What is casing drilling system

In the drilling industry, overcoming the challenge of drilling through overburden (the loose soil, gravel, sand, and other surface material lying above solid bedrock) is critical for successful drilling operations. Overburden drilling systems are specifically designed to cope with these unstable and varied ground conditions. Here, we will explore different types of overburden drilling systems and their suitable use scenarios.

There are two types of casing drilling systems:   Eccentric drilling system and symmetric drilling system.   How to choose them depends on the rock formation and

customer's reqirement about the projects.   Comared with symmetric drilling system,   there are some advantages for eccentric drilling system below.

Faster Drilling: Eccentric systems are designed to cut a ring around an existing pilot hole, thus removing less material than symmetric systems and allowing for quicker progression.

Flexibility: More adaptable to different soil and rock types; can handle a wider range of conditions where core quality might not be the primary concern.

Cost-Efficiency: Generally cheaper to operate due to less material removal and faster drilling speeds.

TF Eccentric drilling system products data sheet

Procedure for drilling by casing system

1. Casing Advancement Systems

These systems are used to effectively drill through overburden by advancing a casing simultaneously as the drilling occurs. This protects the borehole walls from collapsing until bedrock is reached.

Advantages:

Ensures stable boreholes.

Allows drilling through mixed soils, loose gravel, and boulders.

Minimizes the risk of borehole collapse.

Optimal Use Scenarios:

Constructing foundations for buildings and bridges in areas with large amounts of loose material.

Environmental drilling where borehole stability is key to maintaining sample integrity.

2. Casing Drilling

Casing drilling involves using a casing as the drill pipe, which reduces the need for multiple casings in unstable formations. As drilling progresses, the casing is drilled into place, and no further casing is required.

Advantages:

Reduces the risk of hole collapse.

Enhances drilling efficiency by reducing the need for tripping out drill pipes to add casing.

Effective in unstable geological structures.

Optimal Use Scenarios:   

Oil and gas exploration in areas prone to quicksand or loose sediment layers.

Water well drilling in collapsing formations.

3. Continuous Flight Auger (CFA) Drilling

This method involves the use of an auger with a continuous flighting to drill into the overburden. As the auger drills down, it conveys the drilled material up and out of the hole, reducing the risk of hole collapse.

Advantages:

Quick drilling process.

Suitable for near-surface geotechnical exploration where speed is crucial.

Minimally disruptive to the surrounding soil structure.

Optimal Use Scenarios:

Urban construction projects where speed and minimal vibration are important.

Environmental assessments and geotechnical surveys in unconsolidated or loose surface materials.

4. Down-The-Hole Hammer (DTH)

A DTH system can be adapted for overburden drilling by using a hammer drill and a temporary casing system. The hammer provides efficient penetration through tough materials, while the casing supports the borehole walls.

Advantages:

High drilling speed, even through hard materials.

Effective in boulder-rich deposits.

Suitable for deeper drilling projects.

Optimal Use Scenarios:

Construction drilling where rock layers are mixed with loose materials.

Large-scale mineral exploration across varied geological formations.

5. Symmetrix and Odex Systems

These are types of overburden drilling systems designed for simultaneous drilling and casing placement. They are particularly effective in aligning

the casing with the borehole.

Advantages:

Provide excellent alignment between casing and borehole.

Efficient in unstable ground conditions.

Quick installation of casing.

Optimal Use Scenarios:

Geothermal installations where precise casing installation is critical.

Foundation drilling in areas with sandy, watery, or gravel-filled soils.

In conclusion, selecting the right overburden drilling system depends on specific project requirements, including soil type, project scale, economic factors, and environmental impact considerations. Each system offers unique advantages and is tailored for different circumstantial challenges faced in various drilling projects.