Estimation of Combustion Zone Thickness during In Situ Combustion

Energy & Fuels 1998, 12, 1153-1160

1153

Estimation of Combustion Zone Thickness during In Situ Combustion Processes Suat Bagci Petroleum and Natural Gas Engineering Department Middle East Technical University, 06531 Ankara, Turkey Received January 21, 1998

Dry and wet combustion runs were conducted using three different crude oils having 12.4, 19.8 and 28.4 °API gravity. Combustion zone thickness measurements were made with four stationary in-situ sampling gas probes installed on the combustion tube at 36, 48, 60, and 72 cm from the top flange. Experiments were carried out in a thin-walled vertical tube having a 12.4 cm diameter and 124.5 cm length. Adiabatic control of the combustion tube was achieved during dry and wet combustion tests using external band heaters and an adiabatic control system. The average air flux was 23.0 m3 (St)/(m2 h), and injected WAR changed from 0.209 to 0.607 m3/ Mm3(St). Experimental results showed that the average zone thickness was 80 mm for a dry combustion process while it was 50 mm for a wet combustion process. The combustion zone thickness decreased with increasing °API gravity of crude oils. With water injection, the combustion zone thickness decreased, as expected in a wet combustion temperature profile. Temperature and oxygen concentration data were used to evaluate the commonly used combustion reaction rate expression. The experimentally determined relationship between oxygen, combustion temperature, and reaction rate could not be represented by the commonly used first-order, Arrhenius-type reaction rate expression. Relative reaction rate data showed that dry combustion was kinetically controlled, whereas the wet combustion was oxygen-diffusion limited.

Introduction In-situ combustion is an enhanced oil recovery method that has been technically successful in many field applications. In this method, a combustion front supported by air injection is created and subsequently propagated through a reservoir. Most of the heat generated behind the combustion front is wasted due to heat losses to the overburden and underburden; as a result, heat is left unused in the burned out region. Figure 1 shows the series of zones typically associated with dry forward combustion.19 (1) Alexander, J. D.; Martin, W. L.; Dew, J. N. J. Pet. Techol. 1962, 14, 1154-1164. (2) Berry, H. J. An Experimental Investigation of Forward Combustion Oil Recovery. Ph.D. Dissertation, Texas A&M University, 1968. (3) Bousaid, I. S.; Ramey, H. J., Jr. Soc. Pet. Eng. J. 1968, 8, 137148. (4) Bousaid, I. S. Oxidation of Crude Oil in Porous Media. Ph.D. Dissertation, Texas A&M University, 1967. (5) Burger, J. G.; Sahuquet, B. C. J. Pet. Technol. 1973, 25, 11371146. (6) Dietz, D. N.; Weijdema, J. J. Pet. Technol. 1968, 20, 411-415. (7) Ejiogu, G. J.; Bennion, D. W.; Moore, R. G.; Donnelly, J. K. J. Can. Pet. Technol. 1979, 18, 58-66. (8) Fassihi, M. R.; Brigham, W. E.; Ramey, H. J., Jr. The Frontal Behaviour of In Situ Combustion. Presented at the 1980 California Regional Meeting of SPE of AIME, Los Angeles, CA, April 9-11, 1980; paper 8907. (9) Fassihi, M. R.; Brigham, W. E.; Ramey, H. J., Jr. Laboratory Combustion Tube Studies-Final Report. Report submitted to DOE; Stanford University Petroleum Research Institute: Stanford, CA, 1980; SUPRI TR-22. (10) Fassihi, M. R.; Ramey, H. J., Jr.; Brigham, W. E. Soc. Pet. Eng. J. 1984, 24, 399-416. (11) Garon, A. M.; Wygal, R. J., Jr. Soc. Pet. Eng. J. 1974, 14 (6), 537-544.

