Window forming by flame cutting

[0002] This application claims benefit of U.S. provisional patent application Ser. No. 60/115,978, filed Jan. 15, 1999, which is herein incorporated by reference.

[0003] The field of the invention relates to flame-cutting techniques for making windows in casing for drilling laterals in existing wellbores.

[0004] FIG. 1aillustrates a traditional method of window forming wherein a starter mill 10 is directed by whipstock 12 into the wall of the casing 14. The typical shape of a window or opening 16 is shown in FIG. 1b. The window is narrow when initially cut and proceeds to its maximum width when the mill 10 is approximately in the position shown in FIG. 1aas its center is in alignment with the wall of the casing 14. The mill 10 tends to bog down at this point because there is little relative rotation when the center of the mill is in alignment with the wall of the casing 14. As a result, typically mills have been designed to have a build-up of cutting material 18 (shown in FIG. 1c) to prevent coring out the starter mill 10 as it bogs down in the position shown in FIG. 1a. Eventually, the starter mill 10 continues to cut and the remainder of the window (shown in FIG. 1bas the lower half) begins to get progressively narrower until the starter mill 10 exits the window completely.

[0005] The traditional technique of using one or more mills, even if done in a one-trip technique involving orientation tools coupled with an anchor or packer, is still fairly time-consuming. Accordingly, one of the objectives of the present invention is to dramatically decrease the time required for formation of the window. Additionally, another objective of the invention is to be able to cut any desired window shape in a minimum amount of time, with the result that minimum debris or residue is left after employing the technique. Another objective is to eliminate the typical window profile illustrated in FIG. 1bso that shorter kickoff diverters can be used when drilling the lateral through the window that is produced.

[0006] In the past, casing to be cut in two in a wellbore has been cut using techniques involving ignited combustible materials which are directed to a radial nozzle or nozzles to cut cleanly through the casing or tubular. These types of devices using a cutting flame radially to cut through a pipe are illustrated in U.S. Pat. Nos. 4,598,769 and 5,435,394. These devices are limited-purpose tools for cutting radially through a casing.

[0007] Explosive techniques for making a window in casing, using a shaped charge attached to a starter mill which is, in turn, attached to a whipstock, is illustrated in U.S. Pat. No. 5,636,692.

[0008] Another objective of the present invention is to use flame-cutting techniques to produce a window of desired shape rapidly to facilitate further downhole operations.

[0009] These aspects of the method will be more readily understood by those skilled in the art from a review of the details of the preferred embodiment described below.

[0010] A tool containing a solid combustible material is used to provide a pipe-cutting flame and to direct a pipe-cutting flame against a casing or tubular. The nozzles can be configured in any desired array and intensity. In the preferred embodiment, a rectangular window is burned away completely if the nozzles are sufficiently intense or the window is formed in segments if other distributions are used. The device can be anchored by a packer or anchor and can be run in the wellbore on tubing, wireline or electric line. The window can be produced in a single trip. The tool can be removed and a kick-off diverter installed adjacent the window for drilling the lateral.

[0011] FIG. 1ais a sectional elevational view of the prior art technique for milling a window using a starter mill and a whipstock.

[0012] FIG. 1bis the resulting window made by using the technique shown in FIG. 1a.

[0013] FIG. 1cis the view of a typical starter mill used for making windows in the prior art.

[0014] FIG. 2 illustrates a radial flame cut produced by a prior art pipe-cutting apparatus illustrated in U.S. Pat. No. 4,598,769.

[0015] FIG. 3 illustrates the flame jet distribution in a rectangular high-intensity pattern for burning a complete window in a casing or tubular.

[0016] FIG. 4 shows an alternative to FIG. 3 where a rectangular window is burned at its periphery, leaving a single residual piece to come out of the casing wall.

[0017] FIG. 5 is an alternative to FIG. 4, indicating two pieces falling from the casing or tubular when making a rectangular window.

[0018] FIG. 6 is an alternative to FIG. 5, making an overall rectangular window by burning away smaller rectangularly shaped pieces.

