The Optimization and the Engineering Application of the Reamer in HDD Construction

Horizontal Directional Drilling(HDD for short) is a modern trenchless construction technology that combines the directional drilling technology of the petroleum industry with the traditional highway pipe jacking technology.

In recent years, with the improvement of scientific and technological level, the horizontal directional drilling rig and its supporting technical tools have been continuously improved and perfected, the performance of the whole machine has been greatly improved, and the horizontal directional drilling crossing technology has also been widely used, especially in urban municipal pipeline construction and oil and gas pipeline crossing river projects have more unique advantages. The reamer is an important part of the horizontal directional drill bit to complete its reaming operation during the construction process, which will be directly related to the success or failure of the pipe laying.

Reamer is a kind of power equipment used for reaming pipes during reaming operation, including roller cone reamer and PDC reamer. The main function of reamer is to cut and expand the guide hole along the curve of the guide hole. Tungsten carbide alloy teeth and nozzles are installed on the reamer, the former is mainly used for cutting and squeezing rock and soil layers, and the latter is mainly used for mud jet.

The horizontal directional drilling crossing technology principle: through the computer-controlled guidance and detection, a small-diameter pilot hole with the same design curve will be drilled first, and then a reamer will be installed on the head of the drill rod at the outlet end of the pilot hole to pull back and expand the hole to guide. After the hole is expanded to the size that required, the rotary joint, the tube head and the pipeline will be connected to the rear of the reamer, and drag the product pipeline back to the enlarged guide hole to complete the construction process of pipeline crossing. The hole expansion operation is one of the key technical links in the horizontal directional crossing construction, and the key to the hole expansion operation is to select an efficient and safe reamer according to the actual conditions.

During the working procession, the forward movement of the reamer needs to overcome the positive pressure resistance and friction resistance of the rock layer or soil body, and the rotary movement of the reamer needs to overcome the resistance torque of the rock layer or soil body to the tool and the friction torque on the surface of the reamer.

The optimization of the shape and size of the reamer has a great influence on the resistance and torsion torque during the working procession, which is directly related to the working efficiency of the horizontal directional drilling machine. It can be seen that the analysis and research on the selection of reamer and engineering application are of great significance for the smooth progress of horizontal directional drilling construction.

The enlargement of horizontal directional drilling through the rock layer should focus on the following three aspects: the service life of the reamer, the torque value generated by the reamer at each stage of reaming, the efficiency and economics of reaming. In addition, the reaming process also plays a certain role in correcting the guide hole. If the guide hole is only bent at a small angle, after selecting the appropriate reamer, the ideal smooth hole can be achieved through the reaming operation. For example, in a hard and uneven formation, the reamer tends to deflect to the soft formation, that is, to the direction of least resistance, and long-term use will cause damage to the reamer. In practice, flexible choices should be made according to the conditions of the rock formation, the ability to traverse the equipment, the diameter of the hole expansion, and the condition of the traversing mud.