Brazilian Crude Oil Research Articles

Effect of biodegradation on biomarkers released from asphaltenes

The structural features of asphaltenes enable them to occlude other molecules such as biomarkers. This could hinder the secondary alteration of biomarkers that occurs in oil reservoirs; these biomarkers could, therefore, be considered to be remnants of the “original oil”. Asphaltenes from Brazilian crude oils were obtained and submitted to oxidative treatment to disrupt their structure, releasing the trapped oil. The released hydrocarbons were compared with those from the original crude oil, and used to evaluate the alteration of the oils, especially as a result of biodegradation. The crude oils are depleted in n-alkanes, an effect usually related to biodegradation. However, the released products from the corresponding asphaltenes have n-alkane distributions from C 15 to C 35, suggesting protection from biodegradation that is probably related to encapsulation by the asphaltene network. The m/ z 191 chromatograms showed different relative intensities for tricyclic terpanes in the associated crude and released oils. They are less abundant than the hopanes in m/ z 191 mass chromatograms of the hydrocarbons released from the asphaltenes. The occluded saturated hydrocarbons are suggested to represent the original oil derived from kerogen, retained and protected against alteration inside asphaltenes over geological time.

Measuring Salinity in crude oils: Evaluation of methods and an improved procedure

In this work, a novel procedure is developed to determine the amount of salt for crude oils in which the available laboratory techniques are unable to provide accurate salt content values. The technique is based on measuring the salinity of the wash water that is vigorously mixed with the crude oil (forming an emulsion) and then separating it from the water-in-oil emulsion by irradiating microwave energy during few minutes. This three step process involves the emulsification of the wash water exempt of salt in crude oil, followed by the recovery of the water by microwave heating and, finally, the analysis of the salt content using the classical Mohr’s method titration procedure. The novel technique presented here was able to provide reliable information about the salt content on Brazilian crude oils, in a rapid manner, without need of unsafe time-consuming solvent extraction procedures.

Influence of asphaltenes on coke formation during the thermal cracking of different Brazilian distillation residues

This research was conducted to allow the investigation on the influence of asphaltenes on coke formation, during the thermal cracking of atmospheric distillation residues, using thermogravimetry. Asphaltenes of five refinery atmospheric distillation residues, of different API gravity Brazilian crude oils, were isolated by the IP143 methodology. The original samples and the same samples, after asphaltenes extraction, were analyzed by thermogravimetry. It was observed that the heavier the sample, the higher was the contribution of the asphaltenes to the coke formation. The extracted asphaltenes were analyzed under the same TG conditions of the atmospheric distillation residues and all asphaltenes appeared to form approximately the same amount of carbonaceous residue after the thermal cracking. Heavier and lighter atmospheric distillation residues were doped with 10%, 20% and 30% amount of asphaltenes and, again, the higher the asphaltenes amount, the higher would be the carbonaceous material formation. The same tendency was observed for both doped samples.

Desenvolvimento tecnológico na indústria do petróleo: o ambiente organizacional e seus aspectos habilitadores e inibidores da inovação

Two cases of technological development are presented, which are related to the increase of the Brazilian crude oil production and the search for self-sufficiency in the supply of this important energy source and its refined products. The business context is considered, a background report made and the main results presented of the Technological Programs developed by Petrobras, for Deep Water Crude Oil Production and Strategic Refining, with the focus on the RFCC process. Based on interviews with Program and Project Leaders, Managers, Consultants and Specialists that had considerable participation in these developments, an analysis is made of the internal organizational ambience and the enabling factors that foster the generation of these innovations, using as a format, the aspects traditionally cited in the literature. A comparison between the two cases is shown, with regards to their similarity in relation to these aspects. This analysis describes the organizational ambience, considering the following factors: human factor; resources and infrastructure; management processes; organizational citizenship; culture and values.

Inhibition of asphaltene precipitation in Brazilian crude oils using new oil soluble amphiphiles

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.

Speciation analysis of volatile and non-volatile vanadium compounds in Brazilian crude oils using high-resolution continuum source graphite furnace atomic absorption spectrometry

A method is proposed that makes possible determining total and “thermally stable” vanadium in crude oil without prior separation, and to calculate “volatile” vanadium by difference. The volatile fraction is believed to be largely vanadyl porphyrine complexes. The method is based on the unsurpassed background correction capability of high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS), which allows pyrolysis temperatures as low as 300 °C to be used. The samples were prepared as oil-in-water emulsions, and aqueous standards emulsified in the same way were used for calibration. Total vanadium has been determined using a pyrolysis temperature of 400 °C, and “thermally stable” vanadium using a pyrolysis temperature of 800 °C. The content of total vanadium in 12 Brazilian crude oil samples was found to be between less than 0.04 and about 30 mg kg −1. The volatile fraction was between 5 and 51% of the total content, and there was no correlation between the total and the volatile vanadium content. The limits of detection and quantification were 0.04 and 0.12 mg kg −1 of V in crude oil, respectively, based on a mass of 2 g of oil in 10 mL of emulsion. The precision was better than 4% at the 3 mg kg −1 level and better than 1.5% at the 30 mg kg −1 level of V in crude oil.

