Characterizing the Fuel Deposition Process of Crude Oil Oxidation in

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Characterizing the Fuel Deposition of Crude oil Oxidation in air Injection Process Cheng-dong Yuan, Wan-Fen Pu, Fa-Yang Jin, Jian-Jun Zhang, Qi-Ning Zhao, Dong Li, Yi-Bo Li, and Ya-Fei Chen Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.5b01493 • Publication Date (Web): 05 Oct 2015 Downloaded from http://pubs.acs.org on October 6, 2015

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Characterizing the Fuel Deposition Process of Crude oil Oxidation in air Injection Cheng-Dong Yuan*†§, Wan-Fen Pu*†§, Fa-Yang Jin†§, Jian-Jun Zhang║, Qi-Ning Zhao‡, Dong Li†§, Yi-Bo Li†§, Ya-Fei Chen†§ †

State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, §School of Petroleum and natural gas Engineering,

‡

School of Geoscience and Technology, Southwest Petroleum University, Chengdu, People’s Republic of China

║

Research Institute of Engineering Technology, Northwest Oilfield Company, Sinopec, Urumchi, People’s Republic of China

Abstract: Fuel deposition (FD) as an important stage in the oxidation process of the crude oil in air injection technique was less studied in detail as the FD was not obvious in the Thermogravimetry (TG-DTG) experiments in previous study. In this study, the obvious FD in TG-DTG curves and coke formation in the FD process in the isothermal oxidation experiments of the heavy oil were observed. The coke formation and FD characterization of the heavy oil were further investigated using isothermal oxidation experiments and TG-DTG experiments, respectively by making a comparison with light oil. These isothermal oxidation experiments were carried out at 120 ℃ and 30 – 40 MPa. Gas chromatography was employed to analyze the composition of C1–C6, O2, CO, and CO2. The FD characterization was analyzed by TG-DTG curves. Arrhenius method (linear regression) was used to obtain the kinetic parameters. In the isothermal oxidation experiments of the heavy oil, the coke was formed. Both the formed coke and the oxidized oil were flammable under ambient temperature. However, there is no coke being formed for the light oil. Based on the calculated kinetic parameters, a new understanding of the FD was proposed. The whole FD process could be divided into two subzones: positive temperature coefficient zone (PTC) where the activation energy was positive and negative temperature coefficient zone (NTC) where the activation energy was negative. For the heavy oil, both NTC and PTC are obvious, and the detritus could clearly extend the temperature range of the FD, especially for the PTC subzone. However, for the light oil, the FD mostly showed the NTC subzones. Only small PTC subzone was displayed.

1. Introduction Air injection process for enhanced oil recovery (EOR) has attracted extensive attention.1 Air injection not only has the role of the conventional gas injection (N2, CO2, CH4, etc) but also has the advantages of thermal methods.2 In recent years, high pressure air injection technique has been considered as an effective EOR process.3 The successful commercial implementation has been carried out in Buffalo field.4, 5 Whether the air injection could be implemented effectively or not depends on the oxidation reaction between the crude oil and the injected air in the reservoirs. The oxidation of the crude oil has been extensively investigated. Current studies suggested that the oxidation mechanism of the

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crude oil mainly included three stages: low temperature oxidation (LTO), high temperature oxidation (HTO), and a transition stage of the middle temperature. For LTO and HTO, a lot of studies have been carried out. However, less attention was paid on the transition stage. Researchers had different perspectives on the transition stage. Gargar et al6, 7 and Zhao et al8 considered it as the middle temperature oxidation (MTO) where the fuel was formed. At the same time, less bond scission occurred, which produces a small amount of CO, CO2, and H2O. Khansari et al9, 10 called it thermal cracking that breaks down the unoxidized crude oil and some LTO products to coke and gases. Kök et al11,

12

considered it as FD. An unified cognition about this

transition stage was that the fuel was formed in this stage. Therefore, in this study, we called it as FD. FD plays a very important role in the whole oxidation process of the oxidation. If the deposited fuel is not enough to sustain the HTO, the in situ combustion will be infeasible.13, 14 Whereas in previous TG experiments, it was difficult to observe a distinct FD region.12, 15, 16 It was also difficult to calculate its kinetics parameters from the regression curves. Consequently, just the kinetics in the LTO stage and the HTO stage were investigated.11, 16, 17 In our previous research,18 a distinct FD zone was observed for the Tahe heavy oil. Simultaneously, we realized that FD might have to do with the negative temperature coefficient (NTC) behavior reported by Wilk et al.19 Therefore, in this study, the FD characterization and the coke formation related to the FD process were in-depth investigated by making a comparison between the heavy oil and light oil. A new understanding of the FD was proposed.

