The effect of alcoholic polyethylene-vinyl acetate(EVA)product ethylene-vinyl alcohol copolymer(EVAL)on the low-temperature flow properties of model oil containing asphaltene(ASP)was investigated.The change of wax cry...The effect of alcoholic polyethylene-vinyl acetate(EVA)product ethylene-vinyl alcohol copolymer(EVAL)on the low-temperature flow properties of model oil containing asphaltene(ASP)was investigated.The change of wax crystal microscopic morphology of model oil before and after modification were examined,and the influence of asphaltene mass fraction on the rheological improvement effect of EVAL was analyzed.The composite system of EVAL and asphaltene significantly reduced the pour point,gel point,apparent viscosity,storage modulus and loss modulus of waxy oil at low temperatures.When the EVAL concentration is 400 ppm and the asphaltene mass fraction is 0.5 wt%,the synergistic effect of the two is optimal,which can reduce the pour point by 17℃and the modulus value by more than 98%.The introduction of EVAL strengthens the interaction between asphaltenes and wax crystals,forming EVALASP aggregates,which promote the adsorption of wax crystals on asphaltenes to form composite particles,and the polar groups prevent the aggregation of wax crystals and reduce the size of wax crystals,thus greatly improving the fluidity of waxy oils.展开更多
Heavy oil,constituting a significant portion of global oil reserves,presents unique challenges in extraction and processing due to its high viscosity,largely influenced by asphaltenes and their heteroatom content.This...Heavy oil,constituting a significant portion of global oil reserves,presents unique challenges in extraction and processing due to its high viscosity,largely influenced by asphaltenes and their heteroatom content.This study employs molecular dynamics(MD)simulations to investigate the selfaggregation and adsorption mechanisms of heteroatom/non-heteroatom asphaltenes,comparing linear and island structural configurations.Key findings reveal that linear heteroatom asphaltenes form dense,multi-layered aggregates,while island heteroatom asphaltenes exhibit stronger aggregation energy.On solid surfaces,linear asphaltenes display multi-layered adsorption,whereas island asphaltenes adopt a dispersed structure with higher adsorption energy,making them more resistant to removal.Compared to non-heteroatom asphaltenes,heteroatom asphaltenes significantly enhance the aggregation energy of the asphaltene itself and the interaction energy with light oil components,reducing the diffusion capacity of oil droplets and increasing viscosity.Although the viscosity of island heteroatom asphaltene oil drops is the largest,the role of heteroatom in linear asphaltene is more obvious,and linear heteroatom asphaltene and non-heteroatom show great differences in properties.Additionally,heteroatom-containing oil droplets exhibit stronger interactions with solid surfaces,driven by the influence of heteroatom asphaltenes on lighter oil components.These insights provide a deeper understanding of heavy oil viscosity mechanisms,offering a foundation for developing targeted viscosity-reduction strategies and optimizing heavy oil recovery and processing techniques.展开更多
Asphaltenes are the most elusive substances in waxy crude oil,especially the complex structures,which leads to significant precipitation and aggregation characteristics of asphaltenes,and affects the asphaltenes-wax i...Asphaltenes are the most elusive substances in waxy crude oil,especially the complex structures,which leads to significant precipitation and aggregation characteristics of asphaltenes,and affects the asphaltenes-wax interaction.In this study,the concept of the existence state of asphaltenes was introduced to semi-quantitatively investigate the precipitation and aggregation characteristics of asphaltenes.On this basis,the influence of the existence state of asphaltenes on wax deposition was studied by coldfinger device and high-temperature gas chromatography,and the composition and properties of the deposits were analyzed.Four main findings were made:(1)As the asphaltene concentration increases,the existence state of asphaltenes gradually transitions from dispersed state to aggregated state,and the asphaltene concentration of 0.30 wt%in this study is the starting point of the transition.(2)The existence state of asphaltenes in crude oil does affect the process of wax deposition,as shown in the fact that the dispersed asphaltenes promote the occurrence of wax deposition,while the aggregated asphaltenes can inhibit wax deposition.(3)In the presence of the aggregated asphaltenes,that is,when the asphaltene concentration is higher than 0.30 wt%,the shedding phenomenon of deposit layer was observed,and with the increase of aggregated asphaltenes,the deposit layer fell off earlier.(4)With the increase of the dispersed asphaltenes,the wax appearance temperature(WAT)and wax content of the deposits all showed an increasing trend,while with the appearance of the aggregated asphaltenes,the above situation was reversed.The findings of this study can help for better understanding of the interaction between the asphaltenes and wax in wax deposition.展开更多
Resin and asphaltene were separated from Liaohe heavy oil. Catalytic aquathermolysis of asphaltene and resin was investigated by using water soluble catalysts （NiSO4 and FeSO4） and oil soluble catalysts （nickel nap...Resin and asphaltene were separated from Liaohe heavy oil. Catalytic aquathermolysis of asphaltene and resin was investigated by using water soluble catalysts （NiSO4 and FeSO4） and oil soluble catalysts （nickel naphthenate and iron naphthenate）. Before and after aquathermolysis, the properties of the resin and asphaltene was compared by means of ultimate analysis, vapor pressure osmometer （VPO） average molecular weight, X-ray diffraction （XRD）,^13C and ^1H nuclear magnetic resonance （NMR）. The conversion sequence was as follows： No-catalyst〈NiSO4〈FeSO4〈nickel naphthenate〈iron naphthenate. In the presence of catalysts, the amount of H2 and CO increased significantly, while H2S in the gas product decreased. The molecular weight of asphaltene and resin increased after reaction without catalyst. But the catalysts restrained this trend. The H/C ratio of asphaltene and resin decreased after reaction. From the results of average structural parameters and molecular weight, it was found that asphaltene and resin were partly aggregated after aquathermolysis.展开更多
Asphaltenes, complex aromatic compounds from various carbonaceous sources, could be obtained by solvent dissolution, filtration and adsorption. It was difficult to clarify the molecular structures and chemical propert...Asphaltenes, complex aromatic compounds from various carbonaceous sources, could be obtained by solvent dissolution, filtration and adsorption. It was difficult to clarify the molecular structures and chemical properties of asphaltene due to its structural similarity, composition complexity and source dependences. Many techniques, like Mass spectrometry, Chromatography, Nuclear magnetic resonance spectroscopy, Infrared spectroscopy, Roman spectroscopy, Fluorescence spectroscopy, X-ray diffraction analysis and Small-angle scattering techniques and so on, have revealed some valuable descriptions of asphaltenes chemical compositions and fundamental structures. Moreover, advanced Mass spectrometry,Atomic force microscopy and Scanning tunneling microscopy could provide more clear and essential molecular compounds and structures in asphaltenes. In addition, several asphaltenes models have succeeded to illustrate aggregation properties asphaltene. In this work, the progress on asphaltene separation, characterization and application was summarized, and the similarities and differences between coal-derived asphaltenes and petroleum asphaltenes were compared. Furthermore, the reactivity of asphaltenes has been discussed in the aspect of hydroprocessing, pyrolysis and gasification. Asphaltene was excellent carbon precursor for functional carbon material due to its high aromaticity and carbon yield;several porous carbon nanosheets from asphaltenes that would be prospective electrode materials after being graphitized were shown. Pitch-based carbon fiber derived from coal-derived asphaltenes displayed a tensile strength of 1.0 GPa and elastic modulus of 350 MPa, respectively. These powerful advances will provide asphaltenes promising developments.展开更多
