A Novel Air Flooding Technology for Light Crude Oil Reservoirs

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Cite This: Energy Fuels XXXX, XXX, XXX−XXX

A Novel Air Flooding Technology for Light Crude Oil Reservoirs Applied under Reservoir Conditions Tengfei Wang,* Jiexiang Wang, Weipeng Yang, Shem Kalitaani, and Zhiyu Deng Institute of Petroleum Engineering, China University of Petroleum (East China), Qingdao, Shandong 266580, People’s Republic of China ABSTRACT: A novel air flooding technology based on catalyst-activated low-temperature oxidation (CLTO) has been researched by static and dynamic oxidation experiments and can be applied in light crude oil reservoirs under reservoir conditions to improve the safety and oil recovery of air flooding. The catalytic effect of additives on the oxidation behavior of three crude oils was researched. The changes in oil recovery, oxygen distribution, and oil characteristics caused by additives were researched by dynamic oxidation experiments, and the influences of crude oil types, additive injection pattern, injection volume, and injection time on the catalytic effect were also researched. The results show that metallic additives can improve the oxygen consumption capacity of crude oils. Furthermore, the addition of additives can delay the oxygen breakthrough time and reduce the oxygen content in the gas produced. During the catalytic air flooding, the oxygen injected reacts mainly with the residual oil near the injection wells, and the influence of CLTO on the properties of oil produced from light oil reservoirs is minor. The key point to guarantee the success of catalytic air flooding is to select the optimal catalyst for the reservoir oil. The preferred catalyst injection pattern is catalyst alternating air injection, and the recommended catalyst injection volume is 0.03−0.05 PV. Catalytic air flooding technology can improve the safety and widen the application of air flooding technology.

1. INTRODUCTION Due to the advantages of the low cost and unlimited availability of air, the air flooding technology has been widely researched and applied in recent decades. In the oilfields of Zhongyuan, Baise, MPHU, West Hackberry, Coral Creek, Ekofisk, Buffalo, and Horse Creek, pilot air flooding applications have been successfully used and have achieved remarkable results.1−13 Apart from in situ combustion (ISC) technology, the main mechanism of air flooding is actually indirect flue gas flooding. The flue gas will be generated during the oxygen consumption process through lowtemperature oxidation (LTO) reaction, and the flooding gas during air injection process is actually the generated flue gas.14−16 At present, the main problem restricting the application of air flooding is the application safety: the breakthrough of oxygen into the production wells will cause an explosion risk. The main solution usually used is increasing the well spacing to prolong the LTO reaction time, but it is tough work to adjust the well pattern. Therefore, a novel air flooding technology is put forward in order to improve the flooding safety and development result, as this method can increase the oxygen consumption rate of crude oil without changing the well pattern under reservoir temperatures and pressures. The catalytic air flooding technology researched in this work is based on catalyst-activated low-temperature oxidation (CLTO) technology, which is a relatively new application in light crude oil reservoirs at reservoir temperatures. In recent years, the researches on the catalytic oxidation reaction of crude oil have mainly focused on catalytic hightemperature oxidation (in situ combustion) technology, which aims to adjust the amount of coke deposited on rock and control the propulsion speed of the combustion front. The research procedures and results of previous studies17−27 of catalytic oxidation technology are summarized in Table 1. As shown in Table 1, the catalytic oxidations of both heavy and light crude oils have been investigated by many researchers © XXXX American Chemical Society

before, but all the researches above were conducted at temperatures above 120 °C. Hence, the catalytic air flooding technology (CAFT) for light crude oil reservoirs applied under reservoir conditions has seldom been reported in the published literature. In light of the good catalytic performance of metallic elements,28−31 this paper studied the catalytic low-temperature oxidation performance of copper naphthenate, manganese naphthenate, and cobalt naphthenate on light crude oils under reservoir conditions. Additionally, the influence of crude oil type, additive injection pattern, injection volume, and injection time on the catalytic effect was researched with dynamic oxidation experiments. The changes in oil characteristics and oxygen distribution due to CLTO were investigated based on SARA composition tests, element analysis, and gas chromatograph analysis.

