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Title:
WELL TOOL AND METHOD FOR SEVERING AND WITHDRAWING A PIPE SECTION FROM A PIPE STRING IN A WELL
Document Type and Number:
WIPO Patent Application WO/2011/031164
Kind Code:
A1
Abstract:
A well tool (2; 86) and a method for severing and withdrawing a pipe section (16') from a pipe string (16), comprising: a flow-through pipe mandrel (20; 20a, 20b) connected between a work string (6) and a pipe cutter (12); a controllable first gripping means (36, 44) which may be anchored, via controlled relative movement of the pipe mandrel (20; 20a) in a first direction, against the pipe string (16) before and during cutting of the pipe string (16); a controllable second gripping means (56, 64) which may be anchored, via controlled relative movement of the pipe mandrel (20; 20b) in a second direction, against the severed pipe section (16') before and during withdrawing of the pipe section (16'); and a swivel (30) for allowing the pipe mandrel (20; 20a, 20b) to rotate during cutting of the pipe string (16). The well tool (2; 86) comprises, among other things, an expandable sealing body (32) disposed around the pipe mandrel (20; 20a, 20b) and operatively connected to the second gripping means (56, 64) for achieving, upon activation of the second gripping means (56, 64), axial compression and hence radial expansion of the sealing body (32) until sealing contact with the pipe section (16').

Inventors:
FLANDERS BRUCE ALLAN (NO)
Application Number:
PCT/NO2010/000333
Publication Date:
March 17, 2011
Filing Date:
September 09, 2010
Export Citation:
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Assignee:
FLANDERS BRUCE ALLAN (NO)
International Classes:
E21B31/16; E21B29/00
Foreign References:
US4047568A1977-09-13
GB2251015A1992-06-24
Attorney, Agent or Firm:
HÅMSØ PATENTBYRÅ ANS (Sandnes, NO)
Download PDF:
Claims:
C l a i m s

1. A well tool (2; 86) for withdrawing a pipe section (16') severed from a pipe

string (16) in a well, wherein the well tool (2; 86) comprises:

- a flow-through pipe mandrel (20; 20a, 20b) structured for connection between a lower end of a work string (6) and a pipe cutter (12);

- a controllable first gripping means (36, 44) disposed around the pipe mandrel (20; 20a) in an area which, when in its operational position, will be located closest to the pipe cutter (12), wherein the first gripping means (36, 44) is structured for anchoring against the inside of the pipe string (16) through controlled relative movement of the pipe mandrel (20; 20a) in a first direction relative to the first gripping means (36, 44), this anchoring being carried out before and during cutting of the pipe string (16);

- a controllable second gripping means (56, 64) disposed around the pipe mandrel (20; 20b) in an area which, when in its operational position, will be located closest to the work string (6), wherein the second gripping means (56, 64) is structured for anchoring against the inside of the severed pipe section (16') through controlled relative movement of the pipe mandrel (20; 20b) in a second direction, which is opposite the first direction, relative to the second gripping means (56, 64), this anchoring being carried out before and during withdrawing of the pipe section (16'); and

- a swivel (30) disposed around the pipe mandrel (20; 20a, 20b) for allowing the pipe mandrel (20; 20a, 20b) to rotate during cutting of the pipe string (16), c h a r a c t e r i z e d i n that the swivel (30) is disposed between the first gripping means (36, 44) and the second gripping means (56, 64);

- wherein at least one expandable sealing body (32) is disposed around the pipe mandrel (20; 20a, 20b) and between the first gripping means (36, 44) and the second gripping means (56, 64);

- wherein the sealing body (32), at an end located closest to the first gripping means (36, 44), is fixed axially relative to the pipe mandrel (20; 20a, 20b); and

- wherein the sealing body (32), at an end located closest to the second gripping means (56, 64), is operatively connected to the second gripping means (56, 64), whereby activation and anchoring of the second gripping means (56, 64) also causes axial compression and radial expansion of the sealing body (32) until sealing contact with the inside of the severed pipe section (16').

2. The well tool (2) according to claim 1, c h a r a c t e r i z e d i n that said components in the well tool (2) are assembled in one tool part.

3. The well tool (86) according to claim 1, c h a r a c t e r i z e d i n that the well tool (86) is a two-part tool comprising a first tool part (86a) and a separate second tool part (86b);

- wherein the first tool part (86a) comprises said first gripping means (36, 44) and swivel (30); and

- wherein the second tool part (86b) comprises said second gripping means (56, 64) and sealing body (32).

4. The well tool (2; 86) according to claim 1, 2 or 3, c h a r a c t e r i z e d i n that the first gripping means comprises:

- a first support body (36) fixed axially relative to the pipe mandrel (20; 20a) and provided with an axially directed, conical outer surface (42); and

- at least one first gripping element (44) structured so as to be axially movable relative to the first support body (36) and provided with an axially directed, conical inner surface (46) structured for operative cooperation with the outer surface of the first support body (36), whereby the first gripping element (44) is also structured in a manner allowing it to be moved radially upon axial movement of the first gripping element (44); and

- wherein the second gripping means comprises:

- a second support body (56) structured so as to be axially movable relative to the pipe mandrel (20; 20b) and provided with an axially directed, conical outer surface (62); and

- at least one second gripping element (64) structured so as to be axially movable relative to the second support body (56) and provided with an axially directed, conical inner surface (66) structured for operative cooperation with the outer surface (62) of the second support body (56), whereby the second gripping element (64) is also structured in a manner allowing it to be moved radially upon axial movement of the second gripping element (64).