As the efficiency of dispersants with different origins is questionable for each typical oil sample, the present study provides a reproducible and reliable method for screening asphaltene dispersants for a typical asp...As the efficiency of dispersants with different origins is questionable for each typical oil sample, the present study provides a reproducible and reliable method for screening asphaltene dispersants for a typical asphal- tenic crude oil. Four different asphaltene dispersants （polyisobutylene succinimide, polyisobutylene succinic ester, nonylphenol-formaldehyde resin modified by polyamines, and rapeseed oil amide） were prepared and their performance on two oils from an Iranian field under laboratory and reservoir conditions was studied. A thorough analysis including ash content and SARA tests was performed on the solid asphaltene particles to characterize the nature of deposits. Then a highly efficient carrier fluid, which is crucial when injecting dispersant into the wells, was selected from a variety of chemicals by comparing their solubility. In the next step, using an optical microscope, a viscometer, and a Turbiscan, the screening of dispersants under laboratory conditions was done on a mixture of dead oil and dispersant to evaluate the onset of asphaltene precipitation and its stability when titrating by a precipitant. Finally, two different mixtures of the efficient dispersants, live oil, and carrier fluid were used with the solid detection system （SDS） and the filtration method to examine their effects on the onset pressure of asphaltene precipitation and the asphaltene content of the crude oil under reservoir conditions. The results show that the combination of experimental methods used in this work could be consistently applied to screening asphaltene dispersants. Among the four different dispersants applied here, the dispersant based on nonylphenol-formaldehyde resin modified by polyamines showed the best performance on the available live oils. This chemical modified the onset pressure of asphaltene precipitation of light oil from 4300 psi to about 3600 psi and decreased the precipitated asphaltene of heavy oil by about 30 %.展开更多
In this study, the performance of stable nanofluid containing SiO2 nanoparticles dispersed and stabilized in high salinity brine for asphaltene inhibition in dynamic condition is evaluated. In the first stage of this ...In this study, the performance of stable nanofluid containing SiO2 nanoparticles dispersed and stabilized in high salinity brine for asphaltene inhibition in dynamic condition is evaluated. In the first stage of this work, the stability of silica nanoparticles in different range of water salinity(0–100000 mg·L-1) is investigated. Next, stable nanofluid containing highest salinity is selected as asphaltene inhibitor agent to inject into the damaged core sample. The estimated values of oil recovery for base case, after damage process and after inhibition of asphaltene precipitation using nanofluid are 51.6%, 36.1% and 46.7%, respectively. The results showed the reduction in core damage after using nanofluid. In addition, the relative permeability curves are plotted for the base case, after damage process and also after inhibition of asphaltene precipitation using nanofluid. Comparison of relative permeability curves shows, relative permeability of oil phase decreased after damage process as compared with the base case. But after using nanofluid the oil relative permeability curve has shifted to the right and effective permeability of oil phase has been improved.展开更多
In this work,the factors affecting asphaltenes deposition in high-temperature and high-pressure wells were studied using backscattered light and PVT equipment customized to suit the well conditions.In an examination o...In this work,the factors affecting asphaltenes deposition in high-temperature and high-pressure wells were studied using backscattered light and PVT equipment customized to suit the well conditions.In an examination of the intensity of backscattered light,it was revealed that there exists a linear relationship between temperature and asphaltene precipitation within a specific temperature range.Within this range,a decrease in temperature tends to accelerate asphaltene precipitation.However,the impacts of pressure and gas-oil ratio are more pronounced.The pressure depletion induces the asphaltenes to precipitate out of the solution,followed by the formation of flocs below the bubble point.In addition,an increase in the gas-oil ratio causes a more severe asphaltene deposition,shifting the location of asphaltenes to deep well sections.展开更多
Borehole blockage caused by asphaltene deposition is a problem in crude oil production in the Tahe Oilfield, Xinjiang, China. This study has investigated the influences of crude oil compositions, temperature and press...Borehole blockage caused by asphaltene deposition is a problem in crude oil production in the Tahe Oilfield, Xinjiang, China. This study has investigated the influences of crude oil compositions, temperature and pressure on asphaltene deposition. The asphaltene deposition trend of crude oil was studied by saturates, aromatics, resins and asphaltenes （SARA） method, and the turbidity method was applied for the first time to determine the onset of asphaltene flocculation. The results showed that the asphaltene deposition trend of crude oil by the turbidity method was in accordance with that by the SARA method. The asphaltene solubility in crude oil decreased with decreasing temperature and the amount of asphaltene deposits of T739 crude oil （from well T739, Tahe Oilfield） had a maximum value at 60℃. From the PVT results, the bubble point pressure of TH 10403CX crude oil （from well TH10403CX, Tahe Oilfield） at different temperatures can be obtained and the depth at which the maximum asphaltene flocculation would occur in boreholes can be calculated. The crude oil PVT results showed that at 50,90 and 130 ℃, the bubble point pressure of TH 10403CX crude oil was 25.2, 26,4 and 27.0 MPa, respectively. The depth of injecting asphaltene deposition inhibitors for TH10403CX was determined to be 2,700 m.展开更多
Determining the rate of asphaltene particle growth is one of the main problems in modeling of asphaltene precipitation and deposition.In this paper,the kinetics of asphaltene aggregation under different precipitant co...Determining the rate of asphaltene particle growth is one of the main problems in modeling of asphaltene precipitation and deposition.In this paper,the kinetics of asphaltene aggregation under different precipitant concentrations have been studied.The image processing method was performed on the digital photographs that were taken by a microscope as a function of time to determine the asphaltene aggregation growth mechanisms.The results of image processing by MATLAB software revealed that the growth of asphaltene aggregates is strongly a function of time.Different regions could be recognized during asphaltene particle growth including reaction-and diffusion-limited aggregation followed by reaching the maximum asphaltene aggregate size and start of asphaltene settling and the final equilibrium.Modeling has been carried out to predict the growth of asphaltene particle size based on the fractal theory.General equations have been developed for kinetics of asphaltene aggregation for reaction-limited aggregation and diffusion-limited aggregation.The maximum size of asphaltene aggregates and settling time were modeled by using force balance,acting on asphaltene particles.Results of modeling show a good agreement between laboratory measurements and model calculations.展开更多
