Correlation between chemical and mineralogical composition and plasticity characteristics of shales from Northeast Brazil

This work aimed to characterize shales samples from Northeast Brazil and to correlate their chemical and mineralogical composition with their plasticity. Three samples of shales were characterized by x-ray fluorescence (XRF), x-ray diffraction (XRD), granulometric analysis (GA), thermogravimetry (TG) and their plasticity was measured from the determination of Atterberg indexes. The results showed that the mineralogical composition of the shales was the determining factor for plasticity and the predominance of smectitic and illitic clay minerals promotes a higher index of plasticity (IP), which, probably, can cause agglomeration and accretion of drill cuttings in the bottom hole assembly components with average scale. (author)