Double-tube side jet PDC drill bit for core sampling in muddy interlayer with clean water drilling

Abstract

The present invention discloses a double-tube side-spray PDC drill bit for clear water drilling and coring muddy interlayers, comprising a front drill bit, the inner side of which is provided with a first step, the first step being provided with a gap between the first step and the retaining spring seat; a rear drill bit, which is connected to the tail of the front drill bit, the connection between the rear drill bit and the front drill bit forming a second step, which is located outside the front drill bit, and a third step, which is located inside the rear drill bit and is provided below the first step; a guide hole, which is provided on the rear drill bit, has a first port located on the second step, and a second port located on the third step; wherein the flow channel formed by the rear drill bit and the retaining spring seat is connected with the second port of the guide hole. The present invention has an ingenious structure, is easy to use, and has a low maintenance cost. It can minimize or avoid the erosion of muddy interlayer cores when clear water is used as drilling fluid, improve the coring quality of muddy interlayer cores, and meet the requirements of the water conservancy industry for muddy interlayer information identification.

Description

Technical Field

[0001] The invention relates to the technical field of PDC drill bits, in particular to a double-tube side jet PDC drill bit for coring muddy interlayers through clear water drilling. Background Art

[0002] Mud interlayers are mostly found in sedimentary rock formations. They are weak in lithology, poor in hydraulic properties, and low in mechanical strength. They are easy to become potential sliding surfaces for buildings and slopes, which are extremely destructive to the stability of the foundation. Therefore, this item must be clarified in the early survey and design process of water conservancy and hydropower projects. At present, mud interlayer samples are mostly obtained by drilling, and underground information is obtained through analysis. The above-mentioned drilling refers to the operation of making the drill bit penetrate into the rock formation for coring by rotating the drill rod. In order to avoid the influence of non-clean water drilling fluid on the test results during the later tests such as formation penetration, it is required to use clean water as the drilling fluid for drilling. However, the existing drill bit is not suitable for sampling mud interlayers with clean water as the drilling fluid. Clean water will spray out from the gap between the retaining spring seat (extending into the drill bit, in which a retaining spring for clamping the core is provided) and the inner wall of the drill bit, which will have a greater erosion effect on the core that has entered the drill bit but not the core tube and in front of the drill bit, reducing the quality of the drilling sample. The core obtained from this will affect the correctness and accuracy of the geological survey conclusions. Summary of the invention

[0003] In order to avoid the problems of severe core erosion, poor core purity, low core extraction rate, etc. caused by using existing drill bits for coring, the present invention provides a double-tube side jet PDC drill bit for coring muddy interlayers in clean water drilling, and the following technical solutions can be specifically adopted:

[0004] The double-tube side jet PDC drill bit for clear water drilling and coring muddy interlayers of the present invention comprises:

[0005] The front drill bit has a first step disposed on the inner side of the bottom thereof, and a gap is disposed between the first step and the retaining spring seat;

[0006] The rear drill bit is connected to the tail of the front drill bit, and the connection between the rear drill bit and the front drill bit forms a

[0007] The second step, which is located outside the front drill bit, and

[0008] A third step, which is located inside the rear drill bit and is arranged below the first step;

[0009] a guide hole, which is opened on the rear drill bit and has a first port located on the second step and a second port located on the third step;

[0010] Among them, the flow channel formed by the rear drill bit and the retaining spring seat is connected to the second port of the guide hole; when working, after the drilling fluid flowing out of the flow channel reaches the first port through the guide hole, a part of it returns to the ground along the gap between the rear drill bit and the borehole wall, and the other part flows around the front drill bit from its outside to the inside to the second port to form a circulating flow.

[0011] The first step is an annular structure, and an annular buffer groove is formed on the first step.

[0012] The gap between the first step and the retaining spring seat is 2-5 mm.

[0013] The top surfaces of the front drill bit and the rear drill bit are respectively provided with evenly distributed PDC cutting teeth, the PDC cutting teeth are brazed and connected to the front drill bit / rear drill bit at the same inclination angle, and the PDC cutting teeth on the front drill bit and the rear drill bit are arranged correspondingly up and down.

[0014] The welding angle between the PDC cutting teeth and the front drill bit / rear drill bit is -15°.

[0015] A plurality of mounting protrusions are arranged at intervals on the second step, and one side of the mounting protrusion is brazed and connected to the PDC cutting tooth.

[0016] The first port of the guide hole is arranged close to the mounting protrusion.

[0017] A plurality of spiral guide grooves are arranged at intervals on the outer side surface of the front drill bit.