Oxidized asphaltene （OA）, a thermosetting material with plenty of functional groups, is synthesized from asphaltene （A） using HNO3]HzSO4 as the oxidizing agent. Boron, nitrogen co-doped porous carbon （BNC-OA） is...Oxidized asphaltene （OA）, a thermosetting material with plenty of functional groups, is synthesized from asphaltene （A） using HNO3]HzSO4 as the oxidizing agent. Boron, nitrogen co-doped porous carbon （BNC-OA） is prepared by carbonization of the mixture of boric acid and OA at 1173 K in an argon atmosphere. X-ray photoelectron spectroscopy （XPS） characterization reveals that the BNC-OA has a nitrogen content of 3.26 at.% and a boron content of 1.31 at.%, while its oxidation-free counterpart （BNC-SA） has a nitrogen content of 1.61 at.% and a boron content of 3.02 at.%. The specific surface area and total pore volume of BNC-OA are 1103 m2·g^-1 and 0.921 cm3·g^-1, respectively. At a current density of 0.1 A·g^-1, the specific capacitance of BNC-OA is 335 F·g^-1 and the capacitance retention can still reach 83% at 1 A·g^-1. The analysis shows that the superior electrochemical performance of the BNC-OA is attributed to the pseudocapacitance behavior of surface heteroatom functional groups and an abundant pore-structure. Boron, nitrogen co-doped porous carbon is a promising electrode material for supercapacitors.展开更多
Natural gas hydrates can readily form in deep-water oil production processes and pose a great threat to the oil industry.Moreover,the coexistence of hydrate and asphaltene can result in more severe challenges to subse...Natural gas hydrates can readily form in deep-water oil production processes and pose a great threat to the oil industry.Moreover,the coexistence of hydrate and asphaltene can result in more severe challenges to subsea flow assurance.In order to study the effects of asphaltene on hydrate growth at the oil-water interface,a series of micro-experiments were conducted in a self-made reactor,where hydrates nucleated and grew on the surface of a water droplet immersed in asphaltene-containing oil.Based on the micro-observations,the shape and growth rate of the hydrate shell formed at the oil-water interface were mainly investigated and the effects of asphaltene on hydrate growth were analyzed.According to the experimental results,the shape of the water droplet and the interfacial area changed significantly after the formation of the hydrate shell when the asphaltene concentration was higher than a certain value.A mechanism related to the reduction of the interfacial tension caused by the absorption of asphaltenes on the interface was proposed for illustration.Moreover,the growth rate of the hydrate shell decreased significantly with the increasing asphaltene concentration under experimental conditions.The conclusions of this paper could provide preliminary insight how asphaltene affect hydrate growth at the oil-water interface.展开更多
The catalytic cracking of coal tar asphaltene(CTA)pyrolysis vapors was carried out over transition metalion modified zeolites to promote the generation of light aromatic hydrocarbons(L-ArHs)in a pyrolysisgas chromatog...The catalytic cracking of coal tar asphaltene(CTA)pyrolysis vapors was carried out over transition metalion modified zeolites to promote the generation of light aromatic hydrocarbons(L-ArHs)in a pyrolysisgas chromatography/mass spectrometry(Py-GC/MS)micro-reactor system.The effects of ultra stable Y(USY),Co/USY and Mo/USY on the selectivity and yield of L-ArHs products and the extent of deoxygenation(Edeoxygenation),lightweight(Elightweight)from CTA pyrolysis volatiles were investigated.Results showed that the yields of L-ArHs are mainly controlled by the acid sites and specific surface area of the catalysts,while the deoxygenation effect is determined by theirs pore size.The Eligltweight of CTA pyrolysis volatiles over USY is 9.65%,while the Edeoxygenation of CTA pyrolysis volatiles over Mo/USY reaches 20.85%.Additionally,the modified zeolites(Mo/USY and Co/USY)exhibit better performance than USY on L-ArHs production,owing to the synergistic effect of metal ions(Mo,Co)and acid sites of USY.Compared with the non-catalytic fast pyrolysis of CTA,the total yield of L-ArHs obtained over USY(4032 mg·kg^(-1)),Co/USY(4363 mg·kg^(-1))and Mo/USY(4953 mg·kg^(-1))were increased by 27.03%,38.19%and 54.78%,respectively.Furthermore,the possible catalytic conversion mechanism of transition metal ion(Co and Mo)modified zeolites was proposed based on the distribution of products and the characterizations of catalysts.展开更多
Asphaltenes generally exist in the form of molecular aggregates in crude oil or in petroleum residues,and asphaltene aggregates can usually cause serious problems to oil exploitation,transportation,and processing.Achi...Asphaltenes generally exist in the form of molecular aggregates in crude oil or in petroleum residues,and asphaltene aggregates can usually cause serious problems to oil exploitation,transportation,and processing.Achieving deaggregation and separation of asphaltene aggregates is a premise and basis for molecular characterization and processing of heavy oils.Aiming at the intermolecular interactions in asphaltene molecular aggregates,it has proposed and summarized that aspahltene aggregates can be subject to deaggregation by means of five approaches,including solvent diluting,removing active sites,moderate heating,ultrasonication and on-line molecular collision.Moreover,asphaltenes can be further separated to narrow fractions for molecular-level research based on polarity difference,molecular size difference,acid-base properties,and reactivity difference.展开更多
Asphaltene deposition is one of the most seri- ous problems, which usually occurs in oil wells, petroleum production, oil processing, and transportation facilities. Deposition of heavy organic components, especially a...Asphaltene deposition is one of the most seri- ous problems, which usually occurs in oil wells, petroleum production, oil processing, and transportation facilities. Deposition of heavy organic components, especially asphaltene, can lead to wellbore blockage and impacts well economics due to reduction in oil production. Therefore, it is necessary to pay more attention to finding some solution to overcome this problem. In this study, a pipe-loop apparatus for investigation of oil stability was employed to measure deposition thickness using a thermal method. The effects of many factors such as oil type, oil temperature, oil velocity, inhibitors, and solvents on asphaltene deposition were investigated. The results showed that the deposition increased with the increasing value of the colloidal insta- bility index. Besides, the deposition thickness increased with the decreasing velocity of oil, but did not change with oil temperature. In addition, n-heptane could result in more deposition; however, toluene had no effect on the deposi- tion. Branched dodecyl benzene sulfonic acid （Branched DBSA） and Linear DBSA as inhibitors decreased the rate of asphaltene deposition.展开更多
