Heavy Oil Samples Research Articles

Evaluation of Viscosity Reducers for Heavy Oil Reservoirs: Experimental Testing and Numerical Simulation.

The application of thermal recovery methods in Chad's heavy oil fields has proven to be challenging, necessitating the development of chemical cold production technologies. The mechanisms causing heavy oil viscosity remain unclear, and the effects of adding viscosity reducers in wells with varying water contents are not well understood. In this study, the composition and structure of Chad's heavy oil samples were experimentally analyzed, revealing that the viscosity is primarily due to the accumulation of isoprenoid-like components and the high concentration of side-chain naphthenes in the oil's saturated fraction. Based on this mechanism, viscosity reducers were screened, with DG, a high-molecular-weight water-soluble viscosity reducer, demonstrating the most effective results. Numerical simulation was then employed to characterize the mechanism of viscosity reducers and to model the impact of adjusting daily production rates and introducing viscosity reducers in wells with different water contents on the cumulative oil recovery. The field numerical model was used to simulate for 10 years, and the results showed that for high water content wells, the injection of viscosity reducer reduced the daily fluid volume by 10%, and the cumulative recovery rate increased by 6.75%; for low water content wells, the injection of viscosity reducer increased the daily fluid volume by 20%, and the cumulative recovery rate increased by 3.08%. This research aims to provide new insights into the development of heavy oil reservoirs.

Correlating wear with the lubricant properties of heavy-duty diesel engine oils

Wear volumes were correlated with the lubricant properties of 11 used, heavy duty engine oil samples. The most important oil property in predicting wear volume is Total Acid Number, TAN. Here, the TAN value may be indicating ZDDP in its oxidised form and unable to participate in corrosive-abrasive wear. Low wear also correlates with mean soot particle size/circularity, which further suggests the abrasive aspect of this mechanism. Finally, low wear correlates with high calcium concentration in the fresh oil. This suggests a new wear reduction mechanism in which calcium from the detergent replenishes the iron within the ZDDP antiwear film.

Synthesis of Fe3O4-Mn2O3 and Fe3O4-graphene oxide hybrid nanocatalyst and their effects on the electromagnetic properties and their performance on heavy hydrocarbons upgrading

In this research for the first time, the hybrid nanocatalysts with various ratios were syntheses and the impact of the type and ratio of nanocatalyst on heavy oil upgrading was examined. For this purpose, at first, Fe3O4 was synthesized, and then 4 types of hybrids nanocatalysts using Fe3O4, Mn2O3, and reduced Graphene oxide were synthesized (with various ratios, 3:1, 2:1), and characterized. The hybrid nanocatalyst Fe3O4-Mn2O3 (ratio 2:1) was extremely efficient in reducing viscosity and heavy oil upgrading and declined the viscosity of heavy oil by 31%. Additionally, at the optimal result, a sample of crude and upgraded heavy oil was investigated and compared by FTIR and GC analysis. In the optimum sample, the aromatic and sulfoxide functional groups decreased by 21% and 72%, respectively, while the index of aliphatic groups of the alkane branch increased by 15%. In addition, Hexadecane, Nonadecane, and Octadecane compounds have experienced a 77%, 65%, and 56% decrease, respectively. Also, heavy and long chains such as C15-C20 cracked and transformed into light compounds such as C4-C7, which were not present in the heavy crude oil.

An Experimental Study and Numerical Simulation Analysis of Thermal Oxidation Characteristics Based on Kinetic Parameters in Heavy Oil Reservoirs

In situ combustion (ISC), an efficient and economical method for enhancing heavy oil recovery in high-pressure, high-viscosity, and thermally challenged reservoirs, relies on the kinetics of crude oil oxidation. Despite an increased focus on kinetic models, there is a gap in understanding how oxidation kinetic parameters impact ISC effectiveness in heavy oil reservoirs. This study addresses this by selecting heavy oil samples from the G Block in the Liaohe oilfield and the M Block in the Huabei oilfield and conducting ramped temperature oxidation (RTO), pressure differential scanning calorimetry (PDSC), and thermogravimetric analysis (TGA) experiments. RTO detailed the thermal conversion process, categorizing oxidation into low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation (HTO) stages. PDSC and TGA provided thermal characteristics and kinetic parameters. The feasibility of fire flooding was evaluated. Using CMG-STARS, an ISC model was established to analyze the impact of kinetic parameter changes. Activation energy significantly affected coke combustion, while the pre-exponential factor had a notable impact on cracking reactions. The recommended values for activation energy and the pre-exponential factor are provided. This study not only guides fire flooding experiments but also supports field engineering practices, particularly for in situ combustion in heavy oil reservoirs.

