd
Priority date: 2018-02-07
Filing date: 2018-02-07
Publication date: 2019-08-14
Anticipated expiration: 2038-02-07
Also published as: GB2570891B; WO2019155199A1; GB201801991D0

Abstract

A recessed cutter blade for use in a section mill, the cutter blade comprising an elongate blade body 49 including a first edge 54 and a second, longer edge 58, a first cutting structure portion 64 extending along a first portion of the length of the second edge, a recess 59 extending into the blade body from the first cutting structure along a second portion of the length of the second edge, and a second cutting structure portion 67 extending along a third portion of the length of the second edge. The first edge and second edge may meet at a point forming an apex 70 for cutting. Also claimed is a section mill wherein a recessed cutter blade as specified above may be extended to mill a tubular, by first contacting the tubular with the first cutting structure portion, and then the second cutting structure portion.

Description

The present invention relates to apparatus for well abandonment and in particular, though not exclusively, to a cutter blade for use in apparatus for removing a section of tubular across a longitudinal section of the well to enable the placement of a cement plug.

When a well has reached the end of its commercial life, the well is abandoned according to strict regulations in order to prevent fluids escaping from the well on a permanent basis. In meeting the regulations, it has become good practise to create the cement plug over a predetermined length of the well. As a well is constructed by locating conduits such as casing, lining, pipe and tubing (herein collectively referred to as tubulars) into the well, the cement plug must extend over all annuli present in the well. In many cases all conduits are removed leaving the outer casing, including the annulus bounded by the formation.

The integrity of the casing and in particular, the cement in an annulus will determine if a cement plug can just be located in the tubular. Steel casing can leak at the couplings or corrode from acids. Cement can deteriorate with time too, but leaks also happen when cement shrinks, develops cracks or channels, or is lost into the surrounding rock when applied. If integrity fails, gases and liquids can leak out of the casing or, just as importantly, move into, up, and out of the well through faulty cement between the casing and the rock wall. These issues affect the ability to plug a well for abandonment but also for ensuring zonal isolation in unconventional reservoirs. Cement bond logging (CBL) can be used to log the quality of the cement bond but if the CBL shows the bond to be poor intervention is required with access needed to the outermost tubular.

One method of creating or repairing the cement plug is to mill away the inner tubular to expose the annulus behind the tubular and then pump cement into the enlarged area to create the cement plug. This is achieved using a rotatable section mill run on a work string and typically operated downwardly to remove the tubular section. In milling downwardly, the weight of the work string is used to apply downward force to the section mill to cause it to progress through the tubular being milled. This application of force to the mill by weight applied from above creates a wobble in the milling work string, which has a tendency to fracture the cutting inserts on the section mill blades. This, in turn, causes the mill to wear out sooner, resulting in the removal of less tubular footage before replacement of the mill is required. Further, since milling progresses downwardly, cuttings must be removed from the well bore as they are formed, to avoid forming a ball of cuttings around the mill and reducing its effectiveness. Specialized formulation of milling fluid, and maintenance of proper fluid flow rates, are required in order to circulate the cuttings out of the hole.

To overcome these disadvantages, alternative methods have been developed. In US 6,679,328 the section mill arm can be fitted with a standard casing cutter type blade or the arm can be fitted with square type blades typically found on a pilot mill, to provide for milling an extended length of casing. However, in order for the square type blade to be used, the section mill of US 6,679,328 must first be operated to penetrate the casing with the casing cutter type blade, then the arms are exchanged for arms having the pilot mill type blades, for the remainder of the procedure. This requires the section mill to be returned to surface for the cutters on the arms to be replaced. It is disadvantageous to make multiple trips into the well. Additionally, the length of the pilot type mill blades is also limited as they are also pivotally mounted and must retract into the body of the tool.