2. EXPERIMENTAL SECTION 2.1. Experimental Device and Material. The static oxidation experimental device was used to research the oxygen consumption capacity of crude oils, and this device is composed of an oil bath, an oxidation tube, a heater, a precision pressure gauge, a six-way valve, a gas chromatograph (Agilent 7890A), and a high pressure air source (Figure 1). The oxidation tube is a stainless steel cylinder, lined with polytetrafluoroethylene. The dynamic oxidation experimental device is composed of three subsystems: injection subsystem, oxidation subsystem, and detection subsystem (Figure 2). The injection subsystem consists of an advection pump and several transfer vessels containing formation water, crude oil, and high pressure air. As the reaction zone for LTO, the oxidation subsystem is the central part of the experimental device. This subsystem is an 18 m long oxidation tube containing 18 sand packs Received: January 23, 2018 Revised: March 29, 2018 Published: March 29, 2018 A

DOI: 10.1021/acs.energyfuels.8b00302 Energy Fuels XXXX, XXX, XXX−XXX

combustion cell experiments

combustion tube experiments

combustion cell experiments

combustion tube experiments

differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) combustion tube experiments and ramped temperature oxidation tests thermogravimetric testing

ramped temperature oxidation experiments; isoconversional analysis; thermogravimetric analysis

Shallcross et al.22

Ramirez et al.17,18

Fassihi et al.24,25

Castanier et al.19

Drici et al.20

B

Amanam et al.27

Pu et al.26

He et al.21

combustion reaction kinetics experiments

research procedure

Bagci et al.23

researcher

Zuata crude oil (9.8°API)

Tahe heavy crude oil (18.9°API)

heavy (12°API) and light (34°API) oil from Cymric

San Ardo oil (11.2°API), Venezuela oil (9.5°API), Huntington Beach oil (18.5°API), Lynch Canyon oil (10°API) Huntington Beach oil (22°API), Hamaca oil (10°API), Cymric heavy oil (12°API), Cymric light oil (34°API) crude oil from the Iola field (19.8°API)

Karakus (29°API) and Beykan (32°API) crude oils from Turkish oil fields Californian (18.5°API) and Venezuelan (10.5°API) oils heavy oil (12.5°API) from Gulf of Mexico

crude oil used

Additives such as Fe, Sn, and Zn, but the anionic part of the salt was not reported.

Heavy metal oxides such as titanium, ferric, nickel, cupric, vanadium, and chromium oxides

Fe(NO3)3

ZnSO4, CuCl2, FeCl2, and AlCl3·6H2O

copper nanoparticles

Ignition temperature: 315 °C, Pressure: 690 kPa

Temperature was increased to 600 °C at a rate of 10 °C/h at atmospheric pressure

Tube experiments: 400 °C and 690 kPa; RTO tests: Temperature was increased to 470 °C at a rate of 60 °C/h at pressures of 690, 550, or 310 kPa Temperature was increased to 800 °C at a rate of 10 °C/min at atmospheric pressure

Temperature was increased to 600 °C at a rate of 1−3 °C/min at atmospheric pressure

Temperature was increased to 450 °C at a rate of 55 °C/h at pressures of 690, 550, or 138 kPa

Ignition temperature: 300 °C, Pressures: 2070 kPa

FeCl2, SnCl2, CuSO4, ZnCl2, MgCl2, K2Cr2O7, Al2Cl3, MnCl2, Ni(NO3)2, and CdSO4 Additives such as Mo, Co, Ni, Fe, and the anionic part of the salt was acetylacetonate, or alkylhexanoate. Additives such as Cu, Ni, Va, Fe, but the anionic part of the salt was not reported.

