Crude Oil Composition Research Articles

Investigation of Surakhani light crude oil compounds as a case study using modern spectroscopic techniques

The complex application of modern analysis methods (FT-IR, NMR, GC–MS and UV/Vis) allowed us to study in detail the composition of the crude Surakhani light oil with a complex composition. An accurate and comprehensive study of the composition of crude oils makes it easier to find the necessary field of application for them. For this purpose, the studied crude oil was separated into two fractions, such as paraffinic–naphthenic and aromatic (groups 1st, 2nd, 3rd and tar), by absorption column chromatography. The results show that Surakhani light oil is a paraffin–naphthene-based oil that contains 74% of paraffin–naphthene, 11.15% of aromatic hydrocarbons and 14.8% of gases. It has been shown that the aromatic group of compounds is mainly composed of mono- and bicyclic compounds and has alkyl chains with different lengths and branches (with the presence of methylene and methine groups). Based on the parameters of the structural group, it was found that the portion of H atoms in the aromatic nucleus and alkyl chain was 4.4–20.1% and 79.9–95.6%, respectively. The degree of aromaticity of the separated aromatic group is approximately 50%, which proves that these compounds are alkylated. The structure of the isolated paraffin–naphthene fraction has also been investigated by spectroscopic techniques, and it has been determined that this fraction is composed of iso- and cycloalkanes with alkyl chains of different lengths. As it is seen from the obtained results, unlike the other oils existing on the Absheron Peninsula, Surakhani light oil consists of one- and two-ring naphthene and isostructured paraffinic hydrocarbons. The composition of this petroleum mainly consists of isosubstituted alkyl cycloalkanes and relict, viz. biologically active hydrocarbons such as sterane and hopane used in medicine. It seems that the methodology developed for the petroleum industry can be used in other fields such as medicine.Graphical abstract

The impacts of CO2 flooding on crude oil stability and recovery performance

Numerous studies have investigated the fundamental mechanisms by which CO2 flooding can increase oil production by altering the properties of the hydrocarbon fluid, including oil swelling, viscosity and interfacial tension reductions, and the extraction of light-to-intermediate components. However, the interactions between CO2 and hydrocarbon fluid may also cause several problems, such as asphaltene precipitation due to crude oil's instability during the CO2 flooding process. This study investigates the complex factors that affect the instability of crude oil, including CO2 injection pressures, temperatures, and crude oil compositions. The light-dead oil samples taken from two Indonesian oil fields were used. The impacts of the instability of crude oil on CO2 displacement performance were also observed to evaluate oil recovery and minimum miscibility pressure (MMP). The observation was performed using a slim tube under varying CO2 high-pressure injections at 90 °C and 70 °C. The produced oils were analyzed based on their polarity component, saturates, aromatics, resins, and asphaltenes fractions, to observe the changes in oil composition and colloidal index instability. The results showed that increasing temperatures at given pressures resulted in higher oil recovery. Moreover, the asphaltene and resin fractions in the oil produced at a lower temperature significantly decrease compared to those at a higher temperature. It was also shown that asphaltene tends to precipitate more easily at a lower temperature. The other phenomenon revealed that the lighter oil resulted in a lower recovery than the heavier oil at a given pressure and temperature and correspondingly higher MMP. It was also suggested that CO2 flooding is more likely to cause asphaltene precipitation in light oils.

Performance Evaluation of Bacterial Consortia from Low-Permeability Reservoir in Ordos Basin

The combination of strains of different species and genera may enhance the effects of single bacteria, surpass the tolerance upper limit, and optimize the viscosity reduction and degradation. In this study, six strains were isolated in low permeability layers of the Ordos Basin and were combined to verify the effect of the consortium strains. The selected single strains have good emulsifying and viscosity-reducing effects, but their degradation components are different. SC4561 (Bacillus cereus), SC4551 (Bacillus sp.), and H-1 (Brevibacillus sp.) form consortium A, and SC4534 (2) (Bacillus sp.), SC4542 (Bacillus licheniformis), and A-3 (Bacillus licheniformis) form consortium B. The performance of the mixed strains was evaluated by the analysis of change in emulsification rate, crude oil composition, viscosity, and the tolerance (temperature, salinity, and pH) through GC-MS, rotational rheometer, and other methods. The results showed that the temperature tolerance of the consortium strains was improved by 5-7°C. Consortium B had higher emulsibility ( E 24 was higher than 40% in average) and viscosity degradation (above 35%), and the crude oil in consortium B has almost no wall adhesion. The components of crude oil that consortia use were still diverse, including both long- and short-chain hydrocarbons. However, the proportion of long-chain n-alkanes is further reduced compared with that of single bacteria, and the highest ratio was reduced by 23.81% (B-ALL). At the same time, they also had effects on aromatic hydrocarbons with complex structures (phenanthrene and phenanthrene). This research confirms the enhanced effect of consortium bacteria on single bacteria, facilitating the implementation of microbial enhanced oil recovery technology in the future.

