Crude Oil Samples Research Articles

Theoretical Interpretation of pH and Salinity Effect on Oil-in-Water Emulsion Stability Based on Interfacial Chemistry and Implications for Produced Water Demulsification

The petroleum industry produces thousands of barrels of oilfield waters from the initial stage driven by primary production mechanisms to the tertiary stage. These produced waters contain measurable amounts of oil-in-water emulsions, the exact amounts being determined by the chemistry of the crude oil. To meet strict environmental regulations governing the disposal of such produced waters, demulsification to regulatory permissible levels is required. Within the electric double layer theory, coupled with the analytical solutions to the Poisson–Boltzmann Equation, continuum electrostatics approaches can be used to describe the stability and electrokinetic properties of emulsions. In the literature, much of the surface charge density and zeta potential relationship to emulsion stability has been confined to systems with less salinity. In this paper, we have exploited the theoretical foundations of the electric double layer theory to carry out theoretical evaluations of emulsion salinity based on zeta potential and surface charge density calculations. Most importantly, our approaches have enabled us to extend such theoretical calculations to systems of the higher salinity characteristic of oil-in-water emulsions found in oilfield-produced waters, based on crude oil samples from the literature with varying surface chemistry. Moreover, based on the definition of acid crude oils, our choice of samples represents two distinct classes of crude oils. This approach enabled us to evaluate the stability of emulsions associated with these produced oilfield waters in addition to predicting the potential of demulsification using demulsifiers. Given that the salinity range of this study is that encountered with the vast majority of produced oilfield waters, the findings from our theoretical predictions are perfect guides as far as emulsion stability is concerned.

Asphaltene Inhibitor Screening of Next Generation: Automated High-Throughput Experimentation Method

Asphaltene deposition has been a critical flow assurance challenge, and chemical treatment with continuous asphaltene inhibitor injection has been the go-to approach for operators to preemptively tackle this challenge. Development of the right inhibitor chemistry and dosage is challenging and critical. A smart, automated process for screening numerous asphaltene inhibitor formulations based on the design of experiment (DoE) and high-throughput experimentation (HTE) method has been developed and is discussed in this work. Asphaltene inhibitor formulations with distinct base chemistries, boosters, and solvent packages were blended in various ratios to encompass a large chemical and formulation space with the automated blending station of the HTE setup. These formulations were then dosed into a multitude of crude oil samples produced from different regions of the world at constant dosages to represent a uniform and comparable test fluid matrix. The dispersion state of asphaltene clusters within dosed oil samples, in their native state, was then evaluated using the HTE-asphaltene differential aggregation probe test (ADAPT) techniques to generate thousands of performance data points. Furthermore, the efficiency of top-performing formulations was then cross-validated using standard optical transmittance and deposition-based techniques to gauge performance. The four main pillars of the HTE technique are automation, miniaturization, parallelization, and computational design. Each of these pillars contributes to enhancing the current test method into a more accurate, agile, and quicker technique. Through automation, the overall accuracy of formulation blending as well as performance efficiency measurement is increased. With miniaturization, the resource consumption of raw materials and more importantly crude oil is considerably reduced. For this work, each formulation required less than 300 µL of oil per measurement. Parallelization resulted in completing the test evaluation at a rate of 600 evaluations every 4 hours. These results can then be analyzed through the computational design and analytics software to identify the top-performing formulations along with predicting the optimal chemical formulation space that can lead to maximum performance efficiency. The selected formulations were subsequently blended on a bigger laboratory scale, and their efficacy was cross-checked with both dispersion- (optical transmittance and thermoelectric methods) and deposition-based (flow loop setup) techniques against a benchmark asphaltene inhibitor product, known to work successfully in many fields having asphaltene instability related issues. Through this process, several new asphaltene inhibitor formulations were discovered that outperformed the benchmark blend. Automated HTE technology provides a new dimension to asphaltene inhibitor development work that can carry out performance evaluation of numerous formulations at tremendous speed and minimum crude oil volume. With this technique, one can quickly adapt to the changing requirements of asphaltene inhibitor and its dosage with varying crude oil composition, gas/oil ratio, water cut, or any operational change affecting overall asphaltene stability.