Figure 1. Characteristic regions of a detailed dry forward combustion process.19

Wet combustion improves the thermal efficiency of insitu combustion by scavenging residual heat stored behind the burning front. Figure 2 shows a typical schematic representation of different types of wet combustion processes. As shown in this figure, the thickness of the combustion zone may be affected by water injection in normal and optimal wet combustion processes. Injected water has moved some heat forward (12) Garon, A. M.; Geisbrecht, R. A.; Lowry, W. E., Jr. J. Pet. Technol. 1982, 34, 2158-2166. (13) Garon, A. M.; Kumar, M.; Lau, K. K.; Sherman, M. D. SPE Reservoir Eng. 1986, 1, 565-574. (14) Greaves, M.; Tuwil, A. A.; Bagci, A. S. J. Can. Pet. Technol. 1993, 32 (4), 58-67. (15) Greaves, M.; Al-Shamali, O. J. Can. Pet. Technol. 1996, 35, 4955. (16) Guvenir, I. M.; Vossoughi, S.; Willhite, G. P.; Kritikos, W. P.; El-Shoubary, Y. Soc. Pet. Eng. J. 1982, 22, 2158-2166. (17) Kumar, M.; Garon, A. M. SPE Reservoir Eng. 1991, 6, 55-61. (18) Martin, W. L.; Alexander, J. D.; Dew, J. N. J. Pet. Technol. 1958, 10 (2), 28-35. (19) Nelson, T. W.; McNeil, J. S. Oil Gas J 1959, 57, 86-89.

10.1021/ef980013m CCC: $15.00 © 1998 American Chemical Society Published on Web 09/01/1998

1154 Energy & Fuels, Vol. 12, No. 6, 1998

Bagci

Figure 2. Typical schematic representation of different types of wet combustion processes.6

to form a steam condensation front that has moved to the well ahead of the combustion front. Most of the displacement occurs at the condensation front.6 It is important that the laboratory in-situ combustion experiments simulate the conditions that actually exist in underground reservoirs. Thus, the sequence of events in the laboratory combustion tube must be similar to that experienced by a reservoir element during the approach of the combustion front. Laboratory combustion tube runs can be used to derive useful information about in-situ combustion. Experimental runs can be conducted to investigate the effects of such independent variables as air injection flux, pressure, fluid saturations, and crude oil properties on the peak combustion temperature, the rate of combustion front advance, fuel consumption, air requirement, oil recovery, and combustion zone thickness. The progress of the combustion front in an oil-sand-packed tube is followed using thermocouples located in the center of the sand pack. But combustion tube tests do not provide details of the combustion zone or information about the controlling mechanisms during in-situ combustion. The central processes of in-situ combustion are the chemical reactions and the associated rate expressions. The combustion tube is a much larger version of the reaction kinetics cell, packed with several kilograms of sample. This models the residence time distribution and flowing fluid effects better than the reaction cell or TGA methods. Not all of the oil originally packed is consumed by the chemical reactions; the temperature profile is no longer uniform across the tube length and neither is the reaction rate. The exit gas compositions thus correspond to a summation of the reaction rates across the tube lengthsthe data is in integral form and is not easily used for determining rate data. For the cracking and combustion reactions, it is normally assumed that these occur in a relatively narrow region that slowly moves down the combustion tube. The LTO reactions may occur across the length of the tube. Due to the differences in temperature along the combustion

Figure 3. Temperature, coke, oil, and water distributions in forward combustion.3

tube, different reactions may be occurring at different places along the tube at any time. An improvement of crude oil production by an insitu combustion process with linear combustion tube tests1,9,11,16 and 3-D physical model experiments12-15 has been studied in the laboratory by many investigators. Studies describing combustion zone thickness or parameters that influence it are very limited in the literature. The combustion zone is a small and complex region where high-temperature coking and combustion of fuel take place. The fuel here, also known as coke, is a residual oil that undergoes distillation and thermal cracking. The amount of fuel deposited on the sand varies with types of oil and rock. The concept of a combustion zone where fuel is deposited and consumed by a combustion zone has been studied extensively. One approach was to stop a combustion tube experiment and analyze the residual coked material. In such tests, Berry2 found that most of the coked material was deposited in a narrow band about 25.4 mm thick. A dynamic approach3 for determining the combustion zone from a probe placed inside the combustion tube gave an instantaneous measure of the fuel burning rate and temperature distribution. As the front passed the probe, the test results indicate that efficient combustion was limited to an interval of about 20 mm wide with the coke and fluid distribution shown in Figure 3. A similar study by Fassihi et al.8 reported combustion zone thickness measurements made with three stationary gas probes located in a combustion tube 201 mm away from the inlet. The CO2 concentration at these locations coupled with the peak temperature measure-

Estimation of Combustion Zone Thickness

Energy & Fuels, Vol. 12, No. 6, 1998 1155

Figure 4. Schematic diagram of the combustion tube apparatus.