Investigation of petroleum medium fractions and distillation residues from Brazilian crude oils by thermogravimetry

Thermogravimetry was applied to evaluate the heavy distillation residues of different Brazilian crude oils. The thermal characteristic of the samples could be studied by only one experiment. It was possible to evidence the linear correlations among the results obtained by the TG curves and by the patterned methodologies, therefore anticipating volatile and carbonaceous materials (coke) formed during their thermal cracking. The correlations herewith observed, in a short period of time, provided comparisons among the petroleum fractions.

Thermal behavior of refinery atmospheric residue from some different oils

Thermogravimetry (TG) was applied to evaluate the thermal behavior of five refinery atmospheric distillation residues (ATR) obtained from different Brazilian crude oils. The asphaltenes were extracted of each sample and their influence on coke formation was studied. It was observed that they have a great contribution on carbonaceous residues formation during pyrolysis and that the heavier the ATR sample, the higher is the contribution of other heavy components present in ATR samples.

Study of the paraffin deposit formation using the cold finger methodology for Brazilian crude oils

Transportation of paraffinic crude in a cold environment can result in wax depositions, which are solid deposits, on the pipe wall. The formation of paraffin in the bulk of the petroleum is a crystallization process in solution. Such phenomenon occurs along the pipe connected to offshore wells and even onshore. Its main implication is a paraffin blockage with serious economical consequences. This work aims to learn about paraffin deposit formation using a cold finger methodology, in two types of Brazilian crude oils (32 API and 20 API). The polythermal method is used in various experiments using different temperatures in both cold finger and bulk of the fluid. The experiments measure: the thickness of the deposits, as well as the deposition rates, degree of subcooling and, finally, the induction for the onset of wax. The methodology allows the evaluation of the critical time of deposition and the critical temperature difference between the hot petroleum source and the cold seawater temperature. It is shown that the deposit rate depends on this temperature difference, as well as the cooling surface, the nucleation kinetics and the growth of the crystals on the cold finger surface. The work discusses carefully the experiments design under the light of dimensional analysis. The values of critical temperature differences are relatively small and show that the encrustation is easily attained in the offshore petroleum flow. The methodology implemented is simple and allows the prediction of very important information about the mechanism of paraffin encrustation that could pave the way to avoid paraffin deposition in offshore petroleum production due to high temperature differences between the heat petroleum sink source and the cold seawater.

Photochemical transformations of water-soluble fraction (WSF) of crude oil in marine waters: A comparison between photolysis and accelerated degradation with TiO 2 using GC–MS and UVF

Changes in the chemical nature of the water-soluble fraction (WSF) of crude oils caused by photolysis and heterogeneous photocatalysis using TiO 2 were investigated by gas chromatography–mass spectrometry (GC–MS) and ultraviolet fluorescence spectrophotometry (UVF). Two Brazilian crude oil samples with different concentrations of WSF (45 and 15 mg C l −1) were studied. Photochemical driven reactions were investigated under UV-Vis irradiation in the absence and in the presence of the photocatalyst. The presence of aromatic hydrocarbon in the WSF before irradiation, resulting from crude oil slick solubilization on seawater, was confirmed by chromatograms that showed a series of low molecular weight aromatic hydrocarbons together with a unresolved complex mixture (UCM). However, in the irradiated WSF these compounds were not detected. After 6 days photolysis period, WSF from both crude oils did not show peaks of aromatic compounds, whereas the presence of long chains unsaturated hydrocarbons as well as sulfur compounds were detected. In contrast, when TiO 2 was employed, complete photodegradation of both crude oil samples in the WSF occurred after very short light exposure periods (1–2 days). Quantitative data were also obtained and discussed here. The results reinforce photodegradation as an effective weathering process for the transformation of dissolved crude oil fraction, particularly in high solar radiation environments. Complete degradation in a short period of time was only made possible by heterogeneous photocatalysis.

Operational problems related to the preparation of the seawater soluble fraction of crude oil.