How weathering might intensify the toxicity of spilled crude oil in marine environments.

Crude oils are highly complex mixtures containing many toxic compounds for organisms. While their level of toxicity in a marine environment depends on many parameters, one of the main factors is their composition. After oil spills, their compositions are significantly changed, so it changes the toxicity. In this study, different weathering processes such as evaporation, photooxidation, and biodegradation were applied to crude oil to understand how composition changed over time and how this affects its toxicity on phytoplankton. In laboratory settings, three distinct water-accommodated fraction samples of crude oil were prepared, unweathered, evaporated, and weathered and were exposed to phytoplankton communities at different dilution levels. After 3days, evaporation reduced the crude oil concentration by 47%, and the concentration of the crude oil affected by photooxidation, biodegradation, and evaporation reduced by 81%. This study also showed that even though the weathering reduced the overall amount of crude oil substantially, its toxicity increased significantly. In the microcosm experiments, 7-day EC50 values of the unweathered oil, the evaporated oil and the weathered oil were 49.07, 21.09, and 7.16µg/L, respectively. Different processes altered the crude oil composition, and weathered crude oil ended up with a higher fraction of high molecular weight (HMW) polycyclic aromatic hydrocarbons (PAHs). A promising relation between the increasing toxicity and HMW PAH fraction indicates that increasing the fraction of HMW PAHs might be one of the main reasons for the weathering process to cause higher crude oil toxicity. These results could be used as a diagnostic tool to estimate the extent of weathering and toxicity of crude oil after spills.

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.

Assessment of the effect of short-term weathering on the molecular-level chemical composition of crude oils in contact with aquatic environments.

Multiple studies have focused on the effect of long-term weathering processes on oils after spill events, without considering the chemical compositional changes occurring shortly after the release of oil into the environment. Therefore, the present study provides a broad chemical characterization for understanding of the changes occurring in the chemical compositions of intermediate (°API = 27.0) and heavy (°API = 20.9) oils from the Sergipe-Alagoas basin submitted to two simulated situations, one under marine conditions and the other in a riverine environment. Samples of the oils were collected during the first 72 h of contact with the simulated environments, followed by evaluation of their chemical compositions. SARA fractionation was used to isolate the resins, which were characterized at the molecular level by UHRMS. The evaporation process was highlighted, with the GC-FID chromatographic profiles showing the disappearance of compounds from n-C10 until n-C16, as well as changes in the weathering indexes and pristane + n-C17/phytane + n-C18 ratios for the crude oils submitted to the riverine conditions. Analysis of the resins fraction showed that basic polar compounds underwent little or no alterations during the early stages of weathering. The marine environment was shown to be much less oxidative than the riverine environment. For both environments, a feature highlighted was an increase of acidic oxygenated compounds with the increase of weathering, especially for the crude oil with °API = 27.0.

Assessment of Vinca rosea (Apocynaceae) Potentiality for Remediation of Crude Petroleum Oil Pollution of Soil