ments were used to determine the combustion zone thickness. The average thickness from three measurements was 89 mm. Thomas et al.21 used a movable fluid and gassampling probe in a vertical combustion tube to evaluate the kinetics of fuel deposition and fuel combustion (HTO). The probe was manually moved to discrete positions about 38 mm apart, and gas samples were analyzed at 15 min intervals. Combustion zone thickness would be 127 mm or larger. Kumar and Garon17 used an automated, linear traversing, sampling probe to enable real-time gas analysis and temperature measurements within the combustion zone. Results showed that the combustion zone thickness was on the order of 25 mm for a nominal-injected air flux of 1.7 × 10-3 m3 (St)/(m2 s). For the same crude oil and same mesh size sand, the combustion zone thickness was smaller with Berea sand than with Ottawa sand. This finding implied that the combustion zone thickness was kinetically controlled and that the thinner combustion zone for Berea sand was caused by its larger specific surface area. This paper presents the experimental results of examining the combustion zone during dry and wet forward combustion processes. The investigation was designed to improve the understanding of the in-situ combustion process and to delineate the controlling mechanisms. The main objectives of this study were to measure the combustion zone thickness and the (20) Pusch, G. Erdoel-Erdgas Z 1976, 92 (1) 5-10. (21) Thomas, G. W.; Buthod, A. P.; Allag, O. An Experimental Study of the Kinetics of Dry Forward Combustion-Final Report; Report No. BETC-1280-1; DOE, Washington, DC, 1979.

variation of the oxygen concentration and temperature in the combustion zone and to evaluate combustion reaction kinetics and its importance with measured data. Additional gas-sampling probes were installed in the combustion tube for real-time gas analysis within the combustion zone. Experimental Section Equipment. A linear combustion tube (in a vertical position) was designed with the necessary heating devices, center and wall thermocouples, adiabatic control system, air and nitrogen flow rate control system, water injection system, pressure separators, pressure gauges, temperature scanner and digital indicator, and gas-sampling and analysis equipment. A schematic diagram of the combustion tube apparatus is shown in Figure 4. The fluid injection system was designed to inject air, nitrogen, and water into the combustion tube. It consists of an air filter, a flow transducer, a motorized control valve, pressure gauges and pressure transducers, water storage cylinders, and a water injection pump. The combustion tube was constructed from a stainless steel tube, and its dimensions are 124.5 cm in length, a 12.4 cm o.d., and a 1.5 mm wall thickness. The gas-sampling ports installed at different points on the combustion tube were used for gas sampling and analysis as the combustion front passed through those sections. For gas sampling from different sections of the combustion tube, the gas-sampling system was designed as shown in Figure 5. The gas-sampling system consists of specially designed gassampling ports, a pressure separator, a water condenser, a gas filter, a back-pressure regulator, a continuous CO2, CO, and O2 gas analyzer, and a wet test meter. Gas-sampling ports were installed on the combustion tube at 36, 48, 60, and 72 cm from the top flange. A liquid trap was mounted on one


Bagci

Figure 5. Schematic diagram of the gas-sampling system. end of the gas-sampling ports to prevent plugging of the sampling lines. The produced gases can pass through the liquid trap to the outside of the pressure jacket tube by the sampling line. After taking the condensate from the pressure separator, the pressure of the combustion tube was regulated by the back-pressure regulator, the gases produced were passed through the gas filter, and a needle valve was used to lower the gas pressure to the maximum operating pressure of the sample conditioner of the continuous gas analyzer. The exit gas from the continuous gas analyzer was combined in the wet test meter to measure the total gas production from the outlet of the combustion tube. Procedure. The crude oils for the combustion tube runs were from three different crude oil reservoirs in Turkey, namely, Adiyaman, Raman, and Camurlu. The properties of these oils are given in Table 1. The premixing method was used in preparing the sand pack mixtures for combustion runs. The properties of the packing data for combustion tube runs are given in Table 2. During the packing, the crushed limestone, crude oil, and water were mixed to yield the desired fluid saturations and carefully tamped into the combustion tube. The combustion tube was heated to approximately 60 °C, which was the reservoir temperature, and during this time, nitrogen was continuously injected. In wet combustion runs, water injection began as soon as the combustion front was established, as evidenced by the appearance of CO2 and CO in the produced gases and the development of combustion temperatures. Throughout the runs, gas samples were taken by gas-sampling ports on the combustion tube when the combustion front reached these ports and were continuously analyzed by a continuous gas analyzer.