5. The well tool (2; 86) according to claim 4, c h a r a c t e r i z e d i n that the at least one first gripping element (44) is operatively connected to at least one first friction element (78);

- wherein the at least one second gripping element (64) is operatively connected to at least one second friction element (84); and

- wherein the first friction element (78) and the second friction element (84) are structured for stabilizing frictional contact with the inside of the pipe string (16).

6. The well tool (2; 86) according to claim 5, c h a r a c t e r i z e d i n that the friction element (78, 84) is spring-loaded for resilient frictional contact with the inside of the pipe string (16).

7. The well tool (2; 86) according to any one of claims 1-6,

c h a r a c t e r i z e d i n that the first gripping means (36, 44) is operatively connected to a first movement restriction means (74) disposed between the first gripping element (44) and the pipe mandrel (20; 20a), wherein the first movement restriction means (74) is structured in a manner allowing it to counteract anchoring relative movement between the first gripping element (44) and the pipe mandrel (20; 20a) during insertion of the well tool (2; 86) into the pipe string (16), and wherein the first movement restriction means (74) is also structured in a manner allowing it to promote anchoring relative movement between the first gripping element (44) and the pipe mandrel (20; 20a) for anchoring of the first gripping means (36, 44); and

- wherein the second gripping means (56, 64) is operatively connected to a second movement restriction means (80) disposed between the second gripping element (64) and the pipe mandrel (20; 20b), wherein the second movement restriction means (80) is structured in a manner allowing it to counteract anchoring relative movement between the second gripping element (64) and the pipe mandrel (20; 20b) during insertion of the well tool (2; 86) into the pipe string (16), and wherein the second movement restriction means (80) is also structured in a manner allowing it to promote anchoring relative movement between the second gripping element (64) and the pipe mandrel (20; 20b) for anchoring of the second gripping means (56, 64).

8. The well tool (2; 86) according to claim 7, c h a r a c t e r i z e d i n that each of the first and second movement restriction means is comprised of an automatic nut (74, 80).

9. The well tool (2; 86) according to any one of claims 1-8,

c h a r a c t e r i z e d i n that the sealing body (32) is disposed between the swivel (30) and the first gripping means (36, 44).

10. The well tool (2; 86) according to any one of claims 1-8,

c h a r a c t e r i z e d i n that the sealing body (32) is disposed between the swivel (30) and the second gripping means (56, 64). A method for severing and withdrawing a pipe section (16') from a pipe string (16) in a well, c h a r a c t e r i z e d i n that the method comprises the following steps:

(A) using a well tool (2; 86) according to any one of claims 1-10;

(B) connecting the well tool (2; 86) between a lower end of a work string (6) and a pipe cutter (12) so as to provide an assembly thereof;

(C) inserting said assembly into the pipe string (16) to a desired cutting position;

(D) in a controlled manner, moving the pipe mandrel (20; 20a) relative to the first gripping means (36, 44) in a first direction; the relative movement of which causes anchoring of the first gripping means (36, 44) against the inside of the pipe string (16);

(E) via the work string (6), the swivel (30) and the pipe mandrel (20; 20a, 20b), activating and rotating the pipe cutter (12) until the pipe section (16') is severed from the pipe string (16), and then deactivating the pipe cutter (12);

(F) in a controlled manner, moving the pipe mandrel (20; 20b) relative to the second gripping means (56, 64) in a second direction, which is opposite the first direction; the relative movement of which releases the first gripping means (36, 44) from its anchoring against the inside of the severed pipe section (16'); the relative movement of which causes anchoring of the second gripping means (56, 64) against the inside of the pipe section (16'); and the relative movement of which simultaneously causes axial compression and radial expansion of said sealing body (32) until sealing contact with the inside of the severed pipe section (16'); and

(G) withdrawing the severed pipe section (16') from the well.

The method according to claim 11, c h a r a c t e r i z e d i n that the method, between steps (E) and (F), also comprises a step of moving the well tool (2; 86) to a shallower position in the severed pipe section (16').

The method according to claim 11 or 12, c h a r a c t e r i z e d i n that the method, between steps (F) and (G), also comprises a step of pumping a well fluid through the pipe mandrel (20; 20a, 20b) of the well tool (2; 86) and outwards into the well at a position which will be located deeper than the position of the expanded sealing body (32), the pumping of which allows the well fluid to circulate on the outside of the severed pipe section (16') and upwards through the well. The method according to claim 11, 12 or 13, c h a r a c t e r i z e d i n that step (G) also comprises pumping a well fluid through the pipe mandrel (20; 20a, 20b) of the well tool (2; 86) and outwards into the well at a position which will be located deeper than the position of the expanded sealing body (32), the pumping of which supplies an upwardly directed pressure force to the expanded sealing body (32), the force of which assists the withdrawing of the severed pipe section (16') from the well.

