Técnicas avanzadas para la caracterización de petróleos pesados, productos derivados y sus fraccionesaplicaciones en ingeniería de yacimientos y medio ambiente

Abstract

Nowadays, fossil fuels still play a crucial role. As a result, oil companies are exploring the economic viability of non-conventional oil fields to ensure population energy needs. Heavy oils and extra heavy oils signify an important part of the oil reserves worldwide. Their exploitation implies technical problems and environmental risks, and therefore the problematic linked to the oil heavy fractions generates difficulties in hydrocarbons production. Despite the positive trends in the reduction of oil spills, they continue to put marine ecosystems at risk, as well as terrestrial ecosystems, when there are accidents during exploration, extraction or transportation. Heavy oil fractions, in this case, generate serious difficulties in the recovery of land affected by discharges, both marine and terrestrial environments. This is due to the resistance of these fractions to weathering and biodegradation. Heavy oils, and its heavy fractions are not easy to characterize. Difficulties are mostly related to asphaltenes, which are relatively abundant molecules in oil with a very complex analytic. In this context, it is necessary the development of analytical protocols that facilitate heavy oil characterization, and this is the main scope of this thesis. The proposed protocol has revealed the intra reservoir "tarmats" formation mechanisms. In coastal oil spills, the protocol gave the possibility to follow the natural attenuation in the environment. It was also revealed that TD/GC-MS is a rapid forensic tool in combination with pyrolytic analysis. Some of the specific results obtained in the applied cases developed in this work elucidated genetically different oil groups in fields affected with heavy oils in Los Llanos (Colombia) and Ceuta (Venezuela). Moreover, we have been able to identify oil mixing, as well as explaining the "tarmats" formation mechanisms. Finally, it has been possible to identify the oil-oil and oil-source rock correlations thanks to simultaneous analysis of rock, oil and "tarmats". On the other hand, in the context of environmental studies, seasonal climate cycles were shown as the main factor controlling natural attenuation advances after an oil spill, In addition, some diagnostic ratios using saturate compounds were selected to distinguish between distinct types of weathering and aromatic ratios were also useful to obtain a qualitative approach although without distinguishing between biodegradation, volatilization and photodegradation. The sequential pyrolysis of spilled products may be use as a rapid forensic tool, since the compounds identified by GC-MS of thermally desorbed products are identified as well those in saturated and aromatic fractions. In addition, the thermal desorption residue is predominantly asphaltenic, as revealed by the thermal desorption product pyrochromatogram (very similar to the asphaltene pyrochromatogram).