The commonly used drilling techniques for well drilling mainly include the following:

1. Percussion drilling 

Principle: By repeatedly impacting the formation with a drill bit, the rock is fragmented.

Application: Loose formations, such as sand, gravel, etc.

Advantages: simple equipment and low cost.

Disadvantages: Low efficiency and slow progress.

2. Rotary drilling

Principle: The drill bit rotates to cut the stratum, and the mud circulates to remove debris.

Application: Various strata, especially hard rock.

Advantages: High efficiency and strong adaptability.

Disadvantages: Complex equipment and high cost.

3. Reverse circulation drilling

Principle: The mud circulates downwards from the outside of the drill pipe, carrying rock debris back to the surface through the inside of the drill pipe.

Application: Large-diameter wells, loose formations.

Advantages: Good slag removal effect, stable wellbore.

Disadvantages: High equipment requirements and significant cost.

4. Air drilling

Principle: Replace mud with compressed air to cool the drill bit and remove debris.

Application: Arid areas or hard rock formations.

Advantages: fast speed, low cost.

Disadvantages: Not applicable to water-bearing formations.

5. Directional drilling

Principle: Drill a non-vertical well by controlling the direction of the drill bit.

Application: Complex terrain or special requirements.

Advantages: High flexibility and adaptability to complex conditions.

Disadvantages: High technical requirements and high cost.

6. Horizontal drilling

Principle: The drill bit drills in a horizontal direction to increase the contact area with the oil reservoir.

Application: Oil and gas extraction.

Advantages: Increase production and reduce environmental impact.

Disadvantages: Complex technology and high cost.

7. Pipe jacking drilling

Principle: The pipeline is pushed into the ground by a pipe jacking machine, while the drill bit cuts through it.

Application: laying of urban underground pipelines.

Advantages: Minimal impact on the ground and high precision.

Disadvantages: Complex equipment and high cost.