Wells – Means for perforating – weakening – bending or separating pipe... – With disparate below ground feature
Reexamination Certificate
1999-11-29
2001-10-16
Suchfield, George (Department: 3672)
Wells
Means for perforating, weakening, bending or separating pipe...
With disparate below ground feature
C166S117500, C175S080000, C175S082000, C175S385000
Reexamination Certificate
active
06302198
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to downhole drilling systems in which whipstocks are used to deviate a well.
BACKGROUND OF THE INVENTION
A variety of one trip milling systems are known, such as shown in U.S. Pat. No. 5,109,924, issued May 5, 1992. Other examples of one trip milling systems are shown in Canadian patent applications 2,242,026 (published Jun. 30, 1998) 2,221,435 (Nov. 18, 1997); 2,225,201 (Jul. 8, 1996); 2,182,535 (Aug. 1, 1996); 2,200,937 (Mar. 25, 1997); 2,033,048 (Dec. 21, 1990); and U.S. Pat. No. 5,771,972 (Jun. 30, 1998). In general these one trip milling systems include an initial or pilot mill, followed by a second mill on the drill string, and are used in association with a whipstock that is anchored in the well by a variety of means. The pilot mill rides on the whipstock and is deflected outward into contact with casing in the well to mill an initial window. A following mill then mills the edges of the window and drilling then follows the path established by the following mill through the casing.
SUMMARY OF THE INVENTION
In a one trip milling system, the object is to avoid having to make more than one trip to complete the deviation of the well. One problem is that as the mill advances through the casing, it can become worn, with the result that the diameter of the deviated wellbore becomes smaller, thus making tight spots in the well that can impede drilling. It is an object of the present invention to provide an improved one trip milling system that maintains the mill in fill gauge throughout the milling procedure.
There is thus provided in accordance with an embodiment of the invention, a one trip whipstock system which includes both a one trip combination mill and associated whipstock. The one trip mill comprises an upper cutter and lower cutter below the upper cutter. The upper cutter and lower cutter are joined by a cone that widens towards the upper cutter. In operation, a whipstock is connected to the drilling sub by shear bolts. A guide lug on the whipstock faces the drilling sub between the lower cutter and upper cutter for riding on the cone when the drilling sub is advanced along the whipstock. Preferably the shear bolts connect to the lower cutter. Also, the lower cutter has smaller gauge than the upper cutter, to such an extent that the relative gauge sizes of the lower cutter and upper cutter permit the upper cutter to exit casing during drilling before the lower cutter exits casing. Further, there may be provided a watermelon mill above the upper cutter, and optionally but preferably a string mill above the watermelon mill and the watermelon mill, string mill and the upper cutter preferably have the same gauge. To reduce outer diameter wear on the upper cutter, and thus maintain the gauge of the cutter during drilling, the upper cutter has a square leading edge.
These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow.
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Photocopy of International Search Report on corresponding PCT patent application PCT/CA00/01243, dated Feb. 27, 2001, 4 pages.
Heinley Dave L.
Ritorto Leonardo
Holland Joseph W.
Suchfield George
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