How to Correct Deviation During Horizontal Directional Drilling

I. Basic Principles of Deviation Correction

1. Early Detection and Correction: Track data must be measured every 3 meters of drilling. If a lateral or longitudinal deviation exceeds 0.3 meters, the deviation correction procedure should be initiated immediately.

2. Fine-tuning as the Main Approach: The inclination angle change in a single correction should be controlled within 2%~4% to avoid large corrections that could lead to reverse deviation or uneven borehole.

3. Continuous Adjustment: Use "multiple small adjustments" instead of "one-time strong correction" to ensure a natural trajectory transition and reduce subsequent pullback resistance.

II. Specific Deviation Correction Operation Procedure

1. Pullback to a Stable Section: Pull the drill rod back to a position where the trajectory has not deviated significantly, typically 1~2 drill rod lengths (approximately 3~6 meters). Ensure that this section of the borehole structure is intact and unobstructed, serving as the reference starting point for the new trajectory.

2. Determine the tool face orientation. Based on the tool face angle displayed by the guidance system, determine the current drill bit orientation. For downward correction, adjust the tool face to the 6 o'clock position; for upward correction, adjust to the 12 o'clock position; for left or right correction, adjust to the 9 o'clock or 3 o'clock position, respectively.

3. Implement directional drilling. Stop drill bit rotation and apply only axial thrust, causing the drill bit to "push down" or "pull up" along the set direction without rotation. The advance length is generally 2-3 times the drill bit length to form a stable new drilling path.

4. Resume rotation and verify the trajectory. After confirming that the drill bit has entered the new direction, resume rotating drilling. Check the azimuth and dip angle data every 1-2 meters to ensure effective correction and that no over-adjustment has occurred.

5. Mud Mixing and Control

In soft soil layers, appropriately reduce mud viscosity to prevent drill bit drift due to excessive buoyancy.

In hard rock layers, improve mud cooling and lubrication performance to reduce the impact of frictional heat on drill bit attitude and improve correction efficiency.

III. Correction Strategies for Different Formations

1. Soft Soil Layers: Low soil bearing capacity makes drill bit prone to drift. Increase measurement frequency and use high-frequency fine-tuning to control the trajectory.

2. Gravel Layers: Loose particles and poor stability make drill bit slippery. It is recommended to use a highly directional inclined drill bit in conjunction with a high-precision guidance system.

3. Alternating Soft and Hard Layers: Uneven stress can easily cause "head-up" or "head-down" phenomena. Reduce drilling speed and dynamically adjust tool face angle to maintain stable drilling.

4. Rock Formations: High drilling resistance and slow correction response necessitate extended directional drilling time and enhanced mud cooling to prevent equipment overheating.

IV. Special Environment Auxiliary Technologies

1. In areas with high-voltage lines and dense metal structures, wired sensors are used to transmit data, avoiding distortion of wireless signals due to electromagnetic interference.

2. A ground beacon system is used to construct an artificial magnetic field for real-time calibration of the probe position, significantly improving positioning accuracy in complex environments.

3. For ultra-long distances or highly complex projects, bidirectional drilling with intermediate docking technology can be used, drilling simultaneously from both ends and converging at a predetermined point, greatly reducing the pressure of unilateral correction.