WO2020190148A1

WO2020190148A1 - Cutting apparatus

Info

Publication number: WO2020190148A1
Application number: PCT/NO2020/050075
Authority: WO
Inventors: Anders Sandvik
Original assignee: Deepocean As
Priority date: 2019-03-19
Filing date: 2020-03-17
Publication date: 2020-09-24
Also published as: NO20190374A1; NO345293B1

Abstract

A cutting apparatus (1) comprising an elongated frame (11) which is rotatable around a centre axis (18) and is provided with a first end portion (111) and a second end portion (112), a drive station (16) for a continuous cutting wire (17) arranged at the second end portion (112), the cutting wire (17) extending between the drive station (16) and a curved return element (121) arranged at the first end portion (111) of the frame (11), a wire guide (15) being arranged to guide the cutting wire (17) from a direction substantially parallel to the centre axis (18) of the frame (11) to a direction coinciding with a plane which is perpendicular to the centre axis (18), the return element (121) for the cutting wire (17) being displaceable between an inoperative position, in which the return element (121) is arranged in the frame (11), and an operative position, in which the return element (121) projects from the frame (11) with a curve centre axis (1211) substantially parallel to the centre axis (18) of the frame (11), and the return element (121) having a thickness that is smaller than a cutting- wire diameter (D).

Description

CUTTING APPARATUS

A cutting apparatus is described, more particularly a cutting apparatus comprising an elongated frame which is provided with a first end portion and a second end portion, and a drive station for a cutting wire arranged at the second end portion. When a hydrocarbon well has been shut down, there is a need to remove both the wellhead with associated surface installations (including installations placed on a sea bed at a subsea well) and the installations downhole, including at least some of the casing of the wellbore. Removal of the casing is necessary to allow the well to be plugged; that is to say, sealed so that there is no leakage to the surface because of pressure build-up in the formations surrounding the well.

To make it possible for parts of a casing to be pulled out of a wellbore, the casing must be cut into suitable lengths before it is pulled out of the wellbore. Cutting a cas ing is demanding, especially when it is the upper portions of the casing that are to be removed. As is known, a multilayer casing extends a long way down the wellbore from the wellhead, and there may be a need to cut through a triple to quintuple pipe wall with a pipe-wall thickness of over 25 mm and through several annuli filled with cured cement.

Various cutting techniques are used, but because of the restricted space available in the innermost casing downhole, maybe with only a circular cross section of about 20 cm, cutting with an abrasive liquid under high pressure, a so-called abrasive water jet, is almost universal. It is a time-consuming operation, and it is not unusual for it to take between 10 and 50 hours to cut loose a casing section. A major drawback of this cutting technique is that it cannot be known for certain that the cut is complete before the pulling of the casing section starts. When great force is basically required for a casing section to be pulled loose from the cement in the surrounding annulus, it will be difficult to have a reliable indication of whether it is just the cement that is firmly hold ing the casing section, or whether it is lack of cutting through that is preventing or inhibiting the pulling.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

The object is achieved through the features that are specified in the description below and in the claims that follow.

The invention provides a cutting apparatus which is provided with an elongated frame which is rotatable around a centre axis. In a first end portion, the frame is provided with a curved return element for a cutting wire, typically formed as a return pulley or an element with a curved side edge where several supporting rollers are supported, the return element being displaceable perpendicularly to the centre axis between an inoperative, first position, in which the return element is arranged in the frame, and a second, operative position, in which the return element projects from the end portion with a curve centre axis substantially parallel to the centre axis of the frame.

In the frame, there are arranged several wire guides arranged to support the cutting wire. The wire guides may be formed as guide pulleys, especially where the cutting wire bends and changes direction.

The cutting wire is typically a continuous, diamond-coated wire.