Oxidation Kinetics Analysis of Crude Oils with Different Viscosities

In order to compare the oxidation kinetics parameters of crude oils with different properties in the process of crude oil oxidation, six different crude oil samples were selected to analyze the oxidation characteristics of crude oils with different properties. In order to study the oxidation of crude oil, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) synchronous analyzer were used for crude oil in the oxygen environment between 25 °C and 900 °C at a heating rate of 20 °C/min. The experimental results were based on crude oil oxidation using TGA and DTG experimental data to evaluate the oxidation mechanism of different crude oils, so as to better understand the situation in the oxidation reaction process. At the same time, the oxidation stage of crude oil was divided according to DSC data. Arrhenius method was used to analyze the oxidation kinetic parameters of crude oils with different properties, and the activation energies and pre-exponential factors of different crude oils were calculated. The experimental results show that the oxidation stage of crude oil can be divided into three stages: low-temperature oxidation, fuel deposition, and high-temperature oxidation. The low-temperature oxidation reaction begins at 280 °C, and the high-temperature oxidation reaction occurs at 400 °C. The low-temperature oxidation activation energy of an oil sample is 39.73–77.74 kJ/mol. The activation energy of the high-temperature oxidation is in the range of 106.27–264.47 kJ/mol. The activation energy of crude oil in the low-temperature oxidation stage increases with the increase of crude oil viscosity and decreases with the increase of crude oil viscosity in the high-temperature oxidation stage. Therefore, during the high-temperature oxidation stage, high-viscosity crude oil is more prone to reactions.

Molecular dynamics simulation of CO2 dissolution-diffusion in multi-component crude oil

In order to study the dissolution-diffusion process and mechanism of CO2 in multi-component crude oil, a model of multi-component crude oil system with octane as the main component and 16 other alkanes as a compound was constructed by using molecular dynamics simulation method. We estimated the CO2 density distribution in crude oil model and the shift in crude oil model volume change. We then investigated the microscopic influence mechanism of CO2 dissolution-diffusion on the volume expansion of crude oil by simulating the action of CO2 dissolution-diffusion in the multi-component crude oil model. Based on the variation law of mean square displacement between crude oil molecules, the dissolution and diffusion coefficients of CO2 were predicted, and the influence of CO2 dissolution-diffusion on crude oil mobility was analyzed. It is found that temperature intensifies the molecular thermal motion and increases the voids between alkane molecules, which promotes the dissolution of CO2 and encourages CO2 molecules to transmit, making the crude oil expand and viscosity decrease, and improving the flow ability of crude oil; with the enhancement of given pressure, the potential energy difference between the inside and outside of the crude oil model becomes larger, and the voids between alkane molecules become larger, which is favorable to the dissolution of CO2. Nevertheless, the action of CO2 molecules’ diffusing in the crude oil sample is significantly limited or even tends to zero, besides, the mobility of crude oil is affected due to the advance of external pressure. The mechanism of CO2 dissolution and diffusion in multi-component crude oil is revealed at the microscopic level, and provides theoretical guidance for the development of CO2 flooding.

