NO20180950A1 - A downhole tubular verification and centralizing device, and method - Google Patents

Abstract

A device (4; 41) for centralizing a tubular (1) in a bore (2), comprises a body (9; 41) configured to be positioned at a predetermined location within the tubular. A plurality of penetration tools (5; 51) are movably connected to the body via respective motive means (6; 41b) and configured for extension from the body and through the tubular wall. Wall abutment means (5b; 5c; 52, 53) are configured to generate a force between the tubular in order, at least partially shifting the tubular within the bore. The tool which impinges on the wall may be extended further, whereby the casing is moved as a reaction.

Description

A downhole tubular ver ification and centralizing device, and method

Field of the invention

The invention concerns a device and method for centralizing a tubular in a bore, as set out by the preambles of claims 1, 8 and 11. The invention is particularly useful in centralizing a casing, in connection with plugging-and-abandonment operations in subterranean hydrocarbon wells.

Background of the invention

Hydrocarbons (e.g. oil and/or gas) are extracted from subterranean formations, often referred to as a reservoirs, by drilling a wellbore into the formations containing hydrocarbons. When a wellbore has been drilled, the well must be completed before hydrocarbons can be produced from the reservoir. A completion normally involves the design, selection, and installation of equipment and materials in or around the wellbore for conveying, pumping, or controlling the production or injection of fluids. After the well has been completed, production testing of the well can begin.

Hydrocarbon wells normally have an upper and outer conductor, which forms the base of the well, an upper casing arranged into and in extension of the conductor, and further down in the well more casings which are arranged into and overlaps the above casing. A production tubing string is subsequently located in the middle of the well for transporting petroleum from the bottom of the well to the earth's surface or to a seabed facility. Annuli are thus formed between the different casings, as well as between the outer casing and the wellbore wall (i.e. the formation).

Before the well is permanently abandoned, it must be securely plugged, in a manner that is in compliance with regulatory requirements. Cement plugs are normally used to provide a barrier in the well. A common procedure during plug-and-abandonment operations is to place a cement plug inside an inner casing string and a further plug in the annulus between the inner casing string and the outer casing string, and in the annulus between the outer casing and the formation. The plug will then extend across the full section of the well, and extend a predetermined axial distance.

One commonly used method to install such plug, is to make holes in the casing wall and force cement from within the central casing, through the casing wall holes and into the annulus. This procedure, and various variants, are well known in the art.

In order to ensure that the dimensions and integrity of a plug are within acceptable tolerances, there must be a minimum distance between the casing and the wellbore wall (i.e. the formation), allowing the cement (or other barrier element) to form a barrier of a predetermined minimum thickness and density. This is because the structural integrity of the wellbore wall is not always known. Devices and methods for determining the distance between the casing and the formation exist. For example, an acoustic logging tool may be lowered to the desired location and activated to determine the distribution of material outside the casing. Sometimes, the casing-to-formation clearance is found to be too small or non-existing, due to casing movement during several years of production or formation instabilities. The casing is thus too close to the wellbore wall. Such regions of casing are normally unsuitable for plugging, because it is impossible to establish a complete annular barrier in the annulus between the casing and wellbore wall. It is therefore a need for a device and method whereby the above problems may be mitigated.

Summary of the invention

The invention is set forth and characterized in the main claim, while the dependent claims describe other characteristics of the invention.

It is thus provided a device for centralizing a tubular in a bore, characterized by - a body configured for being positioned at a predetermined location inside the tubular; - a plurality of penetration tools movably connected to the body via respective motive means and configured for extension from the body and through the tubular wall; and - wall-abutment means configured for generating a force between the tubular and the bore in order to at least partly shift the tubular inside the bore.

In one embodiment, each penetration tool comprises sensing means configured for sensing the distance travelled by the penetration tool. Each penetration tool may comprise sensing means configured for sensing the distance to a wall of the bore.

The penetration tools may be releasably connected to the motive means. Three penetration tools may be arranged at 120° intervals around the body circumference. Four penetration tools may be arranged at 90° intervals around the body circumference. Five or more penetration tools may be arranged at regular intervals around the body circumference. The penetration tool may comprise a milling tool.

