System description of horizontal directional drilling rig and the difference of guided drilling

1. Drilling rig system: it is the main body of drilling operation and back dragging operation of crossing equipment. It is composed of drilling rig host, rotary table, etc. the drilling rig host is placed on the drilling rig frame to complete drilling operation and back dragging operation. The rotary table is installed at the front end of the main machine of the drilling rig, connected with the drill pipe, and meets the requirements of different operation states by changing the steering and output speed and torque of the rotary table.

2. Power system: it is composed of hydraulic power source and generator. The power source is to provide high-pressure hydraulic oil for the drilling rig system as the power of the drilling rig, and the generator provides power for supporting electrical equipment and construction site lighting.

3. Direction control system: the direction control system is a directional tool that monitors and controls the specific position and other parameters of the drill bit underground through the computer, and guides the drill bit to drill correctly. Due to the control of this system, the drill bit can drill according to the design curve. At present, two forms of direction control systems, portable wireless and wired, are often used.

4. Mud system: the mud system is composed of mud mixing tank, mud pump and mud pipeline to provide drilling rig system with mud suitable for drilling conditions.

5. Drilling tools and auxiliary machines and tools: they are all kinds of machines and tools used in drilling and reaming. Drilling tools mainly include drill pipes, drill bits, mud motors, reamers, cutting knives and other machines and tools suitable for various geological conditions. Auxiliary machines and tools include snap rings, rotary unions and pullers with various pipe diameters.

The difference between horizontal directional drilling and guided drilling

The working principle of directional drilling is to use directional drilling technology to construct a pilot hole according to the designed drilling trajectory. After the pilot hole is completed, the reaming bit with large diameter and the pipeline to be laid with a diameter smaller than the reaming bit are replaced at the end of the drill pipe string. When the drill pipe is pulled back, the pilot hole is expanded, and then the pipeline to be laid is pulled in. In the process of drilling the guide hole, the mixture of bentonite, water and air is used to lubricate, cool and carry the cut soil to the ground. A directional measurement and control instrument is installed on the drill bit, which can change the inclination angle of the drill bit. The length of the drill is the total length of the drill pipe.

The working principle of guided drilling is to change the drilling direction and adjust the bit penetration angle by using the asymmetric bit inclined plane reaction. If the rotary rod of the drill is fed and rotated at the same time, the straight-line drilling will be realized. If only the feed is given without rotation, the reaction force of the inclined plane will change the direction of the drill and realize the oblique drilling. During drilling, the signal sent by the probe or transmitter in the bit is received by the surface detector, and the angle and depth of the bit can be adjusted at any time. When the drill bit reaches the predetermined target point, it will be pulled back and forth several times until the drilling hole is expanded to the diameter of the laid pipeline, and then the pipeline is connected to the soil layer. According to different hole forming methods, guided drilling can be divided into dry drilling and wet drilling. The dry drilling tool is composed of an extrusion drill bit, a probe chamber and an impact hammer. It forms a hole by impact extrusion without dumping. The wet drilling tool is composed of a jet drill bit and a probe chamber. It cuts the soil layer with high-pressure water jet, sometimes supplemented by a top drive impact power head to break large pebbles and hard soil layers.

Directional drilling is generally applicable to clay, silty clay, clayey silt and silty sand. Guided drilling is generally applicable to soft soil. The minor editor of horizontal directional drilling introduced that the pipe laying diameter range of directional and directional drilling is 50-1200mm, and the pipe laying length depends on the soil condition and the capacity of the drill. In cohesive soil, the pipe laying length of large drill has reached 2308m Directional and guided drilling has less interference on the surface, fast construction speed, and can control the direction of pipe laying, with high construction accuracy. However, directional drilling has high requirements on the construction site, and it is difficult to construct in non cohesive soil layer. It is generally applicable to various strata without boulders, including water bearing strata. Guided drilling is not suitable for sand and gravel layers. Due to the limitation of the detection depth of the detector, the depth of guided drilling is limited.