Selection and Application of Diamond Bits
Diamond drill bits refer to watch and impregnated drill bits made of natural diamond, synthetic diamond, composite sheet, sintered body, polycrystalline, etc. as cutting tools. The drill bit itself is a rock fragmentation tool, and its working object is rock. In order to obtain geological effects and technical and economic indicators, the drill bit must be selected reasonably according to the physical and mechanical properties of the rock.
1. The principle of choosing diamond drill bits
1. Soft to medium hard (referring to the drillability classification table 1-6 for diamond core drilling) and complete homogeneous rock formations. Generally, natural surface-set drill bits, composite drill bits, polycrystalline drill bits are suitable, and some sintered body drill bits can be used. .
2, to a hard rock hard and compact (7-12-classification table), is generally appropriate to impregnated bits, or staggered tip and ring groove concentric drill tip and ring groove, or fine diamond bit table.
3, For broken, hard and soft interlayers, well-developed fractures or strong abrasive rock formations, such as coal-measure formations, it is advisable to use pointed-tooth drill bits or electroplated impregnated drill bits with good wear resistance and reinforcement.
4. The principle of selecting the wear resistance of the carcass according to the abrasiveness, weathering and crushing degree of the rock is:
(1) Strong abrasive rock formations, use high wear resistance carcass.
(2) For medium abrasive rock formations, use a matrix with medium abrasion resistance. For weak abrasive rock formations, use low-wear-resistant carcasses.
(3) For complex rock formations, the stronger the abrasiveness, the harder the diamond drill bits with better grades and relatively finer grain sizes.
(4) For highly abrasive and relatively broken rock formations, under the condition of ensuring good diamond enclosing, choose a diamond bit with a higher diamond concentration. On the contrary, for homogeneous, dense, and weakly abrasive rock formations, diamond drill bits with lower diamond concentration should be used.
(5) The rock formation is soft (grade 1-4), with a lot of powder discharge, choose composite drill bit or polycrystalline drill bit. For coring of easy-erosion rock and mineral layers, bottom jet drill bits should be used.
2. Reasonable use of diamond drills
After correctly selecting the drill bit type according to the physical and mechanical properties of the rock, the following eight technical measures must be taken to obtain the technical and economic indicators.
(1) According to the rock formation, design hole depth, etc., drill bits and reamers should be lined up for rotation. Use the one with the larger outer diameter first, and then use the smaller one. At the same time, use the smaller inner diameter first, and then use the larger inner diameter. In the process of rotation, it should be ensured that the queued drill bits and reamer can be normally lowered to the bottom of the hole to avoid sweeping holes and sweeping residual cores.
(2) After the drilling is confirmed, you must use a vernier caliper to accurately measure the outer and inner diameters of the drill and the reamer, and the height of the impregnated drill, and make a record as the basis for selecting the drill size for the next time.
2. The drill bit and the reamer must be reasonably matched
(1) The outer diameter of the reamer should be 0.3mm-0.5mm larger than the outer diameter of the drill bit, and the hard rock layer should not be larger than 0.3mm. If the outer diameter of the reamer is too large, the amount of reaming will increase, wear will increase, and the drilling efficiency will be low. If the outer diameter of the reamer is too small, it will not play the role of reaming.
(2) The inner diameter of the diamond bit and the free inner diameter of the circlip must be reasonably matched. If the free inner diameter of the circlip is too large, the core cannot be taken or stuck tightly, causing the core to fall off in the middle or too much residual core; if the free inner diameter of the circlip is too small, it is easy to block the core. Therefore, before drilling each time, pay attention to checking the size of the drill bit and the matching size of the circlip. The airport should prepare 2 to 3 inch circlips for selection.
3. Create good working conditions for diamond drill bits
(1) Diamond is brittle and easily broken under impact load. Therefore, it is required that the inside of the hole is clean, the bottom of the hole is flat, and the hole diameter is regular.
(2) It is found that there are cemented carbide chips, tire block chips, falling diamond particles, metal chips, falling cores, falling blocks, etc. at the bottom of the hole. Immediately use punching, fishing, ramming, grasping, sticking, sheathing, and grinding. , Suction and other methods to remove.
(3) It is forbidden to use steel pellets for drilling with diamond drilling. Before drilling a new diamond drill bit, it must be grounded.
