JP2018204202A - PDC bit - Google Patents

Abstract

A PDC bit that is less likely to cause chipping even with a small back rake angle and that can improve excavation efficiency. A bit body rotatable around a central axis and a gauge cutter fixed to the outer peripheral surface of the bit body are provided, the back rake angle of the gauge cutter is 20° or more and 25° or less, A PDC bit comprising a cemented carbide substrate and a polycrystalline diamond layer fixed to the cemented carbide substrate, wherein the polycrystalline diamond layer is made of a sintered body of diamond grains having an average grain size of 15 µm or more and 60 µm or less. [Selection drawing] Fig. 1

Description

  The present invention relates to PDC bits.

  2. Description of the Related Art Conventionally, a rotary excavation bit (PDC bit) equipped with a PDC (Polycrystalline Diamond Compact) cutter is known which is equipped with a gauge cutter for reducing bit body wear and maintaining the diameter of the excavation hole. (For example, see Patent Documents 1 and 2).

US Patent Application Publication No. 2008/0190670 US Patent Application Publication No. 2013/0292186

  In the conventional PDC bit, the gauge cutter has a large back rake angle in order to reduce the impact with the wall surface of the drilling hole. For example, Patent Document 1 discloses that the back rake angle is 40 ° to 70 °, and Patent Document 2 discloses that the back rake angle is 70 ° to 85 °. However, by simply adjusting the back rake angle, chipping tends to occur when the back rake angle is reduced, and the excavation efficiency decreases when the back rake angle is increased, so that the excavation efficiency is not substantially improved.

  An object of the present invention is to provide a PDC bit that is less likely to cause chipping even when the back rake angle is reduced and can improve excavation efficiency.

  According to one aspect of the present invention, a bit body rotatable around a central axis and a gauge cutter fixed to an outer peripheral surface of the bit body are provided, and a back rake angle of the gauge cutter is 20 ° or more and 25 ° or less. The gauge cutter has a cemented carbide layer and a polycrystalline diamond layer laminated on the cemented carbide layer, and the polycrystalline diamond layer has diamond particles having an average particle diameter of 15 μm or more and 60 μm or less. There is provided a PDC bit made of a sintered body of

  According to this configuration, the impact resistance of the polycrystalline diamond layer is improved by using diamond particles having a relatively large particle size of 15 μm or more and 60 μm or less as the polycrystalline diamond layer of the gauge cutter. As a result, even when the gauge cutter's back rake angle is set to 20 ° or more and 25 ° or less, which is smaller than the conventional one, and the processing efficiency of the gauge cutter is increased, excavation without causing any damage to the gauge cutter for a long time. Can do. Therefore, according to the present invention, it is possible to provide a PDC bit that is less likely to cause chipping even if the back rake angle is reduced and that can improve excavation efficiency.

  The polycrystalline diamond layer may be composed of a sintered body of diamond particles having an average particle diameter of 20 μm or more and 40 μm or less.

  The polycrystalline diamond layer has a shape in which a part of a disk is cut out linearly, and the gauge cutter has a linear cutout portion of the polycrystalline diamond layer on a radially outer side of the bit body. It is good also as a structure fixed to the said bit body in the state turned, and the length of the said linear notch part being 1 mm or more.

  It is good also as a structure whose length of the said linear notch part is 2 mm or more.

  The length of the linear notch may be 95% or less of the disc diameter of the polycrystalline diamond layer.

  The gauge cutter may have a diameter of 11 mm to 16 mm.

  It is good also as a structure which is a bit for well excavation used for extraction of oil, natural gas, or a geothermal fluid.

  ADVANTAGE OF THE INVENTION According to this invention, even if it makes a back rake angle small, it is hard to produce a chipping and the PDC bit which can improve excavation efficiency is provided.

FIG. 1 is a perspective view of a PDC bit according to the embodiment. FIG. 2 is a plan view of the PDC bit according to the embodiment as viewed from the axial direction. FIG. 3 is a cross-sectional view of the PDC bit of the embodiment. FIG. 4 is a perspective view of the face cutter. FIG. 5 is a perspective view of the gauge cutter. FIG. 6 is an explanatory view showing an attached state of the gauge cutter. FIG. 7 is a graph showing changes in the bit load during the test.

  FIG. 1 is a perspective view of the PDC bit of this embodiment. FIG. 2 is a plan view of the PDC bit of this embodiment as viewed from the axial direction. FIG. 3 is a cross-sectional view of the PDC bit of this embodiment.