Development of a new technology for the fight against wax deposits

One of the most serious complications in the production, transport and treatment of oil is asphaltene-resin-paraffin deposits. Their formation in underground well equipment, as well as in flow lines, collection system pipelines increase the cost of oil production. There are no sufficiently effective reagents to solve these problems. The results of implementation in many other wells testify to the high efficiency of the new reagent. The effect of reagents on the rheological properties of oil was also studied. Sangachal Deniz oil was used as a crude oil sample. We have developed multicomponent and multifunctional reagents M-R, P-R. In addition, due to paraffin formations in the tubing, they had to change 50–60 pipes for new ones every month. As a result of the introduction of M-R reagents, no paraffin deposits were found in the tubing for almost a year The effect of these reagents on the pour point of oils, dispersion, dissolution, and paraffin deposition has been studied. The use of the new reagent was tested at the mines of the oil and gas production department (OGPD) "28 May". The results of implementation in many other wells testify to the high efficiency of the new reagent. The effect of reagents on the rheological properties of oil was also studied. Sangachal Deniz oil was used as a crude oil sample.
 The proposed three-parameter Herschel-Bulkley model can be used to assess the rheological parameters of oils during their transportation. This layer, of course, cannot thicken indefinitely. Highly effective multicomponent composite compositions were developed to combat complications in the production of high-asphaltene-resin-paraffin oils. As can be seen from, during the reagent dosing period, there were no particular changes in the well performance. Treatment with hot oil on certain days was, as it were, of a preventive nature, since no changes were observed in the well parameters before and after heat treatment. When a certain layer thickness is formed in the tubing, the linear velocity of oil increases and begins to wash it away

Characterization of Differential Markers among Crude Oil Samples Using UPLC-QE-MS/MS and Multivariate Statistical Analysis

Characterization of Differential Markers among Crude Oil Samples Using UPLC-QE-MS/MS and Multivariate Statistical Analysis

Correction method of the fluorescence intensity of petroleum hydrocarbons in different soil types based on resonance scattering spectroscopy

Soil types has an obvious impact influence on the fluorescence intensity of soil petroleum hydrocarbons. To reduce the interference caused by soil types, this paper proposes a calibration method using resonance scattering spectroscopy. To establish the correction method, 100 g/kg crude oil samples from six soil types were prepared. The mission and resonance scattering spectrum under 280 nm excitation were measured for all samples. The results showed that the fluorescence spectra and resonance scattering spectra of soil crude oil vary with different soil types. And the fluorescence peak intensity and the resonance scattering peak intensity at 360 nm of soil petroleum hydrocarbons are highly correlated in different soil types. The fluorescence peak intensity at 360 nm was divided by the resonance scattering light intensity at 360 nm to obtain the corrected fluorescence intensity, which can effectively reduce the influence of soil type on fluorescence intensity. The feasibility of correction method was further verified for different types and concentrations of soil crude oil. The results showed better linearity between the fluorescence intensity and the concentration of Petroleum Hydrocarbons after the correction (with a correlation coefficient R2 of 0.96) than before the correction (with R2 of 0.72), the mean relative prediction error of all samples decreased from 31.92 % to 4.71 % after correction. The research can provide theoretical basis and technical support for the accurate and rapid detection of Petroleum Hydrocarbons in soil by fluorescence spectroscopy.

Synthesis of a non-polymeric surfactant from naturally occurring vegetable acid and its use as a viscosity modifier and asphaltene dispersant for heavy oil

The extraction and transportation of heavy oil, which accounts for a significant portion of the world's energy sources, often requires the use of various methods, including the use of chemicals. Surfactants have proven effective in this regard. Therefore, the present study focuses on the synthesis of a non-polymeric surfactant derived from naturally occurring vegetable acid. The synthesized surfactant is subsequently characterized using several analytical techniques, namely FTIR (Fourier Transform Infrared Spectroscopy), NMR (Nuclear Magnetic Resonance), TGA (Thermogravimetric Analysis), and elemental analysis. The surfactant demonstrated promising properties as a viscosity modifier and asphaltene dispersant for heavy crude oil samples. The results obtained at a concentration of 600 ppm were particularly favourable, with minimal improvements observed beyond this concentration. The analysis of asphaltene samples further supported the surfactant's effectiveness through hydrogen bonding and π-π interaction. UV–visible spectroscopy and relative viscosity measurements provided additional evidence of the surfactant's ability to disperse asphaltenes effectively.

