Casing System

The casing system means that the casing tube penetrates with drill bits at the same time. The casing tube provides the enforcement to the hole wall and prevent the hole from collapsing during drilling. It is composed of two parts: the casing and the drill bit.

• Casing shoe: It is an integral part of casing drilling, used to connect the casing and the drill bit and drag the casing  to drill synchronously with the drill bit; it is generally connected with the casing by thread or welding.
• Casing: It is also called casing. When drilling, the drill bit drives the casing shoe and casing to advance together, and the casing acts as a wall to prevent the hole from collapsing. In terms of structure. It is divided into two types: MF thread connection and joint connection.

Features

• It has a wide range of applications and mature construction technology; almost all complex geology that is not easy to form holes can be constructed with casing systems, which can be used for anchoring, pile foundation support, and water well/geothermal well engineering; in addition, it can be used with DTH drills and top hammer drills.
• Large drilling diameter and deep drilling depth. The maximum drilling diameter is more than 1 meter and the drilling depth can reach hundreds of meters with large construction equipment.
• Fast drilling speed and good hole quality. Under complex geological conditions, the casting acts as retaining wall support, avoiding jamming and loss of high-pressure gas in rock crevices, improving the slag removal effect and drill bit service life.
• According to design requirements, the casing can be pulled out and used repeatedly after drilling, or it can be left in the hole without pulling out as an bolt.

1. According to the classification of construction equipment, it includes top hammer casing systems and DTH casing systems.

The composition of the top hammer casing systems: casing drill bit + casing shoe + casing + coupling (Note: MF casing needn’t coupling) + drill pipe (including a coupling sleeve) + centralizer, etc.

Top hammer casing systems are mostly used for small and medium-sized shallow hole construction with a hole diameter of φ90-150mm and a hole depth of fewer than 30 meters.

The composition of DTH casing systems: casing drill bit + casing shoe + casing + coupling (note: MF casing needn’t coupling) + DTH hammer + drill pipe + centralizer, etc.

2. According to the structure of the drill bit, it can be classified into eccentric casing system, symmetric casing system, and dual power head rotary percussion casing system. Symmetric casing systems include symmetric casing system with reamer, symmetric casing system with wings, and symmetric casing system with slide blocks according to the drill bit structure.

Eccentric Casing System

Applicable geology: It is suitable for covering layers with mostly loose materials on the surface of the formation, such as soil, clay, weathered rock, sand and gravel, etc.

Scope of work: It is suitable for drilling geothermal wells, water wells, small and medium-sized grouting holes for construction, mini-piles, etc.

Features:

1. As the main tool for drilling wells, it can ensure the drilling and wall protection at the same time, which can significantly shorten the time of passing through the overburden layer.
2. The eccentric casing system is one of the fastest and most economical casing systems when using casing retaining walls permanently or temporarily in geological conditions such as mud, silt, and gravel.
3. The eccentric structure has uneven force when drilling and the straightness of the hole is relatively poor. It is mostly used for the construction of small and medium-diameter water wells, geothermal wells, and micro piles with a shallow drilling depth (within 40m) with a diameter of 350mm or less.
4. The structure has good strength and can withstand heavy loads.
5. The drilling angle is mostly vertical, which is not suitable for inclined hole drilling.
6. It is not suitable for drilling in geological conditions with large isolated rocks.

Symmetric Casing System

Symmetric casing system can drill holes at any angle (including the horizontal direction) to a depth of more than 100 meters. As an efficient drilling system, the system is composed of pilot bit, ring bit, casing shoe, casing and so on.

Symmetric Casing System With Reamer

Applicable geology: It is suitable for covering layers with complex geological conditions, such as pebble layers, cracks, boulders, construction backfills, etc.

Scope of work: It is mainly used for pile foundation and anchoring projects.

Features:

1. Simple structure, stable and reliable performance, easy to unlock and re-lock, low failure rate.
2. Stable, low vibration and low noise drilling, and the straightness of the hole is the best, which can be used for large-diameter and deep-hole construction.
3. Uniform drilling force and not easy to get stuck, and drilling can be done at any angle without being affected by terrain conditions.
4. Suitable for a wide range of geological conditions.
5. High structural strength, can bear large load, high drilling efficiency.

Symmetric Casing System With Wings

Applicable geology: It is suitable for covering layers with mostly loose materials on the surface of the formation, such as soil, clay, weathered rock, sand and gravel, etc.

Scope of work: It is suitable for drilling geothermal wells, water wells, small and medium-sized grouting holes in buildings, micro piles, etc.

Features:

1. There are various types, which can be selected according to different geological and construction conditions.
2. The symmetric structure bears more uniform force when drilling with good guiding performance, and the hole straightness is relatively good, and can be used for construction not larger than φ600 mm hole.
3. Stable drilling and not easy to get stuck. It can be used for drilling at different angles.
4. It can also drill the geological conditions of boulders.
5. The product structure is relatively complex, and the wings has poor strength, thus only can bear less load.

Symmetric Casing System With Slide Blocks

Applicable geology: It is suitable for covering layers with mostly loose materials on the surface of the formation, such as soil, clay, weathered rock, sand and gravel, etc.

Scope of work: It is suitable for drilling geothermal wells, water wells, small and medium-sized grouting holes in buildings, micro piles, etc.

Features:

1. The structure is simple, greatly reducing the probability of structural failure, and the operation is more convenient.
2. The symmetric structure bears more uniform force when drilling with good guiding performance, and the hole straightness is relatively good, and can be used for construction not larger than φ800 mm hole.
3. Stable drilling and not easy to get stuck. It can be used for drilling at different angles.
4. It can also drill the geological conditions of boulders.
5. The slide blocks have poor strength, thus only can bear less load.

1. What is the role of the centralizer in the drilling construction process?

Play the role of connecting drill pipe;

The centralizer keeps the drill pipe always in the center of the casing.

2. How many ways are there to connect the casing and the casing shoe?

There are 4 types to connect the casing and the casing shoe, namely,  sleeve weld connection, butt welding connection, left-hand thread connection, and right-hand threaded connection.

3. How many ways are there to connect the casing and the casing?

The two ways of connecting the casing to the casing are the MF thread connection and joint connection. Joint connection keeps high connection strength. MF thread connection always be used while drilling depth of thick-walled, small, and medium-diameter shallow holes, the joint connection is mostly used for thin-walled and large and medium-diameter casing deep hole drilling, and used for reused casings.