The return element may be arranged on an end portion of an elongated, sword-shaped arm which is connected to a linear actuator arranged to move the arm and the return element between the first and second positions of the return element and also position the return element in any intermediate position. The arm is bendable in a direction perpendicular to the centre axis of the frame and the longitudinal direction of the arm. The arm may be articulated; that is to say, be composed of several interconnected arm sections rotatable around rotational axes lying in planes that are perpendicular to the centre axis of the frame and the longitudinal direction of the arm. The arm and the return element have a thickness, that is to say an extent in the centre-axis direction of the frame, which is smaller than the effective diameter of the cutting wire, that is to say the width of a groove formed by the cutting wire as it cuts into an element.

The upper end portion of the frame preferably forms an abutment which is arranged to rest supportingly against an upper portion of the casing of a well or against a well head. The abutment may be displaceable along the frame.

The frame is rotatable around its longitudinal axis. The rotation is preferably provided by a rotation actuator forming a connection between the frame and the abutment.

It is an advantage if a slew ring is arranged between the frame and the abutment.

A drive station which is arranged to move the cutting wire in the longitudinal direction of the cutting wire is arranged at a second end portion of the frame, preferably at a distance from the frame. It is an advantage if the drive station is rigidly connected to the frame and follows the rotary motion of the frame.

The cutting wire extends from the drive station in the longitudinal direction of the frame, around the return pulley and back to the drive station.

The wire guides comprise a set of guide pulleys which are arranged in the first end portion of the frame and are arranged to guide the cutting wire from a position sub stantially parallel to the centre axis of the frame into a position in which the direction of the wire substantially coincides with a plane that is perpendicular to the centre axis of the frame, the wire extending out from the frame, around the return pulley and back to the frame.

A tensioning mechanism, for example in the form of a set of tensioning pulleys, may be arranged at the drive station. The tensioning mechanism has a sufficient amount of travel for the cutting wire to be kept taut independently of the movement of the sword.

The lower end portion of the frame forms a supporting abutment for at least the re turn pulley so that the rotational axis of the return pulley is kept substantially parallel to the centre axis of the frame and the return pulley follows the rotation of the frame around its centre axis.

The lower end portion preferably has a conical external side surface forming a guiding surface facilitating the insertion of the cutting apparatus into a well.

The invention is defined by the independent claim. The dependent claims define ad vantageous embodiments of the invention.

The invention relates, more specifically, to a cutting apparatus comprising

an elongated frame which is rotatable around a centre axis and is provided with a first end portion and a second end portion,

a drive station for a cutting wire arranged at the second end portion, the cutting wire being continuous and extending between the drive station and a return element with a curved periphery arranged at the first end portion of the frame,

the frame being provided with a wire guide which is arranged to guide the cut ting wire from a direction substantially parallel to the centre axis of the frame into a direction coinciding with a plane that is substantially perpendicular to the centre axis, and vice versa,

the return element for the cutting wire being displaceable in a direction per pendicular to the centre axis between an inoperative, first position, in which the return element is arranged within the frame, and a second, operative position, in which the return element projects from the frame with a curve centre axis substantially parallel to the centre axis of the frame, and

the return element having a thickness which is smaller than an effective diame ter of the cutting wire.

The first end portion of the frame may be arranged to be insertable into a casing. The second end portion of the frame may comprise an abutment arranged to abut support - ingly against an end portion of a casing or a wellhead. The return element for the cut ting wire may be displaceable in a direction perpendicular to the centre axis between the inoperative, first position, in which the return element is arranged in the frame, and the second, operative position, in which the return element projects from the frame with a curve centre axis substantially parallel to the centre axis of the frame and with the return element directed towards an internal portion of the casing. The return element may be a return pulley. Alternatively, the return element may be pro vided with several supporting rollers supported at the curved periphery of the return element.

The cutting wire may be a diamond-coated metal wire.

The wire guide may comprise deflection pulleys arranged in the first end portion of the frame, a first deflection pulley being arranged to guide the cutting wire from a direc tion along the frame into a direction corresponding to the orientation of the return element, and a second deflection pulley being arranged to guide the cutting wire from a direction corresponding to the orientation of the return element into a direction along the frame.

