Low-molecular-mass asphaltene compounds from Usa heavy oil

By the extraction, adsorption chromatography, it has been shown that asphaltene macromolecules from Usa crude oil contain compounds with a relatively low molecular mass represented by normal and branched alkanes; mono- and polycyclic naphthenes; mono-, bi-, tri-, tetra-, and pentacyclic aromatic hydrocarbons; their phenyl and naphthenic derivatives; benzo-, dibenzo-, and naphthobenzothiophenes; carbazoles and benzocarbazoles; ethyl esters of higher fatty acids; and dibenzofurans and fluorenones; as well as by acids, amides, and sulfoxides.     

Structural features of asphaltene and petroleum resin fractions

It has been found that the amount of the asphaltene fraction soluble in a 1.85: 1 heptane-toluene solvent mixture is at most 12%. The major portion of asphaltenes are insoluble in this mixture. The molecular weight of soluble asphaltenes is lower than that of the insoluble ones. According to thermogravimetric analysis data, the low-molecular-weight asphaltenes are thermally less stable, because their aromaticity is lower than that of the high-molecular-weight asphaltenes, and the number of aliphatic and heteroatomic substituents in them is higher. The aromaticity and the number of paraffinic substituents in the low-molecular-weight asphaltenes are close to those of the resins according to the FT-IR spectroscopy data. Similar to the resins, the total amount of heteroatomic substituents in the low-molecular-weight asphaltenes is higher than that in the high-molecular-weight asphaltenes.     

Composition and structure of resinous components of heavy oil from the Usa oilfield

Resinous components of heavy oil from the Usa oilfield have been studied using a set of instrumental methods. The properties of average molecules of resins and their high- and low-molecular weight nitrogen bases have been presented. It has been found that the structure of the resinous components have moieties linked by ester/ether and sulfide bridges. They are represented by normal and branched alkanes, alkylcyclopentanes, alkylcyclohexanes, mono- and polycyclic aromatic hydrocarbons, benzo- and dibenzothiophenes and their homologs, and aliphatic alcohols and acids. It has been demonstrated that the nitrogen bases are structural units of the resin molecules, rather than their peripheral moieties.     

Composition of volatile products of flash pyrolysis of natural asphaltite and its resin-asphaltene and oil components

Volatile products of the two-step (400, 650°C) flash pyrolysis of Ivanovskoe asphaltite from Oren-burg oblast, its asphaltenes, oils, and benzene and benzene-ethanol resins have been characterized by gas chromatography-mass spectrometry (GCMS) in the on-line mode. The ??unresolvable complex mixture?? of nonidentifiable compounds prevails at both temperatures. The compositions of identified compounds in the products obtained at 400 and 650°C substantially differ, especially, for resins and asphaltenes. At 650°C, the products for all the samples are characterized by the same set of compounds including homologues of alkanes; ??-olefins; cyclohexanes; pregnanes and steranes, cheilanthanes and hopanes; hopenes; mono-, bi-, and tricyclic aromatic hydrocarbons; and benzo- and dibenzothiophenes. This finding confirms that most of these compounds occur in the ??bound?? form as structural units of molecules of resinous-asphaltenic components of the natural asphaltite.     

Composition and sorption properties of asphaltene sulfonates

The sulfonation of the dissolved oil objects by concentrated sulfuric acid was carried out at 60, 80, 100 ^oC and the resulting products with a structural-group composition similar to sulfonated asphaltenes were obtained. Structural-group composition of sulfonated oil products was established by Fourier transform infrared spectroscopy and the relative contents of sulfo-, sulfono- and carboxyl ionogenic functional groups was determined on the basis of spectral coefficients. The sorption capacity of sulfonated oil products (10-13 mg/g for Ca²⁺ and 14–18 mg/g for Cu²⁺) was determined by atom-absorption spectroscopy. It was established that the sorption characteristics of sulfonated oil products are determined by the total contents of asphaltene-resin components in starting oil objects and temperature of the sulfonation process.     

Change of asphaltene and resin properties after catalytic aquathermolysis

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.     

Characteristics of gaseous hydrocarbons generated from asphaltene pyrolysis and the geochemical significance

In order to study the mechanism of gas generation from the asphaltene, the thermal pyrolysis simulation experiment of the asphaltene is carried out by using high temperature and high pressure closed system. During asphaltene pyrolysis, the amount of methane is constantly increased but those of ethane, propane, and butane + pentane are all first increased and then decreased and eventually go to zero with the increase of the experiment temperature. And the dynamic parameters of gaseous hydrocarbon generation can be used to analyze the dynamic procedure of the asphaltene pyrolysis at the geological scale. The experimental results can perfect the theory of the origin of natural gas and provide an evidence for source judgment and resource evaluation of natural gas in marine strata in China.     

塔里木盆地海相原油及其沥青质裂解生气动力学模拟研究

应用50MPa高压封闭体系,对塔里木盆地海相原油及其沥青质进行了热裂解模拟实验,对气态烃产率及碳同位素演化、焦沥青的生成等方面进行了比较,探讨了原油裂解和沥青质裂解生气机理。研究发现,原油和沥青质裂解气各组分及焦沥青的产率变化类似。完全发生裂解时,沥青质裂解的总气体产率为原油裂解的50%,原油裂解和沥青质裂解生成总气体和焦沥青的质量比值分别为6:4和3:7。在裂解过程中,气态烃碳同位素δ¹³C值的特点是δ¹³C₁<δ¹³C₂<δ¹³C₃,且原油裂解气各组分(C₁—C₃)碳同位素δ¹³C值小于沥青质裂解气的相应组分。运用kinetics软件,计算得到原油和沥青质裂解的动力学参数(活化能和指前因子)。在此基础上,将实验结果外推至地质条件下,探讨了动力学模型的实际应用,为原油裂解气的判识、资源评价、勘探决策提供实验和理论依据。     

