Obtenção de argilas organofílicas purificadas para uso em fluidos de perfuração base óleo.

Abstract

In drilling sensible to water it can to use oil based fluids. In these cases, the bentonite clay cannot be used without a previous organic treatment, which makes their surfaces as hydrophobic. After treated, these clays can be dispersed only in organic liquids. These clays after chemical modification are called organophilic clays, and are synthesized through the addition, in aqueous medium, of a quaternary ammonium salt that substitutes Na+ cation in the clay structure. In specific applications, organophilic clays not produce raw material of good quality, mainly because the natural clays have a great amount of other contaminating elements, generally accessory minerals. These accessory minerals have negative influence on the drilling fluids by reducing their properties to levels below the minimum requirements. The aim of this work is to develop a systematic study to synthesize organophilic clays to be used as oil based drilling fluids. So, it is proposed the purification of natural clays, as way to eliminate the accessories minerals by selective sedimentation, by the choice of adequate compatible quaternary ammonium salt with the organic liquids where the clays will be disperse, by the treatment of organic compounds to obtain purified and not purified organophilic clays fit to be used as oil based drilling fluids. The organic treatment was optimized through an attribute of Foster's swelling and X rays diffraction with satisfactory results. The apparent viscosity of obtained fluids with purified and not purified clays was compared with the imported commercial organophilic clay and with the Petrobras standards for oil based drilling fluids. It was observed that the purification treatment increase the apparent viscosity of water based fluids; however the purification process is very expensive. By direct observation of the apparent viscosity, it can be observed that the organophilic clays synthesized in this study presented best results when compared with the current standards and with commercial organophilic clay.