2. Experimental Section 2.1. Materials The crude oil samples were provided by Tahe oil field in Tarim Basin (China). The properties of the crude oil were shown in Table 1. The detritus (squashed reservoir rocks) and quartz sands of 60 − 80 mesh were used in TG experiments. XRD method was employed for whole rock analysis to analyze the mineral composition of the reservoir rocks. The method for the whole rock analysis was described in detail in previous study.18 2.2. Isothermal Oxidation Experiments and Thermogravimetric Analysis Objectives. Some isothermal oxidation experiments were carried out to compare the oxidation behavior and coke formation related to the FD process of the heavy oil with that of the light oil. The experiment design and goals were shown in Table 2. Experimental Device and Procedures. An high pressure oxidation tube was employed for the oxidation experiments under isothermal condition, which has been described in detail in previous studies.18, 20 The flow diagram of the isothermal oxidation experiments is shown in Figure 1. During


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the experimental process, the crude oil samples were injected into the oxidation tube at an injection rate of 1.0 mL/min. The injected crude oil samples occupied the three-fifths of the total volume of the oxidation tube. Therefore, the rest of the free volume was filled with air at required pressures. The automatic acquisition system was employed to collect the pressure data. A rotational rheometer (MARS III Haake, Germany) was used to measure the viscosity of the oxidized oil. The contents of the C1— C6, CO, O2, and CO2 in the produced gases were measured using a gas chromatography (Agilent Technologies, Inc.). The apparent ratio of hydrogen to carbon (H/C) was calculated to depict the oxidation characteristics. It is an useful tool for studying the chemical nature of fuel burned.2, 21 The apparent H/C indicates the nature of the fuel burned, for example, the lower the H/C the more the coke-like fuel is deposited. The apparent H/C ratio was calculated based on the composition of the effluent gases. The apparent H/C ratio is defined as: H⁄C = 4[(γ ⁄v )v − CO − 0.5CO − γ ]/(CO + CO)

(1)

The oxygen consumption was also calculated as follows: oxygen consumption (mol%) = [(γ − γ )⁄γ ] × 100

(2)

In the equations (1) and (2), γ and γ are the injected and produced O2 concentration, mol%, respectively; v and v are the injected and produced N2 concentration, mol%, respectively. 2.3. Thermogravimetric Analysis TG/DTG has been widely and successfully applied in the evaluation of thermal characteristics of fossil fuels.22-24 TG measures the mass change in a specific temperature range. DTG provides the rate of mass change as a function of time, which can help to identify the reaction stages especially when TG curves is more complex. TG/DTG experiments were carried out using NETZSCH STA 409 PC/PG (NETZSCH, Ltd., German). Prior to the TG analysis of crude oil samples, the temperature and sensitivity calibration was carried out. Five metals including In, Sn, Bi, Zn, Al were used for the temperature and sensitivity calibration under the temperature of ambient temperature to 1500 ℃.A linear heating rate of 10 ℃/min was employed for the TG experiments. The samples were heated from 32 ℃ to 700 ℃ under atmospheric pressure. In each experiment, the crude oil sample of 30 mg was used. The weight of the detritus or quartz sands was also 30 mg. 2.4. Kinetic Theory Arrhenius method has been extensively applied to analyze the combustion and pyrolysis kinetic of fossil fuels.15, 25-27 Therefore, it was employed for the calculation of the kinetics parameters. During the TG measurements, a small amount crude oil sample of 30 mg was used and the excess air was supplied outside the crucible, therefore the whole oxidation process did not depend on of the


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concentration of O2. It was assumed that the weight loss rate only depended on the rate constant, the temperature with reaction order of unity, and the mass of the remaining sample. Hence, the kinetic model is expressed as equation (3). d) ⁄d* = +) ,

(3)