РЕГУЛИРОВАНИЕ ВЯЗКОСТИ ТЯЖЕЛОЙ НЕФТИ ПОЛИФУНКЦИОНАЛЬНЫМИ ДОБАВКАМИ НА ОСНОВЕ ПОВЕРХНОСТНО-АКТИВНЫХ ВЕЩЕСТВ

The aim of the work was to determine the influence of concentration and composition of polyfunctional additives consisting of surfactants and organic solvents (isopropyl alcohol and nephras C2) on the viscosity of high-resin heavy oil of the Ashalchinskoye field, which is a highly viscous colloidal disperse system. Viscosity measurements of the samples were carried out on Physica MCR 101 (Anton Paar) using a plate-to-plate instrument in the range of shear rate variation from 1 to 300 s-1. Dependences of effective viscosity on shear rate for the majority of the investigated systems indicate Newtonian flow behaviour, which is also confirmed by flow curves for all investigated heavy oil samples, i.e. the used additives are effective regulators of viscoelastic properties of the investigated oil. The viscosity of heavy oil decreases with increasing concentration of the studied additives, and the most effective additive (with concentration of 3 wt. %) based on surfactants with amino- and phosphate groups and easy-boiling solvent (de-aromatised catalytic reforming petrol) decreased oil viscosity by almost 47 %. As a result of comparing the effect of the studied polyfunctional additives and industrial additives, which are a mixture of polar and non-polar hydrocarbons, on the viscosity of heavy oil, it was found that, as a rule, their efficiency index is higher, and, consequently, their ability to improve the rheological properties of oil is higher, which indicates the potential possibility of their use to facilitate the transportation and processing of highly viscous oil. This article may be of interest to those studying the rheological properties of highly viscous heavy oil systems.

Preparation and evaluation of hydroxyethyl cellulose–based functional polymer for highly efficient utilization of heavy oil under the harsh reservoir environments

Emulsification viscosity reduction and subsequent demulsification are effective strategies to improve the utilization rate of heavy oil. However, traditional surfactants are challenged by unsatisfactory salt tolerance, inadequate stability in emulsification, difficulty in demulsification and pollution problem of oily wastewater discharge. To realize the feasibility and environment-friendliness of heavy oil utilization in the harsh reservoir environments, we designed a functional polymer and conducted a comprehensive evaluation using heavy oil samples from Chenping oil well in Shengli Oilfield. It was synthesized by grafting two hydrophobic monomers, lauryl methacrylate (LMA) and N, N–Diethylaminomethyl methacrylate (DEAEMA), onto the hydrophilia hydroxyethyl cellulose (HEC) by free–radical polymerization. The viscosity reduction rate can reach 99.57 % even under the high salinity of 26,050 mg/L. The stable oil–in–water (O/W) emulsion can be maintained for >48 h, satisfying the actual requirements for heavy oil recovery. Moreover, the emulsion can be completely demulsified in a CO2 atmosphere within 30 min, suggesting its satisfactory demulsification performance. Our study achieved the one–step transformation of heavy oil emulsion between emulsification and demulsification, which provides a green bio–based material and an ingenious strategy for enhanced oil recovery and other chemical engineering applications including oil/water separation.

Hybrid low salinity water and surfactant process for enhancing heavy oil recovery

Combining low salinity water (LSW) with surfactants has an enormous potential for enhancing oil recovery processes. However, there is no consensus about the mechanisms involved, in addition to the fact that several studies have been conducted in model systems, while experiments with rocks and reservoir fluids are scarce. This study presents a core-flooding experiment of LSW injection, with and without surfactant, using the core and heavy oil samples obtained from a sandstone reservoir in southeastern Mexico. The effluents and the crude oil obtained at each stage were analyzed. The study was complemented by tomographic analysis. The results revealed that LSW injection and hybrid process with surfactants obtained an increase of 11.4 percentage points in recovery factor. Various phenomena were caused by LSW flooding, such as changes in wettability and pH, ion exchange, mineral dissolution, detachment of fines and modification of the hydrocarbon profile. In the surfactant flooding, the reduction of interfacial tension and alteration of wettability were the main mechanisms involved. The findings of this work also showed that the conditions believed to be necessary for enhanced oil recovery with LSW, such as the presence of kaolinite or high acid number oil, are not relevant.

Selective Characterization of Olefins by Paternò-Büchi Reaction with Ultrahigh Resolution Mass Spectrometry.