[0018] The direction of the spiral guide groove is opposite to the rotation direction of the drill bit, and one end of the spiral guide groove corresponds to the first port position of the guide hole, and the other end is arranged close to the PDC cutting tooth of the front drill bit.

[0019] The outer sides of the front drill bit and the rear drill bit are respectively provided with evenly distributed vertical gauge strips.

[0020] The double-tube side-jet PDC drill bit for clear water drilling and coring of muddy interlayers provided by the present invention has an ingenious structure, is easy to use, and has low maintenance cost. It can minimize or avoid the erosion of muddy interlayer cores when clear water is used as drilling fluid, improve the coring quality of muddy interlayer cores, and meet the requirements of the water conservancy industry for muddy interlayer information identification. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present invention.

[0022] Figure 2 yes Figure 1 Cross-sectional view of .

[0023] Figure 3 yes Figure 2 Enlarged view of part A in .

[0024] Figure 4 It is a usage state diagram of the present invention. DETAILED DESCRIPTION

[0025] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings. This embodiment is based on the technical solution of the present invention and provides a detailed implementation method, but the protection scope of the present invention is not limited to the following embodiment.

[0026] like Figure 1-3 As shown, the double-tube side jet PDC drill bit for clear water drilling and coring muddy interlayers of the present invention is composed of an integrated front drill bit 1 and a rear drill bit 2, and a guide hole 3 connecting the two. A retaining spring seat M is installed in the front drill bit 1 and the rear drill bit 2, and a gap between the retaining spring seat M and the rear drill bit 2 is set to form a drilling fluid flow channel N.

[0027] Specifically, the diameter of the front drill bit 1 is smaller than that of the rear drill bit 2, and the rear drill bit 2 is connected to the tail of the front drill bit 1. Six evenly distributed PDC cutting teeth 4 are respectively arranged on the top surfaces of the two, and each PDC cutting tooth 4 is brazed and connected to the front drill bit 1 / rear drill bit 2 at the same welding angle (approximately -15°), and the PDC cutting teeth 4 on the front drill bit 1 and the rear drill bit 2 are arranged in correspondence with each other up and down, that is, each PDC cutting tooth 4 on the front drill bit 1 and its corresponding PDC cutting tooth 4 on the rear drill bit 2 are arranged along the same radius. In order to extend the service life of the drill bit and maintain the hole diameter, six evenly distributed vertical gauge strips 5 are respectively arranged on the outer surfaces of the front drill bit 1 and the rear drill bit 2. Six spiral guide grooves 6 are arranged at intervals on the outer surface of the front drill bit 1, and an annular first step 7 is arranged at the bottom of the inner side surface thereof, and the retaining spring seat M is embedded in the first step 7, and its bottom is spaced 2-5mm from the end face of the first step 7. In addition, an annular buffer groove 8 is provided on the first step 7. The connection between the rear drill bit 2 and the front drill bit 1 forms a second step 9 and a third step 10, wherein the second step 9 is located outside the front drill bit 1, and 6 mounting protrusions 11 for welding the PDC cutting teeth 4 are arranged at intervals thereon, and the PDC cutting teeth 4 are located on the same side of the mounting protrusions 11; the third step 10 is arranged inside the rear drill bit 2 and below the first step 7. The guide hole 3 is used to connect the front drill bit 1 and the rear drill bit 2. It is located at the head of the rear drill bit 2, and has a first port located on the second step 9 and a second port located on the third step 10, that is, the guide hole 3 is inclined from the outside to the inside. There are 12 guide holes 3, and the first ports are all arranged close to the mounting protrusion 11, and the second ports are connected to the drilling fluid flow channel N. One end of the spiral guide groove 6 corresponds to the first port of the guide hole 3, and the other end is located at the cutting front end of the PDC cutting teeth 4 on the front drill bit 1, and the direction of each spiral guide groove 6 is opposite to the rotation direction of the drill bit.

[0028] When working, Figure 4 As shown, the drilling fluid flowing out of the flow channel N enters the guide hole 3 at the third step 10, flows from the second port to the first port, and then the drilling fluid is split at the first port, a part of which returns to the ground along the gap between the rear drill bit 2 and the borehole wall, and the other part flows around the front drill bit 1 from its outside to the inside to the second port of the guide hole 3 to form a circulating flow.

