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In this work, a multivariate approach was used to classify diesel/biodiesel fuel blends among 0% to 100% of biodiesel content on fuel mixture through discriminant analysis and cluster analysis associated with Fourier transform infrared spectroscopy (FTIR). The multivariate statistical techniques used in this work were partial least squares discriminant analysis (PLS-DA), principal component analysis (PCA), soft independent modeling of class analogy (SIMCA), hierarchical clustering analysis (HCA), and support vector machine (SVM). Multivariate analysis was performed on the following oil samples: soybean biodiesel, corn biodiesel, diesel S10, and fuel blends prepared from 0% to 100% (v/v) of biodiesel content. All multivariate statistical techniques were able to discriminate between the oil source and the ester percentage in the mixture. It was possible to develop robust multivariate models associated with the FTIR to allow for simultaneous discrimination of the types of oils used for biodiesel production and their content in fuel blends.

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From our work, significant progress has been made in understanding the degradation of cement-casing systems. The CO 2 degradation process was evaluated in specimens with a large interfacial defect, such as large annular spaces, voids and/or channels, which may be the result of a poor cementing job. From the experiments showing no interfacial defect, no signs of degradation were observed, while from experiments showing interfacial defect, both the cement and steel undergo significant degradation. In the well casing, the CO 2 -rich brine affects the steel phase, leaching Fe 2+ ions into solution and promoting FeCO 3 precipitation on the material surface, while on the cement sheath, two processes are occurring: (i) the portlandite dissolution and (ii) the cement carbonation process. Then, iron (Fe 2+ ) starts to migrate into the cement structure, compromising the material's self-healing and pore-blocking features, while calcium (Ca 2+ ) starts to compose the corrosion film from the formation of mixed carbonates (Fe x Ca y CO 3 ) so reducing the corrosion layer's protection. Finally, both ions (Ca 2+ and Fe 2+ ) become so abundant in the material vicinity that they may form calcium carbonate (CaCO 3 ) on the corrosion layer and iron carbonate (FeCO 3 ) in the cement matrix. Thus, from our results, the degradation mechanisms of the cement-casing system in CO 2 -rich brine was revised.

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