Where dW dt is the mass loss rate, k is the rate constant (expressed in equation (4)), + = -. /01(− 2 ⁄34)

(4)

Where -. represents Arrhenius constant, 5 represents the reaction order, 2 represents the activation energy, 4 represents temperature. Usually, it was found that the oxidation of the crude oil follows a first order reaction with respect to oil (i.e. “n = 1”) without the limitation of mass transfer.22 d) ⁄d* ⁄6 = -. /01(− 2 ⁄34 )

(5)

Taking the logarithm of both sides, lg(d) ⁄d* ⁄6)=lgA8 − E⁄2.303RT

(6)

The lg(d) ⁄d* ⁄6 ) was plotted vs. 1⁄4, and then a linear regression was carried out. A straight line was obtained. Through the slope of the straight line, the 2 could be calculated.

3. Results and Discussion 3.1. Oxidation Characteristics of Heavy oil and Light oil Table 3 shows the composition of the effluent gases in isothermal oxidation experiments, which is composed of CO2, CO, N2 and vaporized/stripped hydrocarbons. By comparing run 1, 2 with run 3, 4, it can be concluded that the heavy oil consumed more oxygen than light oil in the same conditions. For the heavy oil, the concentrations of oxygen at 30 and 40 MPa were decreased to 1.85% and 0.15% after oxidizing for 3 days, respectively, and an almost complete oxygen consumption (91.19% and 99.29%, respectively) occurred. However, the content of O2 at 30 and 40 MPa were decreased to 12.01% and 10.1%, and the oxygen consumption were 43% and 52%, respectively, for the light oil. Simultaneously, the oxidation of the heavy oil was compared with light oils in previous study as shown in Table 4.28, 29 For these light oils, the concentrations of the oxygen in the effluent gas were 9.8–12.8% under similar conditions, which is far higher than that of the heavy oil. The comparison between the heavy oil and light oils (both used in this study and previous studies) indicated that the oxygen consumption ability of the heavy oil was stronger. Although the heavy oil had a strong oxygen consumption ability, an ordinary level of produced CO2 (0.15% at 30 MPa, 5.41% at 40 MPa) after oxidizing for three days was obtained. This indicated that, most of the consumed oxygen were not changed into CO2. Usually, oxygen addition and bond scission were considered as two possible oxidation mechanisms for the oxidation of the crude oil


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under the low temperature regions.3, 13 These two reactions are possible to have a competition.30 It is considered that the bond scission reaction is the favored reaction path for light oil.3 It tends to generate more carbon oxides for the oxidation of the light oil under low temperatures, and the oil viscosity after the oxidation has little change.31 Whereas, for the heavy oil, the viscosity of the oxidized oil (15703 mPa·s) was higher than that of the unoxidized crude oil (6452 mPa·s) at the same temperature of 50 ℃ in this study. The addition reactions were believed to predominate under the experimental conditions used for the oxidation of the heavy oil. The high H/C of 41.24 also partly proved the domination of the addition reactions. Under this circumstance, many oxides, such as aldehydes, hydroperoxides, ketones and acids, etc, were generated by O-atom addition into the hydrocarbon molecules. These formed oxides towards further form some undesirably heavier oil fractions oil fractions by polymerization reactions, which leads to the increase of the viscosity of the oxidized oil. However, for the light oil, the viscosity of the oxidized oil had a slight increase. The viscosity of the crude oil before and after the oxidation were 5.65 and 6.21 mPa·s at 50 ℃ , respectively. An ordinary level of CO2 in the effluent gas (0.03% at 30 MPa, 1% at 40 MPa) was obtained as the heavy oil did. This indicated that the bond scission reactions were also not the favored reaction path for the used light oil under the experimental conditions. 3.2. Fuel Deposition in the Oxidation process in Isothermal Oxidation Experiments The pressure in run 2 and 5 was further increased to 40 MPa. Simultaneously, the oxidation time were increased to 7 days. It was found that coke was formed in the reactor for the heavy oil. The coke was ignited for the flammability test at ambient temperate and atmospheric pressure. The formed coke was very inflammable (shown in Figure 2). Meanwhile, the oxidized oil (called LTO residual, was still viscous liquid) was also ignited at room temperature. The LTO residual could burn too. Nevertheless, it was not ignited as easily as the formed coke. There was a “splat” sound and some scattered sparks when the LTO residual combusted, which is a sign that the water existed. For light oil, there was no indication that the coke was formed after the oxidation, which is consistent with the results concluded by Gargar et al.6 There was only a slight increase in oil viscosity. The FD of the crude oil is closely related to the composition of the crude oil. Murugan et al32 suggested that the total coke formed was mainly contributed by the asphaltenes present in the whole oil. Generally, for light oils, the asphaltenes content is relatively low, the FD is not obvious, which determines the difference of the displacement mechanism between in-situ combustion for heavy oil and air injection into light reservoir. In-situ combustion in heavy oil reservoir requires enough fuel to sustain a stable combustion font. However, light oils could not form large quantities of fuel.