Description:
WELL TOOL AND METHOD FOR SEVERING AND WITHDRAWING A PIPE SECTION FROM A PIPE STRING IN A WELL

Field of the invention

The present invention concerns a well tool for withdrawing a pipe section severed from a pipe string in a well. The invention also concerns a method for severing and withdrawing said pipe section in the well.

Background of the invention

In some well contexts it is necessary to sever and withdraw at least one section of one or more pipe strings in a subsurface well, for example a petroleum well. It may relate to plugging and abandoning of a well, or it may relate to re-drilling or sidetracking of a longitudinal section of the well. It may also be advantageous or necessary to sever the particular pipe string as deep as possible in the well.

In context of plugging and abandoning a production well, for example, it may thus relate to severing of a production tubing as deep as possible to be able to isolate one or more reservoir section in the well.

For the severing of such pipe strings in a well, normally a pipe cutter of a suitable type is used and is attached to a drill string and lowered down to the particular cutting location in the well. For example, the pipe cutter may be mechanically operated or hydraulically operated. It is customary to use a hydraulically operated, rotatable pipe cutter provided with at least one radially movable cutting arm for cutting through one or more pipe strings.

However, the prior art solutions for severing and removing one or more pipe sections from a well are encumbered with a number of problems and disadvantages of a technical, safety- related and economical nature. As such, there is a need in the industry for remedying these problems and disadvantages of the prior art. This is what the present technical solution seeks to remedy through more simple, more flexible and more effective technical solutions.

Prior art and disadvantages thereof

A prior art cutting solution requires two or more trips into the well in order to cut and remove a pipe section from one or more pipe strings in the well. This is particularly relevant in context of shallow cutting and removing of pipe sections, i.e. when the cutting is carried out piece by piece from the top of one or more pipe strings. In this context, the pipe cutter is inserted some distance into the pipe string, whereupon a section of the pipe cutter is anchored temporarily at an upper end of the pipe string. Then the pipe string is severed, and the pipe cutter is pulled out of the well. A suitable gripping tool is then inserted into the well in order to grip the severed pipe section and to pull the pipe section out of the well.

In context of deeper cutting of a pipe string, however, it is customary to insert an assembly of an anchoring device and a pipe cutter. Thereby, the cutting and withdrawing of the severed pipe section may be carried out using only one trip into the well. During the insertion to the desired cutting location, such an assembly will typically be attached to the lower end of a drill string. At the cutting location the anchoring device is released, whereupon associated, radially movable and wedge- shaped gripping elements are activated and brought into engagement with the inside of the pipe string. This constitutes well-known activation technology. Then, whilst disposed in this anchoring position, the pipe cutter is activated and severs the pipe string. The pipe cutter may be operated through rotation of the drill string, or by means of a downhole motor attached to the drill string. Thereafter, the severed pipe section may be pulled out of the well by means of the drill string.

Such an assembly of an anchoring device and a pipe cutter is described, for example, in US 4.969.514 (Morris et al.) and in US 4.047.568 (Aulenbacher).

In US 4.969.514, the wedge-shaped gripping elements of the anchoring device are activated by moving the drill string upwards, whereby the gripping elements remain anchored against the pipe string as long as a so-called overpull is maintained in the drill string. This technique is most common in context of cutting pipe strings.

In US 4.047.568, however, the gripping elements are activated by moving the drill string downwards. The purpose of this cutting solution is, among other things, to ensure that the pipe cutter does not move during cutting of the pipe string. This cutting solution is also considered to represent the closest prior art with respect to the present invention.

However, none of the prior art cutting solutions comprise a seal capable of sealing against the surrounding pipe string after cutting of the pipe string. By means of such a seal, it will be possible to circulate a well fluid, for example drilling mud, down through the drill string, past the seal, outwards to the outside of the severed pipe section and further upwards through the well to the surface thereof. By so doing, it will be possible, if required, to circulate the well clean of undesired fluid influxes and possibly introduce a kill mud into the well. Without such a seal, it will not be possible to carry out effective circulation of said well fluid throughout the well, insofar as the well fluid also may be able to flow between said anchoring device and the pipe string and further upwards through the pipe string.

By means of such a seal, it will also be possible to supply an upwardly directed pressure force to the seal, the force of which assists the withdrawing of the severed pipe section from the well. Without such a seal, it will not be possible to supply an assisting pressure force to the pipe section, the force of which facilitates the withdrawing of the pipe section.

Said possibilities achieved by using such a seal therefore are of great significance for the safety, efficiency and economy of such cutting operations.

Objects of the invention

The primary object of the invention is to avoid or reduce the above-mentioned disadvantages associated with the prior art.

A more specific object of the invention is to be able to circulate a well fluid, for example drilling mud, through the well after cutting of a pipe string.