Analysis and Discussion of Experimental Results Dry and wet combustion tube runs were performed using Adiyaman, Raman, and Camurlu crude oils in an unconsolidated linear pack. A total of eight combustion tube runs, four dry and four wet, were conducted. The following parameters were kept relatively constant during the combustion runs: porosity, permeability, air fluxes, and operating pressure. The experimental conditions of the wet and dry combustion runs are presented in Table 3. Temperature Profiles. The temperature profiles along the combustion tube for run DCA-2 and run WCA-3 are shown in Figures 6 and 7. Generally, combustion peak temperatures started with maximum

Table 1. Properties of Crude Oils Used in Combustion Tests crude oil

temp (°C)

specific gravity

viscosity (cp)

Camurlu (12.4 °API)

20

0.9981

64000

38 50 20

0.9831 0.9732 0.9422

17000 7000 52000

38 50 20

0.9351 0.9291 0.8950

6800 1800 64

38 50

0.8850 0.8750

30 17

Raman (19.8 °API) Adiyaman (28.4 °API)

values after stabilized combustion was achieved and finally decreased toward the outlet end of the tube. The drop in peak temperatures toward the outlet end of the tube is believed to be due to decreased fuel concentration per unit volume of sand pack, as little oil will be left due to sweeping of inplace oil by steam or hot gases ahead of the combustion front. In the wet combustion runs, the rate of the combustion reaction and, therefore, the rate of heat generation were reduced with a resultant drop in the peak temperatures. The wet combustion runs show that there is a lowering of the combustion front peak temperature, due mainly to the combined effect of external heat losses and in-situ-generated steam. The results reported by Burger and Sahuquet,5 Garon and Wygal,11 and Ejiogu et al.,7 however, had higher peak temperatures during wet combustion compared with dry combustion. This was attributed to the additional heat input to the combustion zone by the superheated steam that is produced when the injected water contacts the hot rock behind the combustion zone. The instantaneous temperature transverse data for all the probes from runs DCA-2 and WCA-3 are plotted as a function of time in Figures 8 and 9. The combustion zone temperatures at each sampling probe were observed to be higher than the average combustion peak temperatures. The combustion front position was followed from the peak temperature readings. The calculations were made during the period when combustion was stabilized, as indicated by uniform peak temperatures along the tube. The shape of the temperature profiles has been shown to be dependent on the heating schedule, air flux, and



Table 2. Packing Data for Combustion Tube Tests crude oil matrix API gravity pore volume, cc oil volume, cc water volume, cc porosity, % So, % Sw, % Sg, %

DCA-1

DCA-2

WCA-3

WCA-4

DCR-1

WCR-2

WCR-3

DCC-1

Adiyaman limestone 28.4 5965 3926 1326 40.0 66.0 22.0 12.0




Raman limestone 19.8 5965 3517 1264 40.0 58.9 21.2 19.9

Raman limestone 19.8 5965 3191 1065 40.0 53.5 17.9 28.7

Raman limestone 19.8 5965 3149 1082 40.0 53.0 18.0 21.0

Camurlu limestone 12.4 5965 4139 1724 40.0 69.0 20.0 11.0

Table 3. Experimental Conditions air injection pressure kPa permeability, darcies air injection rate, m3(St)/hr air flux, m3(St)/(m2 h) water injection rate, cm3/h injected WAR, m3/Mm3(St)

DCA-1

DCA-2

WCA-3

WCA-4

DCR-1

WCR-2

WCR-3

DCC-1

689 29 0.147 12.2 0.0 0.0

689 29 0.206 17.0 0.0 0.0

689 29 0.276 22.9 85.0 0.308

689 29 0.277 22.9 168.0 0.607

689 29 0.223 24.8 0.0 0.0

689 29 0.195 19.9 40.7 0.209

689 29 0.377 38.4 107.4 0.289

689 29 0.199 15.6 0.0 0.0

Figure 6. Temperature profile along the combustion tube (run, DCA-2).

Figure 8. Instantaneous temperature transverse data for all the probes (run, DCA-2).

Figure 7. Temperature profile along the combustion tube (run, WCA-3).

