Combustion Tube Research Articles

OPTIMIZATION OF PROCESS PARAMETERS FOR A SOLID-STATE-WELDED AISI 430 STEEL JOINT WITH THE GRG REINFORCED RESPONSE SURFACE METHODOLOGY

High-temperature applications such as heat exchangers and burner tubes employ AISI 430 steel. A larger heat-affected zone, undesired metallurgical changes and higher hardness in the weld area occur when fusion welding this type of steel. The study investigates the feasibility of welding ferritic stainless steel AISI 430, utilizing a solid-state method (continuous drive friction welding). The experiment uses an L27 orthogonal array and three levels of variation in the welding parameters such as frictional pressure, forging pressure, friction time, forging time and rotational speed. Tensile strength, axial shortening and impact toughness are the observed quality characteristics. In an integrated approach of the grey incidence reinforced response surface methodology, the benefits of the grey relational theory are merged with the statistical analysis of the response surface methodology to determine the ideal friction welding inputs (frictional pressure – 59.95 MPa, friction time – 4 s, upset pressure – 68.5 MPa, forging time – 3 s and rotational speed – 1399 min–1). The AISI 430 steel joint’s qualities are improved by 2.25, 12.74 and 7.89 % in terms of the maximum ultimate tensile strength, axial shortening and impact toughness, respectively.

Investigation into the key factors influencing the establishment and propagation of combustion front in ultra-deep high-temperature heavy oil reservoirs

The in-situ combustion technique is currently on the exploratory stage for ultra-deep high-temperature heavy oil reservoirs. In this work, the oxidation experiments of heavy oil were conducted using thermogravimetry, high-pressure differential scanning calorimetry, and combustion tube. Based on these experimental results, a reaction kinetics model was developed, which was then integrated into the Computer Modeling Group (CMG) STARS reservoir simulation software by adjusting stoichiometric numbers, kinetic parameters, and reaction enthalpy to match the experimental data obtained. Furthermore, a corrected reservoir simulation approach was employed, combining the variance analysis and a Pareto chart, to identify the key factors influencing the establishment and propagation of combustion front in the absence of electrical ignition. The results indicate that a reservoir temperature of 148 °C leads to the establishment of combustion front approximately 7 m away from the injection well, with a delay time of around 25.21 days. The Pareto chart reveals that reservoir temperature and water saturation are the primary controlling factors for combustion occurrence. Specifically, a reservoir temperature above 148 °C and water saturation below 60% increase the likelihood of combustion front formation. Among the examined factors, the reservoir temperature has the most significant effect on combustion front propagation. Once the reservoir temperature reaches 208 °C, a stable combustion front is formed, and the average temperature of combustion front remains around 400 °C throughout 8 years of model operation. When the water saturation was 50%, a consistently stable combustion front can be established within the first 6 years of model operation. However, beyond the 6th year, the average front temperature decreases below 400 °C. Therefore, it is recommended to introduce a certain amount of oxidation catalysts into the oil reservoirs after 6 years of air injection to enhance the combustion reactions. Increasing the air injection rate or pre-exponential factor does not have a significant effect on the average front temperature after 8 years of model operation, which remains below 350 °C. This study can provide significant references for future assessments and decision-making processes related to the application of ISC in ultra-deep high-temperature heavy oil reservoirs.

Combination Effect of in-Situ Combustion and Exhaust Gases Recirculation on 1D Combustion Tube: Numerical Approach

ABSTRACT Despite the widespread use of renewable and green energy, the demand for fossil fuels is also rising due to increasing global energy demand. Therefore, unconventional solutions, with safe environmental impacts, are being pursued to solve this problem. Instead of getting rid of the exhaust gases in the surroundings, one solution might be to inject them with the oxidizer into the oil reservoir, to initiate an in-situ combustion (ISC) process to enhance oil recovery. A numerical study of a 1-D combustion tube has been conducted and validated to simulate the in-situ combustion process using enriched air as the oxidizer. The effects of injecting exhaust gases with the oxidizer are studied. Different ratios of oxygen to nitrogen are used in the enriched air as well as different ratios of exhaust gases. If enriched air which is mostly oxygen, i.e. 95% O2 +5%N2, is used, it is found that replacing 10% of the enriched air with exhaust gases can increase the oil recovery factor (ORF) from 94.7% to 94.9% and replacing 20% can improve oil recovery to 95.1%. For another enriched air, 60% O2 +30% N2, it is found that replacing portions of the enriched air with exhaust gases will reduce the oil recovery factor. In all previous cases, it was found that replacing the proportions of enriched air with exhaust gases reduces the amount of fuel burned and increases hydrogen production.