The return element may be arranged in an end portion of an arm which is movable in a longitudinal direction of the arm, is bendable in a direction perpendicular to the cen tre axis of the frame and transversely to the longitudinal direction of the arm, is ar ranged in a rotationally rigid manner relative to the centre axis of the frame and has an extent in the extent, in terms of length and width, of the return element, and the thickness of the return element and the arm is smaller than the effective diameter of the cutting wire.

The arm may be formed of several arm sections which are interconnected by arm joints that are perpendicular to the longitudinal direction of the arm. The arm may be connected to a linear actuator which is arranged parallel to the centre axis of the frame.

The first end portion of the frame may comprise arm guides which are arranged to keep the return element substantially perpendicular to the centre axis of the frame and move the return element together with the frame in accordance with the rotation of the frame around its centre axis.

The drive station may comprise a tensioning mechanism for the cutting wire.

The abutment may comprise a rotation actuator arranged to rotate the frame relative to the casing.

The abutment may comprise a slewing ring. In what follows, an example of a preferred embodiment is described, which is visual ized in the accompanying drawings, in which:

Figure 1 shows a principle drawing in perspective of a cutting apparatus accord ing to the invention;

Figure 2 shows a section, on a larger scale, of a first, lower end portion of the cutting apparatus with an outer end portion of an articulated arm with a return element in the form of a return pulley projecting from a recess in a frame portion;

Figure 3 shows a section of a second, upper end portion of the cutting apparatus with an abutment and a rotation actuator; Figures 4a-4d show axial sections, on a smaller scale, through a portion of a well with three casings with cement-filled annuli, the return pulley of the cutting apparatus having brought the cutting wire successively through each of the casings; Figure 5 shows a perspective drawing, on a smaller scale, partially in axial sec tion of a portion of a well, the cutting apparatus being in the process of cutting through the casings;

Figure 6 shows a side view, on a smaller scale, of a wellhead with an associated casing into which the cutting apparatus has been inserted; and

Figure 7 shows a ground plan, on a larger scale, of a curved return element pro vided with several supporting rollers;

Figure 8 shows an alternative embodiment of the lower portion of the cutting apparatus in greater detail; Figure 9 shows, on a larger scale, a portion of an articulated arm with a deflec tion pulley for a cutting wire; and

Figure 10 shows, on a larger scale, an axial section through a return pulley.

Reference is first made to figure 1, in which a cutting apparatus 1 according to the invention comprises an elongated, tubular frame 11 with a first, lower frame portion 111 and a second, upper frame portion 112. A drive station 16 which is arranged to move a cutting wire 17 in the longitudinal direction of the wire is provided with a ten sioning mechanism 161, shown here as displaceable, preferably spring-loaded tension ing rollers, is attached to an extension of the frame 11 at a distance from the second end portion 112 of the frame. The second end portion 112 is provided with an abut- ment 1121 which is arranged to rest supportingly against an end portion of a casing 21 or a wellhead 24 (see figure 6), so that the frame 11 with the first end portion 111 extends downward in the casing 21 that is to be cut. The first end portion 111 com prises a return element 121 in the form of a return pulley which is movable in a plane substantially perpendicular to a centre axis 18 of the frame 11 from an initial position in which the return element 121 is directed towards an inside portion of the pipe 21 which is to be cut. The cutting wire 17 extends from the drive station 16 along the frame 11 via several wire guides 15 to the return element 121 and via further wire guides 15 and the tensioning mechanism 161 back to the drive station 16. The cutting wire 17 is typically formed as a diamond-coated wire of a design known per se. Reference is now made to figure 2, in which the first end portion 111 of the frame 11 is shown in greater detail. Said end portion 111 forms a housing for the return pulley 121 which is shown, here, connected to an end portion of an articulated arm 12. The arm 12 is formed of several arm sections 122 which are interconnected by arm joints 1221 lying transversely to a longitudinal direction of the arm 12 and in planes that are perpendicular to the centre axis 18 of the frame 11 (see also figure 9). The arm joints 1221 are formed in such a way that, relative to each other, they can only be pivoted upwards from a horizontal position in that a first joint portion 1222 is connected to a second joint portion 1223 on an adjacent arm section 122 by means of a hinge pin 1224 and the joint portions 1222, 1223 form abutments resting supportingly against each other when two adjacent arm sections 122 are oriented identically in the longitu dinal direction of the arm 12, see figure 9. By means of an arm actuator 13 lying in the longitudinal direction of the frame 11, the arm 12 can move the return pulley 121 between an inoperative position, in which the return pulley 121 is substantially fully retracted into the end portion 111 and a substantial part of the arm 12 extends in the longitudinal direction of the frame 11, and an extended, operative position, in which the return pulley 121 has its prescribed reach and part of the arm 12 lies in a plane which is perpendicular to the centre axis 18 of the frame 11, and the arm 12 is sup- ported by lower arm guides 1111 arranged in the end portion 111 of the frame 11.