In Improvements in or Relating to Well Abandonment GB1713525.2 by the Applicants of the present application, a section mill having elongate rectangular cutting blades which operate as dual purpose cutting, then milling blades, is detailed. The cutting faces and apex of the blades, upon actuation, cut through the tubular. The section mill then moves the blades upwards as the blades continue to be deployed and rotated thus opening a window in the tubular through which the entire length of the blade can project when it is fully deployed to the milling position. Circulation and rotation is continued as the section mill then continues to move upwards causing a section of the tubular to be milled.

Opening a window in the tubular through which the full blade is allowed to project when deployed, prior to milling, is disadvantageous as the cutting of the opening is a time-consuming and costly process.

It is therefore an object of the present invention to provide a cutter blade for use in a section mill for removing a section of well tubing which obviates or mitigates at least some of the disadvantages of the prior art.

According to a first aspect of the present invention there is a cutter blade for use in a section mill, the cutter blade comprising an elongate blade body including: a first edge, a second edge which is longer than the first edge, a first cutting structure extending along a first portion of a length of the second edge, from the first edge, and at least a first portion of a width from the second edge, a recess extending into the blade body from the first cutting structure along at least a second portion of a length of the second edge and a second portion of a width from the second edge, and a second cutting structure extending along a third portion of a length of the second edge and at least a first portion of a width from the second edge.

By providing a blade with a recess, the first cutting structure can be used to initially cut a tubular and then the entire length of the blade is made available to mill the tubular. This reduces wear to the blade, reduces torque required to form a window in the tubular and allows longer lengths of tubular to be milled before blade replacement is required which reduces the number of trips out of the well to change the blades.

The first edge and first portion of the second edge may meet forming a first apex at which a first cutting point is provided.

By providing a cutting point at the first cutting structure, the cutting blade can, more efficiently, circumferentially cut an opening slot for a window in through a tubular.

The recess and the third portion of the second edge may meet forming a second apex at which a second cutting point is provided. The first apex and second apex may each have the form of a right angle. Alternatively, the first apex and second apex may have the form of an acute angle. By having a perpendicular or acute angle apex, the resistance met as the first cutting point cuts into the tubular is minimised.

The first portion of a width from the second edge is greater than a wall thickness of a tubular to be milled. The wall thickness may be considered as the tubular width. By having the first portion of a width from the second edge being greater than the tubular width, the cutting structure is able to be used to mill the tubular once it has been cut, without the need for alternative or replacement milling blades to be provide.

In an embodiment there is a third cutting structure joining the first and second cutting structures at the recess. In this way, the first and second portion of a width are over a majority of the first edge and the cutting structure is continuous over a majority of a length of the blade.

The first portion of a length from the second edge is less than the third portion of a length from the second edge. By having a short first portion of a length, the first cutting structure can act like a cutter blade without requiring the second edge to mill the tubular as the cut is made.

According to a second aspect of the present invention, there is provided a section mill for removing a section of well tubing comprising: a tubular body having a central longitudinal axis;

a plurality of elongate cutter blades, each elongate cutter blade comprising a cutter blade according to the first aspect, and an actuating mechanism to move the elongate cutter blade relative to the tubular body between:

a first position wherein the elongate cutter blades are located inside the tubular body with the second edge being substantially parallel to the central longitudinal axis, and a second position wherein the cutting structures are located outside the tubular body with the second edge being substantially parallel to the central longitudinal axis, by presenting the first cutting structure then the second cutting structure to the tubular.

In this way, the cutter blades can be retracted for running in but then expanded to first cut the tubular in two separate locations before being deployed such that the first cutting structure creates a first cut in the tubular and the second cutting structure increases the milling structure available.

Preferably, the tubular body includes a plurality of longitudinally arranged elongate recesses spaced around a circumference of the tubular body wherein an elongate cutter blade is located in each recess. In a preferred embodiment there are three elongate cutter blades.

Providing a recess to house each cutter blade allows the elongate cutter blades to be supported during the rotational cutting action to maintain adequate torque.

The actuation mechanism may be a pivot arrangement. The pivot arrangement may include a wedge which is driven longitudinally against the blade to cause the blade to come into contact with the casing and cut the casing using the first and second cutting structures respectively. The blade may then pivot outwards to be orientated in the second position. In this way, the blades do not require to be machined to co-operate with a cam mechanism.

