Method of using radial thrust elements to re-enter a previously-installed tubular in a lateral

Abstract

A method of re-entering a previously-installed tubular in a lateral borehole from a primary borehole connected to the lateral borehole includes passing a downhole tool from the primary borehole into the lateral borehole, activating one or more radial thrust elements proximate to a nose portion of the downhole tool to apply a radial thrust to the downhole tool and lift the nose portion into alignment with the tubular, and inserting the nose portion of the downhole tool into the tubular.

Description

BACKGROUND OF THE INVENTION

The invention relates generally to multilateral well operations. More particularly, the invention relates to a method and apparatus for accessing a branch of a multilateral well.

A multilateral well, also known as a multi-branch well, is a well having one or more lateral boreholes branching off a single primary wellbore. The primary wellbore may be vertical, horizontal, or deviated. The lateral boreholes may branch off the primary wellbore in any number of directions to allow production from several target reservoirs or formations through the primary wellbore. Multilateral wells are advantageous in comparison to single wells in that their lateral boreholes can be brought into close contact with several target reservoirs, thereby allowing production from the reservoirs to be maximized.

Tubulars are often installed in lateral boreholes. For example, in unconsolidated or weakly consolidated formations, liners are often installed in lateral boreholes to prevent the boreholes from collapsing. After such installation, it is often desirable to re-enter the tubular in order to perform one or more operations in the lateral borehole. Such re-entry operations generally include inserting a downhole tool into the tubular. In some cases, there may be eccentricity between the tubular and the lateral borehole, for example, due to formation washout. In this case, there is the likelihood that a downhole tool inserted into the lateral borehole would be misaligned with the tubular and may not be able to enter the tubular or may even become stuck in between the tubular and the lateral borehole.

From the foregoing, a method of assuring entry of a downhole tool into a tubular in a lateral borehole would be useful.

SUMMARY OF THE INVENTION

In one aspect, the invention relates to a method of re-entering a previously-installed tubular in a lateral borehole from a primary borehole connected to the lateral borehole. The method comprises passing a downhole tool from the primary borehole into the lateral borehole, activating one or more radial thrust elements proximate to a nose portion of the downhole tool to apply a radial thrust to the downhole tool and lift the nose portion into alignment with the tubular, and inserting the nose portion of the downhole tool into the tubular. In one embodiment, activating the one or more radial thrust elements comprises radially extending one or more bow springs coupled to the downhole tool. In another embodiment, activating the one or more radial thrust elements comprises radially extending one or more plugs coupled to the downhole tool. In yet another embodiment, activating the one or more radial thrust elements comprises generating one or more hydraulic jets from the downhole tool.

In another aspect, the invention relates to a downhole tool for re-entering a previously-installed tubular in a lateral borehole of a multilateral well. The downhole tool comprises a downhole tool body sized for insertion into the tubular and one or more radial thrust elements proximate to a nose portion of the downhole tool body and operable to apply a radial thrust to the downhole tool body and lift the nose portion into alignment with the tubular.

Other features and advantages of the invention will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, described below, illustrate typical embodiments of the invention and are not to be considered limiting of the scope of the invention, for the invention may admit to other equally effective embodiments. The figures are not necessarily to scale, and certain features and certain view of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness.

FIG. 1 is a schematic of a multilateral well in which a tubular installed in a lateral borehole is eccentric with the lateral borehole.

FIG. 2A is an example of a downhole tool for re-entering a tubular that is eccentric with a lateral borehole.

FIG. 2B shows the downhole tool of FIG. 2A aligned for entry with the tubular.

FIG. 2C shows a method of radially extending the bow springs of FIG. 2A.

FIG. 3A is another example of a downhole tool for re-entering a tubular that is eccentric with a lateral borehole.

FIGS. 3B and 3C illustrate a partial cross-section of the aligning mechanism of FIG. 3A and a method of radially extending the plugs of FIG. 3A.

FIGS. 3D and 3E illustrate a partial cross-section of the aligning mechanism of FIG. 3A and an alternate method of radially extending the plugs of FIG. 3A.