Experimental investigation of hydrocarbon-ion interaction in water-oil emulsions: A new insight into asphaltene structure and chemistry

Emulsification has been proved as one of the mechanisms contributing to improving oil recovery. Regarding the amphiphilic nature of the asphaltene and other polar hydrocarbons, their role should be understood. This research aims to investigate the chemistry and structure of the asphaltene molecules in the emulsions generated by the oil and ion-tuned water. The static bottle tests, containing the aqueous, emulsion, and bulk oil phases, were generated to study the emulsification. To have a mechanistic insight into the participation of asphaltene molecules in the emulsion phase, two oil samples of crude oil and asphaltene-rich toluene were used to generate the emulsions. After extracting the asphaltene from the bulk phases, the analytical techniques of Nuclear Magnetic Resonance (NMR), Fourier transform infrared (FTIR), and Energy-dispersive X-ray (EDX) were employed to study the asphaltene structural parameters, functional groups, and elemental content, respectively. Based on the NMR technique, the asphaltenes with smaller aromatic cores and shorter aliphatic chains, which contain polar functional groups have more tendency to adsorb onto the emulsion phase. It was shown that the magnesium and calcium ions have stronger electrostatic interactions with the asphaltene, leading to more attraction of the asphaltenes in the emulsion phase. In contrast, the sulfate ions showed a weaker attraction force to adsorb the asphaltenes in the emulsion phase. Based on the EDX spectroscopy, the heteroatom (oxygen, nitrogen, and sulfur) contents of the crude asphaltene is more than the bulk one, representing more affinity of the polar asphaltenes toward the emulsion phase. According to the FTIR spectroscopy of the bulk oil, while the aromatic hydrocarbons have a lower affinity toward the emulsion phase, the longer alkanes have more affinity to adsorb onto the emulsion phase. It should be mentioned that the chemistry and structural parameters of the bulk asphaltenes in the emulsions, which were generated by crude oil and asphaltene-rich toluene, were different. This observation indicated that the chemistry of the asphaltenes participating in the emulsion phase is influenced by the presence of other amphiphilic hydrocarbons. In this study, it was shown that chemical functional groups and structural parameters of asphaltene affect the emulsification process. Hence, studying the chemistry of asphaltene and other polar hydrocarbons is a vital step for the formulation of optimum ion-tuned water.

Geochemical characteristics and genetic types of crude oils from a variety of geological reservoir rocks (Cretaceous–Palaeogene) in the Melut Basin, southern Sudan based on biomarker and carbon isotope composition

This study uses physical and geochemical characteristics of crude oil samples representing the Cretaceous and Palaeogene reservoir sequence of the Melut Basin, southern Sudan to gain information about source rock properties, including organic matter characters, depositional environment and thermal maturity. The overall results show that the Melut Basin's oils have API values between 14.6° and 33.3° and indicate that most of oils are not biodegraded; except one heavy oil sample with low API gravity of 14.6°, which is likely biodegraded. The studied oils were generated from clay‐rich source rocks, containing a blend of organic matter derived primarily from a mixed organic matter of aquatic and terrestrial origin and deposited in a lacustrine setting under suboxic to relatively oxic conditions as demonstrated by their biomarker and carbon isotopic compositions (δ13C). The biomarker maturity indicators show that most of the Melut Basin's oils were generated in the main stage of oil generation, exhibiting a range of peak‐mature to late‐mature. The biomarker environmental indicators reveal that the shale source rocks of the Al‐Gayger and Galhak formations contributed to these oil samples.