Temperature was increased to 450 °C at a rate of 50 °C/h at pressures of 280 or 550 kPa

additives used CuCl2, FeCl3, and MgCl2

The cell was heated to 500−600 °C with 1 °C/min heating rate at pressures of 172 or 345 kPa

experiment condition (temperature/pressure)

Table 1. Summary of Previous Research on Catalytic Oxidation Technology main results

The combustion reaction catalytic mechanism was cation exchange of metallic salts with clay to create activated sites that enhance combustion reactions between oil and oxygen. The combustion of light oil could also be improved by metallic additives. Metallic additives exhibit varied catalytic effects on heavy oil oxidation. CuCl2 is found to be an excellent catalyst for upgrading the performance of an air injection project through positively influencing the oxidation reactions of Tahe heavy crude oil. The apparent activation energy of the high-temperature oxidation region decreased. The presence of Cu-NP helps maintain a greater front temperature. Cu-NP changes the type of oil produced and decreases the amount of water created during the process.

The effect of titanium oxide was similar to that of silica and alumina. Vanadium, nickel, and ferric oxides behaved similarly in enhancing the endothermic reactions. The effect of small amount of metal oxide was weak in the presence of a large surface area such as with silica.

The combustion efficiency and front velocities could all be improved by the metallic additives, and also H/C ratio of the fuel, heat of combustion, air requirements, and density of the crude produced could be changed after the addition of metallic salts.

Iron and tin salts could enhance fuel formation, while copper, nickel, and cadmium salts had no significant effects. The addition of metallic additives could accelerate the propagation velocity of the combustion front, improve combustion efficiency, and increase the oil production. The additives could lower the activation energy of the combustion reaction and lower the temperature at which the combustion reaction occurred under the same reservoir conditions.

The catalyst type and concentration had a great influence on the kinetic parameters (reaction order and activation energy) of high temperature oxidation.

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the inlet, the distance between the inlet and the first sampling site then the second one is 6 and 12 m, respectively. Additionally, the outlet of the oxidation tube is used as the third sampling site. The detection subsystem is composed of a back pressure regulator, a gas−liquid separator, and a gas chromatograph. The gas and oil samples can be taken from the sampling sites and then tested for composition changes at any desired time. Three light crude oils produced from different reservoirs in China are used to conduct the catalytic air flooding technology (CAFT) research: Dong 69-57 and An 234-47 crude oil from the Dongzhi and An 83 reservoirs, respectively, in the Changqing oilfield and SW 10-14 crude oil from the Shiwu reservoir of the Northeast Oil and Gas Company. The initial crude oil characterization is shown in Table 2. The formation water corresponding to the oil used was applied in the dynamic oxidation experiments. The organometallic additives used are copper naphthenate, manganese naphthenate, and cobalt naphthenate. The concentration of the metallic additives used in this study was 0.08 mol/L.

Figure 1. Schematic of the static oxidation experimental device (oxidation tube volume is 100 mL). connected to each other; each sand pack is 100 cm long and has an inner diameter of 1 cm. There are two sampling sites arranged along the long oxidation tube with a uniform interval space. Starting from

Figure 2. Schematic of the dynamic oxidation experimental device.

Table 2. Initial Crude Oil Characterization crude oil type

SARA composition/% (saturate/aromatics/resin/asphaltene)

density/(g/cm3)

viscosity at 70 °C/(mPa·s)

Dong 69-57 An 234-47 SW 10-14

70.91/16.07/9.78/3.24 66.50/18.16/10.78/4.55 68.18/17.56/10.28/3.99

0.850 0.876 0.860

2.14 4.62 3.16

Table 3. Influence of Additives on the LTO of Crude Oils at 70 °C and 16 MPa experimental parameters pure crude oil

crude oil + copper naphthenate

crude oil + manganese naphthenate

crude oil + cobalt naphthenate

O2/CO2 content after reaction /% SARA composition after reaction/% aromatics/resin/asphaltene) reaction rate/(mol O2/d·m3[oil]) O2/CO2 content after reaction /% SARA composition after reaction/% aromatics/resin/asphaltene) reaction rate/(mol O2/d·m3[oil]) O2/CO2 content after reaction /% SARA composition after reaction/% aromatics/resin/asphaltene) reaction rate/(mol O2/d·m3[oil]) O2/CO2 content after reaction /% SARA composition after reaction/% aromatics/resin/asphaltene) reaction rate/(mol O2/d·m3[oil])