Commonly used flow improvers in oilfields,such as ethylene–vinyl acetate copolymer(EVA),poly(octadecyl acrylate)(POA),and polymethylsilsesquioxane(PMSQ)are proven to be effective to enhance the flowability of crude o...Commonly used flow improvers in oilfields,such as ethylene–vinyl acetate copolymer(EVA),poly(octadecyl acrylate)(POA),and polymethylsilsesquioxane(PMSQ)are proven to be effective to enhance the flowability of crude oil.However,the addition of these flow improvers may change the stability of the emulsion and make the crude oil treatment process challenging.In this research,the impacts of different flow improvers on the interfacial properties of the emulsions containing asphaltenes are systematically investigated.The co-adsorption behaviors of the flow improvers and asphaltenes are analyzed through dynamic interfacial tension(DIFT).The rheological properties of the interfacial layer after the adsorption are explored via dilational viscoelasticity.Significant difference is observed in the structural properties of the interface adsorbed by different flow improvers,which is attributed to different interactions between the flow improvers and asphaltenes.To investigate these interactions,conductivity,asphaltenes precipitation,dynamic light scattering(DLS),and contact angle experiments are conducted systematically.Results show that EVA and POA can alter the interfacial properties by changing the asphaltene dispersion state.The interaction between EVA and asphaltenes is stronger than that between POA and asphaltenes due to the difference in molecular structures.Unlike EVA and POA,the change of interfacial property with the addition of PMSQ is attributed to the partial adsorption of asphaltenes on PMSQ.展开更多
Asphaltene aggregation is a subject under vivid discussion:There are several parameters one needs to determine before its behavior can be mastered and better target solutions can be tailored.The nature of asphaltene a...Asphaltene aggregation is a subject under vivid discussion:There are several parameters one needs to determine before its behavior can be mastered and better target solutions can be tailored.The nature of asphaltene aggregation(colloidal or supramolecular)and the role of solvents and their mixtures are among the least understood parameters in asphaltene science.This paper addresses molecular dynamic simulations to correlate the aggregation properties of asphaltenes,their molecular structure and the concentration of these solvents.We show that the formation of the nanoaggregate depends,primarily,on the size of the conjugated core and on the eventual presence of polar groups capable of forming H-bonds.Heteroatoms on the conjugated core do not change their shape or type of aggregation but may induce stronger π-π interactions.The macroaggregation formation depends upon the length of the lateral chains of asphaltenes and also on the presence of polar groups at its end.Moreover,n-heptane and water may interact selectively with asphaltenes in function of their molecular architecture.Given this fact and the aggregation behavior observed,we advocate toward the assumption that a colloidal behavior of asphaltenes might be a particular case of a more general model,based on a supramolecular description.展开更多
Cubic equation-of-state solid models are one of the most widely used models to predict asphaltene precipitation behavior.Thermodynamic parameters are needed to model precipitation under different pressures and tempera...Cubic equation-of-state solid models are one of the most widely used models to predict asphaltene precipitation behavior.Thermodynamic parameters are needed to model precipitation under different pressures and temperatures and are usually obtained through tuning with multi asphaltene onset experiments.For the purpose of enhancing the cubic Peng–Robinson solid model and reducing its dependency on asphaltene experiments,this paper tests the use of aromatics and waxes correlations to obtain these thermodynamic parameters.In addition,weighted averages between both correlations are introduced.The averaging is based on reported saturates,aromatics,resins,asphaltene(SARA)fractions,and wax content.All the methods are tested on four oil samples,with previously published data,covering precipitation and onset experiments.The proposed wax-asphaltene average showed the best match with experimental data,followed by a SARA-weighted average.This new addition enhances the model predictability and agrees with the general molecular structure of asphaltene molecules.展开更多
Many wellbores are blocked by asphaltene deposits,which lead to production problems in the oilfield development process.In this paper,methods such as elemental analysis,and solvent extraction are adopted for the study...Many wellbores are blocked by asphaltene deposits,which lead to production problems in the oilfield development process.In this paper,methods such as elemental analysis,and solvent extraction are adopted for the study of wellbore blockages.The content of organic matter in blockages is higher than 96% and asphaltene is the main component of the organic matter with n-heptane asphaltene content of 38%.Based on the above analyses,an agent for asphaltene dispersion and removal（named as SDJ） was developed.The performance of the SDJ agent was evaluated,and it was found that the dissolution rate of asphaltene can reach 2.9 mg.mL-1.min-1 at 60 oC.SDJ agent（1wt%） was added to crude oil with a colloid instability index greater than 0.9 can effectively inhibit asphaltene deposition in the wellbore.By the viscosity method,the dissolution amount of SDJ agent was calculated,and it was found that when the viscosity of the system is around 2,000 mPa.s（the common viscosity of crude oil）,the amount of SDJ agent added to the blockage was at least 96 g per 100 g blockages.Therefore,SDJ agent has promising application for dispersion and removal of asphaltene deposition in high-asphaltene wells.展开更多
Molecular simulations were carried out to investigate the self-diffusion coefficient of asphaltene in asphaltene-xylene systems,used as heavy oil models.The self-diffusion behavior of asphaltene in the asphaltene-xyle...Molecular simulations were carried out to investigate the self-diffusion coefficient of asphaltene in asphaltene-xylene systems,used as heavy oil models.The self-diffusion behavior of asphaltene in the asphaltene-xylene equilibrium system was mainly affected by the interaction between asphaltene molecules,with stronger interactions corresponding to a slower diffusion of asphaltene.The interactions between asphaltene molecules mainly includedπ-πinteractions between aromatic rings and hydrogen bonds between strongly electronegative heteroatoms.These results are expected to provide theoretical guidance for reducing the viscosity of heavy oil.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52076036)。
文摘The effect of alcoholic polyethylene-vinyl acetate(EVA)product ethylene-vinyl alcohol copolymer(EVAL)on the low-temperature flow properties of model oil containing asphaltene(ASP)was investigated.The change of wax crystal microscopic morphology of model oil before and after modification were examined,and the influence of asphaltene mass fraction on the rheological improvement effect of EVAL was analyzed.The composite system of EVAL and asphaltene significantly reduced the pour point,gel point,apparent viscosity,storage modulus and loss modulus of waxy oil at low temperatures.When the EVAL concentration is 400 ppm and the asphaltene mass fraction is 0.5 wt%,the synergistic effect of the two is optimal,which can reduce the pour point by 17℃and the modulus value by more than 98%.The introduction of EVAL strengthens the interaction between asphaltenes and wax crystals,forming EVALASP aggregates,which promote the adsorption of wax crystals on asphaltenes to form composite particles,and the polar groups prevent the aggregation of wax crystals and reduce the size of wax crystals,thus greatly improving the fluidity of waxy oils.
