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Asphaltenes (isolated by preparative TLC) from Potiguar Basin (Brazil) crude oils were submitted to mild oxidation to disrupt their structure, releasing the occluded oil. The released hydrocarbons were compared with those from the original crude oil, in order to provide an additional insight regarding composition in biomarkers and depositional paleoenvironment. It was possible to suggest that the oil samples present low thermal evolution, marine depositional environment and anoxide. The results showed that the release of these occluded hydrocarbon, which are remnants from the original oil, can be a tool for the geochemical study of highly biodegraded oils, leading to better maturation and origin information. [ABSTRACT FROM AUTHOR]

The Campos Basin is considered an important Brazilian petroleum province, with the most of its oils consisting in a mixture of biodegraded and non-biodegraded oils, which is related to more than one generation and migration pulse coupled with biodegradation events during successive stages of reservoir filling. Its turbidites reservoirs are also structural controlled through faults generated by halokinesis comprising the main route of oil migration from underlying source rocks. Throughout the biomarkers analyses of free hydrocarbons in oil, adsorbed, and occluded in the asphaltene structures, samples from different oilfields, and distances from the main fault responsible for its reservoirs filling, were comprehensive studied. The gas chromatography coupled mass spectrometer (GC-MS) methodology was applied. The results of biodegradation, source, and thermal maturation parameters reveals that the free and adsorbed saturated hydrocarbons are similarly altered, but differ in biodegradation degrees and pathways between oils, while occluded hydrocarbons and all fractions of aromatic compounds are well preserved. The predominance of biodegradation process over the recharge is suggested for distant samples from the main fault in each area, contributing to the local models of oil migration. The occluded hydrocarbons showed source similarities regardless of oilfield. According to thermal maturity based on unaltered aromatics compounds, the occluded hydrocarbons showed lower mature ratios than those free. This study introduces the application and limitations concerning biodegradation, source, and thermal maturation inferences from occluded hydrocarbons in asphaltenes covering Brazilian oils, in view to improve a concise geochemical tool in petroleum exploration. • Free hydrocarbons in oil, adsorbed and occluded by asphaltene were evaluated. • Oil samples were biodegraded at different degrees and pathways. • The occluded biomarkers is well preserved. • Introduces the application of occluded hydrocarbons covering Brazilian oils. • Highlighting a potential tool in petroleum exploration. [ABSTRACT FROM AUTHOR]

Abstract: Quantum yields of singlet oxygen formation by diesel oil, samples of four different crude petroleum and some fractions of a Brazilian intermediate petroleum were measured at 315nm, 355nm, 400nm and 450nm both by pulsed LASER or Xe lamp, with analysis of singlet oxygen emission at 1270nm. All samples generated singlet oxygen in dilute solution. Diesel oil has the highest quantum yield (0.49) and a Venezuelan crude the poorest (0.17). The aromatic, polar, asphaltene and maltene fractions of the Brazilian crude all generate singlet oxygen. Singlet oxygen formation was also observed when undiluted crude petroleum was analyzed. [Copyright &y& Elsevier]

Abstract: Asphaltene and resins are heavy fractions of petroleum responsible for serious problems during petroleum production. These problems include the formation of organic deposits in oil reservoirs; wells, transport pipelines and equipment, and can significantly increase the production operational costs. The nature and behavior of asphaltene in crude oils is complex and changes in temperature, pressure and composition of crude oils during production can result in precipitation of asphaltene components. Potential solutions for these problems include physical removal of deposits, solvent washes and treatment with dispersant agents. The use of soluble amphiphile oils provides the most practical and economical solution for deposits treatment. In this work, the inhibitory capacity of a number of new chemical additives to asphaltene precipitation was examined in three types of Brazilian crude oils. Low molar mass ethoxylated nonylphenols, vegetable oils (coconut essential oil, sweet almond, andiroba and sandalwood oil) and organic acids (linoleic, caprylic and palmytic) displayed highest capacity to inhibit asphaltene deposition. The dissolution capacity of some additives was evaluated for two asphaltenic deposits in aliphatic solvents. The remarkable solubilization effect displayed by dodecylbenzenesulfonic acid, confirmed the importance of acid–base interactions in this process. The results also revealed distinct mechanisms for asphaltene solubilization/dispersion in aliphatic solvents and inhibition of asphaltene precipitation in crude oils. [Copyright &y& Elsevier]

Hydraulic flow units (HFUs) are recognized as volumetric regions that favor the flow of reservoir fluids. Their determination is made possible through correlations between data that are transferred from miscroscale to reservoir scale by upscaling. However, the strong dependence on microscale parameters inherited by commonplace analytical methods based on flow indicators is still less tractable to achieve models having uniform continuity of HFUs at reservoir scale. This paper is intended to propose a class of partitioning algorithms to deal with the problem of identifying hydraulic flow units in petroleum reservoirs. As a result, a novel viewpoint inspired on constrained clusterwise linear regression is presented to describe the identification problem. We have studied the micro-to-macroscale correspondence through a mathematical isomorphism that maps the sample domain onto the reservoir domain by using the so called flow zone indicator (FZI) as underlying parameter. Each HFU is theoretically identified by a partition of FZI points that must lie on a straight line of unitary slope in a log–log plot of two quantities: porosity and reservoir quality index (RQI). By setting up constrained clustering approaches with different must-link hard constraints, we have found multiple HFUs directly from the dataset without resorting to usual conversion formulae. Pros and cons of each approach are discussed from analyses performed over the UNISIM-I-D dataset (a reservoir model for the Namorado oilfield, Campos Basin, Brazil), as with their feasibility to devise new data-driven workflows turned to reservoir modeling and characterization, especially at the interest of exploration and production oil industry upstream. Besides, a short overall comparison by taking a correlative flow zone indicator (namely, FZI*) as underlying parameter is appended to the text. We point out that an existent tradeoff between analytical and physical requirements is a limiting factor to properly identify hydraulic flow units at reservoir scale regardless the flow indicator. In particular, it turns out that algorithms that find highly correlated partitions indicate HFUs that lack of uniform continuity and are less physically meaningful. Oppositely, algorithms that produce less correlated partitions determine HFUs with satisfactory local continuity and compactness, being more physically acceptable. Additionally, we show that a inter-clustering process is recommended when selecting data points associated to representative volumes and local spots characterizing HFUs. • Introduces partitioning algorithms to deal with hydraulic flow unit identification. • Applies constrained clustering approaches with different must-link hard constraints. • Discusses pros and cons of each approach applied to a Brazilian oilfield model. • Singles out a tradeoff between analytical and physical requirements. • Points out modeling difficulties as for uniform and local continuity. [ABSTRACT FROM AUTHOR]