Petroleum olefins play important roles in various secondary processing procedures and are important feedstocks for the modern organic chemical industry. It is quite challenging to analyze petroleum olefins beyond the gas chromatography (GC)-able range using mass spectrometry (MS) due to the difficulty of soft ionization and the matrix complexity. In this work, a Paternò-Büchi (PB) reaction combined with atmospheric pressure chemical ionization and ultrahigh resolution mass spectrometry (APCI-UHRMS) was developed for selective analysis of olefins. Through the PB reaction, C═C bonds were transformed into four-membered rings of oxetane with improved polarity so that soft ionization of olefins could be achieved. The systematic optimization of PB reaction conditions, as well as MS ionization conditions, ensured a high reaction yield and a satisfied MS response. Furthermore, a sound scheme was set up to discriminate the coexisting unsaturated alkanes in complex petroleum, including linear olefins, nonlinear olefins, cycloalkanes, and aromatics, making use of their different behaviors during the PB reaction and chemical ionization. The developed strategy was successfully applied to the analysis of olefins in fluid catalytic cracking oil slurry, a complex heavy oil sample. This method extended the characterization of petroleum olefins from lower to higher with high efficiency and selectivity to provide a comprehensive molecular library for heavy petroleum samples and process optimization.

Study on Oil Composition Variation and Its Influencing Factors during CO2 Huff-n-Puff in Tight Oil Reservoirs

With immense potential to enhance oil recovery, CO2 has been extensively used in the exploitation of unconventional tight oil reservoirs. Significant variations are observed to occur in the oil’s composition as well as in its physical properties after interacting with CO2. To explore the impacts of oil properties on CO2 extraction efficiency, two different types of crude oil (light oil and heavy oil) are used in CO2 huff-n-puff experiments. Moreover, numerical simulation is implemented to quantitatively inspect the impacts of different influencing factors including production time, reservoir pressure and reservoir temperature on physical properties as well as on the oil composition variation of the crude oil. The findings of the experiments demonstrate that, whether for the light oil sample or for the heavy oil sample, hydrocarbon distribution becomes lighter after interacting with CO2 compared with the original state. In addition, it is also discovered that the hydrocarbon distribution variation is more significant for the light oil sample. The findings of the numerical simulation suggest that production time, reservoir pressure and reservoir temperature have significant impacts on the produced oil composition and properties. The hydrocarbon distribution of the oil becomes lighter with the increasing of production time and formation pressure, while it becomes heavier with the increasing of reservoir temperature. At the very beginning of the oil production, the properties of the produced oil are worsened. Compared with the original state, the oil density and viscosity are 25.7% and 200% higher, respectively. It is suggested that viscosity reducers are added into the well to improve the oil properties in this period. With the continuing of the oil production, the oil properties are continuously promoted. At the end of the simulation time, the oil density and viscosity are 3.5% and 15.1% lower compared with the original oil, respectively. This paper has great significance for the implementation of CO2 huff-n-puff in tight oil reservoirs.

The Catalytic Upgrading Performance of NiSO4 and FeSO4 in the Case of Ashal’cha Heavy Oil Reservoir

Aquathermolysis is a promising process for improving the quality of heavy oil under reservoir conditions. However, the application of catalysts during the process can significantly promote the transformation of the heavy fragments and heteroatom-containing compounds of crude oil mixtures into low-molecular-weight hydrocarbons. This research paper conducted a comparative analysis of the catalytic effectiveness of water-soluble metal salts like NiSO4 and FeSO4 in the process of aquathermolysis to upgrade heavy oil samples extracted from the Ashal’cha reservoir. The temperature of the experiment was 300 °C for a duration of 24 h. Compared to the viscosity of the native crude oil, the Fe nanoparticles contributed to a 60% reduction in viscosity. The viscosity alteration is explained by the chemical changes observed in the composition of heavy oil after catalytic (FeSO4) aquathermolysis, where the asphaltene and resin contents were altered by 7% and 17%, accordingly. Moreover, the observed aquathermolytic upgrading of heavy oil in the presence of FeSO4 led to an increase in the yield of gasoline fraction by 13% and diesel fraction by 53%. The H/C ratio, which represents the hydrogenation of crude oil, increased from 1.52 (before catalytic upgrading) to 1.99 (after catalytic upgrading). The results of Chromatomass (GC MS) and Fourier-transform infrared spectroscopy (FT-IR) show the intensification of destructive hydrogenation reactions in the presence of water-soluble catalysts. According to the XRD and SEM-EDX results, the metal salts are thermally decomposed during the aquathermolysis process into the oxides of corresponding metals and are particularly sulfided by the sulfur-containing aquathermolysis products.

Analysis of the Contribution of Petroleum Acid Components to the Viscosity of Heavy Oils with High TAN.