FIGS. 4A and 4B depict another example of a downhole tool for re-entering a tubular that is eccentric with a lateral borehole.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described in detail with reference to a few preferred embodiments, as illustrated in the accompanying drawings. In describing the preferred embodiments, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the invention may be practiced without some or all of these specific details. In other instances, well-known features and/or process steps have not been described in detail so as not to unnecessarily obscure the invention. In addition, like or identical reference numerals are used to identify common or similar elements.

FIG. 1 illustrates an example of a multilateral well 100 in which the method and apparatus of the invention may be employed. The multilateral well 100 includes a primary borehole 102 and a lateral borehole 104 branching off the primary borehole 102. The multilateral well 100 may have one or more lateral boreholes. Casing 106 may be installed in the primary borehole 102 and may include a window 107 through which the lateral borehole 104 can be accessed, in a manner well known in the art. A tubular 108 has been installed in the lateral borehole 104, in a manner well known in the art. For example, the tubular 108 may be a liner, such as a slotted or perforated liner, installed in the lateral borehole 104 to prevent the lateral borehole 108 from collapsing. The tubular 108 includes a bore (not shown) for receiving a downhole tool 110 at the end of a tool string 112. In the illustrated example, the tubular 108 is eccentric with the lateral borehole 104. This may be due, for example, to formation washout at 114. Also, the downhole tool 110 is not aligned for entry with the tubular 108. In accordance with the invention, a downhole tool is provided with an aligning mechanism to facilitate entry of the downhole tool into the tubular 108. In general, the aligning mechanism includes radial thrust elements proximate to the nose portion of the downhole tool. The radial thrust elements can be activated to apply radial thrust to the downhole tool which would lift the nose of the downhole tool into alignment with the tubular.

FIG. 2A shows an example of a downhole tool 200 having an elongated downhole tool body 202 with a rear portion 201 and nose portion 203. The downhole tool 200 is adapted to facilitate entry into a tubular in a lateral borehole when the tubular is eccentric with the lateral borehole, more specifically when the nose portion 203 is not aligned for entry into the tubular. The tool body 202 is sized for insertion into the target tubular 108. In one example, the nose portion 203 of the tool body 202 includes a tubular sealing element 204 for sealing engagement with a sealing surface, such as a sealing bore of a tubular. The rear portion 201 may also include additional sealing elements 205 for sealing engagement with a sealing surface. In this example, the nose portion 203 includes a nozzle 206 with orifices 207 for fluid circulation when the sealing elements 204, 205 are in the sealing position. However, it is not necessary that the downhole tool 200 includes the nozzle 206. Further, any suitable means of conveying the downhole tool 200 into the lateral borehole, such as a string of pipes or wireline, may be coupled to the rear portion 201 of the downhole tool 200.

The downhole tool 200 includes an aligning mechanism 208 disposed between the rear portion 201 and the nose portion 203. In this example, the aligning mechanism 208 includes a sleeve 210 coupled to the nose portion 203. A plurality of radial thrust elements 212 are mounted in a spaced relation about a circumference of the sleeve 210. Alternatively, the radial thrust elements 212 may be provided on only a portion of the circumference of the sleeve 210, such as the portion of the sleeve 210 that would be adjacent to the bottom of the lateral borehole. In one example, the radial thrust elements 212 are radially extendible bow springs. One of the ends of the bow springs 212 is fixed to the sleeve 210 while the other of the ends of the bow springs 212 is attached to a sleeve 214 that is concentric with and slidable over the sleeve 210. The bow springs 212 are in a retracted (or flat) position, as shown in FIG. 2A, until they are actuated or activated. To align the nose portion 203 with the tubular 108, the bow springs 212 are actuated or activated such that the bow springs 212 become radially extended (or bow out). FIG. 2B shows the bow springs 212 radially extended away from the sleeve 210 upon actuation. The radially extended bow springs 212 apply a radial thrust which lifts the nose portion 203 of the downhole tool 200 and maintains the nose position 203 in a lifted position, thereby aligning the nose portion 203 for entry into the tubular 108.