The present embodiment is an example in which the configuration of the present invention is applied to a reaming bit.
As shown in FIGS. 1 to 3, the PDC bit 10 of the present embodiment includes a substantially bottomed cylindrical bit body 11 centering on an axis O. The bit body 11 is generally made of steel or a matrix material (WC + Co, Ni, Fe, etc.). The bit body 11 of this embodiment is a bit body made of a matrix material.

  The bit body 11 has a cylindrical skirt portion 12 having a predetermined outer diameter on the rear end side (lower side in FIGS. 1 and 3), and on the front end side (upper side in FIGS. 1 and 3) than the skirt portion 12. A reaming portion 13 having a larger outer diameter, and a pilot portion 14 projecting from the reaming portion 13 toward the tip side. The reaming unit 13 includes a face cutter 15 and a gauge cutter 20 that are cutting edges during excavation.

  The skirt portion 12 has a male screw portion 12 a centering on the axis O at the rear end portion. The male screw portion 12 a is a tapered screw that tapers toward the rear end side of the skirt portion 12. The tip of a drilling rod (not shown) is screwed into the male screw portion 12a. The bit body 11 is made up of a face cutter 15 and a gauge by means of thrust and striking force toward the axial front end transmitted from the rock drill through the excavating rod, and rotational force about the axis in the rotational direction T during excavation. The rock mass is crushed and excavated by the cutter 20, and a small-diameter excavation hole formed in advance is expanded.

  The bit body 11 has a blow hole 16 that opens to the end face on the rear end side of the male screw portion 12a and extends to the front end side of the bit body 11 along the axis O. As shown in FIG. 3, the blow hole 16 diverges radially in eight directions from the center in the small diameter portion 14 </ b> A of the pilot portion 14. The branched blow hole 16 opens on the outer peripheral surface of the small diameter portion 14A.

  The pilot portion 14 includes a small diameter portion 14A that is continuous with the distal end surface of the reaming portion 13, and a large diameter portion 14B that is continuous with the distal end of the small diameter portion 14A and has an outer diameter larger than that of the small diameter portion 14A. Each of the small diameter portion 14A and the large diameter portion 14B has a disk shape centered on the axis O. Accordingly, the pilot portion 14 has a multi-stage columnar shape including the small diameter portion 14A and the large diameter portion 14B. The large diameter portion 14 </ b> B has an outer diameter that is smaller than the reaming portion 13 and larger than the skirt portion 12.

The reaming portion 13 includes a tip end surface 13A located on the radially outer side of the pilot portion 14 when viewed from the tip end side in the axial direction, a substantially cylindrical outer peripheral surface 13B extending from the outer peripheral end of the tip end surface 13A to the rear end side, And a rear end surface 13C extending in a tapered shape from the rear end of the surface 13B.
The front end surface 13A is an annular convex curved surface that inclines toward the rear end side as it goes toward the outer peripheral side. A plurality of face cutters 15 are fixed to the tip surface 13A. A plurality of gauge cutters 20 are fixed to the outer peripheral surface 13B.

  As shown in FIGS. 2 and 3, the reaming portion 13 is provided with a plurality of (eight in this embodiment) discharge grooves 17 extending in the axial direction from the front end surface 13 </ b> A to the rear end surface 13 </ b> C of the reaming portion 13. The discharge groove 17 is a groove for discharging the flour and the drilling water to the rear end side during excavation. Each discharge groove 17 has a concave curved surface shape. The eight discharge grooves 17 are arranged at equal intervals in the circumferential direction of the reaming portion 13. An opening of the blow hole 16 is disposed above each discharge groove 17. A face cutter 15 and a gauge cutter 20 are arranged along the outer shape of the side surface on the side surface 17A facing the rotation direction T of the discharge groove 17. In the present embodiment, since the tip surface 13A is a convex curved surface, the excavation tip is also arranged following the convex curve along the outer shape of the tip surface 13A. On the other hand, the gauge cutters 20 provided on the outer peripheral surface 13B are arranged in a straight line along the axial direction.

FIG. 4 is a perspective view of the face cutter 15. FIG. 5 is a perspective view of the gauge cutter 20.
As the face cutter 15 and the gauge cutter 20, a disk-like PDC cutter can be used. Both the face cutter 15 and the gauge cutter 20 of this embodiment are a laminate of the polycrystalline diamond layer 1 and the cemented carbide layer 2. For example, the PDC cutter is formed by laminating single crystal artificial diamond particles and tungsten carbide containing powdered cobalt, and then firing at a temperature of 1500 to 1600 ° C. and a pressure of about 50 to 60,000 atm. Can be manufactured by tying.