Petroleum oil pollution is a worldwide problem that results from the continuous exploration, production, and consumption of oil and its products. Petroleum hydrocarbons are produced as a result of natural or anthropogenic practices, and their common source is anthropogenic activities, which impose adverse effects on the ecosystem’s nonliving and living components including humans. Phytoremediation of petroleum hydrocarbon-polluted soils is an evolving, low-cost, and effective alternative technology to most traditional remediation methods. The objective of this study is to evaluate the phytoremediation potentiality of Vinca rosea for crude oil-contaminated soil by understanding its properties and involvement in the enhanced degradation of crude oil. The remediation potentiality was determined by evaluating the total petroleum hydrocarbon degradation percentage (TPH%) and changes in the molecular type composition of saturated and aromatic hydrocarbon fractions. TPH% was estimated gravimetrically, and changes in the molecular type composition of saturated and aromatic fractions were measured using gas chromatography and high-performance liquid chromatography, respectively. Sulfur concentration was measured using X-ray fluorescence. Cadmium and lead quantification was measured using Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). The results revealed that V. rosea enhanced total petroleum hydrocarbon (TPH) degradation and altered the molecular composition of the crude oil. The saturated hydrocarbons increased and the aromatic hydrocarbons decreased. The saturated hydrocarbon fraction in the crude oil showed a wider spectrum of n-paraffin peaks than the oil extracted from unplanted and V. rosea-planted soils. Polyaromatic hydrocarbon degradation was enhanced in the presence of V. rosea, which was reflected in the increase of monoaromatic and diaromatic constituents. This was parallel to the increased sulfur levels in planted soil. The determination of sulfur and heavy metal content in plant organs indicated that V. rosea can extract and accumulate high amounts from polluted soils. The ability of V. rosea to degrade TPH and alter the composition of crude petroleum oil by decreasing the toxicity of polyaromatic hydrocarbons in soil, as well as its capability to absorb and accumulate sulfur and heavy metals, supports the use of plant species for the phytoremediation of crude oil-polluted sites.

The role of water in the laboratory thermal advancement of immature type I kerogen from the Cretaceous Qingshankou Formation in China

To understand variations in geochemistry, organic petrology, and chemical composition of crude oil and byproducts, an immature sample from the Cretaceous Qingshankou Formation in the Songliao Basin, China, was analyzed by anhydrous and hydrous pyrolysis (AHP/HP) at a wide range of temperatures ranging from 300 °C to 450 °C. The geochemical parameters: TOC, S2, HI, and Tmax obtained from Rock–Eval pyrolysis showed both a decrease and an increase as thermal maturity progressed under HP and AHP conditions. Gas chromatography (GC) analysis showed the presence of n-alkanes in the C14 to C36 range in both expelled and residual byproducts, a Delta-shaped configuration although many samples had a gradually reducing (tapering) trend toward the high range. Gas chromatography-mass spectrometry (GC–MS) analysis revealed both an increase and a decrease in biomarker and very small changes in aromatic compound variations with increasing temperature during pyrolysis. To be more specific, C29Ts biomarker increased with temperature for the expelled byproduct, while the opposite trend was observed for the residual one. Next, The Ts/Tm ratio initially increased and then decreased with temperature while the C29H/C30H ratio fluctuated for the expelled byproduct but increased for the residual. Moreover, the GI and C30 rearranged hopane to C30 hopane ratio remained unchanged whereas the C23 tricyclic terpane/C24 tetracyclic terpane ratio and the C23/C24 tricyclic terpane ratio showed varying trends with maturity alike the C19/C23 and C20/C23 tricyclic terpane. Ultimately, based on organic petrography observations, increasing the temperature resulted in higher bitumen reflectance (%Bro, r) and optical and structural alterations in the macerals. The findings of this study provide valuable insights for future exploration endeavors in the studied region. Moreover, they contribute to our understanding of the significant role of water in the generation and expulsion of petroleum and associated byproducts, thereby facilitating the development of updated models in this field.

Comparative Catalytic Study for Upgrading Mexican Heavy Crude Oil

In this work, the study of three transition metal mixtures: cobalt-molybdenum (CoMo), nickel-molybdenum (NiMo), and nickel-cobalt-molybdenum (NiCoMo) with phosphorus supported on a γ-Al2O3 were studied for the hydroprocessing of heavy crude oil. The different metallic compositions were incorporated on gamma-alumina support by incipient wetness impregnation. The materials obtained were dried at 110°C and calcined to 450°C (4 h). The catalysts were evaluated using a Parr stainless steel batch reactor at 10.6 MPa and 380°C, for one hour. Mexican heavy crude oil named Ku-Ma-Loob Zaap was used and characterized according to its chemical composition: saturates, asphaltenes, resins, and aromatics (SARA). Sulfur and nitrogen were also determined by chemiluminescence techniques. The physical measurements for qualifying the transport properties were API gravity and kinematic viscosity. Among the tested catalysts, NiCoMoP/γ-Al2O3 presented the highest activity, increasing the API gravity from 12.6 to 24.5°API and decreasing the kinematic viscosity from 9.896 to 45 cSt at 25°C. The increasing activity was strongly related to the reducibility of the metals and weakly to the metals content. The surface area and pore volume did not change with the amount of metal, so no effect related to these properties was observed. Phosphorus presence was not discussed, since approximately the same amount was used in the three samples. However, it is known that phosphorus increased the hydrotreating activity due to the increased acidity of the catalyst, making trimetallic catalysts more active than bimetallic ones. In terms of the chemical composition of the upgraded crude oil, it was evident that the asphaltenes, sulfur, and nitrogen contents decreased sharply.