Experimental Study of Catalytically Enhanced Cyclic Steam-Air Stimulation for In Situ Hydrogen Generation and Heavy Oil Upgrading

The current study was performed for the experimental modeling of cyclic steam-air injection in a heavy oil reservoir model of dual porosity in the presence of a nickel-based catalyst for in situ oil upgrading enhanced by simultaneous hydrogen generation. The research was realized in the combustion tube setup with a sandpack core model under reservoir conditions due to the consistent injection of air followed by oil in situ combustion (ISC) and steam (water) injection. As a result, the original oil was upgraded regarding fractional composition and oil properties. In addition, simulated reservoir heterogeneity and cyclic stimulation intensified the hydrogen synthesis, which, in turn, could also contribute to oil upgrading.

Nitriding Effects of Ammonia Flames on Iron-based Metal Walls

Effects of NH3/O2/N2 premixed flame/mixture on iron-based metal walls have been investigated experimentally. A premixed NH3/O2/N2 flame or mixture formed by a quartz tube burner impinged on the disc-shaped metal test plate, of which the temperature was kept at 550 oC by an infrared lamp heater. As materials for the test plate, SACM645, SUS304 and SUS310S, which are widely used as industrial steels, were examined. After being exposed to either the NH3/O2/N2 flame or mixture for 5 hours, the surface hardness was measured by using a nano indenter. Distributions of nitrogen atom diffused into the metal wall were measured by means of the Electron Probe Micro Analyzer (EPMA) and Secondary Ion Mass Spectrometry (SIMS). In addition, spatial distributions of the NH3 concentration in the NH3/O2/N2 flame and mixture were measured by employing a two-photon absorption laser-induced fluorescence (TALIF) technique. It was found that the surface hardness of the test plates increased significantly after being exposed to the NH3/O2/N2 flame/mixture. The distributions of surface hardness and nitrogen atom concentration show that nitriding occurred by the present NH3/O2/N2 flame/mixture with the equivalent level of the conventional gas nitriding method. Moreover, it is also found that NH3 concentration in the vicinity of the wall plays an important role in the surface hardness increase, and a wider distribution of NH3 can result in a broader surface hardness distribution.

Integration of ramped temperature oxidation and combustion tube tests for kinetic modeling of heavy oil in-Situ combustion

In-situ combustion (ISC) has been applied as a follow-up process after steam injection-based technologies to improve heavy oil recovery and lower operating costs. Comprehensive understanding of the oxidation behavior and reliable prediction of the ISC performance are of great importance in the design of a ISC process. In this work, a calibration workflow was proposed to investigate the oxidation behavior and then establish a reaction kinetics model. A Ramped Temperature Oxidation (RTO) experiment was firstly conducted to capture the detailed oxidation behavior at elevated temperature conditions. Subsequently, a Combustion Tube (CT) test was performed to further evaluate the overall performance of ISC. Based on the integration of RTO and CT results, a comprehensive reaction kinetics model was developed to predict the ISC performance within a wide temperature range, including Low Temperature Oxidation (LTO), Negative Temperature Gradient Region (NTGR), and High Temperature Oxidation (HTO) reactions. It is found that the NGTR of heavy oil with high saturate and low asphaltene exhibits a narrow temperature range. The combustion front velocity in the RTO is comparable with that in the CT. In a stable HTO region, the CO2 concentrations in the RTO experiment and CT test were kept around 17% and 14%, respectively. The existence of LTO reactions in the RTO experiment caused the deviation of CO2 concentration. With the incorporation of the reaction model into simulation, a good agreement between measured and predicted results was obtained. This demonstrates that the established reaction model is capable of capturing the key oxidation mechanisms. In addition, the proposed workflow also helps upscale the oxidation behavior from a RTO experiment to a CT test and provide benchmarks for field operations.

