When to Use Concentric Drilling System？

Concentric drilling and eccentric drilling are two different approaches to drilling that involve the placement of drill bits or casings relative to each other:

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Concentric Drilling:

In concentric drilling, the drill bit and casing are aligned along the same central axis.

The drill bit is positioned within the casing or drill string in such a way that it rotates concentrically (around the same center) with the casing.

This alignment allows for drilling directly through the center of the casing, resulting in a borehole with a consistent diameter.

Concentric drilling is commonly used in many drilling applications, including water well drilling, geotechnical drilling, and mineral exploration.

Eccentric Drilling:

In eccentric drilling, the drill bit is offset or positioned eccentrically (away from the center) within the casing or drill string.

The eccentric placement of the drill bit allows for the creation of a larger borehole diameter compared to the casing size.

Eccentric drilling is often used in applications where casing advancement or borehole enlargement is desired, such as in overburden drilling or certain well construction methods.

Eccentric drilling can also refer to the use of eccentric drill bits with offset cutting structures, which may be employed in specialized drilling applications to achieve specific objectives.

In summary, the main difference between concentric and eccentric drilling lies in the alignment of the drill bit and casing relative to each other. Concentric drilling involves aligning them along the same central axis, while eccentric drilling involves offsetting or positioning the drill bit away from the center of the casing or drill string.

Description

Once bore a hole in the unstable soil formation, there is potential risk of hole collapsing. Casing drilling is an ideal drilling method that combine the drilling and casing process together to stabilize the hole. Powered by DTH hammer, the casing system has a pilot bit which drives a ring bit to drill a hole wide enough so that a casing tube can slide down to the hole. As the drilling process and casing process are performing at the same time, the casing tube can stabilize the hole immediately.

For more information, please visit Concentric Drilling System.

Overburden casing drilling system can be classified into concentric casing system, eccentric casing system and slide block casing system.

Concentric casing system also called symmetric overburden casing system, it can drill a hole at any angle (including horizontal) and the hole depth can be up to 100m. Concentric overburden casing system is composed of a central pilot bit, ring bit (reamer), casing shoe

The central pilot bit is attached to the DTH hammer and the casing shoe is welded to the casing tube. Powered by the DTH hammer, the central pilot bit drives the ring bit to drill a hole large enough and meantime the casing tube slide down to stabilize the hole. Once drilling the hole into the required depth, unlock the pilot bit by reverse rotation of the drilling string and then pull out the pilot bits through the casing tube. As for the ring bits and casings, they can be left in the hole for the permanent casing system or can be retrievable for the retrievable casing system.

Advantage:

• Drilling a hole straight and fast, even drilling in the gravel, sand, pebble formation;

• Requiring less torque of the rig, even the drilling rig with small torque can drill a large hole;

• It&#;s easy to unlocking and relocking the concentric casing system due to its simple structure;

• Drilling a straight hole at any angle;

• It&#;s easy to operate and cost-effective

Casing Tube

We have a range of casing tube from diameter 108mm to 377mm for concentric/ eccentric casing system.

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