How core drilling works

How Core Drilling works

Core Drilling Services Pretoria, Gauteng

Here's how core drilling works

The core drilling has three main processes.

  • The actual drilling
  • Retrieving of the core sample
  • Continuation of core drilling

The process together is referred to as a Round trip.  Core samples are stored in a core sample box. The exact time and date of the drillings are recorded as well as the conditions of the day. High quality core samples are the main goal of the core drilling process. These core samples are then analyzed to see if the project at hand will be doable and or if any adjustments in construction plans need to be made.

The actual drilling

In understanding how core drilling works one must understand the concepts and practices behind the actual drilling process.

When the core drilling process commences, the Core Drill Is placed in position to start the core drilling process. The core drill then starts twisting and turning, burrowing its way into a surface. Core drills can drill their way into concrete, ice, wood and rock. The tips or drill bits of the core drill may vary according to the type of surface. The power, size and other features vary from small to large, depending on the project at hand. The drill bits are usually coated with diamonds or carbide. As these materials are effective when it comes to cutting into hard materials such as rock and concrete.

How a core drill works

The core drill rotates and twists its way into a surface by cutting out pieces of the material below. As the bits or tips of the drill rotate, the drill burrows its way into the materials below. While cutting the material drilled into  are passed through a hollow tube. These materials are collected in the tube and brought back up to the surface for analysis. While core drills burrow their way into materials fluids are sent down with the drill to keep the drill cool and send the excess materials back to the surface leaving a clean hole. The materials captured in the cylindrical tubing is called a core sample.

Retrieval of the core samples

How does core drilling retrievals work? There are two main methods:

  • The conventional core drilling method.
  • Wire line

The whole drilling string has to be taken out of the drill hole regardless of the drilling method used.

Core drill bits do ware out and are taken out and new drill strings with different or new drill bits are replaced to keep drilling as effective and productive as possible. Choosing the correct drill bits are essential for productivity and experienced core drillers will know exactly what drill bits will work best for the material to be drilled into. All the core samples, conditions and losses if any are logged.

Conventional core drilling method

In conventional core drilling the entire drill string is pulled up to the surface. Then the drill rod threads are broken upon retrievals and stored in the core sample box for analysis. This process of drilling and retrieval may be done over and over until the desired outcome has been reached. Depending on the quality of the core samples, depth and other objectives.

Wireline core drilling method

In wireline core drilling an overshot is sent down to retrieve the inner tube. The overshot and inner tube are then brought back to the surface with a wire. A new innertube is then loaded and sent back down for further drilling.

Conclusion: 

Core drilling requires quality equipment and in-depth knowledge of core drilling. Knowing what bits are needed, knowledge of core sample retrievals and accurate logging is essential to successful retrieval of samples. The core drilling team needs to be well experienced and well rehearsed with the correct safety methods and skills. To successfully and safely complete core drilling tasks.

How the core drilling process works (Short write up) 

  • Core drills are fitted with the correct drill bits.
  • Once fitted the core drill spins and rotates cutting into the material below.
  • The core drill has a hollow cylinder which collects core samples.
  • Core samples are brought up to the surface and stored in a box for analysis at a later stage.
  • The whole process from start to finish along with any errors are logged accordingly.

Here is a great video to explain more about  core samples and core logging >

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