基金supported financially by the National Natural Science Foundation of China(No.52204069,No.22306171)the Natural Science Foundation of Zhejiang Province(No.LQ24B070005)the Jinhua Natural Science Foundation of China(2023-4-024)。
文摘Heavy oil,constituting a significant portion of global oil reserves,presents unique challenges in extraction and processing due to its high viscosity,largely influenced by asphaltenes and their heteroatom content.This study employs molecular dynamics(MD)simulations to investigate the selfaggregation and adsorption mechanisms of heteroatom/non-heteroatom asphaltenes,comparing linear and island structural configurations.Key findings reveal that linear heteroatom asphaltenes form dense,multi-layered aggregates,while island heteroatom asphaltenes exhibit stronger aggregation energy.On solid surfaces,linear asphaltenes display multi-layered adsorption,whereas island asphaltenes adopt a dispersed structure with higher adsorption energy,making them more resistant to removal.Compared to non-heteroatom asphaltenes,heteroatom asphaltenes significantly enhance the aggregation energy of the asphaltene itself and the interaction energy with light oil components,reducing the diffusion capacity of oil droplets and increasing viscosity.Although the viscosity of island heteroatom asphaltene oil drops is the largest,the role of heteroatom in linear asphaltene is more obvious,and linear heteroatom asphaltene and non-heteroatom show great differences in properties.Additionally,heteroatom-containing oil droplets exhibit stronger interactions with solid surfaces,driven by the influence of heteroatom asphaltenes on lighter oil components.These insights provide a deeper understanding of heavy oil viscosity mechanisms,offering a foundation for developing targeted viscosity-reduction strategies and optimizing heavy oil recovery and processing techniques.
基金This work was supported by the National Natural Science Foundation of China(Grant No.52174057)the Science and Technology Project of Changzhou City(Grant No.CJ20210136)+1 种基金the General Project of Natural Science Research in Jiangsu Universities(Grant No.20KJB440004)the Science and technology program of Changzhou University(Grant No.ZMF22020068).
文摘Asphaltenes are the most elusive substances in waxy crude oil,especially the complex structures,which leads to significant precipitation and aggregation characteristics of asphaltenes,and affects the asphaltenes-wax interaction.In this study,the concept of the existence state of asphaltenes was introduced to semi-quantitatively investigate the precipitation and aggregation characteristics of asphaltenes.On this basis,the influence of the existence state of asphaltenes on wax deposition was studied by coldfinger device and high-temperature gas chromatography,and the composition and properties of the deposits were analyzed.Four main findings were made:(1)As the asphaltene concentration increases,the existence state of asphaltenes gradually transitions from dispersed state to aggregated state,and the asphaltene concentration of 0.30 wt%in this study is the starting point of the transition.(2)The existence state of asphaltenes in crude oil does affect the process of wax deposition,as shown in the fact that the dispersed asphaltenes promote the occurrence of wax deposition,while the aggregated asphaltenes can inhibit wax deposition.(3)In the presence of the aggregated asphaltenes,that is,when the asphaltene concentration is higher than 0.30 wt%,the shedding phenomenon of deposit layer was observed,and with the increase of aggregated asphaltenes,the deposit layer fell off earlier.(4)With the increase of the dispersed asphaltenes,the wax appearance temperature(WAT)and wax content of the deposits all showed an increasing trend,while with the appearance of the aggregated asphaltenes,the above situation was reversed.The findings of this study can help for better understanding of the interaction between the asphaltenes and wax in wax deposition.
基金supported by the Chinese Natural Science Foundation (No. 40472061)Funding Project for Academic Human Resources Development in Institutions of Higher Learning of Beijing Municipality (No. PXM2007-014222-044654)Funding Project of Organization Department of Beijing Municipal Party Committee (No. 20071D0500500163)
文摘Resin and asphaltene were separated from Liaohe heavy oil. Catalytic aquathermolysis of asphaltene and resin was investigated by using water soluble catalysts （NiSO4 and FeSO4） and oil soluble catalysts （nickel naphthenate and iron naphthenate）. Before and after aquathermolysis, the properties of the resin and asphaltene was compared by means of ultimate analysis, vapor pressure osmometer （VPO） average molecular weight, X-ray diffraction （XRD）,^13C and ^1H nuclear magnetic resonance （NMR）. The conversion sequence was as follows： No-catalyst〈NiSO4〈FeSO4〈nickel naphthenate〈iron naphthenate. In the presence of catalysts, the amount of H2 and CO increased significantly, while H2S in the gas product decreased. The molecular weight of asphaltene and resin increased after reaction without catalyst. But the catalysts restrained this trend. The H/C ratio of asphaltene and resin decreased after reaction. From the results of average structural parameters and molecular weight, it was found that asphaltene and resin were partly aggregated after aquathermolysis.