[0029] It can be seen that compared with the existing drill bit, the above-mentioned guide hole 3 can change the flow direction of the drilling fluid from the flow channel N between the retaining spring seat M and the drill bit. Firstly, since most of the drilling fluid flows out of the guide hole 3 and returns to the ground through the gap between the rear drill bit 2 and the borehole wall, it can not only cool and flush the PDC cutting teeth 4 on the rear drill bit 2, but also avoid a large amount of drilling fluid directly eroding the core and causing the sample quality to deteriorate; secondly, when another part of the drilling fluid flows to the first step 7, it contacts the annular buffer groove 8 on it to reduce the flow rate, and then forms a buffer groove in the annulus of the front drill bit 1. Positive circulation, while cooling the front drill bit 1, the above-mentioned drilling fluid can also ensure that the flow rate of the positive circulation drilling fluid will not be too high, thereby reducing or avoiding the erosion effect of the drilling fluid participating in the positive circulation on the core; thirdly, a spiral guide groove 6 is provided on the front drill bit 1 in the opposite direction of the drill bit rotation, and one end of the spiral guide groove 6 corresponds to the first port of the guide hole 3, and the other end is located at the cutting front end of the PDC cutting tooth 4 on the front drill bit 1, which can appropriately increase the supply of drilling fluid at the front end of the PDC cutting tooth 4 on the front drill bit 1, thereby carrying the rock powder away in time and avoiding the occurrence of mud-packing drill bit events.

[0030] It should be noted that, in the description of the present invention, terms indicating orientation or positional relationships, such as "front", "rear", "left", "right", "vertical", "horizontal", "inside", "outside", etc., are based on the orientation or positional relationships shown in the drawings and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

Claims

1. A double-tube side jet PDC drill bit for drilling muddy interlayers with clean water, characterized by: include The front drill bit has a first step disposed on the inner side of the bottom thereof, and a gap is disposed between the first step and the retaining spring seat; The rear drill bit is connected to the tail of the front drill bit, and the connection between the rear drill bit and the front drill bit forms a The second step, which is located outside the front drill bit, and A third step, which is located inside the rear drill bit and is arranged below the first step; a guide hole, which is opened on the rear drill bit and has a first port located on the second step and a second port located on the third step; Among them, the flow channel formed by the rear drill bit and the retaining spring seat is connected to the second port of the guide hole; when working, after the drilling fluid flowing out of the flow channel reaches the first port through the guide hole, a part of it returns to the ground along the gap between the rear drill bit and the borehole wall, and the other part flows around the front drill bit from its outside to the inside to the second port to form a circulating flow.

2. The double-tube side jet PDC drill bit for clear water drilling and coring muddy interlayer according to claim 1, characterized in that: The first step is an annular structure, and an annular buffer groove is formed on the first step.

3. The double-tube side jet PDC drill bit for clear water drilling and coring muddy interlayer according to claim 1, characterized in that: The gap between the first step and the retaining spring seat is 2-5 mm.

4. The double-tube side jet PDC drill bit for clear water drilling and coring muddy interlayer according to claim 1, characterized in that: The top surfaces of the front drill bit and the rear drill bit are respectively provided with evenly distributed PDC cutting teeth, the PDC cutting teeth are brazed and connected to the front drill bit / rear drill bit at the same inclination angle, and the PDC cutting teeth on the front drill bit and the rear drill bit are arranged correspondingly up and down.

5. The double-tube side jet PDC drill bit for clear water drilling and coring muddy interlayer according to claim 4 is characterized by: The welding angle between the PDC cutting teeth and the front drill bit / rear drill bit is -15°.

6. The double-tube side jet PDC drill bit for clear water drilling and coring muddy interlayer according to claim 4, characterized in that: A plurality of mounting protrusions are arranged at intervals on the second step, and one side of the mounting protrusion is brazed and connected to the PDC cutting tooth.

7. The double-tube side jet PDC drill bit for clear water drilling and coring muddy interlayer according to claim 6, characterized in that: The first port of the guide hole is arranged close to the mounting protrusion.

8. The double-tube side jet PDC drill bit for clear water drilling and coring muddy interlayer according to claim 1, characterized in that: A plurality of spiral guide grooves are arranged at intervals on the outer side surface of the front drill bit.

9. The double-tube side jet PDC drill bit for clear water drilling and coring muddy interlayer according to claim 8, characterized in that: The direction of the spiral guide groove is opposite to the rotation direction of the drill bit, and one end of the spiral guide groove corresponds to the first port position of the guide hole, and the other end is arranged close to the PDC cutting tooth of the front drill bit.

10. The double-tube side jet PDC drill bit for clear water drilling and coring muddy interlayer according to claim 1, characterized in that: The outer sides of the front drill bit and the rear drill bit are respectively provided with evenly distributed vertical gauge strips.

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