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Therefore, the primary mechanism for air injection into light oil reservoir is low temperature oxidation. The LTO residual and the formed coke in run 2 were further oxidized (run 3) under 40 MPa and 120 ℃. The H/C of less of 2 was achieved. The conversion rate of the consumed O2 to CO2 and CO reached approximately 80%. Moore et al3 indicated that when the conversion rate of the consumed O2 to CO2 and CO exceeded 50 % and the H/C was less than 3.0, it implied that the crude oils were reacting with O2 in a proper pathways (bond scission or combustion). Simultaneously, the content of the CO2 in the effluent gas reached up to approximately 15 %. According to Montes et al,33 a CO2 level of exceeding 12% indicated that combustion-like reactions occurred. The above-mentioned data implied that the combustion reaction was dominated for the further oxidation of the formed coke. 3.3. Analysis of Fuel Deposition by DTG Analysis Three distinct reaction regions were identified (Figures 3–6) known as LTO, FD and HTO in TGDTG curves of both the heavy and light oils.15 The reaction intervals, peak temperatures and mass loss of crude oils, crude oil + detritus, and crude oil + quartz sands are given in Table 5. The results were similar with that of Kök et al.12, 15, 16 Whereas, no distinct FD region was observed, and it was also difficult to calculate its kinetics parameters from the regression curves in their researches. In this study, the heavy oil had a very distinct FD stage. Compared with the heavy oil (Figure 4), the FD stage of the light oil was weaker. This is consistent with the results obtained in the isothermal oxidation experiments where there is no coke being formed in the oxidation of the light oil.(Section 3.2) The reaction intervals of the FD for heavy oil alone, heavy oil + quartz sands, and heavy oil + detritus were 410–498 ℃, 400-502 ℃, and 365–505 ℃, respectively. For the light oil (Figure 6), the reaction intervals of the FD for light oil alone and light oil + quartz sands are 387–476 ℃ and 390– 477 ℃, respectively. One can conclude that the quartz sands had a little influence on FD stage, while the detritus had an important influence on the FD stage. The addition of the detritus expanded the reaction intervals of the FD. Meanwhile, the reaction intervals of the LTO was zoomed out. The effect of the reservoir detritus included two aspects: surface area effect34 and catalyst effect. Generally, it is considered that the quartz sands have no catalytic effect and only provide more surface area for the deposited fuel. In this study, it was found that the surface area effect was not strong by comparing the experiments of crude oil with that of crude oil + quartz sands. Therefore, the effect was more came from the chemical composition of the detritus, which has been proven to have catalytic effect for the oxidation of the crude oils.35 The XRD results showed that the detritus was mainly made up of 97.95 % calcite and 2.05 % quartz. As mentioned before, the catalytic action of