基金financial support by the National Key R&D Program of China (2016YFE0203500)National Science Foundation of China (No. U1510122)
文摘Asphaltenes, complex aromatic compounds from various carbonaceous sources, could be obtained by solvent dissolution, filtration and adsorption. It was difficult to clarify the molecular structures and chemical properties of asphaltene due to its structural similarity, composition complexity and source dependences. Many techniques, like Mass spectrometry, Chromatography, Nuclear magnetic resonance spectroscopy, Infrared spectroscopy, Roman spectroscopy, Fluorescence spectroscopy, X-ray diffraction analysis and Small-angle scattering techniques and so on, have revealed some valuable descriptions of asphaltenes chemical compositions and fundamental structures. Moreover, advanced Mass spectrometry,Atomic force microscopy and Scanning tunneling microscopy could provide more clear and essential molecular compounds and structures in asphaltenes. In addition, several asphaltenes models have succeeded to illustrate aggregation properties asphaltene. In this work, the progress on asphaltene separation, characterization and application was summarized, and the similarities and differences between coal-derived asphaltenes and petroleum asphaltenes were compared. Furthermore, the reactivity of asphaltenes has been discussed in the aspect of hydroprocessing, pyrolysis and gasification. Asphaltene was excellent carbon precursor for functional carbon material due to its high aromaticity and carbon yield;several porous carbon nanosheets from asphaltenes that would be prospective electrode materials after being graphitized were shown. Pitch-based carbon fiber derived from coal-derived asphaltenes displayed a tensile strength of 1.0 GPa and elastic modulus of 350 MPa, respectively. These powerful advances will provide asphaltenes promising developments.
文摘As the efficiency of dispersants with different origins is questionable for each typical oil sample, the present study provides a reproducible and reliable method for screening asphaltene dispersants for a typical asphal- tenic crude oil. Four different asphaltene dispersants （polyisobutylene succinimide, polyisobutylene succinic ester, nonylphenol-formaldehyde resin modified by polyamines, and rapeseed oil amide） were prepared and their performance on two oils from an Iranian field under laboratory and reservoir conditions was studied. A thorough analysis including ash content and SARA tests was performed on the solid asphaltene particles to characterize the nature of deposits. Then a highly efficient carrier fluid, which is crucial when injecting dispersant into the wells, was selected from a variety of chemicals by comparing their solubility. In the next step, using an optical microscope, a viscometer, and a Turbiscan, the screening of dispersants under laboratory conditions was done on a mixture of dead oil and dispersant to evaluate the onset of asphaltene precipitation and its stability when titrating by a precipitant. Finally, two different mixtures of the efficient dispersants, live oil, and carrier fluid were used with the solid detection system （SDS） and the filtration method to examine their effects on the onset pressure of asphaltene precipitation and the asphaltene content of the crude oil under reservoir conditions. The results show that the combination of experimental methods used in this work could be consistently applied to screening asphaltene dispersants. Among the four different dispersants applied here, the dispersant based on nonylphenol-formaldehyde resin modified by polyamines showed the best performance on the available live oils. This chemical modified the onset pressure of asphaltene precipitation of light oil from 4300 psi to about 3600 psi and decreased the precipitated asphaltene of heavy oil by about 30 %.
基金the support of the Department of Petroleum Engineering, Amirkabir University of Technology during this study
文摘In this study, the performance of stable nanofluid containing SiO2 nanoparticles dispersed and stabilized in high salinity brine for asphaltene inhibition in dynamic condition is evaluated. In the first stage of this work, the stability of silica nanoparticles in different range of water salinity(0–100000 mg·L-1) is investigated. Next, stable nanofluid containing highest salinity is selected as asphaltene inhibitor agent to inject into the damaged core sample. The estimated values of oil recovery for base case, after damage process and after inhibition of asphaltene precipitation using nanofluid are 51.6%, 36.1% and 46.7%, respectively. The results showed the reduction in core damage after using nanofluid. In addition, the relative permeability curves are plotted for the base case, after damage process and also after inhibition of asphaltene precipitation using nanofluid. Comparison of relative permeability curves shows, relative permeability of oil phase decreased after damage process as compared with the base case. But after using nanofluid the oil relative permeability curve has shifted to the right and effective permeability of oil phase has been improved.
基金This work was supported by the National Natural Science Foundation of China(No.52174047)the China Scholarship Council(No.202106440102)the PetroChina Strategic Cooperation Science and Technology Project(No.ZLZX 2020-01).
文摘In this work,the factors affecting asphaltenes deposition in high-temperature and high-pressure wells were studied using backscattered light and PVT equipment customized to suit the well conditions.In an examination of the intensity of backscattered light,it was revealed that there exists a linear relationship between temperature and asphaltene precipitation within a specific temperature range.Within this range,a decrease in temperature tends to accelerate asphaltene precipitation.However,the impacts of pressure and gas-oil ratio are more pronounced.The pressure depletion induces the asphaltenes to precipitate out of the solution,followed by the formation of flocs below the bubble point.In addition,an increase in the gas-oil ratio causes a more severe asphaltene deposition,shifting the location of asphaltenes to deep well sections.
基金National High Technology Research and Development Program of China(No.2013AA064301)National Natural Science Foundation of China (No.51274210)12th National Science and Technology Major Project of the Ministry of Science and Technology of China (No.2011ZX05049-003-001-002)
文摘Borehole blockage caused by asphaltene deposition is a problem in crude oil production in the Tahe Oilfield, Xinjiang, China. This study has investigated the influences of crude oil compositions, temperature and pressure on asphaltene deposition. The asphaltene deposition trend of crude oil was studied by saturates, aromatics, resins and asphaltenes （SARA） method, and the turbidity method was applied for the first time to determine the onset of asphaltene flocculation. The results showed that the asphaltene deposition trend of crude oil by the turbidity method was in accordance with that by the SARA method. The asphaltene solubility in crude oil decreased with decreasing temperature and the amount of asphaltene deposits of T739 crude oil （from well T739, Tahe Oilfield） had a maximum value at 60℃. From the PVT results, the bubble point pressure of TH 10403CX crude oil （from well TH10403CX, Tahe Oilfield） at different temperatures can be obtained and the depth at which the maximum asphaltene flocculation would occur in boreholes can be calculated. The crude oil PVT results showed that at 50,90 and 130 ℃, the bubble point pressure of TH 10403CX crude oil was 25.2, 26,4 and 27.0 MPa, respectively. The depth of injecting asphaltene deposition inhibitors for TH10403CX was determined to be 2,700 m.
