Bits ‘n Pieces – The Driller’s Blog

Diamond  Drilling in Ground with Clay or Shale

Posted by Rod McCoremick on May 8, 2017 1:51:37 PM
Rod McCoremick

I’m often going on about how choosing the equipment for the type of ground you will be drilling in is the first step to success and good drilling performance. Choosing the right drilling fluid additive to match the ground you will be drilling in beforehand, will make a world of difference. This is certainly the case in ground with clay or shale. Swelling clay can have disastrous results on your drilling operation.

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When drilling in clay conditions and your drilling water comes into contact with the clay, the water causes the clay to expand and swell. This swelling can squeeze and put pressure on the drill rods, greatly increasing in-hole torque and causing your equipment to become stuck in the hole.

How bad can this swelling get? We’ve seen situations where equipment was left in the hole overnight and the next morning the clay have swelled up and out of the hole. Keep in mind that some of this clay-like ground may not have come in contact with water for centuries. When water touches it, the reaction can be impressive. Now imagine that your equipment is in the middle of this reaction. You can be pretty sure you will get stuck in the hole.

Drilling in difficult ground conditions can often be improved through the use of drilling fluid additives. Many drillers still don’t use additives either because they are not familiar with them or because they don’t think they will make a big difference. This is not the case at all as drilling fluid additives have been proven to bring many benefits.



For example, DD-955 is a product that is absorbed directly into the clay and shale and reduces in-hole swelling and instability. To help you improve drilling performance, we’ve created our latest guide on using drilling fluid additives, one that addresses ground with clay or shale. Keep in mind that other considerations such as the right core bit and the best core bit configuration will have an impact on your success. And as always, our technical team is available to help make your life easier. Don’t hesitate to call us.


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Topics: Drilling mud, fluids and additives, Basic drilling information

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