Estudo do mecanismo de inchamento e desintegração de folhelhos da região Nordeste do Brasil.

Abstract

This work intends to understand the mechanisms of swelling and disintegration of shales from the Northeastern Region of Brazil. Nine samples of shales and a sample of sodium bentonite clay were analyzed. The study was carried out in three distinct stages: in the first one, the samples were characterized by the cation exchange capacity (CEC), specific surface (SS), particle size analysis, x-ray fluorescence (XRF), differential thermal analysis (DTA), thermogravimetric analysis (TGA); X-ray diffraction (XDR) and Fourier transform infrared spectroscopy (FTIR); in the 2nd stage, the samples were evaluated according to their swelling capacity by means of the ASTM swelling test, Foster swelling and determination of free water by the capillary suction time test (CST). Finally, in the third step, the disintegration of the samples was assessed in pressurized (100psi) and non-pressurized aqueous media. According to the results, the shale samples studied presented moderate to high reactivity and low or zero swelling. Furthermore, formations that do not present reactive clay minerals can be considered unstable and the higher reactivity of formations to aqueous fluids does not necessarily imply higher levels of disintegration. It is also concluded that the presence of calcium oxide has a direct influence on the disintegration of the shales, thus showing that different mechanisms not associated to the swelling of the clay minerals may assume greater or less importance in the instability of the formation.