Dong 69-57

SW 10-14

An 234-47

(saturate/

19.17/0.24 67.77/13.95/13.21/5.07

18.55/0.21 67.06/16.76/11.53/4.65

18.48/0.16 65.56/17.43/11.96/5.05

(saturate/

53.37 16.27/0.77 66.31/12.73/14.58/6.07

65.25 6.73/1.19 61.64/12.90/16.35/6.69

71.41 10.92/1.20 62.33/14.44/15.32/6.16

(saturate/

154.35 14.01/1.07 65.43/12.09/15.32/6.16

248.10 5.69/1.33 61.16/12.56/16.79/6.89

223.82 7.80/1.19 61.04/13.29/16.72/6.65

(saturate/

204.46 10.76/1.67 64.56/11.61/16.08/6.14

262.64 3.96/1.40 60.37/11.99/17.53/7.22

276.10 5.81/1.50 60.22/12.56/17.61/6.97

271.69

285.91

309.75

C


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Energy & Fuels 2.2. Experimental Procedure. 2.2.1. Static Oxidation Experiment. The catalytic effect of the additives on the oxygen consumption capacity of three light oils was researched by using static oxidation experiments. After checking the integrity of the system, the oxidation tube was filled with crude oil or the additive-added oil; then the tube was heated to 70 °C and maintained for half an hour to reach thermal equilibrium. After that, the reactor was filled with air (21% oxygen, 79% nitrogen) until the pressure reached 16 MPa. The pressure in the tube was recorded during the experiment. The experiment was stopped when the pressure no longer changed, and the changes in the gas and oil composition were analyzed. The volume ratio of air to oil

was 7:9 for blank runs and 8:7 for CLTO runs. The LTO reaction rate is determined by the material balance method. The amount of oxygen consumed during LTO could be obtained from the changes in gas pressure and composition before and after the reaction. The compressibility factor was calculated by applying the Key mixing rule and the P-R equation.32 The additives dispersion procedure: The dehydrated crude oil was heated to 80 °C under a nitrogen atmosphere, and the catalyst precursor was dispersed in crude oil using an ultrasonic disperser. 2.2.2. Dynamic Oxidation Experiment. During air flooding, the contact of oxygen and crude oil is a dynamic process,16 so the dynamic oxidation experiments were conducted to investigate the safety and EOR potential of catalytic air flooding technology (CAFT). First, sand with an average diameter of 125−149 μm was packed inside the 18 sand packs, and then the sand packs were saturated with formation water and oil successively. Second, the long oxidation model was assembled by connecting the 18 sand packs in a lamellar arrangement. Third, a back pressure regulator at 16 MPa was connected to the outlet of the oxidation model, and high-pressure air was pumped into the model at a rate of 0.01 mL/min. The experiment was stopped when the outlet no longer produced oil. The experimental temperature was 70 °C. During the experiment, the gas and oil samples were collected from the sampling sites and the changes in oxygen distribution and oil characteristics were analyzed.

3. RESULTS AND DISCUSSION 3.1. Catalytic Effect of Metallic Additives. The catalytic effect of the additives on the oxygen consumption capacity of different oils at 70 °C and 16 MPa is shown in Table 3. The SARA is an acronym for a group of analytical procedures that separate oil, mainly by liquid chromatography, into fractions called saturate, aromatics, resin, and asphaltene.33 SARA fractions have been used to research the crude oil oxidation reactions in several previous studies.34−37 The oil SARA composition was analyzed according to NB/SH/T 0509-2010 in this research. The oxygen consumption capacities of the three crude oils were different; the oxidation rates of crude oils at 70 °C and 16 MPa were as follows: An 234-47 > SW 10-14 > Dong 69-57. The additives researched can improve the oxygen consumption capacity of the crude oils significantly, especially the cobalt naphthenate, which increases the oxygen consumption rate by more than 4.3 times. Massive amounts of oxygen were consumed, and some carbon dioxide was generated, confirming the coexistence of oxygen addition reactions and bond scission reactions during the LTO process.14 After the addition of additives, the oxygen consumed and carbon dioxide generated both increased, indicating that the additives can promote both the oxygen addition reaction and bond scission reaction. Table 4. Changes in the Oil Characteristics during CAFT oil sample oil from the first sampling site isolated oil around the first sampling site oil from the second sampling site isolated oil around the second sampling site oil from the third sampling site isolated oil around the third sampling site

