Hole opener and drillable casing guide and methods of use

[0001] This invention relates generally to hole opening operations and casing insertions in deviated hole bores and more particularly to a guide tool used to facilitate such operations.

[0002] Generally hole-opening operations down-hole involve the use of a hole-opening tool to enlarge a well bore. Such tools include a tool body configured for attachment at an upper end to a rotary drill string or the like and a lower end connected to a bull nose or radial member used for positioning and guiding the tool into and though the well bore to be enlarged. The tool further includes plurality of vertically extending slots each of which is configured to receive a removable cutter assembly adapted for rotation and retention therein. As the tool rotates, the cutters also rotate as a result of contact with the walls of the borehole, thus enlarging the bore to the size of the major diameter of the cutters. The bull nose serves as a guide through the previously drilled borehole. However, the previously drilled bore hole is by no means a well defined smooth or straight bore and often contains numerous cavities due to the differences in materials in the formation. It has been observed that the bull nose tip attached to the hole opening tool often jams into the crevices and sharp formations, especially in deviated holes approaching the horizontal, causing severe damage to the tool requiring retrieval and replacement of the hole opening tool. Therefore, a more reactive guide is needed to deflect the hole-opening tool around pits and in-penitratable projections.

[0003] In addition, it has also been observed that significant problems arise when attempting to insert and set casing in a bored hole. Intermediate casings are equipped with a flared flange at the lower end, extending outward between the casing outside diameter and the hole bore size, thus forming the base of the casing annulus. This flared or flanged casing must be negotiated though the bored hole and often becomes wedged or jammed in the crevices or pockets, discussed above, causing withdrawal and rotation of the casing in order to get past the obstruction. Therefore, a more reactive guide is needed to defect the casing flange around the pits and crevices. The following description of a down-hole guide tool has proved effective in solving the above-described problems.

[0004] A down-hole tool guide is disclosed for deflecting various down-hole tools having a tendency to hang or bind in uncased bore holes. The down-hole tool guide or ball guide assembly being adaptive to the down-hole tool extends forwardly there from and includes an eccentric rotatable ball and high-pressure jets. In cases where the guide is used to guide casing, the ball guide assembly is constructed from a drillable material thereby allowing the hole bore to be extended beyond the last set casing depth without side deviation from the original bore.

[0013] As may be seen in FIG. 1, hole opening tool assemblies 6 are generally fitted with a bull nose guide 8 when sizing the rough bore 9. Such bull nose guides 8 are usually fabricated from a drill pipe sub and are seldom of uniform shape, size or construction. These guides 8 are easily produced and are often replaced due to the abusive nature of the environment to which they are subjected. Sharp rocks and acute variations of the bore 9 often badly distort the bull nose guides 8 making them unusable. Utilizing the heavy-duty down-hole ball guide assembly 10, as seen in FIG. 2, in place of the bull nose sub 8 ensures a smother transition of the hole opener assembly 6 through the bore 9 by rolling over and around obstacles and by providing jetting to clean the path of the hole opening tool assembly 6 while rotating.

[0014] A second operation involves the installation of jointed casing in the bored hole, as shown in FIGS. 3A, 4A and 3B, 4B. As those in the art are aware, an initial drive casing 12 is set and subsequent casings, 14, 16 are set and cemented in place as the well bore progresses. A flared lip or flange 18, at the lower end of each string of casing, is sized to establish the annulus of the bore to be filled with cuttings and cement. This flared flange 18 is difficult to insert in the bore, even in smooth bores, and is made even more difficult in deviated holes especially as the deviation approaches the horizontal, as shown in FIG. 3B. The final casing string may be fitted with a casing bull nose guide 20 to help guide the casing to its final depth. Since the casing is not withdrawn and is set in place, the casing must be perforated above the casing bull nose 20, so it can be displaced down-hole, to allow for the production tubing string to be installed in the well. It is therefore anticipated that a ball guide tool assembly 10, seen in FIG. 4B, may be adapted to the casing to better assist in guiding the final casing string 16. Further, if the ball guide tool is made of a drillable material such as aluminum, bronze, brass, copper or other such relatively soft metal or composite materials having equivalent strengths. It would then be possible to simply drill through the ball guide assembly 10 with an earth boring drill bit thereby destroying the ball guide assembly and allowing continuation the well bore if necessary.

[0015] As shown in FIG. 5, the down-hole tool ball guide assembly 10 includes a tubular body portion 22 having an upset threaded end 24 which is bored and fitted with an internal ball check assembly 25 to prevent back flow from the well bore through the tool but still allow pressurized fluids from the surface to reach jetting nozzles 26 through the central bore 30. The pressurized fluids also provide lubrication to bearings in the ribbed ball assembly 32 via porting 34 and help flush debris from the ball. The ball assembly 32 is generally spherical in shape having external ribs or teeth 33 defined by a plurality of longitudinal grooves extending parallel to the central axis of the ball. The ball assembly 32 is a minor non-aggressive cutting bit, having the ability to clear minor obstacles and thus provide a reaming action as it rolls against the wall of the bore 9 as it spirals downward without side tracking the well bore 9. It should also be noted, that the ball 32 is arranged in a manner whereby the major diameter of the ball extends diametrically beyond the major diameter of the offset eccentric portion 36 of the body portion 22. The ball is rotatable about a tubular shaft 35 attached to the truncated portion 28 of the eccentric portion 36 of the body portion 22. The tubular shaft 35 is also ported to allow the previously mentioned pressurized surface fluids to lubricate internal bearings. Seals located within the ball assembly 32 prevent internal contamination of the internal bearings from down-hole debris.

[0016] An adaptor 38 may be provided that is threadably connected at one end to the ball guide assembly 10 and welded to the casing 16 in a seamless manner to reduce the possibility of hang-ups by the flared end of the casing.

[0017] Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in any limiting sense.