Prediction of asphaltene precipitation in crude oil

Asphaltene are problematic substances for heavy-oil upgrading processes. Deposition of complex and heavy organic compounds, which exist in petroleum crude oil, can cause a lot of problems. In this work an Artificial Neural Networks (ANN) approach for estimation of asphaltene precipitation has been proposed. Among this training the back-propagation learning algorithm with different training methods were used. The most suitable algorithm with appropriate number of neurons in the hidden layer which provides the minimum error is found to be the Levenberg–Marquardt (LM) algorithm. ANN's results showed the best estimation performance for the prediction of the asphaltene precipitation. The required data were collected and after pre-treating was used for training of ANN. The performance of the best obtained network was checked by its generalization ability in predicting 1/3 of the unseen data. Excellent predictions with maximum Mean Square Error (MSE) of 0.2787 were observed. The results show ANN capability to predict the measured data. ANN model performance is also compared with the Flory–Huggins and the modified Flory–Huggins thermo dynamical models. The comparison confirms the superiority of the ANN model.     

The control of asphaltene precipitation in oil wells

Asphaltene instability can occur in petroleum reservoirs leading to permeability reduction and deposition in transportation pipes restricting fluid flow. In this work, effect of reservoir pressure on amount of asphaltene precipitation was investigated. Two different asphaltene inhibitors (a new developed and an industrial) were used for preventing asphaltene deposition under static and dynamic conditions. Viscosity measurements of the oil, core flooding experiments and transmittance measurement were conducted to understand asphaltene precipitation and deposition behavior as well inhibitor efficiencies. Optimum concentration of the new asphaltene inhibitor was 200 ppm. Experiments show inhabitation efficiency of new inhibitor can reach up to 90% and showed better performance when compared with industrial one. In addition, squeeze lifetime of new inhibitor was 1.86 times longer than the industrial inhibitor in carbonate core samples. In the presence of new inhibitor formation damage and percent of transmittance was lower than in the presence of industrial asphaltene inhibitor.     

成熟度与热模拟产物分步萃取对滞留油生物标志物的影响

明确抽提过程中不同极性有机溶剂对所获得的生物标志物参数的影响,对基于生物标志物的生烃母质研究具有重要意义。选用鄂尔多斯盆地延长组低熟富有机质泥页岩进行生、排烃热模拟实验,并结合热模拟固体残样的实测随机镜质体反射率(R_O)值,准确剖析热演化程度和溶剂极性对生源和沉积环境参数适用范围的影响。结果表明：有机溶剂极性的大小不仅会影响抽提物的产率和族组分特征,而且会显著影响抽提物中正构烷烃、三环萜烷的分布特征,但对甾烷的分布特征影响并不明显。溶剂极性和热演化的双重影响导致生物标志物参数的适用范围存在明显区别,∑C_21^-/∑C_22⁺和(nC₂₁+nC₂₂)/(nC₂₈+nC₂₉)仅在低熟—高成熟的中期阶段(R_O值介于0.70%～1.48%之间)可作为有效的生源参数,而沉积环境判识参数∑三环萜烷/∑藿烷值适用范围更窄,仅在低熟—高成熟早期阶段(RO值介于0.70%～1.34%之间)有...     

Study of asphaltene deposition from Tahe crude oil

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 o C. From the PVT results, the bubble point pressure of TH10403CX 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 o C, the bubble point pressure of TH10403CX 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.     

Study of resin fraction of Nigerian crude oil using spectroscopic/spectrometric analytical techniques

Organics and trace metals of the resin fraction of Nigerian crude oil were analysed in order to characterise the fossil fuel. The crude oil samples were deasphaltened by n-pentane, while maltene fraction was fractionated into its components (saturates, aromatics and resin) using column chromatography. The organic compounds and elemental concentrations of the resin fraction were investigated using Fourier Transform Infrared Spectroscopy and Inductively Coupled Plasma Optical Emission Spectrometry respectively. The infrared spectra showed characteristic bands containing polar functional groups expected confirming that the resin was purely eluted. The elemental concentrations were found to be high compared to other fractions and was confirmed by their T-test values. Zinc had the highest mean concentration of 32.13 ± 35.66 mg/kg, while Mn had the least (1.14 ± 0.17 mg/kg). Results indicated that processing of the crude oil resin may cause catalyst poisoning/fouling, corrosion of equipment/pipelines. Therefore, adequate consideration of these trace metals must be taken before processing.     

Study of asphaltene dispersion and removal for high-asphaltene oil wells

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.     

温度和沥青质含量对重质油黏度的影响

将委内瑞拉脱水油样与不同的正构烷烃配制成混合液,然后对其进行抽提得到不同的沥青质和脱沥青油,并制备了重组油样。考查了沥青质含量和温度对油样黏度的影响。实验结果表明,Arrhenius关系式能较准确地描述重质油黏度与温度之间的定量关系。沥青质在重质油高黏度中起着关键作用,当温度低于35℃时,重组油样的黏度随沥青质含量的增加而急剧增大。当温度高于40℃时,随沥青质含量的增加,重组油样的黏度几乎不再增加。利用重组油样黏度和沥青质含量之间的关联式lnlnlnμ=a+b_1lnw+b_2(lnw)~2+b_3(lnw)~3能较准确地描述重组油样的动力黏度和沥青质含量之间的关系。