Figure 3. Changes in oil recovery and oxygen distribution in dynamic oxidation experiments (experiment conditions: 70 °C and 16 MPa; crude oil: Dong 69-57; additive: cobalt naphthenate; L = 6 m, L = 12 m, and L = 18 m correspond to the first sampling site, the second sampling site, and the outlet, respectively). D

SARA composition/% (saturate/aromatics/resin/ asphaltene)

element analysis/% (C/H/N/O)

68.56/15.25/11.56/4.63

83.13/11.16/0.27/0.69

65.62/11.80/16.34/6.24

83.06/11.12/0.29/1.34

70.88/16.01/9.83/3.28

83.15/11.17/0.26/0.34

69.66/15.72/10.60/4.02

83.14/11.17/0.27/0.43

70.90/16.05/9.79/3.26

83.15/11.18/0.26/0.33

70.72/15.96/9.95/3.37

83.15/11.17/0.26/0.35


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3.2. Dynamic Oxidation Experiment Results. Two dynamic oxidation experiments were conducted to research the catalytic effect of metallic additives under flow conditions. The changes in oil recovery, oxygen distribution, and oil characteristics in the oxidation tube were mainly analyzed. The difference between the two experiments was the oil samples used: one with pure Dong 69-57 crude oil and another with additive added crude oil. 3.2.1. Oil Recovery. Figure 3a shows the relation curve of air injection volume versus oil recovery efficiency. With the injection of air, the oil recovery increased gradually and then tended to be stable, but the gas breakthrough time was delayed and the ultimate oil recovery was increased by 4.7% after adding cobalt naphthenate. The reasons were as follows: (1) The oxygen consumption capacity of crude oil was enhanced dramatically by cobalt naphthenate; therefore, the actual gas flooding rate of the CAFT experiment was smaller than that of the LTO experiment, so the CAFT experiment had a weaker gas fingering problem. (2) More carbon oxides were generated after adding cobalt naphthenate, which can enhance the oil recovery by reducing the viscosity and expanding the volume of crude oil.40 (3) Traces of insoluble solid20,21 deposited on the micropore surface reduced the gas channeling and enhanced the oil recovery. 3.2.2. Changes in the Oxygen Distribution. Figure 3b,c shows the oxygen distribution in the oxidation tube during air flooding and catalytic air flooding. The oxygen content

The oil SARA composition was changed by the LTO. A decrease in the saturate and aromatics content was accompanied by an increase in the resin and asphaltene content. Similar behavior was observed by Ranjbar.38 The use of additives, especially cobalt naphthenate, can magnify the changes in the SARA composition. A black toluene insoluble was found in the oil sample after CLTO with cobalt naphthenate. This product was caused by the limited asphaltene solubility of crude oil, and the excessive asphaltene generated during LTO was precipitated out and formed the toluene insoluble.39 According to the above results, the metallic additives have a good catalytic effect on the oxygen consumption capacity of crude oils from different reservoirs, so the CAFT is a viable technology to improve the safety of air flooding. Table 5. Influence of Crude Oil Type on the Oil Recovery of Air Flooding oil sample Dong 69-57 crude oil Dong 69-57 + catalyst An 234-47 crude oil An 234-47 + catalyst SW 10-14 crude oil SW 10-14 + catalyst

permeability (10−3 μm2)

oil recovery at gas breakthrough (%)

oil recovery of air flooding (%)