The actuation mechanism may be a cam arrangement. The cam arrangement may move the blade axially and radially causing the cutter blade to come into contact with the casing using the first and second cutting structures respectively. The cam arrangement then extends the blades to the second position. In this way, the cam allows blades to be extended by a distance less than the diameter of the tubular body.

In the description that follows, the drawings are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form, and some details of conventional elements may not be shown in the interest of clarity and conciseness. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce the desired results.

Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. Furthermore, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope. Language such as including, comprising, having, containing, or involving, and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers or steps. Likewise, the term comprising is considered synonymous with the terms including or containing for applicable legal purposes.

All numerical values in this disclosure are understood as being modified by about. All singular forms of elements, or any other components described herein including (without limitations) components of the apparatus are understood to include plural forms thereof.

There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which:

Figures 1A to 1C are schematic diagrams of a cutter blade for a section mill according to embodiments of the present invention;

Figure 2 is a view of a section mill provided with cutter blades of Figures 1A and IB, according to embodiments of the present invention, and

Figures 3A to 3F are views of the cutter blade of Figures 1A and IB, according to an embodiment of the present invention.

Referring initially to Figures 1A and IB of the drawings there is illustrated an elongate cutter blade generally indicated by reference number 14 in front and back view respectively. The elongate cutter blade 14 is substantially rectangular in shape having a body 49 providing a leading side face 50, a following side face 52, a top face 54, a bottom face 56, an outer face 58 and an inner face 60. Recess 59 is formed into body 49 from outer face 58. A first edge 62 is provided between the top face 54 and the leading side face 50. A second edge 64 is provided between the outer face 58 and the leading side face 50. A third edge 65 is provided between the recess 59 and the leading side face 50. A fourth edge 67 is provided between the outer face 58 and the leading side face 50. The first edge 62 and the third edge 65 each of the same length which is shorter than the length of second edge 64 and the fourth edge 67 respectively. The second edge 64, recess 59 and fourth edge 67 provides a length for the blade 14. In the embodiment shown the combined length of the second edge 64, recess 59 and fourth edge 67 is at least five times the length of the first edge 62 or third edge 65. While the first edge 62 and second edge 64, and the third edge 65 and fourth edge 67, are shown as perpendicular to each other it will be appreciated by those skilled in the art that the edges may be at an acute angle to each other.

The blade 14 includes a cutting structures 66a,b on the leading side face 50. The cutting structures 66a,b may be a portion of the blade 14 or be applied to a surface of the blade 14 as is known in the art. The cutting structures 66a,b may be over the entire surface 50 or any portion thereof. A cutting structure 66 may also be applied to other surfaces or parts thereof such as the top face 54, the outer face 58 and recess face 63. A length of the cutting structure 66 along the first edge 62 is greater than the thickness of the wall of the tubular intending to be milled. The length of the cutting structure 66 along the second edge 64 and fourth edge 67 is over a majority of the length of the blade 14 to provide a large length of cutting structure 66 with the length of the cutting structures 66a,b along the second edge 64 and fourth edge 67 being several times greater than the length along the first edge 62.

Figure 1C illustrates an alternative embodiment of a blade 14a, showing the front view. Like parts to those of Figure 1A have been given the same reference numeral and suffixed 'a' to aid clarity. Blade 14a has a second edge 64a appreciably shorter than the fourth edge 67a. Preferably the fourth edge 67a is as at least five times the length of the second edge 64a. Consequently the recess 59a is off-centre and the blade is nonsymmetric. Also shown in this embodiment, but not dependent therefrom, is the extension of the first and second cutting structures 66a,b over a majority of the width of the blade 14a along the first edge 62a, with a third cutting structure 71a at the recess 59a so that a continuous cutting structure 66 lies along the longest aspect of the blade 14a. The cutting structure 66 covers a majority of the surface 50a.