Purification and characterisation of post-consumer plastic pyrolysis oil fractionated by vacuum distillation

Valorisation of post-consumer plastic pyrolysis oil in steam crackers and their application as precursors to chemicals is currently hindered by the complexity of these oils in terms of their boiling range, the risk of fouling by unsaturated compounds, and the presence of contaminations (heteroatoms, metals, and halogens). To gain insights into which of these challenges is actually a potential showstopper, we have studied the vacuum distillation of pyrolysis oil derived from two sorted post-consumer waste plastics, i.e. polypropylene (PP) rigids and mixed polyolefins (MPO) rigids, in a batch fractionating column. The crude pyrolysis oil samples were distilled in three fractions i.e., the light fraction (final boiling point <175 °C), middle fraction (175–360 °C), and heavy fraction (initial boiling point >360 °C). Subsequently, comprehensive characterisation, such as physicochemical properties, the level of contaminations, and chemical composition, was performed. The suitability of the light and middle fractions for steam cracking and precursors to chemical feedstock was assessed. It was found that the density and viscosity values of light and middle fractions from the two pyrolysis oil samples were comparable to fossil naphtha and diesel, whereas total acid number (TAN) values were notably higher compared to petroleum-based oil fractions (>0.5 mgKOH/g). Analyses via GC-MS and ATR-FTIR revealed predominant concentrations of olefins. ICP-OES analysis showed that distillation removes more than 97.5% of metals in all fractions. The chlorine content (>3 ppm), nitrogen (≥0.1%), and oxygen (≥0.1%) exceed thresholds. Hence, this study shows that vacuum distillation effectively improved most, but not all, of the properties of the distilled fractions and can thus be an essential downstream process step for the application of post-consumer plastic pyrolysis oils as feedstock in steam crackers and precursors to chemicals.

Application of robust principal component analysis–multivariate adaptive regression splines for the determination of °API gravity in crude oil samples using ATR-FTIR spectroscopy

The robust principal component analysis-multivariate adaptive regression splines (r-PCA-MARS) has been applied and verified for analysis of the quantitative determination of American Petroleum Institute (°API) gravity values in crude oils. Seven principal component (PC) scores using 95.00% variance by principal component analysis (PCA) were applied as inputs in the MARS model. The calibration and prediction sets were obtained using duplex algorithm for the construction of the model and the then for the validation of the model. The calibration set (67*7) was used for the r-PCA-MARS model. The partial least squares regression (PLS-R), and support vector machine regression (SVM-R) models were utilized for comparison the quantitative value of the °API gravity in crude oils. In this paper, we also conducted a comparison study of Kennard-stone (KS) and duplex splitting methods on PLS-R and SVM-R models. The efficiency of the r-PCA-MARS model was evaluated using coefficient of determination (R2), R2 estimated by generalized cross-validation (R2GCV), root mean square error of calibration (RMSEC), root mean square error of prediction (RMSEP), and mean absolute error (MAE). The optimal r-PCA-MARS model uses 32 basis functions to characterize the °API gravity values in crude oils. The correlation coefficients value for calibration and prediction sets were 0.997 and 0.926, respectively. The RMSEC, RMSEP, MAE, and R2GCV in the piecewise-cubic r-PCA-MARS model was 6.726*10-13, 0.538, 0.290 and 0.988, respectively. According to the results, the r-PCA-MARS model provided high efficiency than commonly used regression models for prediction of °API gravity values in crude oils. The result of this study confirmed that the r-PCA-MARS model is the best model with more successful than the PLS-R and SVM-R models. It can be concluded that the r-PCA-MARS model is an appropriate model for describing the physicochemical properties of crude oil samples in the oil industry.

Feasibility of CO2 Injection for Enhance Oil Recovery: A Case Study in the KMJ Layer of HKY Field

Carbondioxide (CO2) injection is a very effective and proven technology for enhanced oil recovery (EOR). Minimum miscibility pressure (MMP) and oil swelling are two important factors of the CO2 gas displacement mechanism that occurs in the reservoir when CO2 injection is applied to enhance oil recovery. In this study, MMP determination between crude oil samples and CO2 gas has been conducted using three methods, i.e., empirical equation, correlations method, and laboratory experiment using slimtube. The determination of the swelling factor was conducted using a PVT cell, where recombined fluid is injected at the reservoir temperature. The MMP value from the empirical equation (2810 psig) is relatively close to the MMP value from the laboratory experiment (2807 psig), with a difference of 3 psig. The swelling test results show that the bubble point pressure and the swelling factor increase from 410 psig to 2200 psig and from 1.0 to 1.442, respectively, as the CO2 gas injection reaches 46.82% mole. Since the fracture pressure of the KMJ Layer in the HKY Field is 2200 psig and the MMP is 2807 psig, only immiscible CO2 flooding can be applied in the field because the CO2 MMP is higher than the fracture pressure.

