The most professional and core classification method directly determines the technical characteristics and applicable formations of the drilling rig.

1. Percussion Drill (Drill Rig)

Working Principle: A heavy drill bit (drill bit) is dropped freely from a certain height, breaking the rock layer by impact force. The rock debris is then removed through a pump. This is a very old technology that is still used in certain areas.

Features:

Advantages: Simple structure, low cost, minimal disturbance to the formation, and the ability to retrieve intact rock samples.

Disadvantages: Extremely low efficiency, slow speed, limited drilling depth, and unsuitable for deep wells and complex formations.

Applications: Shallow water wells, geological exploration sampling, and certain advantages in special formations such as gravel.

2. Rotary Drill (Drill Rig)

This is currently the most popular type of drilling rig and can be divided into the following subcategories:

a. Positive circulation drilling rig 

Working principle: The drill pipe rotates the drill bit to cut the rock layer. The high-pressure mud pump forces the drilling fluid (mud) into the interior of the drill pipe, flows out from the bottom of the drill bit, cools the drill bit and carries the rock debris, and then returns to the surface along the annular space between the drill pipe and the borehole wall. 

Features: The equipment is relatively simple and the drilling cost is low. It is one of the most widely used types of drilling machines at present. 

Applicable scenarios: Small-diameter water wells, engineering pile foundation holes, suitable for various soil layers, sandy layers and some soft rock layers. 

b. Reverse circulation drilling rig 

Working principle: Opposite to the positive circulation. The drilling fluid (usually fresh water or mud) flows from the annular gap at the drill hole opening into the bottom of the hole under the force of gravity. Then, carrying the rock debris, it is sucked to the ground by the powerful sand pump through the hollow inside the drill pipe. 

Feature:

Advantages: High sludge discharge efficiency, stable borehole wall, fast drilling speed, and excellent well formation quality. 

Disadvantages: The equipment is relatively complex and has low efficiency in extremely hard rock formations. 

Application scenarios: Large-diameter water wells, ground source heat pump holes, pile foundation projects. Particularly suitable for collapsible strata such as sandy layers and gravel layers. 

c. Submersible hammer drill (pneumatic drill) 

Working principle: High-pressure air is used as both the power source and the medium for discharging debris. The high-pressure air drives the "submerged impactor" at the bottom of the hole to generate high-frequency impacts, which break the rocks and blow the rock debris along the hole wall out of the ground. 

Feature:

Advantages: It can drill through hard rock layers (such as granite and limestone) at an extremely fast speed, making it an excellent tool for tackling tough tasks. 

Disadvantages: Dependent on large-capacity air compressors, high energy consumption, loud noise, and a large amount of water is required for dust control (during dry drilling). 

Applicable scenarios: Deep water wells in bedrock layers and hard rock layers, as well as blasting holes in mines. 

d. Compound drilling rig (multi-functional drilling rig) 

Working principle: A drilling rig integrates multiple functions. Usually based on a rotary drilling rig, it can be equipped with sub-bit drills, dual power heads, etc. to perform "combined attack" operations. For example, the upper part uses a tricone bit for mud drilling, and when encountering hard rock, it switches to sub-bit drilling. 

Features: Extremely adaptable, versatile in use, capable of handling complex and variable geological formations. 

Applicable scenario: In areas with complex geological conditions, it is necessary to handle the entire drilling process ranging from soil layers to hard rocks.