Construction Technology of Horizontal Directional Drilling Rig(I)

1.Guide construction


Avoid curve deviation and the formation of “S” shape in guided construction.

In the construction process of directional drilling through, whether the guide hole is smooth or not, whether it is consistent with the original design curve, and avoid the appearance of “S” shape of the guide hole is the prerequisite for the successful completion of the crossing construction. To avoid the formation of an “S” shape, the following measures can be taken:

 (1)In the process of measuring and setting out, use the total station to retest and confirm the exit and entry points for more than three times to ensure that the crossing pipeline conforms to the design.

(2)Before drilling, the drilling instrument is calibrated, and multiple points of repeated measurement to ensure its accuracy.

(3)Analyze the geological conditions before starting work, draw the traverse curve in the way of connecting each drill pipe on coordinate paper according to the design curve, label each drill pipe, and indicate the corresponding geological conditions at different depths; In the drilling process, according to the drilling position of the formation conditions to control the mud viscosity performance, at any time according to the geological conditions to adjust the mud pressure, mud ratio and other parameters.

(4)After the drilling rig is in place, accurately measure the size of the included angle, calculate the horizontal drift and record it, and gradually correct it according to the allowable value of the crossing curvature during the drilling process, so as to avoid the “S” shape of the drill pipe in the formation type to ensure the smoothness of the drilling curve and improve the drilling quality of the pilot hole.

(5)Understand the surface, geological and hydrological conditions, and measure the azimuth on the crossing center line without magnetic interference. The measurement of the azimuth Angle is carried out on both sides of the burial site and the excavation site.

(6)The coil should be encrypted above the crossing axis, and the deviation should be measured frequently to ensure that the crossing axis is consistent with the design axis and the excavation accuracy of the top pile at the unearthed point.

(7)Direction control records must be complete, accurate and effective. In the process of pilot hole drilling, any abnormality and stop of drilling shall be recorded.

(8)Observe the mud pressure difference and mud changes at all times to provide a basis for judging the working condition of the mud pump; observe the change of the propulsion pressure to provide a basis for the operation of the drilling tool.

(9)In order to ensure that the drilling curve is consistent with the design crossing curve, the steering system will be tested when the pilot hole is drilled, mainly including: testing the driller’s console, testing the data interface device, probe diagnosis (including probe calibration check, data, etc.) continuous detection. After all tests and adjustments are completed, proceed to normal drilling.

2.Treatment measures when the drill bit is stuck

(1) During the drilling of the pilot hole, the drill bit may get stuck, which is manifested by a sharp increase in mud pressure, or an instantaneous increase in the torque of the drilling rig (during rotary drilling). At this time, the torque generated by the mud motor cannot overcome the action of the rock torque on the drill bit, the drill bit stops rotating.

There are two options:

● When the pressure drop of the mud can be maintained within the range of 500psi, it is possible to immediately stop the advancement of the drill pipe, and instead pull the drill pipe towards the direction of the drilling rig to make the drill bit leave the rock quickly, reduce the pressure difference of the mud, and then use a slower Thrust and thrust speed drilling;

●When the pressure drop of the mud exceeds 500psi, the mud pump should be turned off immediately, the mud pumping should be stopped, and the drill pipe should be retracted towards the drilling rig to prevent the mud motor from being damaged due to excessive pressure on the seal.

 (2) During the construction of the guide hole, the drill is stuck when replacing the drill tool or pumping the drill pipe under other special circumstances. The main reason is that the deviation of individual sections is too large, the hole cleaning is not thorough, excessive accumulation of drilling cuttings caused by “shrinkage hole”, resulting in stuck drilling.

Treatment: First, the mud should be kept working normally, and there is enough mud to pump into the hole. At this time, the drill pipe should not simply continue to pull back, otherwise it will easily get stuck. The drill pipe should continue to move forward with pumping mud, patiently clean the hole, adjust the high edge of the bit according to the first drilling record, stop the rotation of the drill pipe pumping back, pay attention to control the tension of the rig, and then rotate the drill pipe forward, clean the hole, many times, until the smooth through the “shrinkage hole” section.


3.Reaming construction


(1) Countermeasures for the falling of the cone in the hole during reaming

During reaming construction, due to excessive rock strength or variable rock layer structure, the cone of the cone reamer may fall into the hole, affecting the next reaming construction.

Treatment method: According to the guidance record data, the stress change in each part of the rock layer can be determined. After the rock reamer has been used for 80 hours, replace it with a new one for reaming; Before the reamer enters the area where the rock stress increases, if the rock reamer has been used for more than 60 hours, replace it with a new one.

(2) Countermeasures for broken reaming drill pipe

The crossing geology of the project is uneven in hardness and hardness, and the requirements for reaming forming quality are extremely high. When encountering places with large changes in rock stress during reaming, it is easy to cause drill pipe fracture, which is manifested by the instantaneous reduction of drill torque and tension.

Treatment method: during the construction, the construction process of connecting drill pipe at the excavation point shall be adopted. After the drill pipe breaks, timely adjust the equipment to the excavation point and pull back the drill pipe reamer. After all the drill pipe reamers are fished, the guide system shall be installed on the side into the soil to guide again along the original guide hole.

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Post time: Feb-07-2023