Air Foam Flooding Research Articles

Corrosion Evaluation and Mechanical Life Prediction of J55 Tubing Steel under Air-Foam Flooding Oil Well Conditions

Corrosion Evaluation and Mechanical Life Prediction of J55 Tubing Steel under Air-Foam Flooding Oil Well Conditions

Effect of pore-throat structure on air-foam flooding performance in a low-permeability reservoir

In this study, effect of pore-throat structure on air-foam displacement performance in a low-permeability reservoir has been experimentally examined. More specifically, porosity and permeability of samples collected from the Upper Triassic Yanchang Formation of the Chang 6 low-permeability oil reservoir in the Ordos Basin, China, were measured, and then their petrological and petrophysical properties as well as pore and throat size distributions were determined by integrating thin-section analysis, x-ray diffraction analysis, high-pressure mercury injection (HMI) and rate-controlled mercury injection (RMI) tests, and NMR technique. Based on the ultimate displacement efficiency and the measured washing efficiency, the underlying recovery mechanisms associated with air-foam flooding in two sub-member samples which have different pore-throat distributions (i.e., sample C6-1: Concentrated throat distribution and sample C6-2: Dispersed throat distribution) are rather different, implying that the timing for converting water injection to air-foam flooding shall be different as well. Also, the difference of throat-distribution characteristics between sub-members C6-1 and C6-2 is found to impose a great but different influence on the air-foam displacement performance by improving their oil washing and microscopic sweep efficiencies, respectively. This finding is of a great significance to help design, evaluate, and optimize the injection-production strategies in a low-permeability reservoir with different pore-throat distributions.

The Phase Behavior Study of Air-foam Flooding in Changqing Ultra-Low Permeability Reservoirs

For phase change characteristics of air foam flooding in Changqing ultra-low permeability reservoirs,  experiments were performed with the air and the gas-phase oxidation of P-X diagram under reservoir conditions using the PVT high pressure physical device and gas chromatograph. The phase behavior of crude oil and air bubbles after multiple contacts was determined by PVT simulation and the phase equilibrium model. The critical temperature and critical pressure of crude oil were determined to be 424.4? and 9.85MPa. Results show gas dissolved in crude oil after oxidation was strong in the air under the same pressure. Because the foam system and crude oil emulsification during contact have produced multiple contact oxidation, the effect was less than that in air and oil, resulting in a relatively small oxidation of C2-C6, while the oxidation of C7-C16 was relatively more. Furthermore, the trend of gas phase composition approaching C2-C6 was relatively slow, while oil phase composition was closer to C7+, due to the increase in the C7-C16 component. The study provides important insight for miscible flooding and non-miscible flooding applications, as well as for gas injection project design.

Dynamic Behaviors and Mechanisms of Air-Foam Flooding at High Pressure and Reservoir Temperature via Microfluidic Experiments.

Air injection has been proven to be an effective improved oil recovery technique for deep and light oil reservoirs with low permeability and poor water injectivity. But the efficiency of air injection in highly heterogeneous reservoirs is low due to poor gas sweeping that may lead to early oxygen breakthrough caused by gas channeling and viscous fingering. Foam can be used to assist air injection to overcome the obstacles of early gas breakthrough and to increase the displacement and sweeping efficiency. In this paper, laser-etched visual microscopic pore models were used as microfluidic devices to study the air-foam flooding process in porous media at reservoir temperature and high pressure. The dynamic behaviors and relevant mechanisms of air-foam flooding were investigated. Typical mechanisms of foam generation in porous media are achieved in different parts of the micromodel, which can be listed as follows: lamella leave-behind, lamella division, and snap off. Analysis on flow states of air foam showed that foams migrate in porous media by bursting and regenerating during the flooding process. It can be observed that the flow mode of foam in porous media is the separate flow of gas and liquid through microscopic displacement experiments, suggesting that foam should not be treated as a homogeneous phase in heterogeneous porous media. The pressing, occupying, and selective blocking effects of foam in porous media exhibited different oil displacement performances with the presence of various pore geometries and networks. Tiny foams also showed stripping and carrying effects on larger oil droplets benefiting from the lipophilicity of foam. Through comprehensive analysis on overall and local oil displacement mechanisms, air-foam injection could enhance the microscopic sweep volume and improve the oil displacement efficiency.

Application of BP neural network to prediction of recovery effect of air-foam flooding in heavy oil

Air-foam flooding is an effective technology to enhance oil recovery in heavy oil production. In this study, Back Propagation (BP) neural network model is built and optimized to predict the recovery effect of heavy oil with the injection parameters data of the oxygen-reduced air-foam flooding obtained through experiments. The study shows that the prediction results of the BP neural network is quite accurate, and the average absolute relative error of prediction results is less than 0.21%. This also illustrates the feasibility of using the BP network prediction model in predicting heavy oil recovery effect.