At the apex 68 where the first 62 and second 64 edges meet, being the point where the leading side face 50, outer face 58 and top face 54 also meet, a pilot cutter 70 is provided. The pilot cutter 70 will be the first contact point with the tubing to be milled and provide a first cut through the tubing before milling begins.

There will also be an apex 69 where the third 63 and fourth 67 edges meet, being the point where the leading side face 50, outer face 58 and recess 59 also meet.

The inner face 60 of each blade 14 can be provided with a suitably profiled surface to co-operate with the blade activation mechanism. This may be a cam profile actuation as detailed in Improvements in or Relating to Well Abandonment GB1713525.2 by the Applicants. Alternatively, the activation mechanism may be a pivot mechanism such as is known in the art which acts upon the blade 14 includes the blade 14 being provided with pivot point 72.

In use, cutter blades 14 are incorporated with a section mill 10 as shown in Figure 2 which is a plan view showing the section mill 10 having a tubular body 12 of a substantially cylindrical form around a central longitudinal axis 13 having a first end 18 at which the mill 10 can be connected to a work string (not shown). The diameter of the tubular body 12 will be selected to fit within the tubing which requires to be milled. The tubular body 12 has an outer surface 36 provided with pockets or recesses 32a, b, each with a blade 14a and 14b arranged therein in a first position. The number of pockets 32 will match the number of elongate cutter blades 14, while the figures show two elongate cutter blades 14, it will be realised that three cutter blades is most typical however more or less blades could be used. Each pocket provides a longitudinally arranged slot (not shown) extending from the outer surface 36 of the body 12 through the body 12 over the majority of the diameter of the body 12. Each body pocket 32 passes to one side of the central axis 13. In the first position, each blade 14 is retracted in the pocket 32 sitting entirely within the pocket 32 such that the second edge 64 and fourth edge 67 lie parallel to the central axis 13. The first edge 62 is perpendicular to the central axis 13. This first position is used for running the mill 10 into the tubing to be milled.

On deployment of the mill 10, the blade, in the first position, is orientated relative to a tubular 150 which is to be cut as is shown in Figure 3A. When the mill 10 is at the location for cutting and milling to begin, circulation and rotation of the mill 10 is commenced and the blade 14 is actuated such that the first apex 68 is moved outwards radially from the central axis 13 thus the pilot cutter 70 will contact the tubular 150 as is shown in Figure 3B. Continued rotation means the contact of the pilot cutter 70 will cut into the tubular 150 circumferentially. This first cutting process is shown in Figure 3C.

The movement of the blade 14 continues to move apex 68 radially outwards until apex 68 has cut through the tubular 150. This position of the blade 14 may be considered as a mid-position and is shown in Figure 3D. It is noted that at this position the second apex 69 is near but not in contact with the tubular 150. The recess 59 has allowed the pilot cutter 70 and the first cutting structure 66a to cut through the tubular wall without requiring the long edge of the blade to mill through the tubular as would occur had the recess not been present. This advantageously reduces the torque required to cut the slot for the window in the tubular 150.

This cutting step is performed at a first depth in the well. Once the pilot cutter 70 has cut through the tubular wall, the section mill 10 is raised, by being drawn upwards by the work string, so that the first cutting structure 66a at the first edge 62 mills the tubular above the blade 14. This upward milling process is shown in Figure 3E.

As the blade 14 is moved upwards during this process the cutting structure 66a on the leading side face 50 and at first edge 62 will mill the tubular 150 in an upward direction as cutting continues. Note that the second cutting structure 66b is not used by virtue of the recess 59 being present. The work string (not shown), on which the section mill 10 is deployed, is raised to move the mill 10 upwards so the first edge 62 is used to open a window in the tubular 150 for the entire blade 14 to fit through. This is shown in Figure 3E. The blades 14 can then be moved outwardly to lie longitudinally and parallel to the tubular wall. This can be considered a second position as is shown in Figure 3F with the blades 14 now at their maximum extension. Cut end 150a of tubular 150 is found above the cutting blade 14 and cut end 150c is found below cutting blade

14. To assist in milling, the blades 14 can be locked in the second position as is known in the art.

Continued circulation and rotation while raising the mill 10 relative to the tubular 150, using milling processes as are known in the art, will see a section of the tubular 150a milled by the top first edge 62 and first cutting structure 66a. Wear to the top face 54 during continued upward milling will cause erosion of the blade 14 along the cutting structures 66a,b. However, as the second edge 64 and fourth edge 67 are significantly longer than prior art blades, the mill 10 can be used until the entire cutting structures 66a, b are removed along the length of the second edge 64 and fourth edge 67.

