Completion liner delivery method with bridge plug capture

Abstract

In an underbalanced or overbalanced completion, the packer that isolates a portion of the wellbore is preferably a composite mechanically set bridge plug. The composite materials are selected to expedite mill out the plug. A coring mill envelopes the plug as it cuts away the grip of the slips. Internal uphole oriented wickers inside the coring mill grab hold of it before the slip grip is lost to capture the plug in the coring mill. The liner string is rotated to operate the mill or alternatively a downhole motor can be used to run the coring mill. After the bridge plug is milled to a release and capture position, the liner string that can be slotted liner or screen or other tubular is advanced into position further down the usually deviated wellbore.

Description

FIELD OF THE INVENTION

The field of the invention is downhole underbalanced completions where a bridge plug has to be removed and a liner advanced in a single trip or in overbalanced conditions as a fluid loss device.

FIELD OF THE INVENTION

When wells are being drilled, it is always desirable to complete the well including the bottom hole assembly liner in a manner so as to minimize the applied pressure on the formation. In essence, it is undesirable to apply excess pressure to the formation, known as killing the well, during the completion process. In prior situations, particularly those involving deviated wellbores, the initial portion of the well is drilled and a casing is set. The casing is then cemented. After the cement sets, the deviated portion of the wellbore is drilled. Prior designs have involved running a liner string into the wellbore after completion of the drilling of the deviation in the wellbore beyond the cemented casing. An inflatable packer has been inserted through the liner string to isolate the formation while the bottom hole assembly is assembled into the wellbore above an inflatable bridge plug. However, certain problems have developed in particular applications with the use of through-tubing inflatable bridge plugs. For one thing, the ability of the through-tubing inflatables to hold particular differentials can be problematic, especially if there are irregularities in the sealing surface where the plug is inflated. Additionally, due to the compact design required in certain applications, the through-tubing inflatable element cannot expand far enough to reliably hold the necessary differential pressures that may exist across the inflated bridge plug. Finally, there could also be difficulties in retrieval of the through-tubing inflatable bridge plug back through the string from which it was delivered. The flexible nature of the through-tubing inflatable design could also create problems if it was decided simply not to retrieve the plug after putting together the bottom hole assembly above it. The slender design of the through-tubing inflatable plug could create advancement problems if the plug were to be merely pushed to the bottom of the hole with the production tubing. If any washouts in the deviated portion of the wellbore are to be encountered by the bottom hole assembly with the deflated through-tubing plug at the front, then the entire assembly may get stuck prior to its being advanced to the bottom of the wellbore for proper positioning. Generally, the through-tubing designs have not provided a circulation passage therethrough to facilitate advancement of a deflated plug into the uncased portion of a wellbore using circulation.

More recently an inflatable bridge plug that is not through tubing has been tried with the intent on deflating it with the advancing liner string and capturing the deflated inflatable and moving the string in tandem with the now deflated inflatable. This technique is illustrated in U.S. Pat. No. 5,749,419. However, there were issues with using this technique as well. The inflatable would lose grip or deflate. The deflated inflatable would not be cleanly captured and would tend to ball up to prevent forward progress of the liner string behind it. Sometimes the deflated liner would simply release from the advancing string and prevent subsequent string advancement downhole. U.S. Pat. No. 6,915,858 addressed some of these issues, most notably the tendency of the deflated packer to wad up or swab as it was being advanced downhole. The idea was to mechanically extend the deflated inflatable packer so that the tendency to swab would be reduced. While this design removed some of the issues in using inflatables for this application, it still left others unaddressed and various failure modes were still encountered.

The present invention moves away from efforts to use inflatables and instead uses a non-inflatable. In the preferred embodiment, a composite mechanically set bridge plug is used and a core mill is brought down to it with a liner string behind the coring mill. The mill breaks loose the slip grip and retains the bridge plug as the string is then advanced. These and other benefits of the present invention will be more apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings, which appear below, while recognizing that the scope of the invention is determined by the claims.

SUMMARY OF THE INVENTION

In an underbalanced or overbalanced completion, the packer that isolates a portion of the wellbore is preferably a composite mechanically set bridge plug. The composite materials are selected to expedite mill out the plug. A coring mill envelopes the plug as it cuts away the grip of the slips. Internal uphole oriented wickers inside the coring mill grab hold of it before the slip grip is lost to capture the plug in the coring mill. The liner string is rotated to operate the mill or alternatively a downhole motor can be used to run the coring mill. After the bridge plug is milled to a release and capture position, the liner string that can be slotted liner or screen or other tubular is advanced into position further down the usually deviated wellbore.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view showing the composite bridge plug in place with slips set;

FIG. 2 shows the coring bit and liner assembly moving into mill out position;

FIG. 3 is the view of FIG. 2 showing the bridge plug milled out and retained by the bottom hole assembly;

FIG. 4 shows the bottom hole assembly advancing toward the well bottom beyond the former position of the bridge plug;

FIG. 5 is an enlarged view of the mill shown in FIGS. 2-4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a well bore 10 that is lined with casing 12 and cemented 14. The lower end 16 of the wellbore 10 is preferably open hole. A bridge plug 18 that is preferably made of composite (or mostly non-metallic) materials is set in wellbore 10. The use of composite materials allows a more rapid milling rate. The bridge plug is of a known design and has upper slips 20 and lower slips 22 on either side of a resilient sealing element 24.

