Drill Cuttings Solidification and Stabilisation

Oily drill cuttings from the shale shakers may not be suitable for direct disposal to land without further treatment.  Regulations in some countries require the “waste” to meet certain criteria such as the leachability of specified contaminants. Solidification and stabilisation of the drilling waste is a method whereby the raw cuttings from the shaker / centrifuge are mixed with additives in order that the treated wastes will meet the criteria for land disposal.

Solidification typically refers to encapsulating the waste such that the leachability of contaminants is reduced by minimising the surface area of the waste exposed to leaching, or by totally encapsulating the waste with an impervious layer. Stabilisation refers to chemical techniques that reduce the mobility of contaminants by changing their form into less soluble, mobile or toxic forms.  There are concerns that the long term stability of these waste is not yet understood and as such this technique is now limited in its application around the world to just a few countries.

NADF Drill cuttings are typically mixed with cement or lime and at least one more additive such as sodium silicate or organophilic clay.  The mixing is completed either by the use of a backhoe or through more automated equipment such as a ploughshare mixer and associated silos for the cement and additives.  In most cases some water will also be added to ensure complete hydration and reaction of the cement or lime.

The final product will normally be required to meet a specification that covers the leachability of specific contaminants and in some cases a number of physical properties.  The leachability requirements typically cover heavy metals and hydrocarbons whilst the physical tests cover the final strength of the product. The Louisiana State-wide Order 29-B provides a useful reference for these requirements and can often be quoted as a standard in the absence of local regulat

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