A further object of the invention is to be able to supply an assisting pressure force to the severed pipe section, the force of which facilitates the withdrawing of the pipe section.

Description of how the objects are achieved

The objects are achieved by virtue of features disclosed in the following description and in the subsequent claims.

According to a first aspect of the present invention, a well tool for withdrawing a pipe section severed from a pipe string in a well is provided. The well tool comprises the following components:

- a flow-through pipe mandrel structured for connection between a lower end of a work string and a pipe cutter;

- a controllable first gripping means disposed around the pipe mandrel in an area which, when in its operational position, will be located closest to the pipe cutter, wherein the first gripping means is structured for anchoring against the inside of the pipe string through controlled relative movement of the pipe mandrel in a first direction relative to the first gripping means, this anchoring being carried out before and during cutting of the pipe string;

- a controllable second gripping means disposed around the pipe mandrel in an area which, when in its operational position, will be located closest to the work string, wherein the second gripping means is structured for anchoring against the inside of the severed pipe section through controlled relative movement of the pipe mandrel in a second direction, which is opposite the first direction, relative to the second gripping means, this anchoring being carried out before and during withdrawing of the pipe section; and

- a swivel disposed around the pipe mandrel for allowing the pipe mandrel to rotate during cutting of the pipe string.

The distinctive characteristic of the well tool is that the swivel is disposed between the first gripping means and the second gripping means;

- wherein at least one expandable sealing body is disposed around the pipe mandrel and between the first gripping means and the second gripping means;

- wherein the sealing body, at an end located closest to the first gripping means, is fixed axially relative to the pipe mandrel; and

- wherein the sealing body, at an end located closest to the second gripping means, is operatively connected to the second gripping means. Thereby, activation and anchoring of the second gripping means also causes axial compression and radial expansion of the sealing body until sealing contact with the inside of the severed pipe section.

Hereinafter, references to downwardly directed, upwardly directed, upper and lower will refer to directions or positions relative to the surface of the well.

Said relative movement between the pipe mandrel and said gripping means may be achieved through axial movement or rotation of the pipe mandrel relative to the particular gripping means. In one embodiment, said components in the well tool may be assembled in one tool part.

In another embodiment, the well tool may be a two-part tool comprising a first tool part and a separate second tool part;

- wherein the first tool part comprises said first gripping means and swivel; and

- wherein the second tool part comprises said second gripping means and sealing body.

Further, the first gripping means may comprise:

- a first support body fixed axially relative to the pipe mandrel and provided with an axially directed, conical outer surface; and

- at least one first gripping element structured so as to be axially movable relative to the first support body and provided with an axially directed, conical inner surface structured for operative cooperation with the outer surface of the first support body. Thereby, the first gripping element is also structured in a manner allowing it to be moved radially upon axial movement of the first gripping element.

In this context, the second gripping means may comprise:

- a second support body structured so as to be axially movable relative to the pipe mandrel and provided with an axially directed, conical outer surface; and

- at least one second gripping element structured so as to be axially movable relative to the second support body and provided with an axially directed, conical inner surface structured for operative cooperation with the outer surface of the second support body. Thereby, the second gripping element is also structured in a manner allowing it to be moved radially upon axial movement of the second gripping element.

Such a gripping element may be formed as a wedge ("slips") provided with external teeth, gripping surfaces or similar structured in a manner allowing them to grip in an anchoring manner into the internal pipe wall of the pipe string upon outwardly directed, radial movement of the gripping element.

This at least one first gripping element may also be operatively connected to at least one first friction element, whereas the at least one second gripping element may be operatively connected to at least one second friction element, wherein the first friction element and the second friction element may be structured for stabilizing frictional contact with the inside of the pipe string. Such a friction element may also be spring-loaded for resilient frictional contact with the inside of the pipe string. This spring-loaded friction element is commonly termed as a friction block in this technical field.

Yet further, the first gripping means may also be operatively connected to a first movement restriction means disposed between the first gripping element and the pipe mandrel, wherein the first restriction means is structured in a manner allowing it to counteract anchoring relative movement between the first gripping element and the pipe mandrel during insertion of the well tool into the pipe string, and wherein the first restriction means is also structured in a manner allowing it to promote anchoring relative movement between the first gripping element and the pipe mandrel for anchoring of the first gripping means.

In this context, the second gripping means will be operatively connected to a second movement restriction means disposed between the second gripping element and the pipe mandrel, wherein the second movement restriction means is structured in a manner allowing it to counteract anchoring relative movement between the second gripping element and the pipe mandrel during insertion of the well tool into the pipe string, and wherein the second movement restriction means is also structured in a manner allowing it to promote anchoring relative movement between the second gripping element and the pipe mandrel for anchoring of the second gripping means.

