AU2011101138A4 - Adjustable eccentric bushing assembly for wireline-operated directional core barrel drill - Google Patents

Abstract

Abstract Eccentric bushing assembly (40) for a wireline-operated directional core barrel drill, especially for rock drilling of curved holes with a predetermined path. The eccentric bushing assembly (40) is an adjustable eccentric bushing assembly (40) which includes a bushing 5 (41) and two eccentric sleeves in the form of an outer sleeve (42) and an inner sleeve (43) engaging each other so that eccentricity can be changed seamlessly without the need of replacing components of the directional core drill to change the oblique position of the drill bit (12). Figure 2. 20 Figure 1.

Description

1 Adjustable eccentric bushing assembly for a wireline-operated directional core barrel drill The present invention relates to an eccentric bushing assembly for a wireline-operated 5 directional core barrel drill, and especially to an adjustable eccentric bushing assembly according to the preamble of claim 1. The invention provides an accurate, time saving and easy way to adjust bushing eccentricity without the need for replacing components of the directional core barrel drill. 10 Background A directional core drill is described in NO 168962 which is provided with a locking device or packer which is supplied with drilling fluid under pressure in order to push out locking elements or pressure pads which can be brought in contact with the borehole wall and lock the main body of the directional core drill head and its eccentric bushing relative to the wall. 15 Such pressure pads may be utilised for locking the high side of an eccentric housing in a certain position or be used to bring upon the drill bit a skewed position, for thereby performing directional drilling. It is known to make directional core drills with a rotary core barrel extending through an 20 eccentric bushing arranged in a non-rotatable outer tube. A packer is also described in NO 308552, where drilling fluid is used to press pressure pads against the borehole wall. Directional core drill heads may also carry navigational instruments, such as geotechnical instruments, as well as magnetometers, accelerometers, etc. 25 From NO 305713 it is known a rock drill where several pressure pads are arranged in at least two ring sections, so that the pressure pads become oriented in axial rows with projecting guiding bars oriented in a row. This solution is intended to reduce the frictional forces, which are effective in the axial direction when the drill is moved forward and shall at the same time ensure a frictional force against rotation sufficient to avoid a rotational movement. 30 The guidance is in this case ensured by a permanent eccentric bushing positioned between the packer and the drill bit, known from the patent publication mentioned above. A publication which improves the above presented solutions is patent publication NO 316286. In NO 316286 it is known a wireline-operated directional core barrel drill for rock 35 drilling, especially for rock drilling of curved holes with a predetermined path, having an outer drilling tube with a foremost rotatable drill bit and a part connected behind arranged for being locked against rotation. The outer body of the directional core drill is provided with 2 pressure pads which can be pressed against the borehole by means of pressure from supplied drilling fluid. In the front section of the main body it is arranged an eccentric bushing for bending the front part of the rotating internal drive shaft, so that the shaft and the drill bit are provided with a rotational axis deviating from the existing borehole and the non-rotatable 5 central section of the main body. In the drive shaft it is arranged an inner tube for receiving core samples when drilling, as the upper end is provided with space for a survey instrument to be able to measure and log data, such as inclination, direction and angle of rotation central section of the main body, incl. high side of the eccentric bushing. 10 The disadvantage with this solution is however that the eccentric bushing is arranged so that it is not possible to change the oblique position of the drill bit in a simple manner, due to the eccentric bushing assembly being of a fixed design. To be able to change the oblique position of the drill bit one must either move the eccentric bushing assembly in the longitudinal direction of the directional core drill, or replace the entire eccentric bushing 15 assembly with an assembly that have a different eccentricity. Adjusting the eccentricity as described above is time consuming and results in high costs when performing a drilling operation. Furthermore, a large numbers of outer tubes or eccentric bushing assemblies are needed to cover the necessary range of deviation angles for the drill hole. It is thus identified a need for an eccentric bushing assembly which makes it possible to do multiple fine-tuned 20 changes in the oblique position of the drill bit, without the need for replacing components of the directional core drill. Object The main object of the invention is to provide an eccentric bushing assembly for a 25 wireline-operated directional core barrel drill, which solves the above mentioned problems with prior art. More specifically it is an object to provide an eccentric bushing assembly where the eccentricity can be adjusted without the need for replacing components of the directional core drill for adjusting the eccentric bushing assembly in longitudinal direction, or having to 30 replace the entire eccentric bushing assembly. Further objects of the invention will be disclosed by the more detailed description below. The invention 35 An eccentric bushing assembly for a wireline-operated directional core barrel drill according to the invention is described in claim 1. Preferable features and details of the eccentric bushing assembly are described in the remaining claims.