A solar-driven degradation-evaporation strategy for membrane self-cleaning in the efficient separation of viscous crude oil/water emulsions

Membrane separation techniques are promising methods for effectively treating hazardous emulsified oily wastewater, but membrane fouling remains a serious challenge because the high viscosity and complex composition of crude oil make it easy to adhere to membranes and difficult to be removed by conventional physical or chemical cleaning means. Herein, a two-stage solar-driven (photo-Fenton degradation/evaporation) strategy was proposed to realize the self-cleaning of membranes fouled by viscous crude oil (>60,000 mPa s), wherein the photo-Fenton process helped to degrade the heavy components into light components, and all light components removed during the solar-driven evaporation process. A 1D/2D heterostructure membrane with photo-Fenton activity and anti-crude-oil-fouling performance was prepared via a facile self-assembly vacuum-assist method. The addition of rod-like g-C3N4 (RCN) increased the interlayer distance of α-FeOOH/porous g-C3N4 (FPCN) nanosheets, resulting in a high permeation flux. The FPCN–RCN membrane exhibited both high permeation flux of 779 ± 19 L m–2h–1bar–1 and a separation efficiency of 99.4% for highly viscous crude oil-in-water emulsion. Importantly, the viscous crude oil fouled on the membrane was completely removed by the photo-Fenton degradation/solar-driven evaporation strategy, and the flux recovery rate of the membrane was ∼100%. Therefore, the FPCN–RCN membrane combined with the novel self-cleaning strategy exhibits great potential for practical emulsified oily wastewater treatment.

Effect of crude oil composition and process parameters on the catalytic performance of immobilized lipase during enzymatic deacidification of high-acid soy sauce by-product oil and its bioprocess scale-up

Heterogeneities and impurities in high-acid soy sauce by-product oil (SSBO) and the complex process of enzymatic deacidification led to the low stability of immobilized lipase. This study aimed to investigate the effects of non-acylglycerol components and process parameters (glycerol amount and vacuum) on improving catalytic performance of immobilized lipase during deacidification. The non-acylglycerol components significantly affected the performance of immobilized lipase. Fatty acid salts remarkably activated enzyme to catalyze deacidification, in which 0.8 and 1.6 g/100 g sodium oleate obtained the highest deacidification efficiency (97%). High-acid substrate oil with various acid values could be used to deacidify and showed a high deacidification efficiency (over 83%). The excessive addition of glycerol resulted in activity loss, which was associated with the marked changes in the secondary structure of lipase induced by excessive remaining glycerol with low water content. Thus, reaction process should be controlled at a low remaining glycerol content (under 0.9 g/100 g) with proper water content against the deactivation of lipase. Finally, enzymatic deacidification of high-acid SSBO was successfully scaled up to an industrial scale, in which immobilized lipase was recycled for 30 consecutive batches, suggesting that enzymatic deacidification of high-acid SSBO is feasible for industrial implementation.

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.

Effect of CO2 Huff and Puff Rounds on Crude Oil Properties

In view of the deterioration of oil well liquid supply capacity and oil increase effect after multiple rounds of carbon dioxide (CO2) huff and puff, according to the actual conditions of the Ng12 reservoir in the XA oilfield, an indoor physical simulation experimental model was established. The experimental parameters were determined, five rounds of CO2 huff and puff experiments were carried out, and the crude oil produced in the water flooding stage and different rounds of CO2 huff and puff were collected. The effects of CO2 huff and puff rounds on crude oil viscosity, density, composition, paraffin content, and gum asphaltene content were studied. The results show that with the increase in CO2 huff and puff rounds, the viscosity and density of produced crude oil decrease. The content of light component (C2∼C6) and intermediate component (C7∼C10) increased, while the content of heavy component (C11+) decreased. CO2 has the strongest extraction effect on light components and the weakest extraction effect on heavy components. At the same time, the content of paraffin and gum asphaltene in the produced crude oil is reduced. For oil wells with multiple rounds of CO2 huff and puff, colloidal asphaltene precipitation inhibitor and scavenger should be considered to reduce the impact of colloidal asphaltene on formation permeability and liquid supply capacity.