Figure 9. Instantaneous temperature transverse data for all the probes (run, WCA-3).

initial oil and water saturations. Because the temperature profiles reflect the oxidation kinetics, changes were apparent in both the maximum temperature and the axial extent of the elevated temperature region. Any alteration in the kinetics should also be apparent from the produced gas compositions. Produced Gas Compositions. The gases produced during the runs, from the outlet of the combustion tube, were analyzed using gas chromatography. The composition profiles of the produced combustion gas from runs DCA-2 and WCA-3 are shown in Figures 10 and 11. In

wet combustion runs, excess carbon dioxide production was recorded. The increase in CO2 production may be due to the conversion of CO to CO2 in the presence of steam at high temperatures or alternatively due to a steam reaction between fuel and the injected water in the presence of minerals of the matrix which could have catalytic effects. Figures 12 and 13 show the instantaneous gas compositions as a function of time for run DCA-2 at probe-2 and probe-3. As gas (air) traveled through the combustion zone, it lost oxygen and gained combustion reaction


Bagci

Figure 10. Composition profiles of the produced combustion gas (run, DCA-2).

Figure 12. Instantaneous gas compositions as a function of time at probe-2 (run, DCA-2).

Figure 11. Composition profiles of the produced combustion gas (run, WCA-3).

Figure 13. Instantaneous gas compositions as a function of time at probe-3 (run, DCA-3).

product gases (CO2, CO), and this is shown by the oxygen concentration. The fuel quantity increased in the same directionsfrom a negligible amount in the swept zone to higher levels inside the combustion zone. All the oxygen concentration profiles are similar in shape to those shown in Figures 12 and 13. The slopes of the curves are greatest near the leading edge of the combustion zone and decrease in the upstream direction. The oxygen profiles consistently indicate that the oxygen-consumption rate is highest near the leading edge of the combustion front; consequently, the reaction and fuel consumption rates are also highest there. Combustion Zone Thickness. Combustion zone thickness was calculated from the oxygen and carbon dioxide concentration profiles taken during each pass of the combustion front through the stationary gas sampling probes. When the combustion front reached gas sampling probe-1, the percentage of carbon dioxide increased to values near that observed at the end of the combustion tube toward a maximum. The produced gases from the outlet of the combustion tube represent a mixture of gases which passes through the combustion front at various temperatures. Since the gas-sampling probe was located halfway between the wall and the axis of the combustion tube, at this cross-section of the combustion tube, the combustion temperature would be higher than the average combustion temperature. Under ideal combustion conditions, the maximum temperatures are the same as the peak temperatures, where the peak temperature is defined as the localized maxi-

mum temperature associated with the leading edge. This is not the case for tests that exhibit energy generation in the swept zone, as the maximum temperatures may occur well after the leading edge passes a given location. Thus, the arrival time of the combustion front at the sampling probe (t1) was taken to be the time when the amount of carbon dioxide was at a maximum. When carbon dioxide reached zero percent volume of the probe gas, the combustion front had completely passed the sampling probe at time (t2). The required time for the combustion front to pass the gas-sampling probe is the difference between t1 and t2. To calculate the combustion zone thickness, this difference can be multiplied by the combustion front velocity. The center of the combustion zone is defined as the midpoint between the locations of the 10% and 90% maximum oxygen concentration, as schematically shown in Figure 14. After comparing data from all tests, the offset value between the combustion zone center and the peak temperature location was not statistically different from zero, i.e., the center of the combustion zone nearly coincides with the peak temperature. Table 4 summarizes the average combustion zone thickness for each run, and the average values were calculated using all sampling probe data. As seen in this table, the average combustion zone thickness is found to be 80 mm for a dry combustion process and 50 mm for a wet combustion process. With the water injection, the combustion zone thickness decreased, as expected, in the temperature profile of normal wet combustion.