3 The invention relates to a wireline-operated directional core barrel drill for rock drilling, especially a directional core barrel drill with high accuracy, where one desires to retrieve core samples without retrieving the drill string. 5 The wireline-operated directional core barrel drill according to the invention is significantly simpler, and thereby more sturdy in use, than those previously known. This also gives the possibility to ensure a stable fine-tuned directional drilling by means of simple adjustment steps. 10 According to the invention there is provided an eccentric bushing assembly for a wireline operated directional core drill which makes it possible to change the oblique position of a drill bit of the wireline-operated directional core barrel drill without the need for replacing components of the directional core drill. In prior art solutions the eccentric bushing assembly 15 has a fixed design. This means that one to be able to change the oblique position of the drill bit will have to move the eccentric bushing assembly in the longitudinal direction of the directional core drill, i.e. in relation to the drill bit, by installing shorter or longer set-up tubes before and after the eccentric bushing assembly, in order to move it closer or further away from front stabilizer and its bushing. Another prior art solution which has been used is 20 to replace the entire eccentric bushing assembly with an eccentric bushing assembly with different eccentricity when the oblique position of the drill bit is to be changed. Accordingly, both prior art solutions results in that one must replace parts of the directional core drill to change the oblique position of the drill bit when one desires to drill with a different curvature, i.e. with an angle deviating from a straight borehole. 25 The present invention provides an adjustable eccentric bushing assembly which includes two eccentric sleeves, in the form of an outer sleeve with centralizers and an inner sleeve, which sleeves are engaging each other so that eccentricity can be changed seamlessly and without the need for replacing components of the directional core drill to change the oblique position 30 of the drill bit. A bushing is arranged inside the inner sleeve and kept in place by a retaining ring. The outer sleeve is designed so that the inner sleeve with the bushing can be rotated by using a special hand tool, and the eccentricity of the eccentric bushing assembly will change accordingly. Furthermore, the eccentric bushing assembly is provided with a scale where an operator can see the actual eccentricity setting and adjust it accordingly via a window 35 arranged in the outer sleeve. With the present invention one will save time and costs in a drilling operation.