If a blade according to the embodiment in Figure IB is used, continuous milling across the entire length of the blade is achieve, if the blade is positioned so that the tubular is outside the recess.

The principal advantage of the present invention is that it provides a cutter blade for use in a section mill in which the full length of the cutting structures of the blade can be used to extend the section of tubular which can be milled on a single trip in a well.

A further advantage of an embodiment of the present invention is by having a blade with a recess, a cutter and associated cutting structures for milling, a single blade can cut and mill a section of tubular in a quicker and more efficient manner.

A still further advantage of an embodiment of the present invention is that it provides a cutter blade which enables a section mill to first cut the tubing then mill the tubing concurrently on a single trip in a well in a rigless arrangement.

The foregoing description of the invention has been presented for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best 5 explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of 10 the invention herein intended. For example, while the cutting blade is described for cutting and milling tubular, it will be appreciated that couplings can be milled using the blade of this invention. In addition, whilst the cutting blade has been described in relation to a section mill which moves upwards to mill the tubular, the blades could also operate in 15 a section mill which moves downwards to mill the tubular.

Claims

1. A cutter blade for use in a section mill, the cutter blade comprising an elongate blade body including:

a first edge, a second edge which is longer than the first edge, a first cutting structure extending along a first portion of a length from the first edge and at least a first portion of a width from the second edge, a recess extending into the blade body from the first cutting structure along at least a second portion of a length of the second edge and a second portion of a width from the second edge, and a second cutting structure extending along a third portion of a length of the second edge and at least a first portion of a width from the second edge.

2. A cutter blade as claimed in claim 1 wherein the first edge and first portion of the second edge meet forming a first apex.

3. A cutter blade as claimed in claim 2 wherein a first cutting point is provided at the first apex.

4. A cutter blade as claimed in any of claims 2 or 3 wherein the first apex is in the form of a right angle.

5. A cutter blade as claimed in any one of claims 2 or 3 wherein the first apex is in the form of an acute angle.

6. A cutter blade as claimed in any preceding claim, wherein the recess and the third portion of the second edge meet forming a second apex.

7. A cutter blade as claimed in claim 4 wherein a second cutting point is provided at the second apex.

8. A cutter blade as claimed in any of claims 6 or 7 wherein the second apex is in the form of a right angle.

9. A cutter blade as claimed in any one of claims 6 or 7 wherein the second apex is in the form of an acute angle.

10. A cutter blade as is claimed in any preceding claim wherein the first portion of a width from the second edge is greater than a width of a tubular to be milled.

11. A cutter blade as claimed in any preceding claim wherein the first portion of a width from the second edge is less than the second portion of a width from the second edge.

12. A section mill for removing a section of well tubing comprising:

a tubular body having a central longitudinal axis;

a plurality of elongate cutter blades, each elongate cutter blade being according to any one of claims 1 to 11; and an actuating mechanism to move the elongate cutter blades relative to the tubular body between:

13. A section mill as claimed in claim 12 wherein the tubular body includes a plurality of longitudinally arranged elongate recesses paced around a circumference of the tubular body wherein an elongate cutter blade is located in each recess.

14. A section mill as claimed in claim 12 or claim 13 wherein the section mill is provided with three elongate cutter blades.

15. A section mill as claimed in any one of claims 12 to 14 io wherein the actuation mechanism is a pivot arrangement.

16. A section mill as claimed in any one of claims 12 to 14 wherein the actuation mechanism is a cam arrangement.