[0019] FIG. 7 is an alternative to FIG. 6, illustrating the technique for making a rectangular window, leaving triangular and diamond-shaped pieces.

[0020] FIG. 8 illustrates the tool in casing having a rectangular pattern with an intensity sufficient to burn away a rectangular opening in the casing.

[0021] FIG. 9 is the tool of FIG. 8 shown as fired.

[0022] FIG. 10 shows the window made from firing as reflected in FIG. 9.

[0023] FIG. 11 illustrates the use of an anchor or packer or bridge plug for support of the tool in the run-in position.

[0024] FIG. 12 shows the fully supported position for the tool prior to firing.

[0025] FIG. 13 shows the formation of a rectangular window and the subsequent removal of the tool, exposing an anchor for a kick-off diverter.

[0026] FIG. 14 shows the installation of the kick-off diverter and the drillstring for drilling the lateral through the window.

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0028] The method of the present invention is illustrated in the attached figures. The flame-cutting apparatus, first described in U.S. Pat. No. 4,598,769, is reconfigured to have a plurality of nozzles arranged in a variety of patterns. FIG. 3 illustrates a generally rectangular orientation of nozzles 20, placed in very close quarters so that when actuated, as shown in FIG. 9, a rectangular opening 22, shown in FIG. 10, can be produced without any casing segments falling into the wellbore. In essence, the intense heat delivered by the nozzles 20 in a closely confined array, such as shown in FIG. 3, essentially at 6000° F. or higher, results in the formation of the window 22 without any significant debris in the wellbore.

[0029] Referring to FIG. 4, a rectangular window is formed by cutting the periphery of the window, leaving a piece of the casing 24 as debris in the wellbore. FIG. 5 is similar to FIG. 4 except that an additional longitudinal row 26 has been added so that the debris comprises of two pieces 28 and 30. FIGS. 6 and 7 illustrate alternative nozzle patterns which result, respectively, in a series of rectangular pieces of debris 32 when making a rectangular window, or, as shown in FIG. 7, a combination of triangular and parallelogram shapes 34 and 36, respectively.

[0030] FIG. 8 illustrates schematically running the tool T into the casing 38. The support 40 is shown schematically and can be an electric line, wireline, or coiled tubing, and can also include known orientation equipment to properly position the tool T before it is fired. FIG. 9 illustrates the tool with a layout of nozzles 20 akin to that shown in FIG. 3 being fired, while FIG. 10 illustrates the window 22 after the tool has been removed.

[0031] FIG. 11 is a more detailed view of the method of the present invention. Here, a packer or bridge plug 42 supports an anchor 44, which eventually accepts a short diverter 46 as shown in FIG. 14. The packer or bridge plug 42 has slips 48 which are retracted in FIG. 11 and set in FIG. 12. The orientation is determined prior to setting the slips 48, using a known measurement-while-drilling (MWD) tool, which is part of the assembly of support 40. Thereafter, as shown in FIG. 13, the tool T is fired to make the window 22 and is subsequently released from the anchor 44. The diverter 46 is configured so that when it is secured to the anchor 44, it points into window 22. In using the method of the present invention, the shape of the window can be more certainly relied upon as being rectangular, as opposed to techniques in the prior art which resulted in a more elliptical shape, as shown in FIG. 1b. Thus, the diverter 46 can be of fairly short length. Another advantage is that with the window 22 being produced essentially rectangular, the mill 50 does not bog down when it is about half-way through the window, as in the prior art illustrated in FIG. 1a. The reason for this is that there is no longer any metal to mill through at a time when there is little relative rotation between the bit 50 and the casing 38.

[0032] Since the opening 22 is reliably rectangular, the placement of the diverter 46 is not as critical as in the prior art, where the shape of the window was more elliptical, as shown in FIG. 1b. With the window 16 having the shape shown in FIG. 1b, it was more important to position the diverter to get the bit kicked off toward the widest spot in the window. With a reliably made rectangular opening, vertical placement of the diverter 46 is not critical.

[0033] The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.