The viscosity of heavy oil hinders its cold production, posing a major challenge to its exploitation. The high viscosity of heavy oil can be attributed to the content of asphaltene. However, during the collection of heavy oil samples from various regions in China, we observed that heavy oils with high total acid number (TAN) but low asphaltene content also exhibit relatively high viscosity. Hence, the viscosity mechanism of high-acid crude oil, the influence of petroleum acid on heavy oil viscosity, should be investigated. In this study, Xinjiang Chunfeng heavy oil was selected for analysis, possessing a viscosity of 16,886 mPa·s at 50 °C and a high total acid number (TAN) of 17.72 mg KOH/g. Separation was performed on the deacidified oil and the acid component using an alkali-modified silica gel column. The viscosity changes of the deacidified oil and its blends with varying proportions of the acid component were determined, along with the viscosity changes of the deacidified oil and acid components in a toluene solution. The molecular composition was analyzed using a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). The findings indicated successful separation of petroleum acid from the heavy oil, the acid component yield being 16.65 wt %. Furthermore, the viscosity of the petroleum acid was significantly higher than that of the deacidified oil. The rate of viscosity change of the acid component in the toluene solvent exceeded that of the deacidified oil, and the viscosity of the deacidified oil notably increased upon the addition of acid. In conjunction with the viscosity data, it was observed that the deacidified oil exhibited the removal of O2 and O4 compounds, resulting in a 43.11% viscosity reduction at 30 °C compared with crude oil. Thus, the monoacid and diacid components considerably affected the viscosity of heavy oil.

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.

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.

Research on molecular mechanism and prediction model of viscosity reduction of heavy oil by different types of gas

ABSTRACT Dissolved gas flooding techniques are widely used in the later stages of heavy oil reservoir development. The role of foam oil in enhancing oil recovery from heavy oil solution gas has been researched. However, it is difficult to analyze the molecular mechanism of foam oil in the dissolved gas property theory and viscosity prediction model proposed by other scholars. In this study, the microscopic mechanism of the interaction between gas molecules and heavy oil molecules in foaming oil was analyzed by the variation of bubble point pressure and viscosity of different dissolved gases (CO2, N2, CH4) in heavy oil samples. By comparing the variation of bubble point pressure of different dissolved gas samples, it was found that the interaction between gas molecules and heavy oil molecules seriously affected the solubility of gas in heavy oil at the same temperature and pressure. An increase in the solubility of the gas in the dissolved gas sample of heavy oil increases the bubble point pressure. The factors influencing the viscosity of heavy oil show that pressure has the least effect on the viscosity reduction of dissolved gas. The higher the concentration of dissolved gas, the more pronounced the viscosity reduction effect. However, the viscosity reduction performance of the dissolved gas in heavy oil became less effective as the temperature increased. Samples A, B, and C, at 15 mol% CO2 concentration, the dissolved gas viscosity reduction effect decreases by 13.75%, 9.7%, and 12.2% when the temperature is increased by 40°C. In addition, samples A, B, and C, at 50°C and 10 mol% gas solubility, the viscosity reduction effect of CO2 is 25.6%, 8.6%, and 19.7% lower than that of N2. Based on the influencing factors of viscosity reduction of heavy oil dissolved gas, this study modified the FJ viscosity prediction model and proposed a physically meaningful heavy oil viscosity prediction model. The model predicts the viscosity of heavy oil dissolved gas with over 90% accuracy (R2 > 0.9) and has some applicability to mixed component gases.

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.

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.

Chemical Viscosity Reduction of Heavy Oil by Multi-Frequency Ultrasonic Waves with the Main Harmonics of 20–60 kHz

Ultrasound technologies are well-known for their ability to intensify the heat and mass transfer processes. Hence, ultrasonic treatment processes are widely applied for the separation of oil–water emulsions, optimization of oil pumping processes, cleaning the bottomhole zone, etc. However, the main phenomenon under the positive influence of ultrasonic waves on such processes is the cavitation bubbles implosion on the water–oil boundary. It is well-known that ultrasound energy contributes to the reversible viscosity reduction in heavy oil systems. However, it is possible to exhibit chemical destruction of the weakest carbon–heteroatom bonds in the structure of the asphaltenes. This study investigates the influences of controllable ultrasound waves with frequency ranges of 20–60 kHz under the exposure time of 60 s on the rheology of a heavy crude oil sample produced from the Ashalcha reservoir (Tatarstan Republic, Russia). The specific feature of this study is the application of multi-frequency ultrasonic exposure with a wide spectrum of side harmonics with the frequency up to 400 kHz. The results of the Saturates, Aromatics, Resins and Asphaltenes (SARA) analysis method support the chemical consequences of ultrasonication of crude oil. The content of resins under the irradiation of ultrasound waves altered from 32.5 wt.% to 29.4 wt.%, while the number of aromatics hydrocarbons raised from 24.3 wt.% to 34.1 wt.%. The Gas Chromatography—Mass Spectroscopy (GC-MS) analytical analysis method was applied to qualitatively compare the composition of saturated and aromatics fractions between the initial and upgraded heavy crude oil in order to show the chemical destruction of asphaltene bonds after the ultrasonic treatment. It was demonstrated that ultrasound waves allowed chemical conversion of asphaltene fragments that led to irreversible viscosity reduction. The viscosity of the heavy oil sample under the favorable ultrasonic irradiation conditions reduced from 661.2 mPa·s to 178.8 mPa·s. This advantage can be used to develop enhanced oil recovery methods and partial upgrading processes in downstream conditions.