For example, the first and the second movement restriction means may be comprised of a so-called automatic nut. Typically, such an automatic nut will comprise internal, spring-loaded thread elements peripherally distributed along the inner circumference of the nut. These thread elements are structured for contact with an external thread area on the pipe mandrel. Upon rotating the pipe mandrel in one direction of rotation, the automatic nut simultaneously moves in one particular axial direction so as to drive the associated gripping elements radially outwards until anchoring engagement with the surrounding pipe string. A subsequent release of the gripping elements is achieved by moving the pipe mandrel in the same axial direction, and without rotation thereof. Given that the internal thread elements of the automatic nut are spring-loaded, they will be able to move some distance radially outwards and thus will slide over the external thread area of the pipe mandrel when the pipe mandrel is moved axially for release of the gripping elements.

When the movement restriction means are comprised of a first and a second automatic nut, the thread elements in the respective automatic nut, and in the respective thread area on the outside of the pipe mandrel, must necessarily have opposite thread directions. This is necessary for allowing the first gripping means to be activated and set through rotation of the pipe mandrel in one direction of rotation, and for allowing the second gripping means to be activated and set through rotation of the pipe mandrel in an opposite direction of rotation. This is also necessary for allowing the first gripping means to be released through movement of the pipe mandrel in one axial direction, and for allowing the second gripping means to be released through movement of the pipe mandrel in an opposite axial direction.

In order to avoid simultaneous rotation of the respective gripping elements upon rotation of the pipe mandrel, the gripping elements may be connected to said friction elements, for example in the form of friction blocks.

Further, said sealing body may be disposed between the swivel and the first gripping means, or between the swivel and the second gripping means.

Moreover, said pipe cutter may be comprised of a hydraulically operated and rotatable pipe cutter provided with at least one movable cutting arm for cutting through the pipe string.

As an alternative, the pipe cutter may be comprised of a hydraulically operated and rotatable pipe cutter provided with at least one high-pressure jet nozzle for cutting through the pipe string.

As a further alternative, the pipe cutter may be comprised of a mechanically operated and rotatable pipe cutter provided with at least one radially movable cutting arm for cutting through the pipe string.

Furthermore, said work string may be comprised of a drill string.

According to a second aspect of the present invention, a method for severing and withdrawing a pipe section from a pipe string in a well is provided.

The distinctive characteristic of the method is that it comprises the following steps:

(A) using a well tool according to the first aspect of the present invention;

(B) connecting the well tool between a lower end of a work string and a pipe cutter so as to provide an assembly thereof;

(C) inserting said assembly into the pipe string to a desired cutting position;

(P) in a controlled manner, moving the pipe mandrel relative to the first gripping means in a first direction; the relative movement of which causes anchoring of the first gripping means against the inside of the pipe string; (E) via the work string, the swivel and the pipe mandrel, activating and rotating the pipe cutter until the pipe section is severed from the pipe string, and then deactivating the pipe cutter;

(F) in a controlled manner, moving the pipe mandrel relative to the second gripping means in a second direction, which is opposite the first direction; the relative movement of which releases the first gripping means from its anchoring against the inside of the severed pipe section; the relative movement of which causes anchoring of the second gripping means against the inside of the pipe section; and the relative movement of which simultaneously causes axial compression and radial expansion of said sealing body until sealing contact with the inside of the severed pipe section; and

(G) withdrawing the severed pipe section from the well.

Between steps (E) and (F), the method may also comprise a step of moving the well tool to a shallower position in the severed pipe section. This may prove very useful if the severed pipe section is stuck in the well and cannot be released after the severing. Then the well tool may be released and moved to a shallower position in the pipe section where a new cut is carried out. This may possibly be repeated several times, if required.

Movement of the well tool to a shallower position in the pipe section may also be used in order to obtain a safety advantage. This is related to the fact that the shear ram in the well's blowout preventer ("BOP"), when in an emergency situation, may

experience big problems and possibly fail during attempts of cutting through a pipe string containing the well tool or its work string. For example, by anchoring the well tool in immediate vicinity of the upper end of the pipe section before withdrawing the pipe section, only a short longitudinal interval of the pipe section will contain the well tool and some of the work string. It is possible to pull this short longitudinal section quickly through the well's blowout preventer. By so doing, the risk of malfunction in the blowout preventer is reduced substantially.

Further, between steps (F) and (G), the method may also comprise a step of pumping a well fluid through the pipe mandrel of the well tool and outwards into the well at a position which will be located deeper than the position of the expanded sealing body. Such a pumping will allow the well fluid to circulate on the outside of the severed pipe section and upwards through the well.

Thereby, it will be possible to circulate a well fluid, for example drilling mud, down through the drill string, past the expanded sealing body, outwards to the outside of the severed pipe section and further upwards through the well to the surface thereof. By so doing, it will also be possible, if required, to circulate the well clean of undesired fluid influxes, for example hydrocarbons, and possibly introduce a kill mud into the well.

Yet further, step (G) of the method may also comprise pumping a well fluid through the pipe mandrel of the well tool and outwards into the well at a position which will be located deeper than the position of the expanded sealing body. Such a pumping will supply an upwardly directed pressure force to the expanded sealing body, the force of which assists the withdrawing of the severed pipe section from the well.

Hereinafter, non-limiting exemplary embodiments of the present invention will be shown.