453

25.7

34.1

461

29.8

38.8

468 445 458 466

27.2 31.7 26.5 32.3

36.0 42.5 35.3 41.5

Figure 4. Influence of oil type on the oxygen distribution of air flooding. E


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Energy & Fuels decreased gradually from the inlet to the outlet. After the addition of the catalyst, the oxygen contents at each sampling site all decreased significantly, and the oxygen breakthrough time was delayed. At the end of air injection, the oxygen content at the outlet was reduced to 6.9% from 14.1% due to the catalyst. So the addition of metallic catalyst during air flooding in light oil reservoirs can improve the air flooding safety significantly. In addition, the use of catalysts can broaden the application of air flooding, and the reservoirs with low reaction activity, which were previously unsuitable for air flooding, can be developed by applying catalytic air flooding. 3.2.3. Changes in the Oil Characteristics. The SARA compositions and element distributions of six oil samples were analyzed to investigate the influence of CLTO on the oil characteristics. Three samples were produced from the three sampling sites when the air injection volume was 0.4 PV. The other three samples were separated from the sand matrix corresponding to the sampling sites. The isolation method was based on the method of Freitag et al.41 involving the application of toluene and roto-evaporation. The device used for the oil element analysis was an Elementar Vario EL elemental analyzer. The results are shown in Table 4. The oil characteristics near the inlet changed considerably during the CAFT process. The content of resin and asphaltene increased, and the oxygen element content also increased. However, the characteristics of the oil samples corresponding to the second site and the outlet were almost the same as the original crude oil, especially for the flowing oil samples produced from the two sites. Thus, when CAFT is applied, the influence of CLTO on the properties of the oil produced from light oil reservoirs is minor. The oxygen injected reacts mainly with the residual oil (oil that cannot be produced) near the injection wells. This finding is consistent with the viewpoint of Niu et al.16 So during the CAFT process, although the catalyst will increase the oxidation degree of the residual oil when enhancing the oxygen consumption, the advantages of an oxidation catalyst far outweigh the disadvantages. 3.3. Influence Factors Affecting CAFT. 3.3.1. Crude Oil Type. The influence of crude oil type on CAFT was analyzed using Dong 69-57, An 234-47, and SW 10-14 crude oils (Table 5, Figure 4). Cobalt naphthenate was added to the oil samples used in the CAFT experiments. The crude oil type had a significant effect on the application result of the catalyst. The addition of a catalyst can improve the oil recovery. For An 234-47, SW 10-14, and Dong 69-57 crude oil, the oil recovery was increased by 6.5%, 6.2%, and 4.7%, respectively, due to the catalyst. These values are consistent with the CLTO reaction rate order in the static oxidation experiments. The oxygen contents at the outlet of the An 234-47 and SW 10-14 CAFT experiments were below 1%, so the safety of air flooding is greatly improved. The selection of the proper catalyst for the reservoir oil is a vital factor when applying CAFT. 3.3.2. Catalyst Injection Pattern. Two injection patterns were researched: catalyst continuous injection and catalyst alternating air injection (Table 6, Figure 5). The oil used was

Figure 5. Influence of the catalyst injection pattern on the oxygen distribution of air flooding.

An 234-47 crude oil, the catalyst used was cobalt naphthenate, and the catalyst injection volume was 0.05 PV. In the catalyst alternating air injection experiment, the ratio of catalyst to air was 1:8, and the catalyst was injected in three cycles. The catalyst injection pattern can affect the flooding result but not significantly. The oil recovery of catalyst alternating air injection is only 1.6% more than that of catalyst continuous injection, and the difference in outlet oxygen content is only 0.77%. For both injection patterns, the reduction in the oxygen content between the inlet and the first sampling site is the most obvious, indicating the significant oxygen consumption efficiency in this region. 3.3.3. Catalyst Injection Volume. The crude oil used was An 234-47, and the cobalt naphthenate injection volumes researched were 0.03 PV, 0.05 PV, and 0.07 PV. The catalyst injection pattern was catalyst alternating air injection. The results are shown in Table 7 and Figure 6. Table 7. Influence of the Catalyst Injection Volume

Table 6. Influence of the Catalyst Injection Pattern injection pattern continuous injection alternative injection




463

28.8

38.2

451

30.2

39.8

injection volume




0.03 0.05 0.07

469 451 447

27.9 30.2 30.0

37.5 39.8 40.4

When the injection volume increased from 0.03 PV to 0.05 PV, the oil recovery increased by 2.3% and the outlet oxygen F