It is also provided a method of centralizing a tubular in a bore, characterized by a) arranging the invented device a predetermined location inside the tubular;

b) extending a plurality of penetration tools radially from the device body and make an opening in respective portions of the tubular while securing at least a portion of the tool to the tubular; and

c) extending at least a portion of the tool a predetermined distance towards a wall of the bore, or until at least one of the tools impinges on the wall.

Following step c), the tool may which impinges on the wall may be extended further, whereby the casing is moved as a reaction.

The device body may be subsequently be disconnected from the tools and retrieved out of the bore upon completion of the steps.

It is also provided a method of centralizing at least a portion of a tubular in a bore, characterized by

a) arranging a device according to the invention at a predetermined first location inside the tubular;

b) extending penetration tools from the device body to make a first circumferential window in the tubular;

c) installing at least one force member, through the first window, between the tubular outer wall and the bore;

d) relocating said device to a predetermined second location inside the tubular;

e) extending penetration tools from the device body to make a second circumferential window in the tubular; and

f) installing at least one force member, through the second window, between the tubular outer wall and the bore.

With the invention, it is possible to verify sufficient distance between a tubular (e.g. a casing) and an adjacent wall (e.g. wellbore wall), and, if necessary, move the casing laterally in order to establish sufficient distance between the tubular and the wall. With the invented device and method, these operations may be conducted in one downhole trip.

Br ief descr iption of the drawings

These and other characteristics of the invention will become clear from the following description of preferential embodiments, given as non-restrictive examples, with reference to the attached schematic drawings, wherein:

Figure 1 is a cross-sectional drawing of an embodiment of the invented device, in an unactuated state, placed in a casing in a formation wellbore;

Figure 2 corresponds to figure 1, and shows the invented device in an activated state, with four tools having been extended through the casing wall;

Figure 3 corresponds to figure 2, and shows how the tools have shifted the casing in the wellbore, to a more centralized position in the wellbore than previously;

Figure 4 corresponds to figure 4, and shows that the invented device has been removed from the casing, while the tools remain in the casing wall;

Figure 5 is a schematic illustration of a tool in an extended position;

Figure 6 is a schematic illustration of an alternative embodiment of a tool;

Figure 7 is a schematic illustration of an alternative embodiment of the invented device, during a first milling operation;

Figure 8 illustrates the device of figure 7, during the installation of a first set of wedges in an annulus between a casing and a formation;

Figure 9 illustrates the device of figure 7, during a second milling operation;

Figure 10 illustrates the device of figure 7, during the installation of a second set of wedges in an annulus between a casing and a formation; and

Figure 11 shows the first and second sets of wedges installed in an annulus between a casing and a formation, and a cement plug having been placed in a section of the annulus and casing.

Detailed descr iption of preferential embodiments

The following description may

the views and orientations as shown in the drawings and that are associated with the illustrated use of the invention

and shall not be limiting.

Figure 1 shows a casing 1 placed in a wellbore 2 having a wall 2a against a subterranean formation 7. As the jagged lines indicate, the formation wall 2 a may be of an irregular shape and contain cracks, fissures and unconsolidated regions. The casing 1 is not properly centralized in the wellbore 2, but is in contact with a portion of the wellbore wall 2a (in the upper, left-hand part, as shown in figure 1). There is thus no complete annulus between the casing and the wellbore wall 2a, or the annulus 3 is insufficiently wide, therefore rendering a cementing procedure impossible at this location.

Figure 1 also shows the invented device 4 in place inside the casing 1. The device 4 may be connected to a drillpipe, coiled tubing (not shown), or other known downhole device conveyance means, and powered and controlled from an uphole location, in a manner generally known in the art. In the illustrated embodiment, the device 4 comprises a body 9 and four individually operated tools 5, which will be described below.