(4) Before changing the diameter and running the casing, the bottom of the hole must be cleaned and trimmed. After changing the diameter and running the casing, use a conical diamond drill bit to make the diameter change step into a cone, and remove the foreign matter at the bottom of the hole before drilling.
4. Improving the stability of the drilling tool During the drilling process, due to the improper selection of drilling technical parameters, serious hole inclination, unreasonable drilling tool grading, drilling over-diameter and other factors, the drilling tool will produce varying degrees of vibration. Although the vibration cannot be completely eliminated, it can be improved by taking the following preventive measures.
(1) The use of round section, straight, on-machine drill pipes, high-speed portable taps, and light high-pressure hoses of the same level as the drill pipes are used to eliminate the heaviness phenomenon, keep the on-board drills running smoothly, and prevent shaking. Do not use drill pipes and large diameter drilling tools with a curvature exceeding the specified.
(2) Use well-graded drilling tools to reduce the annular gap between the drilling tool and the wall of the hole or the inner wall of the casing, thereby reducing the "radial" vibration of the drilling tool.
(3) Do not use excessive drilling pressure and pumping capacity Drill in.
(4) Data reducer, centralizer or stabilizing joint can be used.
(5) In strong abrasive, broken, soft and hard interbedded rock formations, it is forbidden to blindly turn on high speed.
(6) Use emulsified flushing fluid and lubricating paste to reduce the frictional resistance and vibration when the drilling tool rotates.
(7) The center lines of the drive shafts of the drilling rig and the diesel engine should be aligned, the fuselage should be upright and level, and the foundation should be firm.
5. Prevent core blockage
(1) Single-action double-pipe drilling should be used to drill in rock and ore layers with well-developed joints, broken, and large inclination angles, and special coring tools should be designed.
(2) For rock formations that are easy to block due to water swelling, joint development, etc., a drill bit with a smaller inner diameter and better reinforcement should be used to enable the core to enter the inner pipe more smoothly.
(3) In order to ensure that the relatively broken core can enter the inner tube smoothly, the inner tube wall can be coated with suitable grease or sprayed with plastic or plated.
(4) Take corresponding damping measures to reduce blockage caused by rock and core crushing caused by vibration.
(5) During the drilling process, the drilling tool is not allowed to be lifted arbitrarily, the turning on and off of the vehicle must be stable, and the weight on bit and pump volume must be uniform.
6. Prevention of burning drill burning refers to the abbreviation used for the diamond drill bit to be burned out due to improper operation or complicated conditions in the hole during the drilling process. Those who burned the diamond drills scrapped the diamond bit and the cost of the drill bit increased sharply; for the heavy ones, the bit matrix melted and sintered with rock dust and residual core, and even a vicious accident that burned more than 1m along with the core tube occurred, resulting in forced End hole or scrap. Vicious drill burning will cause stuck drill accidents, often accompanied by bending of the drill hole. Therefore, burning drill is one of the accidents that easily occur in diamond drilling, and preventive measures should be taken strictly.
(1) To ensure the smooth circulation of flushing fluid, diamond drilling uses high speed. Due to the small gap between the drill bit, the drill tool and the hole wall, and the insufficient supply of flushing fluid at the bottom of the hole or the interruption of the circulation, the drill bit is poorly cooled and the powder is not discharged in time, and the drill bit can be burnt instantly. Therefore, during the drilling process, always keep the circulation unblocked, namely: ①Ensure that the mud pump is in good working condition. If possible, use variable pumps as much as possible, cancel the water transfer three-way valve, and be equipped with anti-vibration pump pressure gauges, flow meters and pump volume alarms. When there is no alarm, a dedicated person should be set up to measure the water volume. ②Keep the good sealing performance of the drill string and prevent the flushing fluid from leaking in the middle. The unscrewing end of the drill pipe and the large diameter drill must be coated with threaded oil, wrapped with cotton silk or cushioned with nylon ring. , Put an end to the phenomenon of mixing and leakage.