FIG. 2 shows what happens in preparation for lining the lower end 16 of the wellbore. A drill string 26 supports a liner hanger 28 that is located above a liner string 30. A float collar 32 is within liner string 30. At the lower end 34 is a coring mill 36 that is shown in more detail in FIG. 5. The mill 36 has circumferential cutters 38 that are sized to encounter the slips 20 and 22 to break loose their grip. As the coring mill 36 descends when cutting the slips 20 and 22 the bridge plug enters the core 40 and comes into a gripping device that still permits fluid flow around the now captured plug 18, as also shown in FIG. 3. The coring mill 36 can be operated by rotation of the drill string 26. Alternatively a downhole motor (not shown) can be attached to the drill string 26 so that only the bottom hole assembly below the downhole motor actually rotates. Alternatively, the drill string 26 can be rigid or coiled tubing.

Referring to FIG. 5, the gripping device for the bridge plug 18 can be a series of circumferential wickers that are preferably oriented uphole to retain the bridge plug 18 after the mill descends enough to capture it in wickers 42. Preferably, the wickers are in spaced segments that leave longitudinal passages 44 to allow flow around the captured bridge plug 18 when retained by wickers 42. The passages 44 allow cooling fluid that is circulated into core 40 to cool the cutters 38 as milling continues. Circulation can be continued while the assembly is then lowered further in the wellbore 10 into position at the lower end 16, as shown in FIG. 4.

Those skilled in the art will appreciate that the problems with prior uses of inflatables have been eliminated with the present invention. The milling rates are high due to the use of composite materials in the preferred bridge plug. While small pieces that are formed in the milling process can be circulated to the surface, the bulk of the body of the bridge plug 18 is retained within core 40 at the conclusion of the milling. The retention devices can be varied although uphole oriented wickers are preferred. Magnets can also be employed to capture magnetic parts, if any. Retention of the milled out packer can continue even with circulation through the core 40 as the liner 30 is advanced to reduce the risk of hanging up during the advance. As an alternative the bridge plug can be mechanically released rather than milled. It is preferred to retain the released bridge plug in a core for the trip downhole even when the release is accomplished mechanically as opposed to by milling. Additional provisions can be incorporated into the retention device for the spent bridge plug to release it to the bottom of the hole if required. This can be done with circulation or through articulated grippers that can fully release it or even extend it out past the core 40 so it can be reset by mechanical manipulation, pressure or other techniques. Alternatively, if the bridge plug is of a resettable design it can be moved downhole and extended from the core 40 and reset above the hole bottom.

The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.

Claims

1. A downhole completion assembly comprising:

a non-inflatable plug settable in a wellbore to isolate one portion of the wellbore from another;

a release tool supported from a string and designed to release said plug and retain it as said string is further advanced downhole.

2. The assembly of claim 1, wherein:

said release tool comprises an internal core to at least in part retain said plug after its release.

3. The assembly of claim 2, wherein:

said release tool mills said plug.

4. The assembly of claim 3, wherein:

said plug comprises at least one slip milled out by said release tool.

5. The assembly of claim 2, wherein:

said plug comprises a slip that is mechanically released by said releasing tool.

6. The assembly of claim 2, wherein:

said core comprises a retaining member to hold said plug after its release.

7. The assembly of claim 2, wherein:

said core defines at least one bypass passage to allow flow around said plug when retained in said core.

8. The assembly of claim 6, wherein:

said retaining member comprises a plurality of wickers oriented in the opposite direction from movement of the release tool that brings said plug into said core.

9. The assembly of claim 8, wherein:

said retaining member defines at least one flow passage running along said wickers.

10. The assembly of claim 2, wherein:

said plug is releasable from said core after its retention therein.

11. The assembly of claim 2, wherein:

said plug is extendable from said core after being retained therein.

12. The assembly of claim 11, wherein:

said plug is resettable after being extended from said core.

13. The assembly of claim 3, wherein:

said plug is made of substantially non-metallic materials.

14. The assembly of claim 13, wherein:

said plug is made of substantially composite materials.

15. The assembly of claim 3, wherein:

said release tool is operated by string rotation from the surface of the wellbore.

16. The assembly of claim 3, wherein:

said release tool is operated by a downhole motor mounted in said string.

17. The assembly of claim 2, wherein:

said string further comprises a hanger.

18. The assembly of claim 17, wherein:

said string comprises openings for subsequent production.

19. The assembly of claim 17, wherein:

said string comprises a float collar.

20. The assembly of claim 2, wherein:

said plug comprises upper and lower slips with a sealing element in between and a substantially non-metallic body;

said release tool milling said slips as it captures said body in said core.