What are some common faults with horizontal directional drilling rigs?

1. Guidance Deviation
Phenomenon: The drilling trajectory deviates from the designed path, affecting pipeline laying accuracy.
Cause:
Drilling rig positioning error (centerline deviation > 0.1°) or magnetic field interference leading to directional control failure.
Complex formations (such as cobblestone layers and fractured zones) causing drill bit deflection.
Solution:
Calibrate the drill rig direction before construction and use PII directional control software and artificial magnetic field compensation.
Use a mud motor drill bit in hard rock formations to reduce deflection.
2. Pullback Obstruction
Phenomenon: Excessive resistance during pipe pullback, even preventing advancement.
Cause:
Excessive hole expansion differential (e.g., hole expansion diameter less than 1.3 times the pipe diameter) or hole wall collapse.
Pebble layers and weakly cemented sand layers cause hole diameter reduction. Solution:
Use a pipe tamping hammer or pipe pusher to assist with pullback, and use a pulley block to increase force if necessary.
Pre-embed casing in alternating soft and hard formations to prevent hole collapse.
3. Drill Pipe Damage
Symptom: Drill pipe breakage, thread wear, or fatigue failure.
Cause:
Uneven formations (such as hard rock grades 5-7) leading to vibration fatigue.
Insufficient thread lubrication or improper torque can cause sticking.
Solution:
New drill pipe should be pre-tightened and liberally applied with thread oil when first used.
When drilling in gravel formations, install a centralizer to reduce swing.
4. Borehole Wall Instability and Slurry Leakage
Symptom: Borehole diameter reduction, hole collapse, or slurry escaping from the surface.
Cause:
Clay minerals absorb water, expand, or cracks develop, resulting in reduced hole wall strength.
Slurry pressure is too high (greater than the formation bearing capacity) or too low (less than the required wall protection). Solution:
In weakly bonded formations, use cement slurry to seal cracks.
If leakage is severe, pre-buried Φ1500 risers can reduce slurry pressure.
5. Equipment Hydraulic System Failure
Symptom: Hydraulic oil leakage, pressure fluctuations, or cylinder seizure.
Cause:
Deterioration of seals or oil contamination (e.g., water intrusion).
Solution:
Regularly replace the hydraulic oil (every 400 hours) and inspect the seals.