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Theoretical Insight into the Effect of Steam Temperature on heavy oil/Steam Interface Behaviors Using Molecular Dynamics Simulation

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Journal of Thermal Science 2023年第6期32卷 2179-2195页

作者： YANG Renfeng CHEN Dongsheng ZHENG Wei MIAO Tingting LIU Fan WANG Taichao CHEN Hengyuan CHENG Tong State Key Laboratory of Offshore oil Exploitation Beijing100028China Beijing Key Laboratory of Process Fluid Filtration and Separation College of Mechanical and Transportation EngineeringChina University of Petroleum-BeijingBeijing102249China CNOOC Research Institute Ltd. Beijing100028China

The interfacial behavior between heavy oil and steam is one of the vital pointers affecting the development efficiency of steam injection for heavy oil recovery.However,the underlying mechanisms of the interaction between heavy oil and steam at high temperature and pressure remain elusive.Herein,we have investigated the molecular-scale interactions on the interface between heavy oil droplet and steam phase at high temperatures(473 K,498 K,523 K,and 548 K)via molecular dynamics simulations.The results show that the interfacial thickness between heavy oil droplet and steam phase increases gradually with temperature,while the interfacial tension decreases constantly.Moreover,high temperature can damage hydrogen bonds,resulting in lower interaction energy between heavy oil droplet and steam phase.The radial distribution function results demonstrate that the interaction between heavy oil fractions and steam phase can be weakened by high temperature.Furthermore,the evolutions of interface are directly observed by the two-dimension density cloud maps at different temperatures,and the mean square displacement and self-diffusion coefficient demonstrate the evolution mechanism of heavy oil fractions and steam.In particular,the heavy oil/steam systems with asphaltenes at the interface are more likely to achieve high diffusivity and emulsifying capacity.This work provides a molecular-level insight for understanding the interfacial interaction mechanisms of heavy oil/steam systems during a steam injection process.

关键词： interfacial behavior heavy oil steam molecular dynamics simulation

Study of steam heat transfer enhanced by CO_(2) and chemical agents: In heavy oil production

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Petroleum Science 2023年第2期20卷 1030-1043页

作者： Ya-Li Liu Chao Zhang Song-Yan Li Zhao-Min Li Key Laboratory of Unconventional oil&Gas Development(China University of Petroleum(East China)) Ministry of EducationQingdao266580ShandongPR China School of Petroleum Engineering China University of Petroleum(East China)Qingdao266580ShandongPR China

Steam flooding with the assistance of carbon dioxide (CO_(2)) and chemicals is an effective approach for enhancing super heavy oil recovery. However, the promotion and application of CO_(2) and chemical agent-assisted steam flooding technology have been restricted by the current lack of research on the synergistic effect of CO_(2) and chemical agents on enhanced steam flooding heat transfer. The novel experiments on CO_(2)–chemicals cooperate affected steam condensation and seepage were conducted by adding CO_(2) and two chemicals (sodium dodecyl sulfate (SDS) and the betaine temperature-salt resistant foaming agent ZK-05200).According to the experimental findings, a “film” formed on the heat-transfer medium surface following the co-injection of CO_(2) and the chemical to impede the steam heat transfer, reducing the heat transfer efficiency of steam, heat flux and condensation heat transfer coefficient. The steam seepage experiment revealed that the temperature at the back end of the sandpack model was dramatically raised by 3.5–12.8 °C by adding CO_(2) and chemical agents, achieving the goal of driving deep-formation heavy oil. The combined effect of CO_(2) and SDS was the most effective for improving steam heat transfer, the steam heat loss was reduced by 6.2%, the steam condensation cycle was prolonged by 1.3 times, the condensation heat transfer coefficient was decreased by 15.5%, and the heavy oil recovery was enhanced by 9.82%. Theoretical recommendations are offered in this study for improving the CO_(2)–chemical-assisted steam flooding technique.