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the proper injection time of CAFT. When the water cut reached 0% (no water injection, only catalytic air flooding), 30%, and 60%, catalytic air flooding was carried out instead of water flooding. The crude oil used was An 234-47, and the cobalt naphthenate injection volume was 0.05 PV. The catalyst Table 8. Influence of the CAFT Injection Time injection time pure catalytic air flooding water cut 30% water cut 60%


oil recovery of oil recovery at water flooding gas breakthrough (%) (%)

453 443 468

27.6 33.2

total oil recovery (%)

29.8

39.4

36.6 37.9

44.6 41.3

Figure 6. Influence of the catalyst injection volume on the oxygen distribution of air flooding.

content decreased by 2.5%. In contrast, when the injection volume increased from 0.05 PV to 0.07 PV, the oil recovery increased by only 0.6%, and the oxygen content decreased by only 0.73%. So, for field applications, the recommended catalyst injection volume is 0.05 PV. The catalytic efficiency of the catalyst in the oxidation of crude oil is high,28−31 so increasing the catalyst concentration in situ has a weak effect. Therefore, when applied in the field, the main focus should be increasing the contact surface between the catalyst and the crude oil rather than simply increasing the catalyst injection volume. 3.3.4. CAFT Injection Time. Air flooding can also be used to develop water-flooded reservoirs,42 so it is necessary to research

Figure 7. Influence of the CAFT injection time on the oxygen distribution of air flooding. G


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(4) Fassihi, M. R.; Gillham, T. H. The use of air injection to improve the double displacement processes. In SPE Annual Technical Conference and Exhibition, Houston, TX, Oct 3−6, 1993; Society of Petroleum Engineers, 1993; SPE 26374. (5) Gillham, T. H.; Cerveny, B. W.; Turek, E. A.; Yannimaras, D. V. Keys to increasing production via air injection in Gulf Coast light oil reservoirs. In SPE Annual Technical Conference and Exhibition, San Antonio, TX, Oct 5−8, 1997; Society of Petroleum Engineers, 1997; SPE 38848. (6) Turta, A. T.; Singhal, A. K. Reservoir engineering aspects of oil recovery from low permeability reservoirs by air injection. In SPE International Oil and Gas Conference and Exhibition in China, Beijing, China, Nov 2−6, 1998; Society of Petroleum Engineers, 1998; SPE 48841. (7) Glandt, C. A.; Pieterson, R.; Dombrowski, A.; Balzarini, M. A. Coral Creek field study: A comprehensive assessment of the potential of high-pressure air infection in a mature waterflood project. In SPE Mid-Continent Operations Symposium, Oklahoma City, OK, March 28− 31, 1999; Society of Petroleum Engineers, 1999; SPE 52198. (8) Adetunji, L. A.; Teigland, R. Light-oil air-injection performance: Sensitivity to critical parameters. In SPE Annual Technical Conference and Exhibition, Dallas, TX, Oct 9−12, 2005; Society of Petroleum Engineers, 2005; SPE 96844. (9) Stokka, S.; Oesthus, A.; Frangeul, J. Evaluation of air injection as an IOR method for the Giant Ekofisk Chalk Field. In SPE International Improved Oil Recovery Conference in Asia Pacific, Kuala Lumpur, Malaysia, Dec, 5−6, 2005; Society of Petroleum Engineers, 2005; SPE 97481. (10) Gutierrez, D.; Kumar, V. K.; Moore, R. G.; Mehta, S. A. Air injection and waterflood performance comparison of two adjacent units in the Buffalo Field. SPE Reserv. Eval. Eng. 2008, 11 (5), 848− 857. (11) Kumar, V.; Gutierrez, D.; Thies, B. P.; Cantrell, C. 30 years of successful high-pressure air injection: Performance evaluation of Buffalo Field South Dakota. In SPE Annual Technical Conference and Exhibition, Florence, Italy, Sept, 19−22, 2010; Society of Petroleum Engineers, 2010; SPE 133494. (12) Gutierrez, D.; Kumar, V.; Moore, R. G.; Mehta, S. Case history and appraisal of the West Buffalo Red River Unit high-pressure air injection project. In Hydrocarbon Economics and Evaluation Symposium, Dallas, TX, April 1−3, 2007; Society of Petroleum Engineers, 2007; SPE 107715. (13) Germain, P.; Geyelin, J. L. Air injection into a light oil reservoir: The Horse Creek Project. In Middle East Oil Show and Conference, Bahrain, March 15−18, 1997; Society of Petroleum Engineers, 1997; SPE 37782. (14) Ren, S.; Greaves, M.; Rathbone, R. R. Air injection LTO process: an IOR technique for light-oil reservoirs. SPE J. 2002, 7 (1), 90−99. (15) Greaves, M.; Ren, S.; Rathbone, R. R. Air injection technique (LTO Process) for IOR from light oil reservoirs. In SPE/DOE Improved Oil Recovery Symposium, Tulsa, OK, April 19−22, 1998; Society of Petroleum Engineers, 1998; SPE 40062. (16) Niu, B.; Ren, S.; Liu, Y.; Wang, D.; Tang, L.; Chen, B. Lowtemperature oxidation of oil components in an air injection process for improved oil recovery. Energy Fuels 2011, 25 (10), 4299−4304. (17) Ramirez-Garnica, M. A.; Mamora, D. D.; Nares, R.; SchachtHernandez, P.; Mohammad, A. A.; Cabrera, M. Increase heavy-oil production in combustion tube experiments through the use of catalyst. In Latin American & Caribbean Petroleum Engineering Conference, Buenos Aires, Argentina, April 15−18, 2007; Society of Petroleum Engineers, 2007; SPE 107946. (18) Ramirez-Garnica, M. A.; Hernandez Perez, J. R.; Cabrera-Reyes, M. D. C.; Schacht-Hernandez, P.; Mamora, D. D. Increase oil recovery of heavy oil in combustion tube using a new catalyst based on nickel ionic solution. In International Thermal Operations and Heavy Oil Symposium, Calgary, Alberta, Canada, Oct 20−23, 2008; Society of Petroleum Engineers, 2008; SPE 117713.

