Abstract
ABSTRACT Rheological measurements together with microscopy observations were used to provide an understanding of the mechanisms of viscosity changes in oil muds. The rheological behavior of mixtures of base oils, organophilic clays, and water (or brine) were studied as a function of oil type, water concentration, organophilic clay concentration and type, shear history, addition of polar activators (such as xylene), addition of calcium chloride and addition of emulsifiers. Examination of these mixtures under an optical microscope showed that there is a relationship between rheological behavior and microscopically visible interactions between organophilic clay and the dispersed aqueous phase. These interactions build structure in the oil that gives thixotropic properties. Dispersion of the organophilic clay, necessary for efficiency in thixotropy building, is affected strongly by the shear history and by the compositions of the base oils, organophilic clays, emulsifiers, and aqueous phase.
Published Version
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