Picture During the drilling process, miserable leaks and leaks are difficult to observe. This is because the flushing is not returned to the bottom of the hole, and the "short circuit cycle" can still be maintained, but a careful and experienced operator can still observe the slight decrease in pump pressure and whether the return water becomes clear (without rock dust). The ground water pressure test of the drill pipe should be carried out regularly. If the joint thread is not well sealed, it should be replaced or repaired in time. ③After each trip, the warm water hole, water gap, and water gap of the double-layer core pipe should be cleaned and checked before drilling The clearance between the circlip seat and the inner shoulder of the drill bit. Check the height of the nozzle of the drill bit and the width and depth of the internal and external water tanks. Those who fail to pass should be polished (the depth of the internal and external water is not less than 1.5mm, and the height of the nozzle is not less than 3mm) to ensure good performance. Water section reduces water pressure loss. ④The residual rock dust at the bottom of the hole shall not exceed 0.5m. When it exceeds, it should be specially punched to discharge the powder, or specially fished. For drilling strong abrasive rock formations, increase the pump capacity to prevent drill burning.
(2) Control the reasonable drilling speed. During the diamond drilling process, do not blindly pressurize and pursue the footage. Excessive drilling speed will result in siltation of rock dust in the hole. If the dust is not discharged in time, the drill will burn out and even the drill hole will bend. Strive to avoid this "malignant chain reaction." The organic coordination of the three elements of diamond drilling technology should also be emphasized again. When drilling hard to hard rock formations, the rotation speed is the main factor to increase the drilling speed of impregnated bits; when drilling hard rock formations, increase the weight on bit. As the drilling speed increases, the pump volume should also increase accordingly. However, never rely solely on blind pressurization to achieve high penetration rates. Generally, in homogeneous rock formations of about 6 grades, the drilling speed is strictly controlled between 2-3m/h and equipped with appropriate pumping capacity.
(3) Concentrate and operate carefully. ① Operate carefully during the drilling process and observe the data displayed by various instruments, as well as the operation and dynamic changes of machinery, transmission belts, hoses, etc. Generally, the drill bit is drilled from hard rock into the soft rock layer, the drilling speed suddenly increases, the pump pressure increases, and the drilling rig rotates hard, all of which are the pre-burning of the drill. At this moment, the drilling speed should be limited immediately, the drilling pressure and speed should be reduced, the pump capacity should be increased or the drilling should be stopped; the drilling tool should be lifted and punched; the drilling can only be continued when the waterway is clear and the judgment is correct. When the treatment is invalid, the drill should be immediately lifted. When the pump pressure drops, the hose will jump suddenly and become stable; the drilling tool rotates hard, which is a symptom of poor water pumping by the mud pump, severe water loss in the middle of the drill string or at the bottom of the hole, and the danger of jamming should be dealt with in time. ②The outer diameter of the diamond drill bit is smaller than the specified size, and it is not allowed to use it under the hole. When the drill bit is grinding the hole, it should not be too much in one shot, and a large pump should be used for flushing. ③It is necessary to configure the circlip seat and the inner diameter of the drill bit in strict accordance with the regulations to prevent the core from clogging. Once the core is blocked, the drill should be immediately lifted and handled properly. ④Drilling is about 0.2m away from the bottom of the hole, and the pump should be opened to punch the hole. After the circulation is unblocked, go down to the bottom of the hole with a slow speed, and start drilling with low pressure, low speed and initial grinding. After it is normal, drill quickly. Never use a diamond drill to sweep holes. ⑤ When the signs of burning drills are found, it is strictly forbidden to turn off the vehicle and move the drilling tools up and down quickly. After the hidden danger is cleared, the drill should be immediately lifted for inspection to find out the cause of the burned drill and take corresponding technical measures.
Picture
7. Pre-grinding and grinding
of impregnated drills (1) After the new impregnated drills go down the hole, use light pressure to rotate slowly, and after roughly drilling 0.2-O-0.3m, the diamond blades are exposed, and Run in with the bottom of the hole, and then proceed to normal drilling.
(2) The sandblasting method is used to promote the diamond blade. The sandblasting method uses a high-speed fluid beam carrying hard particles to spray the lip surface of the rotating bit to expose and sharpen the diamond blade on the lip surface of the bit. The drill bit penetrates effectively. This method can be used when the impregnated drill bit appears "slip".
(3) The impregnated drill bit has a nozzle less than 3mm, and it should be sharpened with a grinding wheel or a knife, and try to keep it consistent, so as to avoid uneven erosion and cause uneven wear of the diamond bit.
+86-523-87213788
中文
English
E-mail：
Tel： 
Add：