4 Further details and preferable features of the invention are disclosed by the example below. Example In the following the invention is described in more detail with reference to the accompanying 5 drawings, where Figure 1 is a perspective view of a main body of a prior art directional core barrel drill including a drill bit, packer and attachment sleeve at the upper end, for connection to a rear body, and a rear body, Figure 2 is a perspective view of an inner barrel bundle of a prior art directional core barrel 10 drill including a core case, inner tube, mule shoe, instrument housing and connection for wire line operation, Figure 3 is an axial cut through the front end of the drill bit and its coupling in Figure 1, Figure 4a is a perspective view of an adjustable eccentric bushing assembly for a wireline operated directional core drill according to the present invention, 15 Figure 4b is a cross section of the adjustable eccentric bushing assembly in Figure 4a, Figure 4c shows details of an outer sleeve of the eccentric bushing assembly according to the present invention, Figure 4d shows details of an inner sleeve of the eccentric bushing assembly according to the present invention, and 20 Figure 4e is a perspective view of a bushing for the eccentric bushing assembly according to the present invention. Reference is now made to Figure 1 which shows a wireline-operated directional core barrel drill according to prior art. In Figure 1 it is shown a steering tool main body 11 which is 25 assembled of several parts in the longitudinal direction. The main body 11 includes in order from below and up, a drill bit 12 with a reamer 13, a front stabilizer 14, a distance pipe 15, an eccentric bushing assembly 16, extension pipe 17, a packer tubing 18 with three pressure pads or packer elements 19, 20, 21, a packer guide bar 22, a pipe 23 for a thrust and radial bearing, a locking recess 24 at the upper end of a carrier pin (driving stud), a sleeve-shaped 30 piston carrier 25 which forms a annular piston space, and a drilling tube rear body 26. These elements will be described below. In Figure 2 it is shown an inner barrel bundle 27 having a lower core catcher sleeve 28 attached to an inner barrel 29 having space for receiving a bore core which at the upper end 35 is connected to a bearing sleeve and a snap connection 30 for connection to a mule shoe connection sleeve 31, which at its upper end carries an instrumentation pipe 32. The instrumentation pipe 32 has a communication port for instruments carrying measuring 5 instruments for measuring direction and inclination, and angle of rotation, for example magnetometer and accelerometer. Further it is arranged a spear head 33 for connection of the inner barrel bundle 27 to a wire line with a quick snap connection (not shown). 5 In Figure 3 the lower part of the main body 11 is shown in an axial cut. The drill bit 12, having exterior water paths, is tubular and has an inner mandrel 34 provided with threads for insertion in the reamer 13, which in a corresponding way is connected at the lower end of the reamer connection 14, which again is connected together with a rotating drive shaft 35. 10 At the front end of the reamer connection 14 it is arranged a sleeve 36 which can retrieve the core catcher sleeve 28. When the core catcher sleeve 28 is seated inside the sleeve 36, circulating water passing through the drive shaft 35 has to pass through one or more exterior channels in the core catcher sleeve 28, which in turn acts like a nozzle for choking drilling fluid which is supplied through the drive shaft 35, so that there is provided a pressure in the 15 drill pipe, which is sufficient for activating the packer 18 (Figure 1). The pressure upstream of the sleeve 36 can be 20-30 bars. The cross section of the channels in the core catcher sleeve 28 and thus the pressure of the packer 18 can be adjusted by replacing the core catcher sleeve 28 with a core catcher sleeve with more or less channels or with core catcher or core catcher channels having a different size. In this way it is possible in an easy way to 20 adapt the directional core barrel drill to different kinds of rock which requires different amounts of water and different packer pressure. To achieve the highest possible wear resistance the sleeve 36 can be manufactured of a very wear resistant material. Alternatively it can be arranged a corresponding sleeve higher up on the drive shaft 35 or the 25 inner barrel 29, at the lower side of the packer housing 18. The directional core drill of Figure 1-3 is so arranged that by supplying drilling fluid under pressure to the sleeve-shaped piston carrier 25, the sleeve-shaped piston carrier 25, the drill bit and its couplings, drive shaft 35 and rear body 26 can rotate independent of the stationary 30 part of the main body 11. The above described apparatus makes it possible to retrieve core samples from a directional core barrel drill. At the same time the directional core barrel drill has a connection mechanism making it easy to monitor, make adjustments and regulate the drilling direction 35 and borehole curvature. Further, it is easy to adapt the packer pressure after need when it is to be drilled in different kinds of rock, which requires different pressure during sliding.