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quartz was little. Consequently, the calcite was believed to be the main factor that affected the FD. However, a further investigation on the catalytic effect of the calcite is still needed. Simultaneously, the weak surface effect can be partly attributed to the TG experiment conditions. In TG experiments, the volume of the used crucible is limited, only a small amount of sands could be loosely loaded. The sands were more like immersed in the crude oil. Therefore, the surface area that could be provided is very limited. However, in the real formation in a reservoir, the surface area is very large, which has a very important effect on the oxidation, especially for the FD stage. 3.4. Kinetic Analysis of Fuel Deposition The activation energies (E) of the FD stage were calculated by linear regression (Figures 7–10). Table 6 shows the calculated values of E. The results revealed that there were two apparent subzones in the FD zone for the heavy oil. The first subzone had positive activation energies called positive temperature coefficient zone (PTC), whereas the second subzones had negative activation energies, called negative temperature coefficient zone (NTC). The negative activation energies represents the negative temperature coefficient behavior. It means reaction rate constant decreases with temperature. For the heavy oil alone, the range of the PTC subzone was almost the same with the NTC subzone. When the detritus was added, the range of the PTC subzone was clearly bigger than the NTC subzone. The activation energies for crude oil + detritus in first and second subzones were 102.59 and -183.85 KJ/mol (105.14 and -147.92 KJ·mol-1 for crude oil alone), respectively. The addition of the detritus clearly expanded the FD zone, especially for the first subzone (PTC). The activation energies were also reduced. Compared with the kinetic parameters calculation curves of the heavy oil, the FD zones of the light oil mostly showed the NTC subzones. Only small PTC subzones were displayed in the kinetic parameters calculation curves. The NTC subzone can be attributed to two reactions that become prominent with increasing temperature. They both involve the decomposition of the alkylperoxy radical:36 RO . → R′ = R′′ + HO . RO . → R. + O

(7) (8)

Between the two reactions, the importance of Reaction (7) was more prominent. Pitz et al37 carried out the simulation of the oxidation behavior of propane. The results indicated that NTC-like behavior could be obtained only when Reaction (7) was included. They explained that the hydroperoxy radical ( HO . ) formed in Reaction (7) was not reactive enough to propagate the reactions of forming hydroperoxides that are sequence of elementary free-radical reactions (reaction (9) and (10) in the initial stage of the oxidation. R. + O → RO .


(9)

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RO . + RH → ROOH + R.

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(10)

Therefore, these two chain reactions were effectively broken. HO . is very stable. HO . does not quickly decompose into hydrogen peroxide and oxygen (reaction 11) until its concentration builds up to the point at which most of it is consumed in a termination reaction with itself. 2HO . → HOOOOH → HOOH + O

(11)

Hydrogen peroxide is much less tend to branching into two free radicals than alkyl hydroperoxides. Hydrogen peroxide does not mainly participate in branching until the temperature reaches up to about 500 ℃, before which the oxidation rate of propane can be decreased by an order of magnitude when temperature is increased by dozens of degrees.38 With the further increase of temperature, other reactions paths begin to become more important, and the reaction rate increases again. Besides Reaction (7), Reaction (8), which is the reverse of Reaction (9), is also believed to affect the NTC region. As the temperature increases, a large proportion of the RO . is driven back into the molecules that formed it. Reaction (10) becomes slower with the decrease of the concentration of RO. . This effect becomes significant at almost the same temperature where the RO. decomposes into an alkene and hydroperoxy radical.36 Consequently, Reactions (8) and (7) are together believed to be the reason that causes the NTC region. However, there are so many problem about the NTC that still need to be further studied. Such as, how the NTC region affects the FD stage, and if the NTC has an important effect on the building and sustaining of the combustion front or not in in-situ combustion in the heavy oil reservoir.

4. Conclusion The FD is an important stage in the oxidation of the crude oil, especially for the air injection process in heavy oil reservoirs. If there is no sufficient fuel being deposited, the in situ combustion will be unfeasible. However, it was difficult to obtain the kinetics parameters for the FD in previous study. Therefore, the FD was less studied in detail. In this study, the FD process and the coke formation related to the FD process were investigated. The TG-DTG curves of the heavy oil displayed a very distinct FD region. The light oil had a relatively weaker FD region. The kinetics parameters of the FD was calculated by Arrhenius method (linear regression). A new understanding of the FD process was proposed. The whole FD included two subzones: PTC zone where the activation energy was positive and NTC subzone where the activation energy was negative. For the heavy oil, both NTC and PTC are obvious, However, for the light oil, the FD mostly showed the NTC subzones. Only small PTC subzone was displayed.