Migration and accumulation mechanisms and main controlling factors of tight oil enrichment in a continental lake basin

Based on the typical dissection of various onshore tight oil fields in China, the tight oil migration and accumulation mechanism and enrichment-controlling factors in continental lake basins are analyzed through nuclear magnetic resonance (NMR) displacement physical simulation and Lattice Boltzmann numerical simulation by using the samples of source rock, reservoir rock and crude oil. In continental lake basins, the dynamic forces driving hydrocarbon generation and expulsion of high-quality source rocks are the foundational power that determines the charging efficiency and accumulation effect of tight oil, the oil migration resistance is a key element that influences the charging efficiency and accumulation effect of tight oil, and the coupling of charging force with pore-throat resistance in tight reservoir controls the tight oil accumulation and sweet spot enrichment. The degree of tight oil enrichment in continental lake basins is controlled by four factors: source rock, reservoir pore-throat size, anisotropy of reservoir structure, and fractures. The high-quality source rocks control the near-source distribution of tight oil, reservoir physical properties and pore-throat size are positively correlated with the degree of tight oil enrichment, the anisotropy of reservoir structure reveals that the parallel migration rate is the highest, and intralayer fractures can improve the migration and accumulation efficiency and the oil saturation.

Application of artificial neural network for prediction of 10 crude oil properties

AbstractThis study aims to develop an industrially reliable and accurate method to estimate crude oil properties from their Fourier transform infrared spectroscopy (FTIR) spectra. We used the complete FTIR spectral data of selected crude oil samples from seven different Canadian oil fields to predict 10 important crude oil properties using artificial neural networks (ANNs). The predicted properties include specific gravity, kinematic viscosity, total acid number, micro carbon content, and production of light and heavy naphtha, Kero, and distillate in oil refineries. The 107 different (65 light oil and 42 heavy/medium oil samples) crude oil samples used in this study came from seven oil fields and reservoirs across Canada. In line with standard practice, we used 80% of the dataset for training the ANN models and used the remaining 20% of the crude oil samples to test the models. In the ANN analysis, the mean squared error (MSE) was used as the loss function in models, and the mean absolute prediction error (MAPE) was used as a reference to compare the performance of different neural networks constructed with different numbers of layers. This work demonstrates that FTIR spectroscopy is a promising technique that provides rapid and accurate estimates for the oil properties of interest to the industry. A comparison of the values predicted by the validated ANN models and their corresponding measured (actual) values showed excellent prediction with the acceptable range of error (below 15%) aimed for by our industry partner for all properties except viscosity, for which building models based on the natural logarithmic values of measured viscosities significantly improved the results.

Microbial communities and their roles in the Cenozoic sulfurous oil reservoirs in the Southwestern Qaidam Basin, Western China