In figure 2, the tools 5 have been extended from the tool body 9 and advanced towards and through the casing wall. Each individual tool 5 is extended by individual arms 6, which may be hydraulically operated telescopic cylinders, known per se in the art. Each tool 5 comprises casing penetration means (not shown) for making a hole or other opening in the casing wall. Such casing penetration means may for example be jet blasting nozzles or a milling tool, all of which are generally known in the art. Each tool 5 also comprises attachment means (not shown in figure 2) for attaching the tool to the casing wall, for example dogs, slips, or other anchoring means generally known in the art. With these means (referring to figure 5) a first tool portion 5a of the tool 5 may be held in position in the hole made in the casing wall, while a second tool portion 5b is advancing (e.g. telescoping) towards and into abutment with the wellbore wall 2a. Other tool advancing means, such as a threaded, rotational configuration, are also envisaged.

Each tool 5 may comprise distance-sensing means (not shown), by which the distance travelled by the tool may be monitored. Alternatively, such sensing means may be integrated in the individual arm 6. It should be understood that the distance-sensing means may comprise generally known devices, including optical, acoustic and electromechanical means. The distance-sensing means will enable the device operator to determine the distance between the casing and the adjacent wellbore wall 2a, thus being able to evaluate whether or not a sufficient clearance between casing and wellbore wall exists.

In figure 3, the tools 5 have been advanced further through their respective casing penetrations, towards the wellbore wall 2a. By virtue of the individual tools' attachment to the casing wall, the casing is pushed away from the wellbore wall 2a when the tool is abutting the formation. In figure 3, this is seen as the casing 1 has been pushed away from the wellbore wall by the tool 5' (towards the right in the figure). Thereby, a complete annulus 3, with a satisfactory casing-to-wall gap, has been established. The distance-sensing means are also in effect casing verification means, inasmuch as they will communicate the extended distance for each tool, and hence the minimum distance between the casing and the wellbore wall.

Figure 6 illustrates an alternative embodiment of the tool, being a deformable plug 5c, pressing against the formation wall.

Figure 4 shows the casing 1 centralized in the wellbore and thus forming an annulus 3 with the wellbore (formation) wall 2a. The tools 5 have been disconnected from their individual arm, and the device has been retrieved to an uphole location. The tools thus function as permanent casing centralizers, and cement (or other barrier element) 8 is placed into the annulus 3. Each tool 5 is disconnectable from its individual arm by means that are known per se.

With the invention, it is possible to verify the distance between the casing and the adjacent wellbore wall, and, if necessary, move the casing laterally in order to centralize the casing and establish sufficient distance between the casing and the wall. These operations may be conducted in one downhole trip. The device and tools may be integrated with an additional tool (not shown), whereby a well barrier placement operation may be performed following the verification and centralization procedure.

Although the invention has been described with reference to a casing and an adjacent wellbore (formation) wall, it should be understood that the invention is equally applicable for verifying and centralizing an inner casing in an outer casing.

Figure 7 illustrates another embodiment of the invented device 41, having a tool section 41a and a milling section 41b. The device is conveyed into the casing 1 and controlled via a drill string 10 (or coiled tubing, or similar). The tool section 41a carries a first (upper) wedge set 52 and a second (lower) wedge set 53. The milling section 41b, which is rotatably connected to the tool section, carries a set of milling arms 51. It should be understood that each set comprises a plurality of wedges and milling arms, respectively. In figure 7, the milling section 41b is rotated (as indicated by arrow R) with milling arms 51 in a deployed position, in a manner well known in the art, thus generating a first (upper) circumferential casing window 54 (see figure 8).

In figure 8, the device has been lowered further into the casing 1, and the second wedge set 53 has been entered (rammed or pushed) into the annulus 3, through the first casing window 54. At this stage, the connection between the first wedge set 53 and the tool section 41 is severed (e.g. sheared), and the device is being moved further into the casing, to a position shown in figure 9. In the position shown in figure 9, the milling section 41b is once again rotated (as indicated by arrow R) with milling arms 51 in a deployed position, to generate a second (lower) circumferential casing window 55 (see figure 10).

In figure 10, the device has been lowered further into the casing 1, and the first wedge set 52 has been entered (rammed or pushed) into the annulus 3, through the second casing window 55. Upon completion of this step, the connection between the first wedge set 53 and the tool section 41 is severed (e.g. sheared), and the device may be retrieved from the casing, e.g. to an uphole location.

