An attempt to understand the microscopic origin of the high viscosity of Brazilian heavy crude oils was made combining macroscopic (rheological measurements) and microscopic [small-angle X-ray scattering (SAXS) measurements] techniques. A clear relationship between the asphaltene content and viscosity was found, while the removal of asphaltene via flocculation led to a large viscosity drop, confirming them as the origin of high viscosity. The SAXS analyses of crude oils confirmed the presence of asphaltene aggregates as fractal-like particles of colloidal dimensions. Afterward, a systematic investigation was performed on the effects of a series of additives and physical treatments on the crude oil viscosity. Physical methods did not cause any significant viscosity drop as well as more than 80 additives tested. SAXS measurements on oil samples containing toluene and heptane indicated little effect on the asphaltene nanoaggregates within the dimensions probed by SAXS, confirming a general mode of action based on aggregate dilution instead of disruption.

representava os níveis altamente abstrato ou concreto, respectivamente. Os resultados evidenciaram uma distribuição bi-modal sugerindo que as palavras podem ser classificadas nas categorias concreta ou abstrata. A confiabilidade média das normas foi r=0,97. Não foram detectadas influências do sexo, idade, freqüência de ocorrência das palavras em materiais escritos ou tamanho da categoria nos julgamentos de concretude. Os resultados sugerem que a concretude pode ser considerada como um atributo independente das palavras.Palavras-chave: concretude; normas para palavras; imagem mental. Concreteness Norms for 909 Portuguese WordsABSTRACT -Concreteness norms were collected for 909 words using a seven point judgment scale, where each extremity highly represented the abstract or concrete levels, respectively. Results showed a bi-modal distribution suggesting that words may be classified either as concrete or abstract. The average reliability of the norms was r=0.97. Concreteness judgments were not influenced by sex, age, word written frequency or category size. The results indicate that concreteness may be considered as an independent word attribute.

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Recently, some works showed that magnetic fields may reduce the paraffin crystallization and the viscosity of some types of oil. This Article shows the main results obtained in an attempt to determine some factors responsible for the oil interaction with magnetic fields, which caused the rheological properties change in crude oil samples. Under the influence of a magnetic field (1.3 T in 1 min exposure), one of the six brazilian crude oil samples studied (sample 1) showed 39% reduction on its viscosity and a reduction on the viscoelastic properties (loss modulus and storage modulus). However, the other five samples did not show any considerable modification of their rheological properties. We analyzed all six samples using spectroscopy to detect what kind of component was present in sample 1 that could interact with the magnetic field and cause the aforementioned rheological properties change and that was not present in the other samples. The major differences observed in sample 1 were the presence of the Mn 2+ paramagnetic ion (EPR spectroscopy); Sr and Br (XRF spectroscopy); highest aromatic/aliphatic molecules ratio (NMR spectroscopy); and the highest water content (10% v/v, NMR spectroscopy). Thus, the results show that the paraffin could not be the unique factor responsible for the change on the rheological properties of the crude oil samples caused by magnetic fields, as some authors suggested previously.

Literature data on the influence of magnetic fields on organic deposition process are most oriented to charged species, e.g., calcium carbonate scale. It has also been claimed that the use of magnetic tools can mitigate paraffin deposition in flow lines. If this technique can be applied to subsea flowlines the benefits are potentially high. However, magnetic tool manufacturers do not provide the necessary level of information to make the customer feel comfortable to rely on such devices. Therefore, a research project has been established to shed some light to this yet controversial subject. The paraffin crystallization process under the influence of magnetic fields and paraffin inhibitors (PIs) has been investigated with the aid of Microscopy. The objective of this study was three-folded - to provide a laboratory evidence to recommend - or not - the use of magnetic tool in the field, - to verify the Microscopy usefulness to study non-isotropic paraffin crystallization process and, - to provide an additional tool to help in selecting PIs. To our best knowledge the technical contributions of this study are- to confirm that magnetic field do alter paraffin crystallization process, - to establish a relationship between PIs and the paraffin crystallization process and, - the development of experimental analytical procedures to investigate paraffin deposition-related processes. Introduction Paraffin deposition is a well-known phenomenon that plagues the oil industry all over the world. As a rule paraffin problems can been solved in onshore fields with inexpensive physical and chemical methods. However, as the oil industry is continually moving to deep water scenarios where paraffin deposition takes place in difficult-to-reach subsea flow lines, manifolds and wet Xmas trees, no inexpensive solutions are known. Conversely, operators are concerned to paraffin deposition problems in deepwater production facilities for they are costly, time-consuming and means a serious menace to the economical feasibility of their enterprises. To cope with operational problems associated to organic deposition in deep waters, Petrobras has been funding an integrated research program - the so-called Petrobras Flow Assurance Program (PROCAP) - aimed at forecasting organic deposition and preventing and/or solving the problem in offshore wells. A set of preventive and remedial solutions were either in-house- or jointly-developed. The major products that arose from this research effort are briefly described as follows: Pigging A jointly industrial project on pipeline pigging simulation was launched by Petrobras in 1996. More than one hundred successful pigging operations have been conducted in subsea flow lines in Campos Basin so far. Nitrogen Generating System (SGN) The SGN method comprises the controlled reaction between two nitrogen-containing chemicals which is capable of generating a large amount of nitrogen gas and heat. The method has been successfully used in more than one hundred operations in Campos Basin area. Paraffin Inhibitors The use of paraffin inhibitor (PI) is another approach to solve paraffin deposition problems in offshore fields. The technology which also includes the correct application of these chemicals in the field has been used in a long-term test in the Albacora field, Campos Basin. On-going research on this subject has been oriented toward finding more cost-effective PI's and understanding how these chemicals prevent paraffin crystals from growing. Magnetic devices A study to investigate the potential of the so-called magnetic fluid conditioners (MFCs) to inhibit paraffin deposition is being carried out at Petrobras Research Center.