The return pulley 121 may thereby be held in a position in which a rotational axis 1211 is substantially parallel to the centre axis 18 of the frame 11, and be moved in a circular path around the centre axis 18 when the frame 11 is rotated, in order for the cutting wire 17 thereby to be able to make a cut 26 through one or more casings 21, 22, 23 (see figures 4a-4d and 5) and any cement filling annuli 211, 221, 231 defined by the casings 21, 22, 23. The arm actuator 13 may be formed with a weight or the like subjecting the arm 12 and thereby the return pulley 121 to a relatively constant load during the extension of the arm 12, and also a hydraulic or electric linear actuator which is arranged to prevent extension of the arm 12 and also to pull the arm back into its inoperative position.

The return pulley 121 and the part of the arm 12 extending into one or more cuts 26 have a thickness, that is to say an extent in the longitudinal direction of the frame 11, which is smaller than an effective diameter D of the cutting wire 17, so that the return pulley 121 and the arm 12 can move freely in the cuts 26 that the cutting wire

17forms in the casings 21, 22, 23 and any cement-filled annuli 211, 221, 231.

In said first end portion 111, wire guides 15 are arranged in the form of deflection pulleys 151a, 151b supporting the cutting wire 17 in the transitions between paths along the frame 11 and paths along the arm 12 to and from the return pulley 121.

The first end portion 111 is provided with a conical end face 1112 which facilitates the insertion of the cutting apparatus 1 into the well 2. Reference is now made to figure 3, in which the second end portion 112 of the frame 11 is shown in greater detail. Here, the abutment 121 is shown with a slew ring 1122 which facilitates the rotation of the cutting apparatus 1 around the centre axis 18 of the frame 11. The rotation is preferably performed with a rotation actuator 1123 which is shown schematically here. The rotation actuator 1123 is typically attached to the frame 11 and can be connected to the wellhead 24 or some other element that is fixed relative to the well 2.

Reference is now made to figures 4a-4d, in which a cutting process is shown in steps. In figure 4a, the lower end portion 111 of the cutting apparatus 1 is positioned in the well 2 which is formed in an underground structure 25 and is cased with three concen tric casings 21, 22, 23, the respective annuli 211, 221, 231 being filled with cement. The return pulley 121 is in its inoperative, retracted position in the end portion 111.

In figure 4b, the cutting wire 17 has formed a cut through the inner, third casing 23 and the respective annulus 231 surrounding said casing 23 by the return pulley 121 having been moved successively outwards in the radial direction of the well 2 while the cutting wire 17 has simultaneously been moved in its longitudinal direction. The cutting wire 17 is in the process of forming a cut in the second casing 22 lying on the outside.

In figure 4c, the cutting wire 17 has formed a cut in the cement-filled second annulus 221 as well.