Determination of Total Sulfur in Graphene with Organic Elemental Analyzer

In the present work, a method for the determination of total sulfur in graphene with the organic elemental analyzer is presented. The effects of combustion temperature, combustion time, oxygen flow rate, filling reagent, and other factors on measurement results were examined. The results showed that the optimum test results can be obtained when the combustion tube temperature is 1050°C, combustion time 80s, the oxygen flow rate 25 ml/min and tungsten oxide/copper scraps used as the filling reagent. The repeatability, stability, and spike recovery of this method fall into the ranges of 3.4%~ 5.1%, 4.5% ~ 6.6%, and 92.5% ~ 108.6%, respectively. The detection limit is 0.09%, and the deviation between this method and the Eschka method as an arbitration method is -0.02%~-0.08%. Since there is no significant difference between the two methods, both can be used for the accurate determination of total sulfur in graphene.

In-situ combustion technique for developing fractured low permeable oil shale: Experimental evidence for synthetic oil generation and successful propagation of combustion front

The idea of in-situ combustion (ISC) for oil shale development and conversion has been proposed recently. Due to the low permeability of oil shale, it usually requires fracturing operation before air injection. However, one of the biggest technical questions is, whether the combustion front can be established and steadily propagate in the low permeable oil shale with fractures. To date, no experimental work has been reported to support this. The target of this work is to provide experimental evidence to answer this question. We have managed to create a novel method for packing and fracturing oil shale core samples in a combustion tube for simulating ISC processes. A systematic analysis for the physical–chemical modeling of ISC process in combustion tube was performed, including temperature profile, pressure drop buildup, composition of produced gases, X-ray computed tomography (CT) and visual inspection, as well as total organic content analysis of oil shale samples before and after combustion, calculation of combustion parameters (air requirement, air/fuel ratio, apparent atomic H/C ratio, oxygen utilization, and O2/fuel ratio), and synthetic oil production. All results indicated the successful establishment and propagation of the combustion front in the fractured, low-permeability oil shale sample. In addition, the permeability of oil shale was increased 2–3 times during combustion, which can be an important factor that supports the stable propagation of the combustion front. Furthermore, the effect of water and catalysts on ISC performance was investigated. It was found that water promotes the cracking reactions of heavy oils to produce CO2 and hydrocarbon gases, and the co-existence of catalysts and water together further improved the performance of the ISC process and synthetic oil production. The findings in this work provide the experimental evidence of the successful establishment and propagation of combustion front in fractured, low-permeability oil shale, and technically proves the feasibility of using ISC technology for in-situ retorting of oil shale to generate synthetic oil for the development and conversion of low permeable oil shale with additional fracturing.

A novel equation for the air injection and oil production during fire-flooding process based on experimental study in developing heavy oil reservoir

Fire flooding (FF) has been one of the important thermal enhanced-oil-recovery technologies in developing heavy oil reservoir. Many scholars have carried out laboratory studies on the complex oil-displacement mechanism due to the complex physical and chemical reactions for fire flooding. However, almost no one had given an equation expression of gas injection and production during fire-flooding process. Therefore, the FF and flue gas flooding (FGF) experiments of one-dimensional combustion tubes were conducted. The oil-recovery differences of FF and FGF experiments under the same conditions were calculated, and a high linear correlation was found. The results showed that the FF effects were mainly affected by the flue-gas when the gas injection was low, and the combustion-front expansion (CFE) effects made the main contribution when the gas injection was high. The gas injection, water and liquid production were logarithmically treated and compared with the oil production. It was found a strong linear relationship between the two sets of experiments, and the linear relationship was stronger in the FGF experiment. Among all the linear relationships, the logarithm of water production and oil production had the strongest linear relationship. Based on this understanding, the water and oil production were connected from flue gas in FF process, and a novel FF equation was derived and obtained. Finally, the production curves on site of the two typical FF cases and the fitting curves of the FF equation were descripted and compared. The results showed that the novel equation can reflect and forecast the field performance by FF process in developing heavy oil reservoir.