Influence of Sodium Metal Nanoparticles on the Efficiency of Heavy Oil Aquathermolysis

In this study, for the first time we investigated the in situ upgrading performance of Na metal nanoparticles, which were obtained by dispersing small pieces of sodium in liquid paraffin up to certain dispersity. In situ aquathermolytic reactions were modeled in a high pressure–high temperature reactor coupled with a Gas Chromatography (GC) system at a temperature of 250 °C for 24 h using a heavy oil sample, produced from the Ashal’cha reservoir, Republic of Tatarstan (Russia). The mean particle size of Na nanoparticles was 6.5 nm determined by the Dynamic Light Scattering (DLS) method. The nanoparticles were introduced to the reaction medium with a concentration of 2 wt.% The upgrading performance of Na nanoparticles was evaluated by several analytical methods such as Gas Chromatography (GC), elemental analysis (CHNS), SARA, Gas Chromatography–Mass Spectroscopy (GC-MS), FT-IR spectroscopy and viscosity measurements. It was revealed that Na nanoparticles interact with water to yield hydrogen gas, the concentration of which increases from 0.015 to 0.805 wt.% Moreover, the viscosity of upgraded heavy oil was reduced by more than 50% and the content of low-molecular-weight hydrocarbons in saturated and aromatics fractions was increased. The Na nanoparticles contributed to the utilization of hydrogen sulfide and carbon dioxide by 99 and 94 wt.%, respectively.

Microstructure of Heavy Oil Components and Mechanism of Influence on Viscosity of Heavy Oil.

The composition of heavy oil is complex, and it is difficult to develop the heavy oil due to its high viscosity and poor fluidity. Therefore, it is very important to clarify the viscous mechanism of heavy oil. In this paper, typical ordinary heavy oil, extra heavy oil, and super heavy oil samples were selected to study the microstructure of heavy oil components and the mechanism of influence on viscosity of heavy oil. The molecular weight, element composition, and polarity of each SARA (short for Saturates, Aromatics, Resins and Asphaltene) component of heavy oil samples were measured and analyzed. The viscosity of heavy oil increases with the increase of the aggregate contents of resins and asphaltene. Resins and asphaltene in heavy oil have a high polarity, high heteroatomic content, and complex molecular structure, which are the key factors affecting the viscosity of heavy oil. On the basis of the experimental results, through simulation calculation and modeling, the microstructure and molecular formula of each component of different heavy oils are obtained, which provides a quantitative reference for revealing the viscosity mechanism of heavy oil. There is little difference in the elemental composition of resins and asphaltene, but the structure is very different and the difference in structure is the key factor leading to the difference in the properties of resins and asphaltene. The content and structure of resins and asphaltene in heavy oil are the key factors leading to the big difference in viscosity of heavy oils.

Machine learning estimation of crude oil viscosity as function of API, temperature, and oil composition: Model optimization and design space.

Measurement of viscosity of crude oil is critical for reservoir simulators. Computational modeling is a useful tool for correlation of crude oil viscosity to reservoir conditions such as pressure, temperature, and fluid compositions. In this work, multiple distinct models are applied to the available dataset to predict heavy-oil viscosity as function of a variety of process parameters and oil properties. The computational techniques utilized in this work are Decision Tree (DT), MLP, and GRNN which were utilized in estimation of heavy crude oil samples collected from middle eastern oil fields. For the estimation of viscosity, the firefly algorithm (FA) was employed to optimize the hyper-parameters of the machine learning models. The RMSE error rates for the final models of DT, MLP, and GRNN are 40.52, 25.08, and 30.83, respectively. Also, the R2-scores are 0.921, 0. 978, and 0.933, respectively. Based on this and other criteria, MLP is chosen as the best model for this study in estimating the values of crude oil viscosity.