In figure 4, the cutting wire 17 has cut through the outer, first casing 21 and some what into the cement-filled first annulus 211 in order thereby to ensure that a com plete cut 26 is formed through all the casings 21, 22, 23 even though the first casing 21 is radially displaced relative to the third casing 23 and the cutting apparatus 1. When the cut 26 has been completed, the return pulley 121 is retracted into its inop erative position in the first end portion 111 of the frame 11 so that the cutting appa ratus 1 can be pulled out of the well 2 or be repositioned to perform another cutting process.

During displacement of the return pulley 121, the tensioning mechanism 161 of the drive station 16 keeps the cutting wire 17 taut.

Figure 5 shows how a complete cut 26 has been formed through all the casings 21,

22, 23 in a sector of about 120 degrees. Reference is now made to figure 6, in which the cutting apparatus 1 extends up the wellhead 24 in a well in an underground structure 25.

The rotation actuator 1123 (see figure 3) and the arm actuator 13 (see figure 2) of the cutting apparatus 1 are connected to a drive unit not shown, for example a hy- draulic pump with associated manoeuvring valves or a power supply with an associat ed control unit placed in a suitable location, typically at a distance from the cutting apparatus 1. Wires for transmitting energy to the arm actuator 13 may advantageous ly be arranged internally in the frame 11.

The frame 11 and the cutting wire 17 may be sectioned in such a way that the length of the cutting apparatus 1 may be adjusted to different operational requirements as regards both transport and positioning a cut 26 in the well 2.

In figure 7, the return element 121 is shown in an alternative embodiment, in which several supporting rollers 1213 are supported at a curved periphery 1212 of the return element 121. In figure 8, which shows an alternative embodiment of a lower portion of the cutting apparatus 1 in greater detail, and in which the lower frame portion 111 has been re moved for the sake of exposition, upper arm guides in the form of guide rails 14 ar ranged to hold the portion of the arm 12 that lies in the longitudinal direction of the frame 1 in a stable, straight position are shown. Figure 8 also shows a pulley guide 14a, typically formed of a plastics material or the like, that guides the return pulley

121 of the arm 12 in an initial part of a cutting operation.

Reference is now made to figure 10, in which an embodiment of the return pulley 121 is shown in greater detail. A pulley support 1214 is connected to the outer arm section

122 of the bendable arm 12, pivotable around an arm joint 1221. The pulley support 1214 comprises an annular bearing support 1214b. A bearing 1215, typically in the form of a ball bearing, is placed in the centre cut-out of the bearing support 1214b and rests supportingly against the bearing support 1214b which has an axial extent corresponding to the axial extent of the bearing 1215. Two substantially identical pul ley sections 1216, which are provided with bearing abutment portions 1216a arranged to rest supportingly against a surface facing radially inwards and an end face of an internal bearing ring 1215a, are provided with centre portions 1216b surrounded by the bearing abutment portions 1216a and being arranged to rest axially supportingly against each other when the bearing abutment portions 1216a are resting supporting ly against said bearing ring 1215a. The pulley sections 1216 are joined together by several screws 1217 arranged axially through the centre portions 1216b of the pulley sections 1216.

The pulley sections 1216 are provided with radial intermediate portions 1216c lying, when the pulley sections 1216 are joined together, with a small clearance to a bearing support arm 1214c projecting from the bearing support 1214b and forming a connec tion to the outer arm section 122 of the bendable arm 12. The radial intermediate por tions 1216c and the bearing support arm 1214c thereby form an axial support for the return pulley 121 and the bearing 1215.

On the periphery of the pulley sections 1216, wire abutments 1216c having a shape and material properties that are adapted to the cross section and surface of the cut ting wire 17 are arranged.

It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art may construct many alternative em bodiments without departing from the scope of the attached claims. In the claims, reference numbers in brackets are not to be regarded as restrictive.

The use of the verb "to comprise" and its different forms does not exclude the pres ence of elements or steps that are not mentioned in the claims. The indefinite article "a" or "an" before an element does not exclude the presence of several such elements.