In Situ Combustion of Heavy Oil within a Vuggy Carbonate Reservoir: Part I—Feasibility Study

Worldwide, the known recoverable heavy oil and bitumen reserves make up more than 64% of the total reserves, of which more than 60% are trapped in carbonates. Air injection has immense potential for hydrocarbon recovery from various reservoirs. While most of the successful air-based techniques are performed within carbonate reservoirs containing light oil, theoretically, in situ combustion (ISC) has also shown great potential for recovering heavy oil and bitumen. Carbonates are complex in terms of geology and are often associated with fractures and vugs that affect the fluid flow, pressure propagation and progression of the ISC reactions. This paper describes the first experiment in which the triple-porosity concept was applied to simulate heterogeneity through artificially induced vugs, core matrix and fractures. This approach was used to study the feasibility of the ISC recovery technique for heavy oil (14° API) within a dolomite reservoir using a combustion tube (CT) in an experiment performed at 1740 psig. The combustion front advanced through 78% of the core length prior to the termination of air injection, producing 80% of the initial oil. To differentiate between the various sources of the CO2 gas (a product of carbonate decomposition vs. the combustion reaction) the atomic ratios of (CO2 + CO)/CO = 6 and (CO2 + CO)/N2 = 0.21 were applied. Additionally, partial upgrading of the produced heavy oil was observed.

Combustion tube experiments on key factors controlling the combustion process of air injection with light oil reservoir

High pressure air injection (HPAI) has unique advantages due to its rich gas source and unique high-energy displacement effect of the thermal front. Thermal effect of air injection after combustion is the key factor affecting the oil displacement effect. Combustion tube experiments are conducted to study the combustion characteristics of light oil and the influence of different factors on combustion process. We find that light oil (content of asphaltene is only 1.13%) can be ignited and combustion front can advance forward stably, which proves that the implement of HPAI in light oil reservoir can achieve good results. High temperature makes combustion more intense and the advancing of combustion front more stable. The experimental results show that when the air injection rate is low, low temperature oxidation of light oil will dominant, or the combustion front cannot successfully advance. But when the injection rate is too high, the combustion front moves forward too fast and gas channeling will occur. With pressure increasing, the solubility of O2 in oil increases, causing a more violent oxidation reaction. Increasing pressure can reduce the air/oil ratio and improve the utilization rate of O2. Thus, HPAI is more ideal for the reservoirs with high temperature and high pressure. And for a specific reservoir, an optimal injection rate exists. The conclusions of the research can provide references for field applications of HPAI in light oil reservoirs.

Study on the Lower Limits of Physical Parameters for Heavy Oil Reservoirs during the In Situ Combustion Process.

As an effective enhanced oil recovery (EOR) method in the late stage of the steam injection process, in situ combustion (ISC) has been verified by more and more researchers owing to its high recovery efficiency and low operation cost. However, the ISC process is prone to bringing about an unfavorable result with a low sweep efficiency and even an extinction process due to the complexity and uncertainty in oil and water distribution as well as the heterogeneity of the actual reservoir. In this work, combustion tube experiments combined with numerical simulations by CMG-STARS were conducted to study the influence of a reservoir's physical parameters on the stability of ISC. It was found that the sustainability of the combustion process is sensitive to permeability and oil saturation, the lower limits of which are determined as 0.2 μm2 and 0.2, respectively. Then, a formula was preliminarily proposed as 0.25 ≤ So/K ≤ 0.8, which could be used as a reference of screening criteria in designing the ISC process.