In the present embodiment, the face cutter 15 has a disc shape shown in FIG. 4, but the gauge cutter 20 has a shape in which a disc is cut out linearly as shown in FIG. As shown in FIG. 1, the gauge cutter 20 is fixed in a state in which the linear notch 1 </ b> A is directed radially outward of the bit body 11. The linear notch 1A and the axis O are substantially parallel.
In addition, as the gauge cutter 20, the disk-shaped PDC cutter shown in FIG. 4 can also be used. As the face cutter 15, a PDC cutter having a notch shown in FIG.

  The face cutter 15 and the gauge cutter 20 are brazed to a mounting seat 22 provided in the reaming portion 13. The mounting seat 22 has at least a support surface that is brazed and joined to the back surface (end surface on the cemented carbide layer 2 side) of the face cutter 15 or the gauge cutter 20. The mounting seat 22 may have a curved surface that is brazed to the side surfaces of the face cutter 15 and the gauge cutter 20.

In the face cutter 15 and the gauge cutter 20, the polycrystalline diamond layer 1 has a thickness of 0.5 mm to 1.0 mm, for example, and the cemented carbide layer 2 has a thickness of 2 to 5 mm, for example.
In the present embodiment, the polycrystalline diamond layer 1 is a sintered body of diamond particles having an average particle diameter of 15 μm or more and 60 μm or less. When the average particle diameter of the diamond particles is less than 15 μm, the polycrystalline diamond layer 1 is likely to be chipped. On the other hand, if the average particle diameter exceeds 60 μm, it becomes difficult to sharpen the corners 1B of the polycrystalline diamond layer 1 and the excavation efficiency decreases.

  The average particle diameter of the diamond particles constituting the polycrystalline diamond layer 1 is preferably 20 μm or more and 40 μm or less. By making an average particle diameter into the said range, it can be set as the PDC cutter which can make impact resistance and excavation efficiency compatible.

The diameter D of the face cutter 15 and the gauge cutter 20 is, for example, 8 mm or more and 50 mm or less, and preferably 9 mm or more and 16 mm or less. If the diameter D is less than 8 mm, it is difficult to secure a sufficient brazing area, and the adhesive strength may be insufficient. When the diameter D exceeds 16 mm, the PDC cutter becomes expensive, but the excavation efficiency is not improved so much.
In addition, when it has the linear notch part 1A like the gauge cutter 20, the diameter D of a PDC cutter is a diameter of a disc part.

  Since the gauge cutter 20 has the linear cutout portion 1A, the gauge cutter 20 makes line contact with the wall surface of the excavation hole at the cutout portion 1A. Thereby, compared with the case where a disk-shaped PDC cutter is used, a contact area with an excavation hole becomes large and it becomes difficult to produce chipping in the polycrystalline diamond layer 1.

  If the length L of the linear notch 1A is 1 mm or more, the effect of suppressing chipping can be obtained. In order to obtain a sufficient chipping suppressing effect, the length L is preferably 2 mm or more. On the other hand, when the length L exceeds 95% of the diameter D of the gauge cutter 20, more than 1/3 of the area of the disk is cut out, so that it is difficult to secure a sufficient brazing area and the adhesive strength. May be insufficient.

  FIG. 6 is an explanatory diagram showing a state in which the gauge cutter 20 is attached. FIG. 6 is a schematic diagram showing a cross section (cross section perpendicular to the axis O) of the bit body 11 at the axial position of the gauge cutter 20. As shown in FIG. 6, the gauge cutter 20 is attached in a posture that forms a predetermined negative radial rake angle (back rake angle β) with respect to the radial reference line J of the bit body 11.

The gauge cutter 20 is fixed to the bit body 11 in such a posture that the back rake angle β is 20 ° or more and 25 ° or less. When the back rake angle β is less than 20 °, even if the above-described PDC cutter (PDC cutter having a sintered body of diamond particles having an average particle diameter of 15 μm or more and 60 μm or less) that hardly generates chipping is used, sufficient chipping is achieved. It cannot be suppressed. On the other hand, when the back rake angle β exceeds 25 °, the gauge cutter 20 is hardly damaged, but sufficient excavation efficiency cannot be obtained.
The gauge cutter 20 may be attached in a posture having a negative axial rake angle of about 5 to 20 °.

