Influence of lithium (Li ⁺ ), sodium (Na⁺ ) and potassium (K⁺ ) on the rheology of Brazilian bentonites for use in water-based drilling fluids

The lithium (Li⁺), sodium (Na⁺) and potassium (K⁺) cations are first in the plane of selectivity for obtaining monocationic bentonite from the polycationic, specifically influencing the rheological behavior of water based drilling fluids. The aim of this work was to study the influence of Li⁺, Na⁺ and K⁺ in the bentonite rheology of Paraíba State, Brazil, for use in waterborne drilling fluids. The new deposits of Brazilian bentonite were compared based on their chemical, physical, mineralogical characteristics, rheological and filtration properties. The bentonite samples were characterized by the chemical composition through the classical method, cation exchange capacity, particle size analysis by laser diffraction, X-ray diffraction and thermal analysis. The rheology of the dispersions was studied and the apparent viscosities, plastic viscosity and flow limit were determined based on API and PETROBRAS standards, in addition to studies of water swelling and filtration. The results showed a significant improvement in the rheological and filtration properties of the dispersions after the additivation with the lithium and sodium carbonates, in that order, with thixotropy being present in the flow curves of the studied clay dispersions. (author)