6 Channels for conveying and chocking drilling fluid can alternatively or in addition be arranged in a sleeve surrounding the front end of the inner barrel. Reference is now made to Figures 4a-e which show an eccentric bushing assembly 40 for a 5 wireline-operated directional core barrel drill according to the invention and details of its elements. The eccentric bushing assembly 16 described in Figure 1 is a prior art eccentric bushing assembly 16 which has a solid non-adjustable eccenter. As mentioned above this solid eccentric bushing assembly 16 can also be used for a changed oblique position of the drill bit 12, but adjustments of its eccentricity in order to change the drill deviation per meter 10 requires that the longitudinal distance between the eccentric bushing assembly 16 and the front stabilizer 14 is changed by replacing the distance pipe 15 and extension pipe 17. Alternatively the eccentric bushing assembly 16 can be replaced with an eccentric bushing assembly 16 with different eccentricity. 15 By the adjustable eccentric bushing assembly 40 according to the invention there will be no need for replacing the distance pipe 15 and extension pipe 17 or replacing the eccentric bushing assembly itself for changing the oblique position of the drill bit 12. The adjustable eccentric bushing assembly 40 according to the invention includes a bushing 41 (shown in Figure 4b and 4e) and two eccentric sleeves in the form of an outer sleeve 42 and an inner 20 sleeve 43 engaging each other so that eccentricity can be changed seamlessly without the need of replacing components of the eccentric bushing assembly 40. The outer sleeve 42 is at its ends provided with threads 44 for connection to the fixed distance pipe 15 and extension pipe 17, respectively. 25 The outer sleeve 42 mainly has a shape as a cylinder but is interior provided with a boring 45 (as shown in Figure 4c) which extends from one side with a diameter and length adapted to receive the inner sleeve 43, and is from the other side provided with a central boring 46 (as shown in Figure 4c) with a smaller diameter than the boring 45 and a length extending 30 throughout the remaining of the outer sleeve 42. The outer sleeve 42 is on its outer diameter provided with centralizing pads 47 (as shown in Figure 4a) made in ultra-hard and wear resistant material. The pads 47 will engage with the borehole wall and centralize the directional core drill. Furthermore, the pads 47 provide a 35 means of creating distance between the main body 11 and the borehole wall, allowing drilling fluid to pass freely. The outer sleeve 42 is further provided with a window 48 (as 7 shown in Figure 4a) where the inner sleeve 43 can be reached for adjustment and inspection of eccentric settings. In Figure 4d it is shown details of the inner sleeve 43. The inner sleeve 43 is a distorted 5 sleeve formed by outer 49 and inner 50 non-concentric cylindrical walls. In this way it is formed a cylindrical bore 51 which is biased from the central axis of the inner sleeve 43. The outer diameter and length of the inner sleeve 43 correspond to the inner diameter of the boring 45 of the outer sleeve 42. The inner sleeve 43 is further provided with a seat for the bushing 41, as well as a retaining ring at its end to prevent the inserted bushing 41 from 10 leaving the outer sleeve 42. The bushing 41 is further provided with recesses 52 for engagement with one or more taps (not shown) arranged in the seat of the inner sleeve 43 for preventing the bushing 41 from rotating in its seat. Furthermore, the inner sleeve 43 is provided grooves or holes 53 (as 15 shown in Figure 4a) on its outer diameter where a tool can be engaged through the window 48 in the outer sleeve 42, to rotate the inner sleeve 43 for adjusting the eccentricity of the bushing 41. The inner sleeve 43 is preferably also provided with a scale (indicated in Figure 4a) on its outer diameter that indicate the degree of eccentricity the bushing 41 is set to have relative to the centre of the drill body, which scale is visible through the window 48 in the 20 outer sleeve 42. The inner sleeve 43 can further be provided with a channel going from the outer diameter to the inner diameter where a lubricant can be pumped in to lubricate the bushing. The inner sleeve 43 is further preferably provided with a groove on its outer diameter that is adapted to 25 a retaining tap 54 screwed into the outer sleeve 42 preventing the inner sleeve 43 from moving out of the outer sleeve 42. The outer 42 and inner sleeve 43 are locked to each other by means of set screws (not shown) arranged in through holes, provided with threads, arranged in the outer sleeve 42. 30 The set screws will come into contact with the inner sleeve 43 when tightened, and thus hold the inner sleeve 43 in position in relation the outer sleeve 42. When the eccentricity of the eccentric bushing assembly 40 is to be adjusted/changed, the complete drill body 11, 26 is brought up to the surface so that one can access the eccentric 35 bushing assembly 40. The set screws holding the inner sleeve 43 are loosened and an adapted adjustment tool is used to rotate the inner sleeve 43 in relation to the outer sleeve 42 via the window 48 to a desired eccentricity of the internal bushing 41, which is given by the 8 scale. The set screws are then tightened again and the complete drill body 11, 26 is again inserted into the borehole with an angle deviating from the prior drilled borehole. The relation between the inner sleeve 43 and outer sleeve 42 is arranged so that the 5 eccentricity can be adjusted to make the drill go straight, i.e. no deviating angle, and up to an eccentricity that makes the drill deviate up to 20 degrees or more per 30 m from the straight borehole. It should be mentioned that when performing drilling with an angle deviating from a straight borehole there is a limit of approx. 9-12 degrees per 30 m for longer sections and 14-16 degrees per 30 m for shorter sections, as the rod joints might break at angles larger 10 than this. In this way a rapid adjustment of the eccentric bushing can be achieved, and no parts of the directional core drill will have to be replaced, and the deviation angel can be fine-tuned to an angel that optimize the deflection per meter without causing problems for the drill rods, 15 consequently the drilling operation can be performed considerably faster and thus with saved costs, compared to prior art. Modifications Wear resistant materials mentioned above can be, but are not limited to: fibre composite or 20 plastic resins, or ultra-hard materials like tungsten, ceramic or PDC or hardened steel.