Impacts of combustion chamber location and tube bundle layout on the performance of three-pass hot-water steel boilers under the steady-state operation

This study discusses the effects of the combustion chamber location and tube bundle layout on the performance of three-pass hot-water steel boilers under steady-state operation. For this goal, three possible nondimensional locations (S) for the combustion chamber of −0.25, 0, and 0.25, and three various nondimensional gap spaces (G/P) between the second and third passes of 1.0, 2.5, and 5.0 are investigated using inward (Layout-A) and outward (Layout-B) right triangular pass layouts. All computations are carried out for the Richardson numbers of 0.1, 1.0, and 10, and the obtained results are successfully validated against the available data in the open literature. It is found that changing the combustion chamber location greatly affects the boiler performance. Additionally, the gap space between the second and third passes and tube bundle layout have considerable influence on the heat and momentum transfer inside the boiler. It is revealed that, regardless of the Richardson number, a three-pass hot-water steel boiler constructed with S = –0.25 and G/P = 5.0 and having Layout-A for second and third passes has the maximum thermal-hydraulic performance and can be considered by boiler designers.

ANALISIS DAN PERANCANGAN ALAT ASAP CAIR MENGUNAKAN SISTEM PENDINGIN KONDENSOR TIPE SPIRAL

Liquid smoke consists of phenolic compounds, carbonyl compounds, acids, water, tar compounds, and benzopyrene. Natural wood material consisting of hemicellulose, cellulose, and lignin decomposes at high temperatures into more than 300 compounds consisting of more than 70 types of carbonyls as ketones and aldehydes, 20 types of acids, 11 types of furans, 45 types of phenols, 13 types of alcohols and esters. , 12 types of polycyclic aromatic carbon, and 13 types of lactones.
 The research method is by designing tools, and cutting/making liquid smoke tools, then drying them in the sun to be completely dry, Weighing the coconut material before putting it into combustion, assembling and connecting the house pipe hose from the reactor to the tar to the condenser pipe, making sure there are no the leak between the connections, before being put in the combustion furnace, turn on the fire in the reactor tube, install the condenser pipe in the condenser tube and fill the water in the condenser tube, record the results of liquid smoke every 8 hours and fill the material into the combustion tube.
 From the results of the research that has been carried out, there are differences in the results of liquid smoke obtained, then the charcoal results obtained, there is a difference in weight produced between the previous tool and the tool that is now designed, the most influencing factor is the condenser design, where the condenser can cool the smoke that comes out , due to the long cooling cycle that affects the results. The results obtained on the previous tool were 3.754 ml of liquid smoke, 6.5 kg of residual charcoal, and liquid smoke yield of 12.5% ​​with a burning time of 48 hours, and the production rate of liquid smoke was 78.2 ml/hour. The results of the research obtained on the new tool produced 7.095 ml of liquid smoke, 5.6 kg of residual charcoal, and 23.6% yield of liquid smoke with a burning time of 48 hours, and the production rate of liquid smoke was 147.8 ml/hour.

Combined Experimental and Numerical Investigation into Combustion Characteristics of Crude Oil under Different Permeability Ranges: Thermal EOR Implication

In situ combustion (ISC) has drawn much attention in the exploitation of heavy oil reservoirs because of its small surface footprint and high recovery efficiency relative to steam injection. As for now, the combustion characteristics of heavy crude oil under different permeability ranges have not been well-understood, particularly in low-permeability conditions. In this work, we systematically conducted the combustion tube (CT) experiments under permeabilities of roughly 650 and 480 mD. Following that, a reaction kinetics model that could simulate the CT results well was established. Finally, the corrected reservoir simulation approach was used to study the ISC characteristics of one heavy oil in the permeability range of 50–1000 mD. The combustion characteristics under different permeability ranges could be classified into four main types on the basis of the experimental studies and numerical predictions. (1) The consecutive combustion front failed to be formed from 50 to 180 mD. (2) The consecutive combustion front was formed and the coking zone appeared from 180 to 250 mD, which was accompanied by weak heat release and serious plugging effect of the oil bank and coking zone. (3) The stable combustion front was formed with obvious heat release from 250 to 500 mD, and there was a weak plugging effect of the oil bank and coking zone at the initial stage of combustion. (4) In the permeability range of 500–1000 mD, the stable combustion front featured with a peak temperature higher than 500 °C was formed with a negligible plugging effect of the oil bank and coking zone. For heavy oil reservoirs with permeabilities lower than 250 mD, much attention should be put on the variations into combustion front temperature and displacement pressure difference at the initial period of combustion. If the temperature continued to decrease and/or the displacement pressure difference continued to rise, some measures should be actively adjusted to increase heat release yielded by combustion, including the increase of the air injection rate and ignition temperature, the injection of catalysts, and so forth. This work could add new insights into the differences and connections of combustion characteristics of heavy oil under different permeability ranges, which should be of great significance for thermal enhanced oil recovery.