Short description of the figures of the exemplary embodiments

Figure 1 shows, in front elevation and partial cross section, a first embodiment of the present well tool when running a casing into a well;

Figure 2 shows the well tool according to figure 1 after having anchored a first anchor against the inside of the casing before and during cutting of the casing;

Figure 3 shows the well tool according to figure 1 after having released the first anchor and after having set an assembly of a second anchor and an expandable packer against the inside of the severed pipe section before and during withdrawing of the pipe section;

Figure 4 shows, in front elevation and smaller scale, the well tool connected to a hydraulic pipe cutter at the lower side thereof, and to a drill string at the upper side thereof, among other things;

Figure 5 shows, in front elevation, the well tool according to figure 4, but wherein a downhole motor is disposed between the well tool and the hydraulic pipe cutter for rotation of the pipe cutter;

Figure 6 shows, in front elevation and smaller scale, a second embodiment of the present well tool, wherein a bumper sub is disposed between the first anchor of the well tool and the assembly of the second anchor and the expanded packer, and wherein figure 6 also shows (with a dashed line) section cut VII and VIII of the well tool; Figure 7 shows, in larger scale, a section cut VII of the first anchor, among other things, of the well tool according to figure 6; and

Figure 8 shows, in larger scale, a section cut VIII of the assembly of the second anchor and said packer, among other things, of the well tool according to figure 6.

In order to facilitate the comprehension of the invention, the figures are drawn somewhat simplified and show only the most essential components and elements of the present well tool. The shape, relative dimensions and mutual positions of the components and elements may also be somewhat distorted. In the following, identical, similar or corresponding details of the figures will be denoted substantially with the same reference numerals.

Description of the exemplary embodiments

Reference is first made to figure 4, which is an overview drawing showing, among other things, a first embodiment of a well tool 2 according to the invention. In this embodiment, all components of the well tool 2 are assembled in one tool part. At its upper side, the well tool 2 is connected in flow-through manner to a first bumper sub 4 and a work string, which in this embodiment is comprised of a drill string 6 comprising drill collars 8 and drill pipes 10. At its lower side, the well tool 2 is connected in flow-through manner to a hydraulic pipe cutter 12. This pipe cutter 12 also comprises hydraulically activated, radially movable cutting arms 14 for cutting through a pipe string 16 (not shown in these figures), which may consist of a number of interconnected casings or production tubings. By pumping a fluid, for example drilling mud, through the drill string 6 and onwards to the pipe cutter 12, the cutting arms 14 are moved radially outwards until contact with the pipe string 16. Whilst disposed in this position, the drill string 6, and hence the pipe cutter 12 and its cutting arms 14, is then rotated so as to eventually cut through the pipe string 16.

Figure 5 also shows the latter assembly of components, but wherein the assembly also comprises a downhole motor 18 for rotation of the pipe cutter 12 during cutting of the pipe string 16. The downhole motor 18 is disposed between the well tool 2 and the hydraulic pipe cutter 12 and is operated by virtue of a fluid, for example drilling mud, being pumped through the drill string 6 and onwards to the motor 18 for rotation of the pipe cutter 12.

Said bumper sub 4, drill collars 8, drill pipes 10, hydraulic pipe cutter 12 and downhole motor 18 constitute prior art equipment and hence will not be discussed in further detail herein. Reference is now made to figures 1-3 showing, in front elevation and partial cross section, details of the first embodiment of the well tool 2. For the sake of simplicity, the well tool 2 is shown disconnected from the other equipment mentioned at the beginning.

Figure 1 shows the well tool 2 when running the pipe string 16 into a well. Figure 2 shows the well tool 2 anchored against the inside of the pipe string 16 before and during cutting thereof, whilst figure 3 shows the well tool 2 anchored against the inside of a pipe section 16' severed from the pipe string 16 before and during withdrawing of the pipe section 16'.

The well tool 2 is constructed around a central, flow-through pipe mandrel 20, the upper end of which is formed as a threaded box 22, and the lower end of which is formed as a threaded pin 24. When in its operational position in the pipe string 16, the threaded box 22 will be connected to a corresponding threaded pin on the bumper sub 4, whereas the threaded pin 24 will be connected to a corresponding threaded box on the pipe cutter 12 (cf. figure 4), or on the downhole motor 18 (cf. figure 5).

A controllable first anchor 26 is disposed around the pipe mandrel 20 in a lower area thereof. The first anchor 26 is structured for anchoring against the inside of the pipe string 16 before and during cutting of the pipe string 16. This anchoring is achieved through controlled movement of the pipe mandrel 20 in a first direction. This will be explained in further detail in the following.

Moreover, a contollable second anchor 28 is disposed aroung the pipe mandrel 20 in an upper area of the pipe mandrel 20. The second anchor 28 is structured for anchoring against the inside of the severed pipe section 16' before and during withdrawing of the pipe section 16'. This anchoring is achieved through controlled movement of the pipe mandrel 20 in a second direction, which is opposite said first direction. Also this will be explained in further detail in the following.