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The coke formation related to the FD process was observed in the isothermal oxidation experiments for the heavy oil. The coke was flammable at ambient temperate and atmospheric pressure. Although the LTO residual could burn too, it was not ignited as easily as the formed coke was. However, for the light oil, there is no coke being formed. Simultaneously, the isothermal oxidation experiments also revealed that the oxygen consumption ability of the heavy oil was stronger than the light oil. The new insight into the FD contributes to a better understanding of the oxidation process of the crude oil in air injection process. However, the reaction mechanism of the FD as well as how the NTC and PTC reaction affect the FD process need to be further studied, which will provide significant guidance for sustaining the combustion process during in situ combustion in the reservoirs and the evaluation of the feasibility of air injection.

Author Information Corresponding Author * E-mail: [email protected] (W.-F.P.); [email protected] (C.-D.Y.) Notes The authors declare no competing financial interest.

Acknowledgments The authors thank Sinopec Northwest Company (China) for providing the crude oil and reservoir core samples.

Nomenclature Abbreviations FD = fuel deposition LTO = low temperature oxidation PTC = positive temperature coefficient NTC = negative temperature coefficient IOR = improved oil recovery HTO = high temperature oxidation MTO = middle temperature oxidation

References (1) Jia, H.; Yuan, C. D.; Zhang, Y.C.; Peng, H.; Zhong, D.; Zhao, J. Z. Recent progress of high pressure air injection process (HPAI) in light oil reservoir: laboratory investigation and field


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(15)Kök, M. V.; Acar, C. Kinetics of crude oil combustion. J. Therm. Anal. Calorim. 2006, 83 (2), 445–449. (16) Kök, M. V. Characterization of medium and heavy crude oils using thermal analysis techniques. Fuel. Process. Technol. 2011, 92 (5), 1026–1031. (17) Jia, H.; Zhao, J.; Pu, W.; Zhao, J.; Kuang, X. Thermal study on light crude oil for application of high-pressure air injection (HPAI) process by TG/DTG and DTA tests. Energy Fuels 2012, 26 (3), 1575–1584. (18) Pu, W. F.; Yuan, C. D.; Jin, F. Y.; Wang, L.; Qian, Z.; Li, Y. B.; Chen, Y. F. Lowtemperature oxidation and characterization of heavy oil via thermal analysis. Energy Fuels 2015, 29(2), 1151–1159. (19) Wilk, R. D.; Cernansky N. P.; Cohen, R. S. The oxidation of propane at low and transition temperatures. Combust. Sci. Technol. 1986, 49(1–2), 41–78. (20) Zhao, J.; Jia, H.; Pu, W.; Wang, L.; Peng, H. Sensitivity studies on the oxidation behavior of crude oil in porous media. Energy Fuels 2012, 26 (11), 6815–6823. (21)Murugan, P.; Mahinpey, N.; Mani, T.; Asghari, K. Effect of low-temperature oxidation on the pyrolysis and combustion of whole oil. Energy 2010, 35 (5), 2317–2322. (22) Gundogar, A. S.; Kök, M. V. Thermal characterization, combustion and kinetics of different origin crude oils. Fuel 2014, 123, 59–65. (23) Kök, M. V.; Gul, K. G. Thermal characteristics and kinetics of crude oils and SARA fractions. Thermochim. Acta 2013, 569, 66–70 (24) Kök, M. V.; Gul, K. G. Combustion characteristics and kinetic analysis of Turkish crude oils and their SARA fractions by DSC. J. Therm. Anal. Calorim. 2013, 114(1), 269–275. (25) Kök, M. V. Gundogar, A.S. DSC study on combustion and pyrolysis behaviors of Turkish crude oils. Fuel. Process. Technol. 2013, 116, 110–115. (26) Kök, M. V.; Pamir, M. R. Comparative pyrolysis and combustion kinetics of oil shales. J. Anal. Appl. Pyrol. 2000, 55 (2), 185–194. (27) Kök, M. V. Non-isothermal DSC and TG/DTG analysis of the combustion of silopi asphaltites. J. Therm. Anal. Calorim. 2007, 88 (3), 663–668. (28)Ren, S. R.; Greaves, M.; Rathbone, R. R. Oxidation kinetics of North Sea light crude oils at reservoir temperature. Chem. Eng. Res. Des. 1999, 77 (5), 385–394. (29)Greaves, M.; Ren, S. R.; Rathbone, R. R. Air injection technique (LTO process) for IOR from light oil reservoirs: oxidation rate and displacement studies. Presented at the Symposium on improved oil recovery, Tulsa, Oklahoma, April19–22, 1998; Paper SPE 40062.