Owing to the importance of dissolution and weathering processes following oil spills, this work focused on the operational (quantitative) aspects related to the dissolution of petroleum-derived products, as well as the influence of solar light on both dissolution and the photoproduction of hydrogen peroxide. Four Brazilian crude oil samples were used to study the transfer process of organic compounds from the crude oil film to the aqueous phase (natural seawater) over a period of up to 45 days. Dissolved organic carbon (DOC), measured by non-dispersive infrared spectroscopy followed by high temperature catalytic combustion, was used to follow the partitioning between the two phases. Aqueous DOC values increased as a function of time (up to 15 days) until equilibrium was reached at concentrations ranging from 5 to 45 mg C L(-1). The final DOC concentration as well as the rate of dissolution depends on the nature of the crude oil. When exposed to sunlight, the dissolution was enhanced by up to 67.3%, and inorganic peroxides were generated in the concentration range from 4.5 up to 8.0 micromol L(-1) after 7.3 h irradiation. These results indicate that there is a need for a standard procedure for the production of the WSF in order to generate a more reliable tool to assess the impact of oil spills on the marine environment.

Interfacial and colloidal behavior of asphaltenes obtained from Brazilian crude oils

In this work, we present new data on the interfacial and colloidal behavior of asphaltenes in model aromatic solvents and crude oils and discuss the implications of these data on the aggregation, adsorption on solid surfaces, inhibition of deposition and emulsion stabilization capacities for two types of asphaltenes obtained from Brazilian crude oils. Surface tension measurements in solutions formed by any of these two types of asphaltenes, pentane insolubles (C5I) or heptane insolubles (C7I), in aromatic solvents suggested the occurrence of an aggregation phenomenon of asphaltenes in each of the solvents studied. Viscosity measurements in these same solutions revealed yet another type of aggregation at higher asphaltene concentrations. Both aggregation processes were found to be a function of temperature and type of asphaltenes. For the asphaltenes investigated, C7I was always more prone to aggregation, a characteristic ascribed to its higher asphaltene and lower resin content as revealed by SARA chromatographic analysis, and to its larger average molecular weight as determined by VPO. The effect of temperature on theses two processes confirmed the exothermic nature of both. A number of block copolymers, ionic and non-ionic surfactants, were tested for their effectiveness as asphaltenes stabilizers in crude oil. The results revealed different and distinct mechanisms for solubilization/dispersion of asphaltenes in aromatic (aliphatic) solvents and for the inhibition of asphaltene precipitation in crude oils. The two types of asphaltenes (C5I and C7I) were found to be effective in the stabilization of water/oil emulsions as well as water/toluene emulsions, with larger effects for C7I in water/toluene emulsions, consistent with its greater surface activity and its larger tendency to self-associate. Finally, the interaction of asphaltenes with solid surfaces was evaluated by determining the adsorption isotherms of asphaltenes on silica and activated carbon. The organic adsorbent was found to be much more efficient in removing asphaltenes due, perhaps, to the similar chemical nature of the adsorbing species and adsorbent. In all cases, evidence points to multilayer formation, in agreement with the previously detected tendency of asphaltenes to aggregate.

Poly(ethylene-co-vinyl acetate) (EVA) as wax inhibitor of a Brazilian crude oil: oil viscosity, pour point and phase behavior of organic solutions

Several techniques have been used to minimize the problems caused by the wax deposition, and the continuous addition of polymeric inhibitors is considered an attractive technological alternative. The addition of copolymers like polyacrylates, polymethacrylates or poly(ethylene-co-vinyl acetate) (EVA) permit to inhibit the deposition phenomenon; nonetheless, this effect is specific, i.e. similar copolymers present different performance depending on their physical–chemical properties in solution. In this work, the influence of the EVA vinyl acetate content on the viscosity and the pour point of a Brazilian crude oil were evaluated. A correlation between both results was also obtained. The phase behavior and the solubility parameter of EVA copolymers, with different vinyl acetate contents, were investigated in various solvents together with an evaluation of the efficiency of these copolymers as pour point depressants for two different samples of crude oil. EVA copolymers containing 20, 30, 40 and 80 wt.% of vinyl acetate were used and tests with the crude oil were carried out using 50, 500, 1000 and 5000 ppm of EVA as additive. The results obtained from viscosity measurements showed that only below the temperature at which wax crystals start forming did the copolymer exhibit a strong influence in the reduction of oil viscosity, at an optimum concentration. The pour point results revealed EVA 30 to be the most efficient. The results obtained from both experiments showed that the viscosity and the pour point behaviors do not show good correlation. Not only the solubility parameter and the vinyl acetate content, but also the molecular weight and polydispersity have an important influence on both phase behavior and pour point depression. Furthermore, it was confirmed that the additive must present a reduced solubility at a temperature close to the crude oil cloud point. This, however, is not the only factor that determines the efficiency of the additive as paraffin/wax deposition inhibitor.