For allowing the pipe mandrel 20 and thus the pipe cutter 12 to rotate during cutting of the pipe string 16, a marine swivel 30 is disposed around the pipe mandrel 20, and between the first anchor 26 and the second anchor 28. In this context, the first anchor 26 is structured in a manner allowing it to remain at rest whilst the pipe mandrel 20 is being rotated. The marine swivel 30 comprises a heavy-duty thrust bearing structured in a manner allowing it to withstand the loads and ambient conditions prevailing down within a well. Such swivels constitute prior art and will not be discussed in further detail herein. An expandable packer 32 is also disposed around the pipe mandrel 20, and between the swivel 30 and the second anchor 28. The packer 32, which for example may be formed from an elastomer material, is structured so as to be axiaily movable relative to the pipe mandrel 20. At its lower end, the packer 32 bears against a shoulder 34 formed on the pipe mandrel 20. Thereby, the packer 32 is fixed axiaily relative to the pipe mandrel 20. At its opposite end, the packer 32 is operatively connected to the second anchor 28. Activation and anchoring of the second anchor 28 through upwardly directed, axial movement of the pipe mandrel 20 will thus cause axial compression and radial expansion of the packer 32 until sealing contact with the inside of the severed pipe section 16'.

The first anchor 26 comprises, among other things, a first support ring 36 fixed axiaily relative to the pipe mandrel 20. For this purpose, the support ring 36 is provided with an internal ring groove 38 attached in a rotatable manner around an external ring 40 on the pipe mandrel 20. The support ring 36 is also provided with an axiaily directed, conical outer surface 42, the diameter of which diminishes in the downward direction in figures 1-3. At its opposite upper end, the support ring 36 bears against the swivel 30.

Further, the first anchor 26 also comprises four first gripping wedges ("slips") 44, for which only three gripping wedges 44 are shown in figures 1-3. The first gripping wedges 44 are structured so as to be axiaily movable relative to the first support ring 36. Each gripping wedge 44 is also provided with an axiaily directed, conical inner surface 46, the diameter of which diminishes in the downward direction in figures 1-3. The conical inner surfaces 46 of the gripping wedges 44 are structured for operative cooperation with the conical outer surface 42 of the support ring 36. Thereby, the first gripping wedges 44 are also structured in a manner allowing them to be moved radially during axial movement thereof on the outside of the conical outer surface 42. At their outermost portions, the gripping wedges 44 are provided with external, tooth- provided gripping surfaces 48. These gripping surfaces 48 are structured in a manner allowing them to grip in an anchoring manner into the internal pipe wall of the pipe string 16 upon outwardly directed, radial movement of the gripping wedges 44, as shown in figure 2. In order to avoid that the gripping wedges 44 disengage from the support ring 36 upon upwardly directed movement along the support ring 36, each gripping wedge 44 is connected to the support ring 36 via an axiaily extending dovetail joint 50, which is a type of spline connection. The first gripping wedges 44 are structured so as to be axially movable relative to the support ring 36. This is achieved by virtue of a lower end of each gripping wedge 44 being rotatably connected, via a first link 51, to an upper end of a first attachment sleeve 52 disposed in an an axially movable manner around the pipe mandrel 20. The gripping wedges 44 are equally distributed around the attachment sleeve 52. A lower shoulder 54 on the pipe mandrel 20 restricts the axial movement of the attachment sleeve 52 in the downward direction.

The second anchor 28 of the well tool 2 will be described now.

The second anchor 28 comprises, among other things, a second support ring 56 attached at the upper end of the packer 32. At its lower end, the support ring 56 is provided with a locking ring 58 structured in a manner allowing it to be locked within an external locking groove 60 on the pipe mandrel 20 upon axial compression of the packer 32, as shown in figure 3. Moreover, the second support ring 56 is structured so as to be axially movable relative to the pipe mandrel 20. The support ring 56 is also provided with an axially directed, conical outer surface 62, the diameter of which diminishes in the upward direction in figures 1-3.

Similar to the first anchor 26, the second anchor 28 comprises four second gripping wedges ("slips") 64, for which only three gripping wedges 64 are shown in figures 1-3. The second gripping wedges 64 are structured so as to be axially movable relative to the second support ring 56. Each gripping wedge 64 is provided with an axially directed, conical inner surface 66, the diameter of which diminishes in the upward direction in figures 1-3. The conical inner surfaces 66 of the gripping wedges 64 are structured for operative cooperation with the conical outer surface 62 of the support ring 56. Thereby, the second gripping wedges 64 are also structured in a manner allowing them to be moved radially during axial movement thereof on the outside of the conical outer surface 62. At their outermost portions, the gripping wedges 64 are provided with external, tooth-provided gripping surfaces 68. These gripping surfaces 68 are structured in a manner allowing them to grip in an anchoring manner into the internal pipe wall of the severed pipe section 16' upon outwardly directed, radial movement of the gripping wedges 64, as shown in figure 3. In this context, the axial movement of the gripping wedges 64 will be downwardly directed, whereby the gripping wedges 64 rest on the support ring 56. For this reason, a dovetail joint or similar is not required for the second anchor 28.