  According to the PDC bit 10 of the present embodiment described above, a polycrystalline diamond layer made of a sintered body of diamond particles having an average particle diameter of 15 μm or more and 60 μm or less is used as the gauge cutter 20 disposed on the side surface of the bit body 11. The impact resistance in the gauge cutter 20 can be improved by using the provided PDC cutter. Thereby, even when the back rake angle of the gauge cutter 20 is set to a small angle of 20 ° to 25 °, chipping can be suppressed. As a result, the excavation efficiency is greatly improved as compared with the conventional PDC bit in which the back rake angle is set to 40 ° to 85 °.

  When the gauge cutter 20 is worn or missing in the PDC bit 10, the machining diameter of the bit is reduced and the excavation hole is narrowed. A stabilizer is usually installed immediately above the PDC bit 10, and the PDC bit 10 must be replaced when the drilling hole becomes thin enough to contact the stabilizer and the inner surface of the drilling hole. In this regard, in the PDC bit 10 of the present embodiment, the gauge cutter 20 is not easily damaged, so that the machining diameter of the bit can be maintained for a long time. As a result, the time until the excavation hole becomes narrower becomes longer, and the replacement cycle (life) of the PDC bit 10 becomes longer.

  In the present embodiment, a reaming bit has been described as an example of a PDC bit. However, a pilot bit may be used.

The PDC bit 10 of the present embodiment described above can be suitably used as a well drilling bit for mining oil, natural gas, or geothermal fluid.
In the PDC bit 10 of the present embodiment, since the gauge cutter 20 is not easily damaged, even in the excavation of an inclined shaft or a horizontal shaft where the gauge cutter 20 is always in contact with the wall surface of the excavation hole, the excavation can be performed with high efficiency for a long time. Can do. Further, even when a hard formation is included, the processing diameter of the PDC bit 10 can be maintained, and the excavation hole is not easily thinned.
Therefore, in addition to oil and gas field mining where PDC bits have been useful in the past, there are many shale oil and shale gas drilling that require drilling of inclined and horizontal shafts, and hard and heterogeneous formations. It can also be suitably used for excavation of geothermal fluid.
More specifically, oil drilling mainly targets relatively soft materials such as sandstone and mudstone (uniaxial compressive strength, UCS: 120 MPa), but geothermal drilling uses medium hard rock (UCS: 180 MPa) Depending on the type, up to hard rock (UCS: 280) can be excavated. In the prior art, high-efficiency excavation is possible with soft rocks as described above, but a relatively small back rake angle is required to excavate cemented carbide efficiently.
Also, in recent years, in order to increase excavation efficiency, bit rotation is used at a higher rotation speed of 150 to 300 RPM by using a mud motor (downhole motor) than the conventional 50 to 60 RPM (using Kelly and top drive). It is also often done.
In these applications, the PDC bit 10 of the present embodiment can be suitably used.

  Next, the PDC bit of the present invention will be described in more detail with reference to examples.

(First embodiment)
In the first example, a polycrystalline diamond layer of a PDC cutter suitable for a gauge cutter was verified.
PDC cutters of Test Examples 1-1 to 1-5 using diamond particles having the particle sizes shown in Table 1 were produced. The diameter of the PDC cutter was 8.2 mm, and the thickness was 3.5 mm (polycrystalline diamond layer 0.7 mm, cemented carbide layer 2.8 mm). In addition, the particle diameter and average particle diameter of the diamond particles shown in Table 1 are values measured by a laser diffraction / scattering method in the state of diamond powder.
The PDC cutters of Test Examples 1-1 to 1-5 were attached to coring bits to which eight cutters can be attached, and test cutting was performed under the following conditions.

Excavation speed: 7cm / min
Rotation speed: 100rpm
Excavation length: 100m or more Rock used for excavation: Inada granite, UCS = 224MPa

  As shown in Table 1, the PDC cutter of Test Example 1-1 using diamond particles having a large particle size is both wear resistant and impact resistant compared to the PDC cutter of Test Example 1-2. Excellent results were obtained. In particular, with respect to impact resistance, there was a significant difference between Test Example 1-1 and Test Example 1-2. Specifically, in Test Example 1-2, all four chips showed large chipping, whereas in Test Example 1-1, only one chipping occurred, and another chipping occurred. Was very minor.