关键词： Steam flooding heavy oil Carbon dioxide Chemical agent Enhanced oil recovery(EOR) Heat transfer

Molecular composition of low-temperature oxidation products of the heavy oil

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Petroleum Science 2023年第5期20卷 3264-3271页

作者： Shuai Ma Yun-Yun Li Ri-Gu Su Xu-Sheng Wang Jing-Jun Pan Quan Shi Guang-Zhi Liao Chun-Ming Xu State Key Laboratory of heavy oil Processing Petroleum Molecular Engineering Center(PMEC)China University of PetroleumBeijing102249China Engineering Technology Research Institute of PetroChina Xinjiang oilfield Company Karamay834000XinjiangChina CAS Lanzhou Institute of Chemical Physics Lanzhou730000GansuChina PetroChina Exploration&Production Company Beijing100007China

Low-temperature oxidation(LTO)is the main reaction that affects fuel formation in the in-situ combustion process,which has important significance for the subsequent combustion propulsion and the successful extraction of crude oil.In this study,heavy oil was subjected to LTO reactions at different temperatures.Three types of reaction products with varying oxidation depths were characterized in terms of the number of oxygen atoms and the polarity of the molecule to reveal the low-temperature oxidation process of the heavy oil.Ketone compounds and acid polyoxides in the oil phase and deep oxidation products with a higher number of oxygen atoms in the coke were identified with increasing oxidation depth.The experimental results showed that the oxidation reaction of the heavy oil changed from kinetic-controlled to diffusion-controlled in the open oxidation system of the heavy oil as the oxidation depth increased.The oxidation reaction of the oil phase reached a maximum and stable value in oxygen content.The molecular compositions of the ketone compound and acid polyoxide did not change significantly with further increase in reaction temperature.The molecular compositions of the deep oxidation products with a higher number of oxygen atoms in the coke phase changed significantly.The coke precursor molecules with a lower oxygen content and condensation degree participated in the coke formation,and the oxidation reaction pathway and the complexity of the oxidation product component also increased.

关键词： Low-temperature oxidation In-situ combustion heavy oil Coke precursor Molecular composition

Investigation of feasibility of alkali-cosolvent flooding in heavy oil reservoirs

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Petroleum Science 2023年第3期20卷 1608-1619页

作者： Yi-Bo Li He-Fei Jia Wan-Fen Pu Bing Wei Shuo-Shi Wang Na Yuan State Key Laboratory of oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengdu610500SichuanChina Mewbourne School of Petroleum and Geological Engineering University of OklahomaNormanOK73019USA

Cold production is a challenge in the case of heavy oil because of its high viscosity and poor fluidity in reservoir conditions.Alkali-cosolvent-polymer flooding is a type of microemulsion flooding with low costs and possible potential for heavy oil reservoirs.However,the addition of polymer may cause problems with injection in the case of highly viscous oil.Hence,in this study the feasibility of alkali-cosolvent(AC)flooding in heavy oil reservoirs was investigated via several groups of experiments.The interfacial tension between various AC formulations and heavy crude oil was measured to select appropriate formulations.Phase behavior tests were performed to determine the most appropriate formulation and conditions for the generation of a microemulsion.Sandpack flooding experiments were carried out to investigate the displacement efficiency of the selected Ac formulation.The results showed that the interfacial tension between an AC formulation and heavy oil could be reduced to below 1o-3 mN/m but differed greatly between different types of cosolvent.A butanol random polyether series displayed good performance in reducing the water-oil interfacial tension,which made it possible to form a Type Il microemulsion in reservoir conditions.According to the results of the phase behavior tests,the optimal salinity for different formulations with four cosolvent concentrations(0.5 wt%,1 wt%,2 wt%,and 3 wt%)was 4000,8000,14000,and 20000 ppm,respectively.The results of rheological measurements showed that Type Ill microemulsion had a viscosity that was ten times that of water.The results of sandpack flooding experiments showed that,in comparison with waterflooding,the injection of a certain Ac formulation slug could reduce the injection pressure.The pressure gradient during waterflooding and AC flooding was around 870 and 30-57 kPa/m,respectively.With the addition of an AC slug,the displacement efficiency was 30%-50%higher than in the case of waterflooding.