Figure 14. Combustion zone definition. Table 4. Combustion Zone Thickness Values combustion API gravity combustion zone injected WAR type (°API) thickness (mm) (m3/Mm3(St)) DCA-1 DCA-2 WCA-3 WCA-4 DCR-1 WCR-2 WCR-3 DCC-1

DRY DRY WET WET DRY WET WET DRY

28.4 28.4 28.4 28.4 19.8 19.8 19.8 12.4

80.8 80.5 47.1 49.6 89.2 47.1 52.0 81.4

0.00 0.00 0.31 0.61 0.00 0.21 0.29 0.00

Reaction Rate in the Combustion Zone. The reaction between fuel and oxygen in the forward combustion process is a heterogeneous flow reaction. The combustion reaction is generally modeled with an Arrhenius-type equation with a first-order reaction dependence on both the oxygen partial pressure and fuel.3,10,22 The combustion zone is only a small part of the combustion tube, but within this zone, almost all of the oxygen is regarded as being consumed. Increasing the oxygen flow without increasing the specific reaction rate (the rate per unit volume) does not result in some of the oxygen not reacting. Instead, the combustion zone is enlarged and all the oxygen is consumed over this larger volume. Similarly, altering the specific reaction rate does not alter the overall oxygen consumption. Instead, the combustion zone thickness changes. Pressure appears to have no effect on the reaction rates because these rates are measured at the combustion tube exitsthey are the global rates not the specific rates. To accurately determine the specific rates, either the thickness of the combustion zone would have to be matched or the reaction rates within the zone would have to be measured, as done by Thomas et al.21 The experimentally obtained profiles shown in Figures 15 and 16 for oxygen concentration, combustion temperature, and relative reaction rate as a function of distance from the leading edge of the combustion zone, however, could not be satisfied by a first-order, Arrhenius-type reaction rate expression. This indicates that the combustion reaction may not be represented accurately by a first-order model. However, the activation energy for dry combustion runs shows a significant increase with the average combustion peak temperature. This indicates that for dry combustion, the reaction rate is kinetically controlled and gas diffusion (22) Thomas, F. B.; Moore, R. G.; Bennion, D. W. J. Can. Pet. Technol. 1985, 25, 60-67.

Figure 15. Relationships and the experimental temperature profile within the combustion zone (run, DCA-2 (probe-2)).

effects are minimal. In wet combustion there is a very significant reduction in the activation energy due to the increased rate of oxygen diffusion.


Bagci

this study is typical of a kinetically controlled process.20 This is in agreement with the findings of Bousaid4 and Fassihi et al.10 Bousaid reported that an increase in gas flux at a combustion temperature of 600 °C resulted in a small decrease in the reaction rate constant while it had a negligible effect at 480 °C. Fassihi et al. also found that an increase in the air injection rate twice that originally did not cause any change in the reaction rate constant, and as Bousaid concluded, the overall rate of the combustion process was kinetically controlled. In wet combustion, however, the activation energy is lower than for dry combustion. The lower activation energy in wet combustion is, therefore, mainly due to the increased role of oxygen diffusion. When the chemical reaction is no longer the controlling factor, the variation of the reaction rate constant with temperature becomes insignificant,18 which is precisely the case for the wet combustion reaction. It is, therefore, concluded that the chemical reaction rate is controlling during dry combustion but shifts to a gas diffusion-controlled mechanism in wet combustion. Pusch20 observed that the reaction rate in wet combustion (above 300 °C) was almost independent of temperature, that is, the chemical reaction rate does not control the process. According to Pusch, the presence of steam causes large areas of the fuel surface to be inaccessible to oxygen. Each oxygen molecule arriving at the free active sites of the fuel surface is then able to react with the carbon atoms. Hence, the overall rate of combustion is determined by the rate at which oxygen is able to diffuse to the fuel surface and not by chemical reaction rate. Conclusions

Figure 16. Relationships and experimental temperature profile within the combustion zone (run, WCA-3 (probe-3)).

The activation energy increases with a higher combustion front peak temperature and higher oxygen concentration. The increase of the activation energy with the average combustion peak temperature observed in

The combustion zone thickness was on the order of 80 mm for a dry combustion process, while it was 50 mm for a wet combustion process for an average air flux of 23.0 m3 (St)/m2-h. The combustion zone thickness decreased with increasing API gravity of crude oils. With the water injection the combustion zone thickness decreased, as expected in a temperature profile of normal wet combustion. The experimentally determined relationship between oxygen, combustion temperature, and reaction rate could not be represented by the commonly used first-order, Arrhenius-type reaction rate expression. Relative reaction rate data showed that dry combustion was kinetically controlled, whereas wet combustion was oxygen-diffusion limited. EF980013M

Estimation of Combustion Zone Thickness during In Situ Combustion

Recommend Documents