The aligning mechanism 208 includes a mechanism for actuating or activating the bow springs 212. The actuation mechanism may take on any suitable form known in the art. The actuation mechanism may be mechanical, hydraulic, or electrical. In one example, a compression spring 216 is mounted between the rear portion 201 and sleeve 210 and arranged to exert a force on the sleeve 214. A load applied to the compression spring 216, which overcomes the force of the compression spring 216, would move the sleeve 214 axially relative to the sleeve 210, thereby moving the movable ends of the bow springs 212 axially and radially extending the bow springs 212. In another example, as illustrated in FIG. 2C, a hydraulic cylinder 218 may be mounted between the rear portion 201 and sleeve 210, and the piston 220 of the hydraulic cylinder 218 may apply the force needed to move the sleeve 214 axially to radially extend the bow springs 212. Pressurized fluid can be supplied to the hydraulic cylinder 218 through the bore of the tool body 202 from the surface or a suitable location downhole. In another example not illustrated, the movable ends of the bow springs 212 may be coupled to the sleeve 210 by pin/slot connections, and movement of the pins within the slots can be controlled by a motor or other means, which may be mechanical, hydraulic, or electrical, to actuate the bow springs 212.

In FIG. 3A, an alternate aligning mechanism 300 is coupled to the nose portion 203 of the downhole tool 200. The aligning mechanism 300 includes a sleeve 302 which carries radial thrust elements 304. In this example, the radial thrust elements 304 are depicted as plugs or mandrels 304 distributed about a circumference of the sleeve 302. Alternatively, the plugs 304 may be provided on only a portion of the circumference of the sleeve 302, such as the portion of the sleeve 302 that would be adjacent to the bottom of the lateral borehole. Referring to FIG. 3B, the plugs 304 are inserted in apertures 306 in the sleeve 302 and are slidable within the apertures 306. The plugs 304 are initially maintained in a retracted position, for example, by means of a spring 308. When the force of the spring 308 is overcome, the plugs 304 radially extend outwardly, i.e., away from the sleeve 302, as shown in FIG. 3C. In the same manner indicated for the bow springs (212 in FIG. 2B), in the radially extended position, the plugs 304 lift the nose portion (203 in FIG. 3A) of the downhole tool (200 in FIG. 3A) and facilitate entry of the downhole tool into the tubular (108 in FIG. 2A). Any suitable mechanism may be used to radially extend the plugs 304. For example, FIGS. 3B and 3C depict an inflatable element 312 that may be inserted into the sleeve 302 and then inflated to apply a radial force to the plugs 304. The applied force would overcome the force of the springs 308, thereby radially extending the plugs 304. Alternatively, as depicted in FIGS. 3D and 3E, a mandrel 313 may be used to apply a radial force to the plugs 304 to thereby radially extend the plugs 304. The diameter of the mandrel 313 controls radial extension of the plugs 304. In FIGS. 3B-3E, any other suitable mechanism besides springs 308, such as J-slot connections, may be used to control radial extension of the plugs 304.

In FIGS. 4A and 4B, a different aligning mechanism 400 is coupled to the downhole tool 200. The aligning mechanism 400 includes a sleeve 402 coupled to the nose portion 203 and the rear portion 201 of the downhole tool 200. Orifices 404 are formed in the sleeve 402. The orifices 404 are distributed about a circumference of the sleeve 402. The orifices 404 are used to create hydraulic jets, which provide the radial thrust that will lift the nose portion 203 of the downhole tool 200 for alignment and entry into the tubular. In this case, the orifices 404 for creating the hydraulic jets are part of the radial thrust elements. Typically, only the orifices 404 located on one side of the sleeve 402 are left open. In other words, the orifices 404 on the side opposite to the intended displacement to achieve alignment are typically plugged. In FIG. 4B, the plugged orifices 404 are not shown. If necessary, the orientation of the downhole tool 200 can be adjusted such that the unplugged orifices 404 are in the orientation to provide the intended displacement of the nose portion 203. Pressure buildup inside the tool body 202 to create the hydraulic jets can be achieved by mechanisms such as ball drop or choke/flow restriction. For example, a ball can be dropped into the tool body 202 to seal off the orifices 207 at the nose portion 203 of the downhole tool 200. Then, hydraulic fluid can be pumped down the bore of the tool body 202 and forced through the orifices 404 to create hydraulic jets 405 that would lift the nose portion 203 into alignment for entry into the tubular 108.