The latest discovery of sulfurous natural gas marked a breakthrough in the Cenozoic natural gas exploration in the southwestern margin of Qaidam Basin. The 16S rRNA analyses were performed on the crude oil samples from H2S-rich reservoirs in the Yuejin, Shizigou and Huatugou profiles, to understand the sulfurous gas origin, which was also integrated with carbon and hydrogen isotopes of alkane and sulfur isotopes of H2S collected from the Yingxiongling Area. Results show that the microorganisms in samples can survive in the hypersaline reservoirs, and can be classified into multiple phyla, including Proteobacteria, Planctomycetes, Firmicutes, Bacteroidetes, and Haloanaerobiaeota. Methanogens are abundant in all of the three profiles, while sulfate-reducing bacteria are abundant in Yuejin and Huatugou profiles, contributing to the methane and H2S components in the natural gas. The carbon, hydrogen and sulfur isotopes of sulfurous natural gas in the Yingxiongling Area show that the natural gas is a mixture of coal-type gas and oil-type gas, which was primarily derived from thermal degradation, and natural gas from the Yuejin and Huatugou profiles also originated from biodegradation. The isotopic analysis agrees well with the 16S rRNA results, i.e., H2S-rich natural gas from the Cenozoic reservoirs in the southwest margin of the Qaidam Basin was primarily of thermal genesis, with microbial genesis of secondary importance.

Stability of spent HCl acid-crude oil emulsion

Acid stimulation may cause formation damage due to incompatibility of the injected acid and crude oil, which may form stable emulsion and ultimately acid sludge. In this process, the pH value of the injected live HCl solution increases during reaction with rocks or minerals. The spent acid may, in turn, be incompatible with the reservoir fluid causing formation damage. Due to the prevalent drawbacks of these unwanted emulsions, this study focused on the stability of spent acid-crude oil emulsions affected by pH, ferric ion concentration and acid to mixture volume ratio (AMR) through a series of systematic experiments. Response surface method (RSM) was applied for design of experiments and using crude oil samples with various properties, which helped to get better insight into acid-crude oil interactions. The results showed that crude oil properties, such as TBN, aromaticity, asphaltene to resin ratio and CII, affect the emulsion stability. A crude oil with higher TBN, CII and asphaltene to resin ratio, and lower aromaticity, has more affinity to interact with the spent acid and to form stable emulsion. The pH value of the spent acid was of lower importance than other properties as stated above, while AMR was found to be the most influential factor in such a way that it reversely influenced the emulsion stability. The impact of ferric ion depended on both pH of the spent acid and chemical properties of the crude oil. Based on the microscopic images of the emulsion droplets, it was concluded that the stability of spent acid-crude oil emulsion is closely associated to characteristics of the interfacial film than the droplet size.

ANALYSIS OF THE COMPOSITION AND STRUCTURE OF HEAVY OILS ACCORDING TO NMR SPECTROSCOPY

The results of studies of 1H and 13C NMR spectroscopy of heavy oil samples from the Timan Pechersk, Volga Ural oil and gas basins are presented. Knowledge of the chemical composition and physicochemical properties of crude oil, along with the particularities of geological and geochemical conditions is of paramount importance for solving the problems of the origin of crude oil and its subsequent processing. Information on the chemical composition of oil allows you to combine samples of crude oil from various fields before refining to achieve the necessary commercial and technical characteristics. 59.7-60.5% of β-CH3 groups were found in the samples, in β-CH2 and CH-groups to the aromatic ring, as well as the content of CH2- and CH-groups of saturated compounds. Dividing 13C NMR spectra into ranges shows a high content of methyl groups with the number of CH-groups in the alkyl fragments and CH and CH2-alkyl groups of naphthenic moieties attached to CH-group being 14.37-24.17%. A specific range of values is from 9.4 to 11.4 ppm. indicates methyl substituted octane, nonane or decane. It was found that the content of primary and secondary carbon atoms was in the range from 59.4-60.7%. The studied samples possess branched alkane chains. Comparison of the content of aromatic / aliphatic components allows us to determine the sample of the Volga Ural basin as a sample with a high content of aromatic component. The content of aromatic fragments varies in a wider range of 17-25.9%. From the data of 1H NMR-spectra of samples of heavy oils with different origin, viscosity and treatment it was found that crude and refined oils can differ in the content of olefin signals. For citation: Kolchina G.Yu., Poletaeva O.Yu., Leontev A.Yu., Movsumzade E.M., Loginova M.E., Kolchin A.V. Analysis of the composition and structure of heavy oils according to NMR spectroscopy. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 94-101. DOI: 10.6060/ivkkt.20236606.6783.