The production of hydrogen through microwave-initiated catalytic dehydrogenation of model hydrocarbon compounds on Fe/AC catalyst without significant CO2 emissions

The utilization of hydrogen as a fuel source through the microwave-initiated catalytic deep-dehydrogenation (MICDD) of Saudi Arabian light crude oil (LCO) using Fe metal supported on activated carbon has been proposed for this study to achieve the current target of limiting global warming to 1.5 °C above pre-industrial levels. Should renewable technologies, for example, wind and solar, be not able to decarbonise the energy industry sufficiently in the near future, other approaches are needed to generate energy without the emission of massive amounts of aerial carbon (CO2). The composition of crude oil varies depending on its source; however, it is mainly composed of three families of hydrocarbons (paraffins, naphthenes, and aromatics). The aim of this work is to gain an understanding into the contribution of a single hydrocarbon model compound and combinations of these model compounds in proportions close to their real proportions in the LCO preparing a “synthetic crude oil”. In this work, hexadecane, cyclohexane, and benzene, toluene, and xylene (BTX) were selected to closely represent paraffins, naphthenes, and aromatics respectively. It was found that this as a facile route to produce both high concentrations of hydrogen from hexadecane (~90 vol. selectivity) and significant amounts of carbon multiwalled nanotubes over 30 wt. % Fe/AC catalyst at 1000 W input power. The results highlighted the effect of the composition of crude oils on the efficiency of H2 production and showed that paraffinic feedstock was relatively better for producing H2 among other hydrocarbons, and the presence of cyclic hydrocarbons, particularly aromatics, may inhibit H2 production. Importantly, this process creates solid carbon as a by-product of the process instead of CO2 and therefore does not contribute to climate change. The approach also has the potential to synthesise other high-value hydrocarbons as by-products.

Physicochemical Approach to Pour Point Depressant Treatment of Waxy Crudes

A physicochemical approach was taken to show wax-based and crude oil-based differences between three waxy crudes (Amenam, Norne, and Varandey), that had similar amounts of wax according to DSC crystallizable areas, that were responsible for very different responses to pour point depressant additive treatments. Varandey crude oil was the most difficult to treat, and the effectiveness of the additives decreased with time when the oil had been aged for 2 years prior to treating with the additives. Detailed compositional analysis of these three crude oils, and their waxes, showed that Varandey contains the highest concentration of longer n-paraffins, significantly more total n-paraffins, a higher wax appearance temperature, the highest amount of wax that can be centrifuged at ambient temperature, a bimodal distribution of crystallizable waxes by DSC, more saturates in the heavy ends by the Saturates, Aromatics, Resins-Asphaltene Determinator, a very high amount of Waxphaltene Determinator Waxy B (–24 °C methyl ethyl ketone precipitated waxes that do not dissolve in heptane at that temperature but melt at 60 °C in heptane) and very little asphaltenes that do not flocculate. These additional characterization methods, including the wax appearance temperature, show that the amount of wax by DSC is not discriminating for some crude oils. Microscopy of Varandey showed large fractal crystalline domains that were different from Amenam, which showed classic large macrocrystalline needle-like crystals, or Norne that had a gelled network with much smaller needle-like crystals. Norne is less responsive to additive treatment than Amenam despite having significantly less n-paraffins, Waxphaltene Determinator Waxy B waxes, and asphaltenes. Simulated distillation shows that Norne is the heaviest oil and has the highest amount of isomeric material in the C24–C34 range and a higher temperature wax appearance temperature. Furthermore, its asphaltenes flocculated with the addition of isooctane at 60 °C, whereas the asphaltenes did not flocculate in Amenam. The higher amount of isomeric material by GCMS and the much smaller needle-like crystallites suggest that Norne wax is more microcrystalline in nature. Centrifuging Varandey waxes and doping them into Amenam and Norne resulted in the doped crude oils having a bimodal DSC profile with a higher wax appearance temperature. The presence of Varandey wax caused the oils to be significantly less responsive to pour point additive treatments. Overall, for these relatively similar crude oils, it is shown that the nature of the highest carbon number waxes, the wax appearance temperature, and the amount of the least soluble waxes are significantly more important than the crude oil composition when treating with additives since they will dictate the temperature at which n-paraffins first self-associate leading to crystal nucleation.

