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How to choose a drill bit for a horizontal directional drilling rig?

  • Time of issue:2021-07-26

How to choose a drill bit for a horizontal directional drilling rig?

(Summary description)Choose different drill bits for different soil quality and hardness, and then the editor will explain them one by one.

  • Time of issue:2021-07-26
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Choose different drill bits for different soil quality and hardness, and then the editor will explain them one by one.

The first type: dental plate drill. There are many names for this kind of drill bit, foot plate drill bit, duck foot drill bit, guide plate drill bit refer to this kind of drill bit. There are different designs for different formations. The plate has a common type with one bend and an enhanced type with two bends. Generally used for soft to medium-hard and relatively uniform clay, or loose to relatively dense sand. Steering method: When drilling a straight hole, the drill pipe rotates and pushes forward; when steering adjustment is needed, stop the drill pipe rotation, correct the work situation to the direction that needs to be adjusted, and only advance the drill pipe without rotating it. Pay attention to the steering angle during the advancing process. The change prevents oversteer.

The second type: swing top drill bit. Rocking-top drill bits are suitable for harder formations and soft rock formations that cannot be penetrated by propulsion alone. Steering method: When skewing towards the required steering direction, make the drill bit swing clockwise/counterclockwise (commonly known as rocking top) to advance the drill rod in a straight line like a dental plate bit.

The third type: Beveling short hole bottom hole assembly (BHA). This kind of drill tool assembly is generally used for large-scale directional drilling through soft formations. Deviation shorting is generally between one degree and thirty minutes to two degrees. It is usually used in combination with a milled tricone bit. If it encounters a harder formation, the thrust will be large; if it encounters a soft formation, the effect of the deviation will not be obvious. The guiding method is the same as that of a dental drill.

The fourth type: mud motor bottom drilling tool assembly (MudMotor BHA). Mud motor is not only a deflection tool, but also a drilling power tool. Generally, it is only used with tri-cone bits. It is mainly used in hard formations. Only mud motors can be used in rock formations. For the penetrating lower soft stratum, it is difficult to raise the head due to the heavy weight of the screw and the sinking.

The direction control in the mud motor is achieved by a maximum bend not exceeding 3 degrees (usually 1.75 degrees). The elbow is located approximately 1.5 meters behind the drill bit, and its function is the same as that of the elbow joint. The shorter the distance from the drill bit to the bend, the greater the bending angle, and the faster the turning. The turning method is the same as that of the dental plate bit.

The fifth type: double-wall drill pipe rock drilling rig guiding system. This kind of drilling rig has two sets of top drive devices, specifically driving the double-wall drill pipe system. The bottom hole assembly is very similar to a mud motor, but there is no driving part of the mud motor. Steering method: The drill bit usually uses a tri-cone drill bit. The drill bit continuously rotates under the drive of the inner drill rod, while the outer drill rod is used to control the steering, that is, adjust the curved cover to the correct direction. The mid-term curved cover serves as a support for the rotary drill bit and accommodates the probe; the inner and outer drill rods rotate and drill straight at the same time. The probe is placed close to the tail of the drill bit, which improves the response speed of steering compared with most mud motors. Due to the structure of the drill pipe, the wired guide system cannot be used. For short distances, where the stratum is soft to medium-hard rock, and the limited area of ​​the workplace does not allow the use of large drilling rigs and mud pumps to drive the mud motor to traverse, this system is very suitable and efficient. But for large-caliber, long-distance hard rock traversal, the efficiency of this system is lower than that of mud motor equipment.

The sixth type: horizontal directional drilling down-the-hole hammer drill assembly. This kind of drilling tool is powered by compressed air and is suitable for small drilling rigs to traverse short distances and medium to high hardness rock formations. The efficiency is higher than other steering tools. This system steering is achieved by an eccentric, flat-end drill bit with tungsten carbide carbide teeth. This kind of drill has a high point, which can better face the required path direction during the process of not rotating but advancing. If straight drilling is needed, just apply a moderate drilling force and rotate slowly.

That's it for today's introduction. If you don't know anything, please feel free to contact us Shenzhen Wisdom Machinery Equipment Co., Ltd., and we will answer you one by one.

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