文摘Determining the rate of asphaltene particle growth is one of the main problems in modeling of asphaltene precipitation and deposition.In this paper,the kinetics of asphaltene aggregation under different precipitant concentrations have been studied.The image processing method was performed on the digital photographs that were taken by a microscope as a function of time to determine the asphaltene aggregation growth mechanisms.The results of image processing by MATLAB software revealed that the growth of asphaltene aggregates is strongly a function of time.Different regions could be recognized during asphaltene particle growth including reaction-and diffusion-limited aggregation followed by reaching the maximum asphaltene aggregate size and start of asphaltene settling and the final equilibrium.Modeling has been carried out to predict the growth of asphaltene particle size based on the fractal theory.General equations have been developed for kinetics of asphaltene aggregation for reaction-limited aggregation and diffusion-limited aggregation.The maximum size of asphaltene aggregates and settling time were modeled by using force balance,acting on asphaltene particles.Results of modeling show a good agreement between laboratory measurements and model calculations.
基金Project supported by the National Natural Science Foundation of China(Grant No.21276045)
文摘Oxidized asphaltene （OA）, a thermosetting material with plenty of functional groups, is synthesized from asphaltene （A） using HNO3]HzSO4 as the oxidizing agent. Boron, nitrogen co-doped porous carbon （BNC-OA） is prepared by carbonization of the mixture of boric acid and OA at 1173 K in an argon atmosphere. X-ray photoelectron spectroscopy （XPS） characterization reveals that the BNC-OA has a nitrogen content of 3.26 at.% and a boron content of 1.31 at.%, while its oxidation-free counterpart （BNC-SA） has a nitrogen content of 1.61 at.% and a boron content of 3.02 at.%. The specific surface area and total pore volume of BNC-OA are 1103 m2·g^-1 and 0.921 cm3·g^-1, respectively. At a current density of 0.1 A·g^-1, the specific capacitance of BNC-OA is 335 F·g^-1 and the capacitance retention can still reach 83% at 1 A·g^-1. The analysis shows that the superior electrochemical performance of the BNC-OA is attributed to the pseudocapacitance behavior of surface heteroatom functional groups and an abundant pore-structure. Boron, nitrogen co-doped porous carbon is a promising electrode material for supercapacitors.
基金supported by National Natural Science Foundation of China(U19B2012,51974349,51991363)Fundamental Research Funds for the Central Universities(20CX06098A)State Key Laboratory of Natural Gas Hydrates(CCL2020RCPS0225ZQN)。
文摘Natural gas hydrates can readily form in deep-water oil production processes and pose a great threat to the oil industry.Moreover,the coexistence of hydrate and asphaltene can result in more severe challenges to subsea flow assurance.In order to study the effects of asphaltene on hydrate growth at the oil-water interface,a series of micro-experiments were conducted in a self-made reactor,where hydrates nucleated and grew on the surface of a water droplet immersed in asphaltene-containing oil.Based on the micro-observations,the shape and growth rate of the hydrate shell formed at the oil-water interface were mainly investigated and the effects of asphaltene on hydrate growth were analyzed.According to the experimental results,the shape of the water droplet and the interfacial area changed significantly after the formation of the hydrate shell when the asphaltene concentration was higher than a certain value.A mechanism related to the reduction of the interfacial tension caused by the absorption of asphaltenes on the interface was proposed for illustration.Moreover,the growth rate of the hydrate shell decreased significantly with the increasing asphaltene concentration under experimental conditions.The conclusions of this paper could provide preliminary insight how asphaltene affect hydrate growth at the oil-water interface.
基金financed by the projects of the National Natural Science Foundation of China(21776229,21908180,22078266)the National Key Research&Development Program of China(2018YFB0604603)the Key Research and Development Program of Shaanxi(2020ZDLGY11-02,2018ZDXM-GY-167)。
文摘The catalytic cracking of coal tar asphaltene(CTA)pyrolysis vapors was carried out over transition metalion modified zeolites to promote the generation of light aromatic hydrocarbons(L-ArHs)in a pyrolysisgas chromatography/mass spectrometry(Py-GC/MS)micro-reactor system.The effects of ultra stable Y(USY),Co/USY and Mo/USY on the selectivity and yield of L-ArHs products and the extent of deoxygenation(Edeoxygenation),lightweight(Elightweight)from CTA pyrolysis volatiles were investigated.Results showed that the yields of L-ArHs are mainly controlled by the acid sites and specific surface area of the catalysts,while the deoxygenation effect is determined by theirs pore size.The Eligltweight of CTA pyrolysis volatiles over USY is 9.65%,while the Edeoxygenation of CTA pyrolysis volatiles over Mo/USY reaches 20.85%.Additionally,the modified zeolites(Mo/USY and Co/USY)exhibit better performance than USY on L-ArHs production,owing to the synergistic effect of metal ions(Mo,Co)and acid sites of USY.Compared with the non-catalytic fast pyrolysis of CTA,the total yield of L-ArHs obtained over USY(4032 mg·kg^(-1)),Co/USY(4363 mg·kg^(-1))and Mo/USY(4953 mg·kg^(-1))were increased by 27.03%,38.19%and 54.78%,respectively.Furthermore,the possible catalytic conversion mechanism of transition metal ion(Co and Mo)modified zeolites was proposed based on the distribution of products and the characterizations of catalysts.
文摘Asphaltenes generally exist in the form of molecular aggregates in crude oil or in petroleum residues,and asphaltene aggregates can usually cause serious problems to oil exploitation,transportation,and processing.Achieving deaggregation and separation of asphaltene aggregates is a premise and basis for molecular characterization and processing of heavy oils.Aiming at the intermolecular interactions in asphaltene molecular aggregates,it has proposed and summarized that aspahltene aggregates can be subject to deaggregation by means of five approaches,including solvent diluting,removing active sites,moderate heating,ultrasonication and on-line molecular collision.Moreover,asphaltenes can be further separated to narrow fractions for molecular-level research based on polarity difference,molecular size difference,acid-base properties,and reactivity difference.
