[en] The aim of this work is to evaluate the influence of the variables: aging time and temperature on rheological properties of clay fluids, using a factorial plan 2³ type with three experiments in the central point. Were studied the aging times of 1, 8 and 15 days and temperatures of 40, 60 and 80 ° C for testing. The fluids were prepared with concentration of 30g clay Brasgel PA / 350mL water and a part additivated with 0.5g of MgO - pH controller. The viscosities were determined on viscometer Fann 35A. From the results of experimental data regression it was observed that the values of apparent and plastic viscosities change with the presence of MgO, increasing the values of the rheological properties of fluids. The test temperature was the variable that conferred great influence in the fluid properties. (author)