Asphaltene flocculation and collapse from petroleum fluids

Deposition of complex and heavy organic compounds, which exist in petroleum crude and heavy oil, can cause a number of severe problems. To prevent deposition inside the reservoir, in the well head and inside the transmission lines, it is necessary to be able to predict the onset and amount of deposition due to various factors. In the present paper, the mechanism of asphaltene deposition, which is the major cause of most organic deposition cases, is modeled based on statistical mechanics of polydisperse polymer solutions joined with the kinetic theory of aggregation and its predictive capability is discussed. Utilization of statistical mechanics of polydisperse polymer solutions joined with kinetic theory of aggregation enables us to develop a realistic model which is able to predict both reversible and irreversible heavy organic depositions. The present model is capable of describing several reversible and irreversible situations, such as the phenomena of organic deposition, growing mechanism of heavy organic aggregates, the size distributions of precipitated organics and the solubility of heavy organics in a crude oil due to variations in oil pressure, temperature and composition. As an example, the present model is applied for heavy organics deposition prediction of two different Brazilian crude oils for which experimental data are available. It is shown that the prediction results of the present model are in good agreement with the experimental data.

THE INFLUENCE OF VINYL ACETATE CONTENT OF THE POLY(ETHYLENE-CO-VINYL ACETATE) (EVA) ADDITIVE ON THE VISCOSITY AND THE POUR POINT OF A BRAZILIAN CRUDE OIL

Petroleum companies have enhanced the offshore exploration, where the fields are located under deep water. In such cases, the low temperature of the water leads to the cooling of the oil and provokes wax deposition. Several techniques are used to reduce the problems caused by wax deposition. Polymeric additives, as ethylene-co-vinyl acetate co-polymers (EVA), are intensively used. In this work, the influence of the EVA vinyl acetate content on the viscosity and the pour point of a Brazilian crude oil was evaluated, and correlations for these properties as a function of the EVA co-polymer concentration were established. EVA copolymers were used containing 22,32,40 and 82 wt% of vinyl acetate and the tests with the crude oil were carried out using 50, 500, 1000 and 5000 ppm of EVA as additive. The results obtained from viscosity measurements showed that only below the temperature in which the wax crystals start forming the copolymer exhibited a strong influence on the oil viscosity reduction at an optimum concentration. The pour point results showed the best efficiency to EVA 32. The results obtained from both experiments showed that the viscosity and the pour point behaviors do not present good correlations to each other.

REVERSIBILITY AND INHIBITION OF ASPHALTENE PRECIPITATION IN BRAZILIAN CRUDE OILS

ABSTRACT A fundamental understanding of the aggregation and precipitation of asphaltenes in petroleum crudes is important for the development of preventive and curative measures for the potential problem of asphaltene deposition occurring during production, transport and refining operations. The question of reversibility of asphaltene precipitation, yet a controversial issue, is crucial for a clear and unequivocal understanding of the precipitation phenomenon, development of mathematical models that describe the behavior of asphaltenes in petroleum fluids, and the design of inhibitors. In this work, the behavior of precipitated asphaltenes in Brazilian crude tank oil samples following flocculant removal and gradual addition of fresh oil was investigated. The results obtained revealed a re-dissolution of precipitated asphaltene particles following flocculant removal and oil addition. On the inhibition of asphaltene precipitation, the capacity of a number of surfactants and block copolymers to inhibit asphaltene precipitation and deposition was also examined. Ethoxylated Nonylphenols and Hexadecyl Trimethyl Ammonium Bromide displayed highest capacity in the inhibition of asphaltene deposition.

Aggregation Behavior of Two Asphaltenic Fractions in Aromatic Solvents

Data on the behavior of crude oil n-pentane- and n-heptane-insoluble fractions in aromatic solvent systems were obtained. Surface and interfacial tensions in systems formed by Brazilian crude oil n-pentane insolubles (C5I) and n-heptane insolubles (C7I) in the aromatic solvents toluene, pyridine, and nitrobenzene were measured at room temperature using the ring method and employing an automatic tensiometer. The results indicated possible asphaltene aggregation as well as the probable existence of critical micelle concentrations for both C5I and C7I fractions in each of the three solvents considered. Critical micelle concentrations measured for the C5I fraction in toluene and pyridine solutions were consistently higher than those in systems containing the C7I fraction, indicating a lower association tendency in the C5I fraction. Average molecular areas for asphaltenes adsorbed at different interfaces estimated from surface tension measurements were found to be in agreement with literature values and appeared to suggest a planewise surface adsorption of asphaltene molecules, which is consistent with currently accepted stacking aggregation mechanism of asphaltenes. The presence of a discontinuous point for the kinematic viscosity of asphaltene/toluene solutions as a function of asphaltene concentration suggested yet another type of aggregation of asphaltenes at concentrations higher than the observed cmc in toluene.

