The Introduction of Reaming

The reaming design includes reaming grading, the selection of reamer, assembly of reaming drill tool, assembly of clearing drill tool, drilling pressure, torque, rotate speed, and mud displacement, etc. The number of grading of reaming mainly depends on the nature of the stratum, the diameter of the final hole, the length of the drill hole, the capacity of the drilling rig, the capacity of the mud pump, the size of the drill rod and the type of the reamer. The choice of the reamer mainly depends on the physical and mechanical properties of the stratum to be drilled. At present, there are two types of reamers suitable for general soil layers and rock reamers for rock stratum. Each type of reamer has a variety of structural shapes. Among them, reamers suitable for soil layers have common structures such as wing plate type, runner type, extrusion-expanding type, and barrel type. Rock reamers have two common structure types: cone type and hob type. The characteristic of the general connection method of the reaming drill tool is that the drill rod behind the reamer does not rotate with the reamer, but the reamer can only move forward and not retreat under normal conditions, which is suitable for short-distance crossing engineering. While in long-distance or large-scale crossing projects, the rear drill rod of the reamer is directly connected to the reamer in a threaded manner, and the rear drill rod rotates with the reamer so that the reamer can advance and retreat.

The diameter of the final hole of the horizontal directional drilling pipeline crossing project is generally 1.2 to 1.5 times the outer diameter of the pipeline, and the design diameter is generally achieved by the method of grading reaming. The number of grading mainly depends on the nature of the stratum and the capacity of equipment and the specifications of drill rods selected. With large equipment capacity and high drill rod strength, the number of grading can be reduced according to the conditions of stratum to speed up the construction progress.

The nozzle of the reamer is the mud outlet. Once it is blocked, the pump pressure on the ground will increase or the mud will not be discharged, which is not conducive to reaming and drilling.

The abnormal torque and tension during the reaming process may be related to many factors such as the stratum, the accumulation of drillings, the collapse of the drill hole, the interruption of the mud circulation, and the excessive wear of the reamer; after the abnormality, the conditions in the hole should be analyzed and judged, which is an effective way to prevent problems from getting worse.

After the first-level reaming is completed, if the torque is found to be too large during the entire reaming process, it may be caused by the excessive amount of drillings in the hole. Before entering the next level of reaming, it is very beneficial to perform a thorough hole washing to reduce the pressure of the next level of reaming.

The main purposes of cleaning the hole after the reaming are completed are as follows:

1. Remove as much of the remaining drillings as possible;

2. Use a large-diameter cleaning drill to trim the hole wall to make the hole wall flat and free of burrs, and reduce the scratches and wear of the surface of pipeline;

3. The hole cleaning can help detect the basic conditions of the entire drill hole, and provide an effective basis for judging whether the condition of back towing is available.