Analisa proses pirolysis dengan variasi jumlah tabung pembakaran terhadap Karaktristik hasil bio-oil

Bio-oil is a blackish liquid fuel derived from biomass such as corn cobs, rice husks and other biomass such as cocoa shells. The organic acid content in bio-oil gives bio-oil acidic properties. Bio-oil can be obtained in the pyrolysis combustion process, using a combustion tube. The number of tubes used can affect the yield characteristics of bio-oil. The purpose of this study was to determine the characteristics of bio-oil bio-oil produced by varying the number of combustion tubes in the pyrolysis process. Such as pyrolysis time, amount of bio-oil, temperature and content of bio-oil. This research method utilizes cocoa shell biomass waste to turn into bio-oil with a pyrolysis process, namely by varying the number of combustion tubes, namely one tube, two tubes and three tubes with a diameter of one tube 27.74 cm, two tubes 19.6 cm and three tubes 16 cm with the same cylinder volume of 18.7 cm3, by carrying out the prolysis process, namely putting the cocoa shell waste into the combustion tube and closing it. Then the combustion tube is inserted into the pyrolysis reactor and then closed and then burned. From the results of the research, the results of bio-oil in a single tube of raw material were 130 ml with a processing time of 113 minutes and bio-oil characteristics, a calorific value of 2177,464 cal/g, a viscosity of 1,574 CPs, and a pH of 4.77. Whereas in the second raw material tube, there were 80 ml with a processing time of 105 minutes and specifications for bio-oil, a calorific value of 2071,151 cal/g, a viscosity of 1,780 CPs and a pH of 4.96. While the three raw material tubes were 50 ml with a processing time of 100 minutes, and bio-oil specifications, calorific value 1983,950 cal/g, viscosity 2,626 CPs and pH 5.42.

Dual-camera high-speed imaging of n-hexane oxidation in a high-pressure shock tube

Shock tubes are widely used in the study of chemical kinetics. Its benefits rely on the almost ideal shock-heating process that provides high temperatures and pressures to a chemical system for a limited test time. Just like any reactor, shock tubes are not immune to non-ideal effects. The study of conditions that might deviate experiments from ideal conditions is thus of the utmost importance. High-speed imaging has been proven to be a powerful tool to analyze non-ideal / non-homogenous combustion in shock tubes. In this work, dual-camera high-speed imaging experiments were performed at 10, 15 and 20 bar in a high-pressure shock tube (HPST). An optical section was designed as an extension of the HPST which enabled simultaneous visualization from the endwall and the sidewall of the driven section of the shock tube. n-Hexane, a fuel with a negative temperature coefficient (NTC) behavior that has been identified as prone to non-homogenous ignition, is used as a test fuel. Reactive mixtures and thermodynamic conditions were selected to visually analyze ignition processes at the high-temperature, NTC and low-temperature regimes. Non-homogeneous ignition was observed mostly at the local maximum of the IDT, which is comprised by the high-temperature and NTC regions. Stoichiometric n-hexane mixture with high fuel loading (5% n-hexane) presented the highest deviation from constant volume chemical kinetic simulations. The inclusion of helium as a bath gas to mitigate preignition was tested and it showed to improve the susceptibility of the mixtures to develop reaction fronts. The modified Sankaran criterion for the identification of ignition regimes in shock tubes was tested and it showed an overall good agreement against the experimental observations.