Investigation of clay-oil interfacial interactions in petroleum-contaminated soil: Effect of crude oil composition

Crude oil, a multi-component complex organic aggregate, causes petroleum-contaminated soil (PCS) with complex properties, which makes PCS unable to achieve rapid and effective oil-soil separation. Therefore, it is crucial to investigate the impact of different crude oil components on oil-soil interactions in PCS. In this study, crude oil was divided into SARA, saturates (S), aromatic (Ar), resin (R) and asphaltene (As) in accordance with polarity and solubility to explore their thermal desorption and thermal variation of adsorption on the kaolinite (Kln) surface. Moreover, the detailed sources of the interactions were investigated using the oil-clay interfacial free energies and interfacial forces. Furthermore, molecular dynamics (MD) simulations were performed to gain insight into the interfacial interaction mechanisms. The results indicated that the polarity of SARA components followed an order of As > R > Ar > S, and the temperature required for thermal desorption and the heat released during oil-clay adsorption increased with an increase in polarity. The van der Waals forces dominated oil-clay interactions. The benzene ring and heteroatom (N, O, and S) in the polar components facilitated the oil-clay van der Waals interactions. Besides van der Waals, the higher number of benzene rings led to the generation of electrostatic interactions as well as hydrogen bonding between heteroatoms and the –OH of Kln, thus increasing the free energy and force at the oil-clay interface. The result of MD was consistent with the experimental results, thus suggesting that van der Waals, electrostatic forces, and hydrogen bonds reliably exist during the interaction between polar oil molecules and clay. Simultaneously, the oil-clay binding energies increased with higher polarity. These findings provide guidance on developing advanced oil-clay separation processes.

Effect of Polar Hydrocarbon Contents on Oil-Water Interfacial Tension and Implications for Recent Observations in Smart Water Flooding Oil Recovery Schemes.

For decades now, low salinity water flooding (LSWF) oil recovery has emerged as an environmentally benign and cost-effective method for improved oil recovery, where research findings have reported pH and interfacial tension effects. Considering the effect of oil chemistry on interfacial tension and the potential of this chemistry to have a direct relationship with LSWF, we measured the interfacial tension of four crude oils with composition varying from those of conventional to unconventional ones. We also characterized the crude oil samples using infrared spectroscopy and a wet chemistry method based on asphaltene precipitation. Our research approach has enabled us to relate the composition of crude oil to the interfacial tension trend at pH encountered in improved oil recovery schemes. Our research methodology, based on an integrated approach to using infrared spectroscopy and interfacial tensiometry, has also enabled us to propose a more robust theoretical explanation for current observations in LSWF related to pH and interfacial tension. In this regard, oil-water interfacial tension depends on the concentration of polar components, such that the higher the concentration of polar groups in crude oil, the higher the interfacial tension at a given pH of aqueous solution. We have also shown that the acid-base behavior of polar groups at the oil-water interface provides a theoretical interpretation of the explicit relationship between oil-water interfacial tension and the electrostatic components of interfacial tension as given by the energy additivity theory.

The role of reservoir fluids and reservoir rock mineralogy on in-situ combustion kinetics

In-situ combustion (ISC) is a complex process with great potential. This study aims to simplify some of the complications associated with the reaction kinetics of ISC and investigate the impact of reservoir rock composition and crude oil fractions on the reaction kinetics of ISC.Sixty-six reaction kinetics experiments were conducted using Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC) on two heavy crude oil samples and two types of porous media (clays and carbonates). In these experiments, a 5 °C/min heating rate was used to simulate the low-temperature-oxidation (LTO) region, and a 20 °C/min heating rate was used for the high-temperature-oxidation (HTO) region. The role of crude oil composition on the reaction kinetics of combustion was also investigated through saturates, aromatics, resins, and asphaltenes (SARA) fractionation. The two crude oils were first separated into their SARA fractions, and then the reaction kinetics of individual fractions and their two and three component pseudo-blends were studied.‘To understand the contribution of aquathermolysis reactions, the crude oils and their SARA fractions were mixed with water, and the reaction kinetics tests were repeated in the presence of water. The chemical reactions occurring in the presence and absence of water in crude oil and their fractions were discussed using control experiments conducted on known simple hydrocarbons: n-decane (C10H22), n-decanal (C10H20O), n-decanol (C10H22O), and decanone (C10H20O). Additionally, the reactivity of the mineralogy of the porous media was examined, and both clay and carbonates were tested. All experiments were analytically modeled to obtain reaction kinetics parameters in terms of activation energy (Ea) and heat generation (ΔH).The results show that while emulsified water decreases the effectiveness of the combustion process, the presence of initial water increases it. This is due to the increase in heat generation and decrease in activation energy, which is mainly caused by the interaction between water and aromatics fractions (aquathermolysis reaction) at elevated temperatures. The amount of clay in the reservoir is critical for the success of the ISC process. If the reservoir has a higher clay content than a certain threshold, the combustion performance will be compromised. Resins fractions have a higher tendency to interact with carbonates during ISC in the HTO region.Overall, this study provides simplified analytical approaches based on experimental results to better understand the ISC chemical reaction kinetics for different types of crude oil and reservoir rocks.

