Wells – Processes – Perforating – weakening – bending or separating pipe at an...
Reexamination Certificate
1999-02-18
2001-03-20
Dang, Hoang (Department: 3672)
Wells
Processes
Perforating, weakening, bending or separating pipe at an...
C175S325200
Reexamination Certificate
active
06202752
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is directed to wellbore milling systems and methods; and, in one particular aspect, to such systems and methods for milling through a liner that projects into a lateral wellbore from a main wellbore to re-establish a pathway to the main wellbore.
2. Description of Related Art
The prior art discloses a wide variety of wellbore milling systems and methods and a wide variety of systems and methods for re-establishing a pathway through a main wellbore after lining a lateral wellbore with a liner. Many such prior art systems and methods require a guide for a milling system so that the milling system mills back through the liner rather than entering the liner itself and milling in the wrong location. Without such a guide a lateral liner can be damaged by the wrongly located milling system, and the pathway through the main wellbore will not be re-established.
Various prior art systems which do not employ a mill guide use a milling system on a rotatable tubular string. If such a string is not sufficiently stiff and is not sufficiently stable, a mill at the end of the string may preferentially attempt to enter a lateral liner rather than mill through the liner to reestablish communication through another (e.g. primary) wellbore.
SUMMARY OF THE PRESENT INVENTION
The present invention, in certain aspects, discloses a milling system for milling through a portion of a lateral liner that projects up into a primary wellbore and which, prior to milling, blocks the lower portion of the primary wellbore. In one particular aspect such a system includes a mill or mills on the end of a tubular string. Disposed above the mill(s) are one or more rigid stabilizing members. The length of one stabilizing member or the combined length of a series of stabilizing members is sufficient to hold the mill(s) against the liner portion to be milled and to prevent the mill from going into the lateral liner itself.
In one particular aspect the stabilizing member(s) is/are sufficiently long that the mill(s) is/are held against the liner while the mill(s) start an opening through the liner. In another aspect the stabilizing member(s) is/are sufficiently long that the mill(s) is/are stabilized sufficiently for milling of the entire opening through the liner.
In a particular embodiment the stabilizing member(s) is/are sized so that space between the exterior of the stabilizing member(s) is minimized, thus preventing stabilizing member wobble which would reduce the stabilizing effect at the mill. In one aspect to achieve this “special drift” tubulars, e.g. casing, are used in the wellbore for the liner. In one aspect of the present invention employing the special drift casing, the drift diameter is in close tolerance to the nominal inner diameter of the tubular string in which it is used. Certain special drift casing has a known interior diameter within a close tolerance, e.g. within forty thousandths of an inch. Also, the exterior diameter of the stabilizing member(s) is, optionally and preferably, sized within a close tolerance, e.g. fifteen thousandths of an inch. The resulting close fit between stabilizing member(s) and casing increases stiffness of the system and enhances stability of the mill(s). In one aspect special drift casing is used at such a length that it includes within it the milling assembly and the area for forming a window.
In one particular aspect the stabilizing member(s) is/are a bladed and/or spiralled-body stabilizer with hardfacing and/or other matrix milling material on the blades and/or spiral part exterior. Such a structure provides for reaming of a portion of a casing that may be slightly out of tolerance and which would, without such reaming, prevent passage of the system through the casing. A reamed portion subsequently provides a desired very close fit with the stabilizing member(s).
In certain embodiments a plurality of stabilizing members are used, e.g., but not limited to, any suitable known stabilizer and/or stabilizer reamer. In one particular aspect spacing is provided between each of a plurality of stabilizers. In certain embodiments, a first stabilizing member above a lower mill is spaced apart from the mill so that the stabilizing member does not enter a bend in the liner (as it projects into the lateral wellbore) until milling has commenced at a desired liner location. In another aspect the stabilizing member is so located that the mill mills through the liner before the stabilizing member enters the bend.
One particular mill useful in such systems has a generally cylindrical body with a flow bore therethrough from a top end to a bottom end. One or more flow ports extend laterally from the flow bore to the body's exterior. The lower end of the mill has a plurality of spaced-apart blades for milling the liner. In various aspects there are two, four, six, eight, ten, or twelve separate blades, although any suitable number is within the scope of this invention. The blades may be dressed with any suitable known matrix milling material and/or inserts by any suitable known method and in any suitable known pattern or array. In one particular aspect the blades extend downwardly with flow paths therebetween and an amount of crushed carbide is disposed within the mill partially adjacent and partially above the blades with a lower cone shape that facilitates maintenance of the mill in a desired milling position.
In one embodiments a system as described above (and in detail below) is releasably secured to a liner and the entire combination is run into a wellbore so that the liner enters and lines a portion of a lateral wellbore. Any suitable known diversion device, whipstock, diverter, etc. may be located in the primary wellbore at a desired location to direct the liner into the lateral wellbore. Following correct emplacement of the liner, the mill(s) is/are selectively released from the liner (e.g. by shearing a shearable member, stud, or pin) and the liner is milled to reestablish communication to the primary wellbore. The mill(s) and interconnected apparatuses are then removed from the wellbore. This operation can be completed in a single trip of the system into the wellbore.
Alternatively, mills and milling systems described herein may be used for any wellbore milling operation, e.g., but not limited to milling a window in a wellbore tubular, milling a fish, a packer, a whipstock, or other apparatus or structure in a wellbore. In other embodiments any mill or mill system described herein may be used in conjunction with a mill guide.
The present invention, in one aspect, discloses a milling system for milling through a lateral bore liner to re-establish a main wellbore. In one aspect the milling system includes a mill with milling blades dressed with milling matrix material and milling inserts; a tubular string connected to and above the mill; and at least one centralizer, rotating centralizer, stabilizer, rotating stabilizer, coupling bushing or the like through which the tubular string extends, the at least one coupling bushing disposed in the main wellbore above a casing window through which the lateral liner extends into the lateral bore.
In one aspect such a system has a plurality of spaced-apart coupling bushings disposed above the lateral bore which serve to position the milling system and prevent it from entering the lateral liner. Such coupling-bushing will facilitate directing of the milling system in the direction of the main wellbore so that the milling system mills through the liner in the direction of the main wellbore, thereby re-establishing the main wellbore. In one aspect one of the coupling bushings is placed above, and in one aspect near the top of, the window at the beginning of the lateral bore.
In some systems a lateral bore liner is supported by an external casing packer, liner hanger, pack-off liner hanger, or similar support positioned in a main wellbore. A milling system as described above that is introduced into the liner through the main wellbore should not abut or hang up on the top
Bailey Thomas Floyd
Barry Andrew Arthur
Blizzard, Jr. William Allen
Carter Thurman Beamer
Haugen David Michael
Dang Hoang
McClung Guy
Weatherford / Lamb, Inc.
LandOfFree
Wellbore milling methods does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wellbore milling methods, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wellbore milling methods will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2505722