AGGREGATION OF ASPHALTENES OBTAINED FROM A BRAZILIAN CRUDE OIL IN AROMATIC SOLVENTS

Surface and interfacial tensions in model systems formed by a Brazilian crude oil n-pentane insolubles (C5I) and n-heptane insolubles (C7I) in three different aromatic solvents: toluene, pyridine and nitrobenzene, were measured at room temperature, employing an automatic tensiometer and using the ring method. The results obtained indicated possible asphaltene aggregation and allowed the determination of critical micelle concentrations (c.m.c) for both C5I and C7I fractions in each of the three solvents considered. In toluene and pyridine solutions, the C5I fraction consistently presented higher c.m.c. values indicating a lower tendency of association for the organic fraction contained in the C5I, and absent in the C7I. In nitrobenzene solutions, this extra organic fraction appears to facilitate asphaltene association, possibly due to the formation of mixed aggregates. Average molecular areas for asphaltenes adsorbed at different interfaces were estimated using measured tensions and found to be in agreement with literature values and suggest a the flatwise surface adsorption of asphaltene molecules. This is consistent with the currently accepted stacking aggregation mechanism of asphaltenes.

Formation of low molecular weight carbonyl compounds by sensitized photochemical decomposition of aliphatic hydrocarbons in seawater

Anthraquinone has been found to be a compound occuring frequently in seawater. Excited by solar radiation it acts as one of many natural and man-made photosensitizers and can thus be used as a model substance for the study of sensitized photochemical reactions of environmental chemicals. Experimentally it has been shown to mediate the oxidative photochemical decomposition of aliphatic hydrocarbons which, lacking absorption bands in the solar UV range at sea level, are by themselves photochemically inert. Formaldehyde, smaller amounts of acetaldehyde and acetone as well as a still unidentified carbonyl compound are the principal low molecular weight products generated in the anthraquinone-sensitized photooxidation, with natural as well as artificial sunlight, of straight chain saturated hydrocarbons accommodated in high purity water. Qualitatively the same results were obtained in natural seawater as reaction medium from which particles were removed by glass fiber filtration and organic compounds by adsorption on activated charcoal. The concomittant generation of homologous series of methylketones and terminal alkenes suggest a decomposition mechanism involving cyclic electron rearrangement in a 6-membered transition state. Based on HPLC analysis of their 2,4-dinitrophenylhydrazones, the rates of volatile carbonyl generation in the sensitized photo-oxidation of n-tetradecane was determined in the liquid phase. Also determined was the rate of formaldehyde formation in the gas phase from n-tetradecane and from two Brazilian crude oils. The rates of generation of acetaldehyde and acetone could not be determined in the experiments with crude oils because of irregular changes of concentrations with time. The rate of concentration increase of formaldehyde in the vapour phase over the hydrocarbon surface film was similar to that in the water underneath. The artifical light source was a high pressure xenon lamp whose emission spectrum closely resembles that of natural sunlight at sea level. It was calibrated against the intensity of natural sunlight using pnitroacetophenone/pyridine as binary chemical actinometer.

Determination of Phosphorus in Brazilian Soya Bean Oils by the Saponification Method

AbstractThe phosphorus contents of crude and degummed Brazilian soya bean oils were determined by a modified saponification method. The method consists in saponifying the oil with a 50% sodium hydroxide solution at 180°C, acidifying with hydrochloric acid, extracting the liberated fatty acids with hexane and determining the phosphorus in the aqueous solution spectrophometrically as molybdenum blue. The determination requires less than 3 hours of work and shows good agreement with the ashing method of the American Oil Chemists' Society. The results showed that Brazilian crude soya bean oils contain less total phospholipids but proportionally more non‐hydratable phosphatides than the North American ones, this being specially evident in the equatorial region of Brazil. The high content of non‐hydratable phosphatides impedes the determination of acetone‐insolubles in crude oils and the application of the conventional conversion factors of phosphorus into phosphatides.