The origin of two distinct diagenetic depth zones in hydrocarbon-bearing sediments of Huanghekou Sag, offshore Bohai Bay Basin, China

Formation waters from the Huanghekou Sag, offshore Bohai Bay Basin, exhibited two depth zones with elevated total dissolved solid (TDS) composition. The shallow diagenetic zone at a depth of ∼1200–2000 m (∼45–70 °C) and the deep diagenetic zone at a depth of ∼3000–4000 m (∼100–130 °C) have TDS concentrations exceeding 70,000 mg/L, while the depth interval in between the two zones has TDS concentrations lower than 35,000 mg/L. Isometric log-ratio interpretations of the reconstructed formation water compositions, crude oil compositions, stable hydrogen and oxygen isotopes, light microscopy and clay mineral analysis were used to interpret the origins of the two diagenetic depth zones. Formation waters within each stratigraphic unit were dominantly composed of Na–K–Cl type. Processes affecting the deep diagenetic zone were attributed to (1) the dissolution of halite, albite and albitization, which predominantly caused the TDS enrichment, and (2) the dilution of TDS caused by the inter-layer H2O released from the transformation of smectite to illite (salinity reversal at depths > ∼3500 m). In comparison, the enrichment in TDS in the shallow diagenetic zone was attributed to hydrocarbon biodegradation, which consumed free water. The crude oil composition indicates severe hydrocarbon biodegradation. Biodegradation of low-molecular-weight organic carbons such as hexadecane (through methanogenesis) and benzene (through microbial sulfate reduction) could consume sufficient H2O to enrich TDS to the observed levels. At the same time, relatively constant Na/Cl and Ca/Cl ratios versus TDS can be explained by water consumption as well. This work could serve as a reference for the interpretation of two diagenetic zones characterised by distinct TDS enrichments in other hydrocarbon-bearing sedimentary basins.

Change Characteristics of Heavy Oil Composition and Rock Properties after Steam Flooding in Heavy Oil Reservoirs

The thermal recovery method of steam flooding is one of the most common development methods for heavy oil reservoirs. However, after multiple rounds of steam injection development, the composition of crude oil and reservoir rock properties have changed greatly, which is unfavorable for the subsequent enhanced oil recovery. It is necessary to study the distribution of the remaining oil after the thermal recovery of heavy oil reservoirs, and clarify the change characteristics of the components of the crude oil under different steam injection conditions. At the same time, the change of porosity and the permeability of the rocks after steam flooding, and its influence on oil recovery, are investigated. In this paper, the composition changes of heavy oil before and after steam flooding are studied through experiments and numerical simulation methods. A numerical model is established to study the retention characteristics of heavy components in heavy oil reservoirs by the CMG software. The effects of different steam injection conditions, and heavy oil with different components on the residual retention of heavy components, are compared and studied. The changes of rock physical properties in heavy oil reservoirs after steam flooding is clarified. The results show that after steam flooding, the heavy components (resin and asphaltenes) of the recovered oil decrease, and the heavy components in the formation increase in varying degrees. With the increase of heavy components in the crude oil, the remaining oil in the formation increases after steam flooding, and the retention of heavy components increases; after steam flooding, the stronger the rock cementation strength, the higher the degree of reserve recovery, and it is difficult to form breakthrough channels; the greater the steam injection intensity, the earlier to see steam breakthrough in the production well, and the lower the degree of reserve recovery. The research reveals the changes of heavy oil components and rock properties after steam flooding, providing support for the subsequent enhanced oil recovery.