Experimental and theoretical investigation of the impact of crude-oil on the wettability behavior of calcite and silicate due to low salinity effect

Wettability alteration is recognized as the main responsible mechanism for enhanced oil recovery during low salinity water flooding (LSWF) in both carbonates and sandstones. However, there is still a lack of understanding about the possible role of oil type on rock wettability alteration during LSWF. In the current study, contact angle (CA), interfacial tension (IFT), and zeta potentials for both oil/brine and rock/brine interfaces are measured for rock/brine/crude oil systems in a wide range of salinity of seawater. Two different crude oil samples and both calcite and silicate as good end-members of carbonate and sandstones are investigated. For oil A, the CA decreases with brine dilution; however, for oil B, the CA showed almost the opposite trend vs. salinity. The increased water-wetness of silicate compared to calcite surface was more highlighted in lower salinity. The results of zeta potentials showed that diluting seawater (SW) reduced the zeta potentials of rock/brine and oil/brine in all systems. The changes in zeta potential suggest that more dilution shall lead to more water-wetness, which is not in agreement with the CA behavior of two minerals in the case of crude oil B. Based on the augmented Young-Laplace equation, it was demonstrated that there is a good correlation between the IFT and the wettability, especially for calcite minerals. To shed light on the competition between the IFT and the EDL force, a comprehensive model was created to predict the CA results by coupling the surface complexation model (SCM), the DLVO theory, and the Young-Laplace equation. The coupled model successfully predicted the experimental contact angle for both crude oil and rock samples. Analyzing the disjoining pressure curves showed that due to the attractive EDL forces of calcite rocks, the oil/brine IFT solely controls the calcite wettability behavior with salinity. However, for silicate substrates, the high repulsive EDL forces are the main reason for the rock water-wetness at low salinity brines.

Aquathermolysis of Heavy Crude Oil: Comparison Study of the Performance of Ni(CH3COO)2 and Zn(CH3COO)2 Water-Soluble Catalysts

Aquathermolysis is one of the crucial processes being considered to successfully upgrade and irreversibly reduce the high viscosity of heavy crude oil during steam enhanced oil recovery technologies. The aquathermolysis of heavy oil can be promoted by transition metal-based catalysts. In this study, the catalytic performance of two water-soluble catalysts Ni(CH3COO)2 and Zn(CH3COO)2 on the aquathermolytic upgrading of heavy oil at 300 °C for 24 h was investigated in a high pressure–high temperature (HP-HT) batch reactor. The comparison study showed that nickel acetate is more effective than zinc acetate in terms of viscosity reduction at 20 °C (58% versus 48%). The viscosity alteration can be mainly explained by the changes in the group composition, where the content of resins and asphaltenes in the upgraded heavy crude oil sample in the presence of nickel catalyst was reduced by 44% and 13%, respectively. Moreover, the nickel acetate-assisted aquathermolysis of heavy oil contributed to the increase in the yield of gasoline and diesel oil fractions by 33% and 29%, respectively. The activity of the compared metal acetates in hydrogenation of the crude oil was judged by the results of the atomic H/C ratio. The atomic H/C ratio of crude oil upgraded in the presence of Ni(CH3COO)2 was significantly increased from 1.52 to 2.02. In addition, the catalyst contributed to the desulfurization of crude oil, reducing the content of sulfur in crude oil from 5.55 wt% to 4.51 wt% The destructive hydrogenation of resins and asphaltenes was supported by the results of gas chromatography-mass spectroscopy (GC-MS) and Fourier-transform infrared (FT-IR) spectroscopy analysis methods. The obtained experimental results showed that using water-soluble catalysts is effective in promoting the aquathermolytic reactions of heavy oil and has a great potential for industrial-scale applications.