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Use of Bentonite Support Fluids

Bentonite is the name used for a range of clays that can swell and gel when dispersed in water. The name “bentonite” originates from the discovery of this type of clay near Fort Benton, USA, in the 19th Century. This was a natural sodium bentonite, and has been mined extensively for many years in Wyoming and Dakota for oil well drilling applications.

Bentonite is now used extensively throughout the world in civil engineering, but the cost of transporting original “Wyoming” bentonite from the USA has led to the use of alternatives from other sources. A large proportion of bentonite now used is therefore from other parts of the world.

It is important to recognise that the properties of bentonites from different sources vary, and to take these variations into account when deciding on the suitability of a particular bentonite for a specific purpose.

The purpose of this document is to provide information that will enable a decision to be made as to whether or not a particular bentonite will produce a satisfactory support fluid, and to give guidance on the preparation, use, re-use and disposal of the bentonite slurry, and also on methods of testing.

Since the first edition of this guide the use of polymer support fluids as an alternative to bentonite has become relatively common. Polymer support fluids are fundamentally different to bentonite support fluids and their scope is too great to be covered in this guide.

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