injection pattern was catalyst alternating air injection. The results are shown in Table 8 and Figure 7. The CAFT can improve the oil recovery of water-flooded reservoirs, especially when applied at the initial stage of water breakthrough. Therefore, when the CAFT is applied in waterflooded reservoirs, the catalyst injection time should be early, and it is best applied before the water cut reaches 30%. This is because the water-channeling path formed during water flooding is also the gas-channeling path when applying CAFT, resulting in a decrease in the gas sweep efficiency43 and a decrease in the oxygen breakthrough time.

4. CONCLUSIONS (1) Metallic additives can improve the oxygen consumption capacity of crude oils significantly. During the LTO process, the oxygen addition reaction coexists with the bond scission reaction. The content of saturate and aromatics decreases, and the content of resin and asphaltene increases. The use of a catalyst can magnify the changes in the SARA composition. (2) When the CAFT is applied, the influence of CLTO on the properties of oil produced from light oil reservoirs is minor. The oxygen injected reacts mainly with the residual oil near the injection wells. During the CAFT process, the advantages of an oxidation catalyst far outweigh the disadvantages. (3) The addition of a catalyst can improve the oil recovery and the safety of air flooding. The selection of the proper catalyst for the reservoir oil is a vital factor when applying CAFT. The preferable catalyst injection pattern is catalyst alternating air injection, and the recommended catalyst injection volume is 0.03−0.05PV. (4) The catalytic air flooding technology can be applied in water-flooded reservoirs, but the catalyst injection time should be early and is best before the water cut reaches 30%.

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Corresponding Author

*E-mail: [email protected]. Tel.: +86-15966916346. ORCID

Tengfei Wang: 0000-0002-9181-627X Weipeng Yang: 0000-0002-9920-581X Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The financial support received from the “Shandong Provincial Natural Science Foundation, China” and “The Fundamental Research Funds for the Central Universities” is gratefully acknowledged.

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REFERENCES

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Article

Energy & Fuels

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A Novel Air Flooding Technology for Light Crude Oil Reservoirs

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