关键词： heavy oil Microemulsion Cold production Chemical flooding Displacement efficiency

Synthesis and mechanism analysis of a new oil soluble viscosity reducer for flow improvement of Chenping heavy oil

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Chinese Journal of Chemical Engineering 2022年第5期35卷 58-67页

作者： Yaqi Ren Shuqian Xia School of Chemical Engineering and Technology Tianjin UniversityTianjin 300072China

oil soluble viscosity reducers have gradually attracted the attention of petrochemical research due to their cleanliness and high efficiency.Considering the high viscosity and non-Newtonian fluid properties of Chenping heavy oil found in China,a series of new oil soluble viscosity reducers with different proportions and molecular weights were prepared by free radical polymerization using octadecyl acrylate,2-allylphenol and N-methylolacrylamide as monomers.The viscosity reducer was applied to different types of heavy oil and found that it exhibited a better effect on heavy oils with high asphaltene content.The test of rheological behavior of heavy oil with additive was performed at wide range of shear rate(3–90 s^(-1))and temperature range(30–100°C).The apparent viscosity reduction rate was up to 70.09%,which was better than the industrially relevant ethylene–vinyl acetate copolymer under the same test condition.In addition,the effect of viscosity reducers on the components of heavy oil and the energy change of the system simulated by molecular dynamics simultaneously was investigated.The consistency of the simulated and experimental results show that the effect of viscosity reduction closely related to the crystallization process of wax and the viscosity reducer can reconstruct the surface structure of asphaltene and diminish the connection of benzene ring.

关键词： heavy oil Viscosity reduction Asphaltene Non-Newtonian fluid

Study on the in situ desulfurization and viscosity reduction of heavy oil over MoO_(3)–ZrO_(2)/HZSM-5 catalyst

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Petroleum Science 2023年第6期20卷 3887-3896页

作者： Rui-Qi Liu Li-Qiang Zhang Hui-Da Pan Yi-Ya Wang Jin-Yu Li Xin-Wei Wang Zheng-Da Yang Xin-Lu Han Ri-Yi Lin College of New Energy Qingdao Engineering Research Center of Efficient and Clean Utilization of Fossil EnergyChina University of Petroleum(East China)Qingdao266580ShandongChina

heavy oil is characterized by high viscosity.High viscosity makes it challenging to recover and transport.HZSM-5,MoO_(3)/HZSM-5,ZrO_(2)/HZSM-5 and MoO_(3)–ZrO_(2)/HZSM-5 catalysts were developed to promote in situ desulfurization and viscosity reduction of heavy oil.The physical and chemical properties of catalysts were characterized by XPS,XRD,TEM,NH3-TPD,etc.The effects of temperature,catalyst type and addition amount on viscosity and composition of heavy oil were evaluated.The results showed that the presence of MoO_(3)–ZrO_(2)/HZSM-5 nanoparticles during aquathermolysis could improve the oil quality by reducing the heavy fractions.It reduced viscosity by 82.56%after the reaction at 280℃ and catalyst addition of 1 wt%.The contents of resins and asphaltic in the oil samples were 5.69%lower than that in the crude oil.Sulfur content decreased from 1.45%to 1.03%.The concentration of H2S produced by the reaction was 2225 ppm.The contents of sulfur-containing functional groups sulfoxide and sulfone sulfur in the oil samples decreased by 19.92%after the catalytic reaction.The content of stable thiophene sulfur increased by 5.71%.This study provided a basis for understanding the mechanism of heavy oil desulfurization and viscosity reduction.

关键词： heavy oil Hydrothermal cracking MoO_(3)-ZrO_(2)/HZSM-5 catalyst Desulfurization Viscosity reduction

Lag times in toe-to-heel air injection(THAI)operations explain underlying heavy oil production mechanisms

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Petroleum Science 2022年第3期19卷 1165-1173页

作者： Wei Wei Ian D.Gates Department of Chemical and Petroleum Engineering University of CalgaryCalgaryAlbertaCanada

From a time value of revenue point of view,it is preferred that the time between reservoir stimulation and oil production response is small.heavy oil combustion processes have a lag time between air injection and liquid production,but the common practice in production data analysis uses simultaneous injection and production data when seeking a relationship between them.In this research,the time scales of production for the Kerrobert toe-to-heel air injection(THAI)heavy oil project in Saskatchewan,Canada,is analyzed by using cross correlation analysis,i.***.time delay analysis between air injection and oil production.The results reveal two time scales with respect to production response with two distinctive recovery mechanisms:(1)a short time scale response(nearly instantaneous)where oil production peaks right after air injection(directly after opening production well)reflecting cold heavy oil production mechanisms,and(2)a longer time scale(of order of 100-300 days)response where peak production occurs associated with the collective phenomena of air injection,heat generating reactions,heat transfer,and finally,heated mobilized heavy oil drainage to the production well.This understanding of the two time scales and associated production mechanisms provides a basis for improving the performance of THAI.

