Estudo de algumas propriedades reológicas de argilas esmectíticas da localidade de Bravo, distrito de Boa Vista, Campina Grande-Paraíba, após cura em câmara controlada.

Abstract

Two smectites clays light brown and dark green coloured proceeding from the Bravo locality District of Boa Vista, Campina Grande, Paraíba were submetted to characterization and technological tests to verify the effects of several cure condi tions in the rheological properties ,keepi ng in mind its applicabi1ity as tixotropic agent in fluids for rotating per foration of oil wells. These clays were cured in a humid and climatized chamber, varying temperature, time, relative humidity and sodium carbonate concentration. The effect of these cure conditions was investigated from apparent and plastic viscosities and filtrate volume according the conditions specified by Petrobras. The dialysis effect after the cure in a climatized chamber was also tested. Carbonates and bicarbonates existing in the 6% solids suspension were detèrmined. These values were used to find correlation in filtrate volume and the viscosities apparent and plastic by simple and multiple linear regression analysis. The results of technological tests showed that the light brown clay presented diferentiated behavoir, not achieved in the conditions studied in this work, rheological properties adequated to the use, as tixotropic agent in fluids for the rotating perforation of oil wells and the dark green clay showed goods results to the use in the perforation of oil wells. when treated with 50 meq of sodium carbonate per 100 g of dry clay, cured in humid atmosphere and temperature below 70ºC or when treated with 100 and 150 meq of sodium carbonate per 100g of dry clay, submetted latter dialysis. With relation to correlations obtained showing to be of limited validity, keeping in mind the reduced number of observation taken; so were obtained correlations coefficients approximately one showing that there exist linear relation between amounts of carbonates, bicarbonates and carbonates plus bicarbonates with apparent and plastic viscosities and the filtrate volume in some cure conditions.