Also similar to the first anchor 26, the second gripping wedges 64 are structured so as to be axially movable relative to the support ring 56. This is achieved by virtue of an upper end of each gripping wedge 64 being rotatably connected, via a second link 69, to a lower end of a second attachment sleeve 70 disposed in an an axially movable manner around the pipe mandrel 20. The gripping wedges 64 are equally distributed around the attachment sleeve 70. An upper shoulder 72 on the pipe mandrel 20 restricts the axial movement of the attachment sleeve 70 in the upward direction.

Further details of the first attachment sleeve 52 will be described now.

The first attachment sleeve 52 is also provided with a first movement restriction means in the form of an internal first automatic nut 74, which includes spring-loaded thread elements. The construction and manner of operation of such an automatic nut is described above. The automatic nut 74 is structured for cooperation with an external first thread area 76 on the pipe mandrel 20. Furthermore, the attachment sleeve 52 is provided with a number of first friction elements in the form of four external first friction blocks 78 qually distributed around the attachment sleeve 52, for which only three friction blocks 78 are shown in figures 1-3. Each friction block 78 is spring-loaded for resilient contact with the inside of the pipe string 16. When the pipe mandrel 20 is rotated in a first direction of rotation, the automatic nut 74, and hence the attachment sleeve 52 and the first gripping wedges 44, will move in an axial upward direction at the same time as the gripping wedges 44 are driven radially outwards until anchoring engagement with the pipe string 16 (cf. figure 2). This situation is controlled through the thread direction for the automatic nut 74 and the thread area 76. Upon rotation of the pipe mandrel 20, the friction blocks 78 will prevent simultaneous rotation of the gripping wedges 44. A subsequent release of the first gripping wedges 44 is achieved by moving the pipe mandrel 20 axially in the upward direction, and without rotation of the pipe mandrel 20. Given that the internal thread elements of the automatic nut 74 are spring-loaded, they will be able to move some distance radially outwards and thus will slide over the external thread area 76 of the pipe mandrel 20 when the pipe mandrel 20 is moved in the upward direction. This manner of operation also renders possible to rotate the pipe mandrel 20 for cutting of the pipe string 16 after having set the first gripping wedges 44 against the pipe string 16.

Further details of the second attachment sleeve 70 will be described now.

Similar to the first attachment sleeve 52, the second attachment sleeve 70 is provided with a second movement restriction means in the form of an internal second automatic nut 80, which includes spring-loaded thread elements. The construction and manner of operation of such an automatic nut is described above. The automatic nut 80 is structured for cooperation with an external second thread area 82 on the pipe mandrel 20. The thread direction for the automatic nut 80 and the thread area 82 is opposite of the thread direction for the automatic nut 74 and the thread area 76. The attachment sleeve 70 is also provided with a number of second friction elements in the form of four external second friction blocks 84 qually distributed around the

attachment sleeve 70, for which only three friction blocks 84 are shown in figures 1-3. Each friction block 84 is spring-loaded for resilient contact with the inside of the severed pipe section 16'. When the pipe mandrel 20 is rotated in a second direction of rotation, which is opposite the first direction of rotation, the automatic nut 80, and hence the attachment sleeve 70 and the first gripping wedges 64, will move in an axial downward direction at the same time as the gripping wedges 64 are driven radially outwards until anchoring engagement with the severed pipe section 16' (cf. figure 3). In other words, this situation is controlled through the opposite thread direction for the automatic nut 80 and the thread area 82. Upon rotation of the pipe mandrel 20, the friction blocks 84 will prevent simultaneous rotation of the gripping wedges 64. A subsequent release of the second gripping wedges 64 is achieved by moving the pipe mandrel 20 axially in the downward direction, and without rotation of the pipe mandrel 20. Given that the internal thread elements of the automatic nut 80 are spring-loaded, they will be able to move some distance radially outwards and thus will slide over the external thread area 82 of the pipe mandrel 20 when the pipe mandrel 20 is moved in the downward direction.

Reference is now made to figures 6-8, which show a second embodiment of a well tool 86 according to the invention. In this embodiment, the well tool 86 is a two-part tool comprising a first tool part 86a and a separate second tool part 86b. The first tool part 86a comprises the first anchor 26, the swivel 30 and a separate pipe mandrel 20a, whereas the second tool part 86b comprises the second anchor 28, the expandable packer 32 and a separate pipe mandrel 20b. These two separate pipe mandrels 20a, 20b are operatively connected via a flow-through second bumper sub 88 (cf. figure 6). Moreover, the components of this well tool 86 are equal to the components of the well tool 2 according to the first embodiment of the invention. Therefore, the manner of operation of the well tool 86 is equal to the manner of operation of the well tool 2. Figure 7 shows details of the first tool part 86a, the upper end of which is formed as a threaded box 90, and the lower end of which is formed as a threaded pin 92. Figure 8 shows details of the second tool part 86b, the upper end of which is formed as a threaded box 94, and the lower end of which is formed as a threaded pin 96.




 
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