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(30)Barzin, Y.; Moore, R. G.; Mehta, S. A.; Mallory, D. G.; Ursenbach, M. G.; Tabasinejad, F. Role of vapor phase in oxidation/combustion kinetics of high-pressure air injection (HPAI). Presented at the SPE Annual Technical Conference and Exhibition, Florence, Italy, September 19–22, 2010; Paper SPE 135641. (31)Ren, S. R.; Greaves, M.; Rathbone, R. R. Air injection LTO process: an IOR technique for light-oil reservoirs. SPE J. 2002, 7 (1), 90–99. (32) Murugan, P.; Mani, T.; Mahinpey, N.; Asghari, K. The low temperature oxidation of Fosterton asphaltenes and its combustion kinetics. Fuel. Process. Technol. 2011, 92(5), 1056–1061. (33)Montes, A. R.; Gutierrez, D.; Moore, R. G.; Mehta, S. A.; Ursenbach, M. G. Is high-pressure air injection (HPAI) simply a flue-gas flood? J. Can. Pet. Technol. 2010, 49 (2), 56–63. (34)Drici, O.; Vossoughi, S. Study of the surface area effect on crude oil combustion by thermal analysis techniques. J. Pet. Technol. 1985, 37 (4), 731–735. (35)Shah, A. A.; Modi, K. Feasibility of high pressure air injection in heterogeneous light oil reservoir using thermal simulation. Presented at the SPE EOR Conference at Oil and Gas West Asia, Muscat, Oman, April 16–18, 2012; Paper SPE 152978. (36)Freitag, N.P. Chemical Reaction Mechanisms That Govern Oxidation Rates During In-Situ Combustion and High-Pressure Air Injection. Presented at the SPE Heavy Oil Conference-Canada held in Alberta, Canada, June 10–12, 2014; Paper SPE 170162. (37) Pitz, W. J.; Westbrook, C. K.; Koert, D. N.; Jaouabi, K.; Miller, D. L.; Cernansky, N. P. Propane oxidation through the negative temperature coefficient region at 10 and 15 atmospheres: results of experimental and modeling studies. Presented at the 24th Int. Symp. on Combustion, Sydney, Australia, July 5–10, 1992. (38) Benson, S.W. The kinetics and thermochemistry of chemical oxidation with application to combustion and flames.. Prog. Energy Combust. Sci. 1981, 7(2), 125–134.


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Figure 1. Flowchart of the isothermal oxidation experiments.


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Figure 2. Formed coke, LTO residual and their combustion at room temperature (25 ℃) and 1 atm.


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Figure 3. TG curves for heavy oil, detritus, heavy oil + quartz sands and heavy oil + detritus in atmosphere environment.


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Figure 4. DTG curves for heavy oil, detritus, heavy oil + quartz sands and heavy oil + detritus in atmosphere environment.


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Energy & Fuels

Figure 5. TG curves for light oil, quartz sands, and light oil + quartz sands in atmosphere environment.


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Figure 6. DTG curves for light oil, quartz sands, and light oil + quartz sands in atmosphere environment.

Figure 7. Kinetic parameters calculation for heavy oil alone by Arrhenius method.


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Figure 8. Kinetic parameters calculation for heavy oil + detritus by Arrhenius method.

Figure 9. Kinetic parameters calculation for light oil by Arrhenius method.


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Figure 10. Kinetic parameters calculation for light oil + quartz sands by Arrhenius method.


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Energy & Fuels

Table 1. The properties of the crude oil. sample heavy oil light oil a

viscosity at 50℃ (mPa·s) 6452 5.65

API (°)

density 3 (g/cm )

CCR (%)

17.92 42.55

0.947 0.813

9.82 3.43

saturated hydrocarbon 14.15 57.5

SARA fractions (%) aromatic resin hydrocarbon 44.31 13.53 31.75 4.89

asphaltene 28.01 5.86

sulphur content (%) 2.32 1.61

metal content(mg/L) Fe

Mg

Na

V

Ni

Al

Cu

104 0.65

45 0.57

1657 4.5

49

Characterizing the Fuel Deposition Process of Crude Oil Oxidation in

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