基金the supports from Islamic Azad University,Kermanshah Branch
文摘Asphaltene deposition is one of the most seri- ous problems, which usually occurs in oil wells, petroleum production, oil processing, and transportation facilities. Deposition of heavy organic components, especially asphaltene, can lead to wellbore blockage and impacts well economics due to reduction in oil production. Therefore, it is necessary to pay more attention to finding some solution to overcome this problem. In this study, a pipe-loop apparatus for investigation of oil stability was employed to measure deposition thickness using a thermal method. The effects of many factors such as oil type, oil temperature, oil velocity, inhibitors, and solvents on asphaltene deposition were investigated. The results showed that the deposition increased with the increasing value of the colloidal insta- bility index. Besides, the deposition thickness increased with the decreasing velocity of oil, but did not change with oil temperature. In addition, n-heptane could result in more deposition; however, toluene had no effect on the deposi- tion. Branched dodecyl benzene sulfonic acid （Branched DBSA） and Linear DBSA as inhibitors decreased the rate of asphaltene deposition.
基金supported by the National Natural Science Foundation of China(51704315)。
文摘Commonly used flow improvers in oilfields,such as ethylene–vinyl acetate copolymer(EVA),poly(octadecyl acrylate)(POA),and polymethylsilsesquioxane(PMSQ)are proven to be effective to enhance the flowability of crude oil.However,the addition of these flow improvers may change the stability of the emulsion and make the crude oil treatment process challenging.In this research,the impacts of different flow improvers on the interfacial properties of the emulsions containing asphaltenes are systematically investigated.The co-adsorption behaviors of the flow improvers and asphaltenes are analyzed through dynamic interfacial tension(DIFT).The rheological properties of the interfacial layer after the adsorption are explored via dilational viscoelasticity.Significant difference is observed in the structural properties of the interface adsorbed by different flow improvers,which is attributed to different interactions between the flow improvers and asphaltenes.To investigate these interactions,conductivity,asphaltenes precipitation,dynamic light scattering(DLS),and contact angle experiments are conducted systematically.Results show that EVA and POA can alter the interfacial properties by changing the asphaltene dispersion state.The interaction between EVA and asphaltenes is stronger than that between POA and asphaltenes due to the difference in molecular structures.Unlike EVA and POA,the change of interfacial property with the addition of PMSQ is attributed to the partial adsorption of asphaltenes on PMSQ.
基金Isifor-Carnot Institute and Total Refining & Chemicals are also acknowledged for their financial support to this research project
文摘Asphaltene aggregation is a subject under vivid discussion:There are several parameters one needs to determine before its behavior can be mastered and better target solutions can be tailored.The nature of asphaltene aggregation(colloidal or supramolecular)and the role of solvents and their mixtures are among the least understood parameters in asphaltene science.This paper addresses molecular dynamic simulations to correlate the aggregation properties of asphaltenes,their molecular structure and the concentration of these solvents.We show that the formation of the nanoaggregate depends,primarily,on the size of the conjugated core and on the eventual presence of polar groups capable of forming H-bonds.Heteroatoms on the conjugated core do not change their shape or type of aggregation but may induce stronger π-π interactions.The macroaggregation formation depends upon the length of the lateral chains of asphaltenes and also on the presence of polar groups at its end.Moreover,n-heptane and water may interact selectively with asphaltenes in function of their molecular architecture.Given this fact and the aggregation behavior observed,we advocate toward the assumption that a colloidal behavior of asphaltenes might be a particular case of a more general model,based on a supramolecular description.
文摘Cubic equation-of-state solid models are one of the most widely used models to predict asphaltene precipitation behavior.Thermodynamic parameters are needed to model precipitation under different pressures and temperatures and are usually obtained through tuning with multi asphaltene onset experiments.For the purpose of enhancing the cubic Peng–Robinson solid model and reducing its dependency on asphaltene experiments,this paper tests the use of aromatics and waxes correlations to obtain these thermodynamic parameters.In addition,weighted averages between both correlations are introduced.The averaging is based on reported saturates,aromatics,resins,asphaltene(SARA)fractions,and wax content.All the methods are tested on four oil samples,with previously published data,covering precipitation and onset experiments.The proposed wax-asphaltene average showed the best match with experimental data,followed by a SARA-weighted average.This new addition enhances the model predictability and agrees with the general molecular structure of asphaltene molecules.
基金the National High Technology Research and Development Program of China (No.SS2013AA060801)National Natural Science Foundation of China (No.51274210)12th National Science and Technology Major Project of Ministry of Science and Technology of China (No. 20112X05049-003-001-002)for financial support
文摘Many wellbores are blocked by asphaltene deposits,which lead to production problems in the oilfield development process.In this paper,methods such as elemental analysis,and solvent extraction are adopted for the study of wellbore blockages.The content of organic matter in blockages is higher than 96% and asphaltene is the main component of the organic matter with n-heptane asphaltene content of 38%.Based on the above analyses,an agent for asphaltene dispersion and removal（named as SDJ） was developed.The performance of the SDJ agent was evaluated,and it was found that the dissolution rate of asphaltene can reach 2.9 mg.mL-1.min-1 at 60 oC.SDJ agent（1wt%） was added to crude oil with a colloid instability index greater than 0.9 can effectively inhibit asphaltene deposition in the wellbore.By the viscosity method,the dissolution amount of SDJ agent was calculated,and it was found that when the viscosity of the system is around 2,000 mPa.s（the common viscosity of crude oil）,the amount of SDJ agent added to the blockage was at least 96 g per 100 g blockages.Therefore,SDJ agent has promising application for dispersion and removal of asphaltene deposition in high-asphaltene wells.
基金This work is financially supported by the National Natural Science Foundation of China(Grant No.41872168).
文摘Molecular simulations were carried out to investigate the self-diffusion coefficient of asphaltene in asphaltene-xylene systems,used as heavy oil models.The self-diffusion behavior of asphaltene in the asphaltene-xylene equilibrium system was mainly affected by the interaction between asphaltene molecules,with stronger interactions corresponding to a slower diffusion of asphaltene.The interactions between asphaltene molecules mainly includedπ-πinteractions between aromatic rings and hydrogen bonds between strongly electronegative heteroatoms.These results are expected to provide theoretical guidance for reducing the viscosity of heavy oil.