A method of re-entering a tubular (108 in FIG. 1) in a lateral borehole (104 in FIG. 1) from a primary borehole (102 in FIG. 1) includes passing a downhole tool (200 in FIGS. 2A, 3A, 4A) from the primary borehole into the lateral borehole, where the downhole tool is equipped with radial thrust elements. The downhole tool may be lowered through casing in the primary wellbore and passed into the lateral borehole through a window in the casing. In general, any suitable method known in the art for locating the lateral borehole and orienting the downhole tool so that it can pass into the lateral borehole from the primary borehole can be used. The method further includes activating the radial thrust elements to lift the nose of the downhole tool into alignment with the tubular in the lateral borehole. Any suitable technique for activating the radial thrust elements, such as those described above, may be used. Once the nose portion of the downhole tool is aligned with the tubular, the nose portion of the downhole tool can be inserted into the tubular. The radial thrust elements can then be de-activated to allow the downhole tool to be fully inserted into the tubular. De-activation is generally the reverse of the process used in activating the radial thrust elements.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims

1. A method of re-entering a previously-installed tubular in a lateral borehole from a primary borehole connected to the lateral borehole, comprising:

passing a downhole tool from the primary borehole into the lateral borehole;

activating one or more radial thrust elements proximate to a nose portion of the downhole tool to apply a radial thrust to the downhole tool and lift the nose portion into alignment with the tubular; and

inserting the nose portion of the downhole tool into the tubular.

2. The method of claim 1, wherein activating the one or more radial thrust elements comprises radially extending one or more bow springs coupled to the downhole tool.

3. The method of claim 2, wherein the bow springs are mounted on a sleeve coupled to the nose portion and radially extending the one or more bow springs comprises axially moving one of the ends of the bow springs relative to the sleeve.

4. The method of claim 1, wherein activating the one or more radial thrust elements comprises radially extending one or more plugs coupled to the downhole tool.

5. The method of claim 4, wherein the plugs are inserted in apertures provided in a sleeve coupled to the nose portion and extending the one or more plugs comprises inserting a tool into a bore of the sleeve and operating the tool to apply a radial force to the one or more plugs.

6. The method of claim 1, wherein activating the one or more radial thrust elements comprises generating one or more hydraulic jets from the downhole tool.

7. The method of claim 6, wherein generating the one or more hydraulic jets comprises forcing fluid through one or more orifices in the downhole tool.

8. The method of claim 1, further comprising de-activating the radial thrust elements after inserting the nose portion of the downhole tool into the tubular.

9. The method of claim 1, wherein passing the downhole tool from the primary borehole to the lateral borehole comprises lowering the downhole tool into the primary borehole.

10. The method of claim 1, wherein the previously-installed tubular is eccentric with the lateral borehole.

11. A downhole tool for re-entering a previously-installed tubular in a lateral borehole of a multilateral well, comprising:

a downhole tool body sized for insertion into the previously-installed tubular; and

one or more radial thrust elements proximate to a nose portion of the downhole tool body and operable to apply a radial thrust to the downhole tool body and lift the nose portion into alignment with the tubular.

12. The downhole tool of claim 11, wherein the radial thrust elements are disposed between the nose portion and a rear portion of the downhole tool body.

13. The downhole tool of claim 11, wherein the radial thrust elements comprise one or more radially extendible bow springs.

14. The downhole tool of claim 11, wherein the radial thrust elements comprise one or more radially extendible plugs.

15. The downhole tool of claim 11, wherein the radial thrust elements comprise one or more orifices for generating one or more hydraulic jets.

16. The downhole tool of claim 11, wherein the radial thrust elements are disposed about at least a portion of a circumference of a sleeve coupled to the nose portion of the downhole tool body.

17. The downhole tool of claim 11, further comprising a mechanism for activating the radial thrust elements to apply a radial thrust to the downhole tool.

18. The downhole tool of claim 11, wherein the nose portion includes a sealing element for sealing engagement with the tubular.

19. The downhole tool of claim 18, wherein a rear portion of the downhole tool body includes a sealing element for sealing engagement with the tubular.