The action of forcing the sets of wedges 52, 53 into the annulus 3 between the casing 1 and wellbore 7 wall, serves to move (se M in figure 11) and centralize the casing portion between the first and second casing window 54, 55, and thus create an annulus 3 where the wall-to-wall distance d is above a predetermined value considered safe for placing a well barrier element. This is illustrated in figure 11, also showing how a plug of well barrier element (e.g. cement) 8 (or other barrier fluid) is placed in the region between the casing windows.

Although the description above with reference to figures 7 to 10 describe a procedure in which the upper (first) casing window 54 is milled before the lower (second) casing window 55, and the sets of wedges are installed in a corresponding sequence, it should be understood that the tool is equally applicable for a reversed method. In such method, the lower casing window 55 is milled first. Then, a lower wedge set 53 is installed through the lower casing window, whereupon the device is pulled to a location above the lower casing window. Here, the upper casing window 54 is milled and the corresponding upper wedge set 52 is installed.

Although the invention has been described with reference to casings, it should be understood that the invention is equally applicable to other tubulars. Although the invention has been described with reference to a plug-and-abandon operation, it should be understood that the invention is applicable to any centralization of tubulars.

Although the invention has been described with reference to figures showing a vertically oriented wellbore and casing, the invention shall not be limited to such orientations, but are equally applicable wellbores having to horizontal or inclined orientations.

Although the invention has been described with reference to a device having four tools, the invention shall not be limited to this number. A device having fewer or more tools shall be considered to be within the scope of this invention. For practical purposes, however, three tools, evenly spaced around the tool perimeter, is considered a minimum number. Five tools have been found to be a suitable number.

Claims (11)

Claims

1. A device (4; 41) for centralizing a tubular (1) in a bore (2), character ized by - a body (9; 41) configured for being positioned at a predetermined location inside the tubular;

- a plurality of penetration tools (5; 51) movably connected to the body via respective motive means (6; 41b) and configured for extension from the body and through the tubular wall; and

- wall-abutment means (5b; 5c; 52, 53) configured for generating a force between the tubular and the bore in order to at least partly shift the tubular inside the bore.

2. The device of claim 1, wherein each penetration tool comprises sensing means configured for sensing the distance travelled by the penetration tool.

3. The device of claim 1 or claim 2, wherein each penetration tool comprises sensing means configured for sensing the distance to a wall (2a) of the bore.

4. The device of any one of claims 1-3, wherein the penetration tools are releasably connected to the motive means (6).

5. The device of any one of claims 1-4, wherein three penetration tools are arranged at 120° intervals around the body circumference, as seen in a tubular crosssectional plane.

6. The device of any one of claims 1-4, wherein four penetration tools are arranged at 90° intervals around the body circumference, as seen in a tubular cross-sectional plane.

7. The device of any one of the preceding claims, wherein the penetration tool comprises a milling tool.

8. A method of centralizing a tubular (1) in a bore (2), character ized by a) arranging a device according to any of claims 1-7 at a predetermined location inside the tubular;

b) extending a plurality of penetration tools (5) radially from the device body (9) and make an opening in respective portions of the tubular (1) while securing at least a portion of the tool to the tubular; and

c) extending at least a portion of the tool a predetermined distance towards a wall (2a) of the bore (2), or until at least one of the tools (5') impi nges on the wall (2a).

9. The method of claim 8, wherein, following step c), extend the tool (5') which impinges on the wall further, whereby the casing is moved as a reaction.

10. The method of claim 8 or claim 9, whereby the device body (9) is disconnected from the tools and retrieved out of the bore upon completion of either step c) or the step described in claim 9.

11. A method of centralizing at least a portion of a tubular (1) in a bore (2), character ized by

a) arranging a device according to any of claims 1-7 at a predetermined first location inside the tubular;

b) extending penetration tools (51) from the device body (41b) to make a first circumferential window (54) in the tubular;

c) installing at least one force member (53), through the fir st window (54), between the tubular outer wall and the bore;

d) relocating said device to a predetermined second location inside the tubular; e) extending penetration tools (51) from the device body (41b) to make a second circumferential window (55) in the tubular; and

f) installing at least one force member (52), through the second window (55), between the tubular outer wall and the bore.