Experimental investigation of the laminar burning velocity of iron-air flames in a tube burner

This paper presents the results of experimental measurements of the laminar burning velocity of iron-air-flames in a model tube burner. Carbonyl iron powder with an average Sauter diameter of about 13 µm was mixed with air at ambient temperature and pressure in an air knife seeder and fed to the tube burner. An iron-air-flame was stabilised without additional fuel, air preheating, increasing the amount of oxygen in the gas phase, or pilot flame. The diameter distribution of the used iron powder was determined under operating conditions. The conical flames were visualised with a camera at short exposure times. The images were used to extract the local angle of the flames. In addition, Particle Imaging Velocimetry was applied to determine the local gas phase and particle velocities at the burner outlet. The local velocity and the local flame angle were used to determine the laminar burning velocity of the iron-air flames. The results show that the laminar burning velocity is about 14 cm/s for the experimental conditions studied and no dependency of the global equivalence ratio or the mean inlet velocity on the laminar burning velocity were found for the investigated conditions. The results are in good agreement with literature data.

Flame characteristics of backward-inclined pulsating combusting jet in crossflow

The flame appearances, thermal characteristics, and combustion product concentrations of a backward-inclined pulsating combusting jet in crossflow were experimentally studied. The time-averaged and streak instantaneous flame images were acquired using a still camera and a high-speed camera, respectively. The flame extinguishment processes were captured and analysed on the basis of streak instantaneous images. The flame temperatures and combustion product concentrations were measured using a homemade fine-wire thermocouple and a gas analyser, respectively. Three characteristic flame modes (crossflow dominated, transitional, and jet-dominated) were found when the backward-inclined jet flame in crossflow was subject to acoustic excitation. These characteristic flame modes were observed in different regimes of pulsation intensity and jet backward inclination angle. Discrete flame puffs with a frequency equal to the acoustic excitation frequency appeared in the jet-dominated flame. Periodic flame puffing became unstable when the pulsation intensity was increased to values near the instability limit. When the pulsation intensity was beyond the instability limit, a strong stretching effect caused the recirculation flame, which played the role of a flame ignitor, to almost vanish (misfire). The flame extinguishment then occurred from the area around the lee side of the burner tube tip. The temperature and gas concentration measurement results showed the significant improvement of combustion performance in low inclination angle even at small pulsation intensity in the regime of the crossflow dominated flame. To enhance combustion performance at a large jet backward inclination angle, the pulsation intensity must be large enough to push the flame in the regime of the jet-dominated flame.

Lessons Learned from a Prematurely Ended High-Pressure Air Injection Test in a Light Oil Naturally Fractured Reservoir

Summary Sixty billion barrels of oil still reside in the matrix of mature onshore and offshore Mexican reservoirs located in the southeast basins after primary and secondary recovery. Capillary and viscous forces are responsible for this amount of oil retained within the pore structure of the matrix (immobile oil). Gravitational forces are not enough to counterattack these forces due to the high fracturing intensity. On the other hand, laboratory testing demonstrates that oil residing in the matrix could be mobilized by the exothermic reaction that takes place with air injection. Air injection in homogeneous heavy and light oil sandstones and nonfractured limestones, at small or large scales during short and long periods of time, is feasible for producing resources technically and economically nonrecoverable by other means. However, to the best of our knowledge, the published literature does not report any application of an air injection project in naturally fractured reservoirs. During 2015, an air injection pilot test was performed in a light oil naturally fractured reservoir in Mexico, referred to as “A” field. The implementation of the pilot test was preceded by its corresponding laboratory study, which consisted of five accelerating rate calorimeter (ARC) tests and two combustion tube (CT) experiments. The analysis of the aforementioned experimental work led us to corroborate that air and oil react at reservoir conditions. Based on the above finding, the pilot test was conducted by injecting air at a rate of 10 MMscf/D with a wellhead pressure of 4,500 psia for 1.5 years, which was followed by a 1.5-year production period giving a total of 3 years for the pilot test. The results indicate that combustion was successfully applied in the reservoir. However, no oil was produced. This paper discusses the results of a prematurely ended air injection pilot test in “A” field and the main lessons learned from it, which could help in the design and its subsequent implementation in other naturally fractured reservoirs.