The fact that some features are indicated in mutually different dependent claims does not indicate that a combination of these features cannot be used with advantage.

Claims

C l a i m s

1. A cutting apparatus (1) comprising

an elongated frame (11) which is rotatable around a centre axis (18) and is provided with a first end portion (111), which is arranged to be inserta- ble into a casing (21), and a second end portion (112), which comprises an abutment (1121) arranged to abut supportingly against an end portion of the casing (21) or a wellhead (24),

a drive station (16) for a cutting wire (17) arranged at the second end portion (112),

the cutting wire (17) being continuous and extending between the drive station (16) and a return element (121) with a curved periphery (1212) arranged at the first end portion (111) of the frame (11),

the frame (11) being provided with a wire guide (15) which is ar ranged to guide the cutting wire (17) from a direction substantially parallel to the centre axis (18) of the frame (11) into a direction coincident with a plane which is substantially perpendicular to the centre axis (18), and vice versa, the return element (121) for the cutting wire (17) being displaceable in a direction perpendicular to the centre axis (18) between an inoperative, first position, in which the return element (121) is arranged in the frame (11), and a second, operative position, in which the return element (121) projects from the frame (11) with a curve centre axis (1211) substantially parallel to the cen tre axis (18) of the frame (11) and with the return element (121) directed to wards an inside portion of the casing (21), and

the return element (121) having a thickness which is smaller than an effective diameter (D) of the cutting wire (17).

2. The cutting apparatus (1) according to claim 1, wherein the return element (121) is a return pulley.

3. The cutting apparatus (1) according to claim 1, wherein the return element (121) is provided with several supporting rollers (1212) supported at the curved periphery (1212) of the return element (121).

4. The cutting apparatus (1) according to claim 1, wherein the cutting wire (17) is a diamond-coated metal wire.

5. The cutting apparatus (1) according to claim 1, wherein the wire guide (15) comprises guide pulleys (151a, 151b) arranged in the first end portion (111) of the frame (11), a first guide pulley (151a) being arranged to guide the cutting wire (17) from a direction along the frame (11) into a direction corresponding to the orientation of the return element (121), and a second guide pulley (151b) being arranged to guide the cutting wire (17) from a direction corre sponding to the orientation of the return element (121) into a direction along the frame (11).

6. The cutting apparatus (1) according to claim 1, wherein the return element (121) is arranged in an end portion of an arm (12) which is movable in a longi tudinal direction of the arm (12), is bendable in a direction perpendicular to the centre axis (18) of the frame (11) and transversely to the longitudinal direction of the arm (12), is arranged in a rotationally rigid manner relative to the centre axis (18) of the frame (11) and has an extent that lies in the plane of the ex tent, in terms of length and width, of the return element (121), and the thick ness of the return element (121) and the arm (12) is smaller than the effective diameter (D) of the cutting wire (17).

7. The cutting apparatus (1) according to claim 6, wherein the arm (12) is formed of several arm sections (122) which are interconnected by arm joints (1221) that are perpendicular to the longitudinal direction of the arm (12).

8. The cutting apparatus (1) according to claim 6, wherein the arm (12) is con nected to a linear actuator (13) which is arranged parallel to the centre axis (18) of the frame (11).

9. The cutting apparatus (1) according to claim 1, wherein the first end portion (111) of the frame (11) comprises arm guides (1111) which are arranged to keep the return element (121) substantially perpendicular to the centre axis (18) of the frame (11) and move the return element (121) together with the frame (11) in accordance with the rotation of the frame (11) around the centre axis (18) thereof.

10. The cutting apparatus (1) according to claim 1, wherein the drive station (16) comprises a tensioning mechanism (161) for the cutting wire (17).

11. The cutting apparatus (1) according to claim 9, wherein the abutment (1121) comprises a rotation actuator (1123) arranged to rotate the frame (11) relative to the casing (21).

12. The cutting apparatus (1) according to claim 9, wherein the abutment (1121) comprises a slew ring (1122).