Influence of ionic hydration inhibitors on triple inhibition system mud properties - technological parameters

The hydration of drilled clay rocks and the related to it risk of complications, due to borehole wall instability, can be reduced by applying inhibited mud [1, 2]. There are numerous mud systems intended for clay rock drilling. Most popular are muds with an ionic-polymeric inhibitive function. This type of mud contains ionic inhibitors in combination with polymeric inhibitors. Nowadays, this system is often completed with polyglycols or amino agents, consequently creating mud with a triple inhibitor system [1]. Various organic and inorganic compounds can be used as hydration inhibitors. Those deliver, as a result of electrolytic dissociation, free ions capable of reaction of ion exchange with clay minerals, causing changes in physico-chemical properties. Useful electrolytes are the ones exhibiting good hydration capacity and not signifi cantly aff ecting technological parameters of the drilling mud [1]. The functions of a ionic hydration inhibitor are to reduce hydration of clay rock, counteract osmotic pressure generation and binding elementary platelets composing of clay minerals [1]. Surface hydration reduction is the result of interlayer clay ions substitution with ions with the lower hydration number. Osmotic hydration adjustment can be achieved by maintaining a greater concentration of ions in the mud/fi ltrate than in the formation. One of the important mechanisms of electrolyte’s inhibitive function is hydrophobization of the clay surface, that causes a decrease in formation wetting due to drilling mud fi ltrate [1]. The earliest applied hydration inhibitors were calcium components (Ca(OH)2, CaSO4·2H2O, CaCl2), which were a foundation of calcium mud development (calcium,