In Test Example 1-3, a PDC cutter was manufactured using relatively large diamond particles (average particle size is 55 μm). Therefore, it became difficult to form a sharp cutting edge, and the excavation efficiency was slightly lowered as compared with Test Example 1-1. This can be confirmed from the fact that the maximum load is a little larger at 50 kN, and it is necessary to press the bit with a higher load than in Test Example 1-1 in order to maintain a constant excavation speed.
On the other hand, in Test Example 1-3, the wear width itself was small. This is because the cutting edge of the PDC cutter is rounded due to the large particle size of the diamond particles, and the same action as the chamfered PDC cutter is obtained.

  In Test Example 1-4, diamond particles having a larger particle diameter than the PDC cutter of Test Example 1-3 were used. As a result, the rounding phenomenon in the cutting edge of the PDC cutter became prominent, and the load during excavation increased to 70 kN. Since an 8.5 inch full cross-section (pilot) bit is usually used with a bit load of about 50 to 100 kN, 70 kN is a very high load in the core bit of φ66 used in this example, and it is a normal double. It is a moderate load.

  In Test Example 1-5, a PDC cutter was manufactured using diamond particles having a slightly smaller particle diameter than Test Example 1-1. In Test Example 1-5, although the wear width was slightly increased, the bit load during excavation was decreased, and the same excellent results as in Test Example 1-1 were obtained.

(Second embodiment)
In the second example, a suitable angle was verified for the back rake angle of the gauge cutter.
In this example, a reaming bit including four types of PDC cutters shown in Table 2 as a gauge cutter was prepared, and the gauge cutter was evaluated by a reaming test.

The test procedure is as follows.
・ Pilot hole drilling:
Excavate Inada granite using a 6-1 / 4 inch bit.
・ Bit exchange:
Replace the bit with a 7-5 / 8 inch reaming bit while keeping the rod and pilot hole axes aligned.
・ Reaming test:
Ream the pilot hole at a constant speed (rotation speed 75 rpm, excavation speed 5 cm / min), and observe the gauge cutter after excavation for a predetermined length.

As shown in Table 2, in the PDC bits of Test Example 2-1 and Test Example 2-2 in which the back rake angle was set to 25 ° and 20 °, the gauge cutter was not lost after excavation and was only slightly worn. Sufficient excavation performance was confirmed. On the other hand, in the PDC bits of Test Examples 2-3 and 2-4 in which the back rake angle was less than 20 °, the gauge cutter had a defect, and the wear progressed from the defective part.
FIG. 7 is a graph showing changes in the bit load during the test. As shown in FIG. 7, in the PDC bits of Test Example 2-1 and Test Example 2-2 in which the back rake angle was set to 25 ° and 20 °, excavation was possible with a low load, whereas the back rake was In the PDC bits of Test Examples 2-3 and 2-4 having an angle of less than 20 °, the load was relatively high.

  DESCRIPTION OF SYMBOLS 1 ... Polycrystalline diamond layer, 1A ... Notch part, 2 ... Cemented carbide layer, 10 ... PDC bit, 11 ... Bit body, 13B ... Outer peripheral surface, 20 ... Gauge cutter, D ... Diameter, L ... Length, O ... axis, β ... back rake angle

Claims (7)

A bit body rotatable around an axis, and a gauge cutter fixed to the outer peripheral surface of the bit body;
The back rake angle of the gauge cutter is 20 ° or more and 25 ° or less,
The gauge cutter has a cemented carbide layer and a polycrystalline diamond layer laminated on the cemented carbide layer,
The polycrystalline diamond layer is a PDC bit made of a sintered body of diamond particles having an average particle diameter of 15 μm or more and 60 μm or less.   2. The PDC bit according to claim 1, wherein the polycrystalline diamond layer is formed of a sintered body of diamond particles having an average particle diameter of 20 μm to 40 μm. The polycrystalline diamond layer has a shape in which a part of a disk is cut out linearly,
The gauge cutter is fixed to the bit body in a state where a linear notch portion of the polycrystalline diamond layer is directed radially outward of the bit body,
The PDC bit according to claim 1 or 2, wherein a length of the linear notch is 1 mm or more.   The PDC bit according to claim 3, wherein a length of the linear notch is 2 mm or more.   5. The PDC bit according to claim 3, wherein a length of the linear notch is 95% or less of a disc diameter of the polycrystalline diamond layer.   The PDC bit according to any one of claims 1 to 5, wherein a diameter of the gauge cutter is 11 mm or more and 16 mm or less.   The PDC bit according to any one of claims 1 to 6, which is a well excavation bit used for extraction of oil, natural gas, or geothermal fluid.

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