Claims (5)

1. Eccentric bushing assembly (40) for a wireline-operated directional core barrel drill, especially for rock drilling, which directional core barrel drill includes a main body (11) 5 including a drill bit (12) with a reamer (13), a reamer connection (14), a distance pipe (15), an eccentric bushing assembly (16, 40), extension pipe (17), a packer tubing (18) with pressure pads or packer elements (19, 20, 21), a packer guide bar (22), a pipe (23) for a thrust and radial bearing, sleeve-shaped piston carrier (25), and drilling tube rear body (26), into which main body (11) is arranged an inner barrel bundle (27) including a core catcher 10 sleeve (28), an inner barrel (29), bearing sleeve and a snap connection (30) for connection to a mule shoe connection sleeve (31) and instrumentation pipe (32), which inner barrel bundle (27) is provided with a spear head (33) for connection to a wire line, characterized in that the eccentric bushing assembly (40) is an adjustable eccentric bushing assembly (40) which includes a bushing (41) and two eccentric sleeves in the form of an outer sleeve (42) and an 15 inner sleeve (43) engaging each other so that eccentricity can be changed seamlessly without the need of replacing components of the directional core drill to change the oblique position of the drill bit (12).

2. Eccentric bushing assembly according to claim 1, characterized in that the outer sleeve 20 (42) mainly has a shape as a cylinder and an interior provided with an eccentric boring (45) which extends from one side with a diameter and length adapted to receive the inner sleeve (43) and is from the other side provided with a central boring (46) with a smaller diameter than the boring (45) and a length extending throughout the remaining of the outer sleeve (42). 25

3. Eccentric bushing assembly according to claim 1, characterized in that the outer sleeve (42) is on its outer diameter provided with centralizing pads (47) made in wear resistant material, for engaging with the borehole wall and centralize the directional core drill and creating distance between the main body (11) and the borehole wall for allowing drilling 30 fluid to pass freely.

4. Eccentric bushing assembly according to claim 1, characterized in that the inner sleeve (42) is provided with an eccentric boring as a seat for the bushing (41), which bushing (41) is provided with recesses (52) for engagement with one or more taps arranged in the seat for 35 preventing the bushing (41) from rotating in its seat. 10

5. Eccentric bushing assembly according to any one of claims 1-4, characterized in that the inner sleeve (43) is provided with grooves or holes (53) on its outer diameter where a tool can be engaged through the window (48) in the outer sleeve (42), to rotate the inner sleeve (43) for adjusting the eccentricity of the bushing (41) relative to the centre of the outer sleeve 5 (42).