关键词： heavy oil In situ combustion Toe-to-heel air injection(THAI) Production analysis Lag time

Comparative pyrolysis kinetics of heavy oil and its SARA fractions using distributed activation energy model

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Petroleum Science 2023年第5期20卷 3231-3239页

作者： Qing-An Xiong Yu-Ming Zhang Pei Qiao Guo-Tong Li Jia-Zhou Li Wei Zhang College of Mechanical and Transportation Engineering China University of PetroleumBeijing102249China

The pyrolysis behaviors of Qingdao vacuum residue(QD-VR)and its SARA(saturates,aromatics,reins,and asphaltenes)fractions were evaluated by thermo-gravimetric with mass spectrometer(TG-MS).The pyrolysis kinetics were determined by Friedman,one-parallel and four-parallel distributed activation energy model(DAEM),respectively.The results indicated that the pyrolysis behavior of QD-VR was similar to that of aromatics.For saturates,the release of H_(2),CH_(4),CO,and CO_(2) occurred in 80-400℃,while the temperature range for QD-VR and other fractions is 200-800℃.The average activation energy(Ea)via Friedman method was 179.72 kJ/mol and increased with the conversion ratio.One-parallel Gaussian DAEM was more suitable to describe the pyrolysis process of the single SARA fractions,while four-parallel Gaussian DAEM was more suitable to describe the pyrolysis process of heavy oil.Furthermore,comparing the weighted E_(a) from one-parallel(227.64 kJ/mol)and four-parallel Gaussian DAEM(204.63 kJ/mol),the results suggested that during pyrolysis process of heavy oil,there was an interaction between the SARA fractions,which could reduce the E_(a) of heavy oil pyrolysis.Specifically,during heavy oil pyrolysis,resins and asphaltenes could increase the E_(a) of saturates and aromatics,while saturates and aromatics could decrease the E_(a) of resins and asphaltenes.

关键词： heavy oil Pyrolysis kinetics SARA fractions DAEM

Petrophysical parameters inversion for heavy oil reservoir based on a laboratory-calibrated frequency-variant rock-physics model

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Petroleum Science 2023年第6期20卷 3400-3410页

作者： Xu Han Shang-Xu Wang Zheng-Yu-Cheng Zhang Hao-Jie Liu Guo-Hua Wei Gen-Yang Tang CNPC Key Laboratory of Geophysical Prospecting China University of Petroleum(Beijing)Beijing102249China Engineering Research Center of the Ministry of Education for Exploration and Development of Complex oil and Gas Reservoirs China University of Petroleum(Beijing)Beijing102249China Shengli oilfield Geophysical Exploration Research Institute SinopecDongying257000ShandongChina

heavy oil has high density and viscosity, and exhibits viscoelasticity. Gassmann's theory is not suitable for materials saturated with viscoelastic fluids. Directly applying such model leads to unreliable results for seismic inversion of heavy oil reservoir. To describe the viscoelastic behavior of heavy oil, we modeled the elastic properties of heavy oil with varying viscosity and frequency using the Cole-Cole-Maxwell (CCM) model. Then, we used a CCoherent Potential Approximation (CPA) instead of the Gassmann equations to account for the fluid effect, by extending the single-phase fluid condition to two-phase fluid (heavy oil and water) condition, so that partial saturation of heavy oil can be considered. This rock physics model establishes the relationship between the elastic modulus of reservoir rock and viscosity, frequency and saturation. The viscosity of the heavy oil and the elastic moduli and porosity of typical reservoir rock samples were measured in laboratory, which were used for calibration of the rock physics model. The well-calibrated frequency-variant CPA model was applied to the prediction of the P- and S-wave velocities in the seismic frequency range (1–100 Hz) and the inversion of petrophysical parameters for a heavy oil reservoir. The pre-stack inversion results of elastic parameters are improved compared with those results using the CPA model in the sonic logging frequency (∼10 kHz), or conventional rock physics model such as the Xu-Payne model. In addition, the inversion of the porosity of the reservoir was conducted with the simulated annealing method, and the result fits reasonably well with the logging curve and depicts the location of the heavy oil reservoir on the time slice. The application of the laboratory-calibrated CPA model provides better results with the velocity dispersion correction, suggesting the important role of accurate frequency dependent rock physics models in the seismic prediction of heavy oil reservoirs.

关键词： heavy oil Rock physics Velocity dispersion Pre-stack inversion Reservoir prediction