Effect of reservoir permeability on oil recovery using air foam flooding: a case study on Ganguyi oilfield

Air foam flooding is an important technology to enhance oil recovery by improving the swept volume of the fluid and the efficiency of displacement of oil. This study uses a literature review, engineering analysis of reservoirs, laboratory tests, and the data on oil production to clarify the relationship among the efficiency of oil displacement, control of the profile of the mechanism of water blockage, and the permeability of the reservoir. The results show that a highly permeable reservoir has a good pore structure with a large pore throat that helps yield a large swept volume and low interfacial tension to improve the efficiency of oil displacement. It also contains large pores that generate more foam for a higher oil mobility ratio and greater oil displacement. A heterogeneous reservoir has a strong Jamin effect and efficient oil displacement when air foam flooding is applied. The results of experiments yielded similar conclusions. The displacement efficiency of highly permeable and heterogeneous reservoirs is higher, and their injection pressure is lower when air foam flooding is applied. The permeability of reservoirs in oil fields should be higher than 1.5 mD for injection using air foam flooding. The results here can be used in applications of air foam flooding.

Flow Pattern and Resistance Characteristics of Gas–Liquid Two-Phase Flow with Foam under Low Gas–Liquid Flow Rate

To reduce the cost of arranging air foam flooding equipment at each wellhead, a method of establishing centralized air foam flooding injection stations is proposed. The flow pattern and resistance characteristics of air foam flooding mixtures in different initial conditions are studied. Experimental results indicate that the probability density function of stratified flow is obtained by comparing stainless steel and transparent pipes. If the gas–liquid ratio is kept constant, then the shape of the probability density function remains unchanged in both stainless steel and transparent tubes. Meanwhile, the flow pattern under the gas–liquid ratio is determined by comparing the image recognition results with the probability density function, and a formula for calculating the resistance and pressure drop of the gas and liquid two-phase flow in the horizontal and upward pipes is established. Compared with the experiments, the error results of the calculation are small. Thus, the proposed equations can be used to predict the flow resistance of real air foam flooding.

Study on associated gas combustion characteristics and inert gas influence rules in air-foam flooding process

Air-foam flooding technology is a potential tertiary oil recovery technology. However, enhancing oil recovery through air injection still indicates risks of explosion. In this study, the upper and lower flammability limit (UFL and LFL) and limiting oxygen concentration (LOC) of the associated gas during air-foam flooding are investigated. The change rules of these combustion characteristics are tested under different initial pressures and temperatures using a high-pressure experimental device. The measurement results indicate that with the increase of initial temperature and pressure, the LFL and LOC decrease, whereas the UFL increases. The flammability limits of the associated gas measured at 15 MPa and 80 ℃ are ranging from 1.14% to 56.67%, far exceeding the calculated value under the room temperature and pressure. The empirical formula of the associated gas combustion performance is also fitted to immediately identify the risk levels of associated gases with similar components. The change in initial pressure and temperature only slightly affects the LOC when CO2 is the inert gas. By contrast, it greatly reduces the LOC when N2 is the inert gas. The maximum difference value of 2.55% between the LOC of the two inert gases is observed at 4 MPa and 80 ℃. Overall, the findings of this study can serve as test data for the combustion limits and limiting oxygen content of associated gases in the process of air-foam flooding.

Experimental Study on Improving Oil Displacement Efficiency by Air Foam Flooding in Tight Oil Layer

The tight oil layer is poor in physical property, small pore throat radius, serious heterogeneity of reservoir, low flooding efficiency, poor water flooding efficiency and final recovery is lower than 10%. In order to further improve the oil displacement yield and simulate the conditions of oil layer, we have carried out the experiment of air foam liquid system to flooding oil, and studied the rule of improving the displacement efficiency of air tight foam reservoir. The experimental results show that the density of Gaotaizi water flooding ultimate oil displacement efficiency is 48.95% on average, after water flooding to air - foam flooding alternating final displacement efficiency is high up 79.63%, the oil displacement efficiency can be increased by 26.92%; a short alternately displacement than the big slug is better, the gas-liquid ratio is too high, the breakthrough time of change in short, flooding effect, direct air - foam liquid slug can achieve good flooding effect. That air foam flooding can improve the oil displacement efficiency of dense oil after water flooding by air - foam liquid slug, gas-liquid ratio, cycle injection parameter optimization, to further improve the dense oil displacement effect, the results of air foam flooding field test has the reference and guiding significance for the tight reservoir.

Preparation and Properties of Foaming Agent for Air Foam Flooding

In order to meet the requirements of air foam flooding in Dagang Gangdong Oilfield, two kinds of foaming agents, GFPA-1 and GFPA-2, were prepared by sulfonation, neutralization and high-temperature hydrolysis of α-olefins with different carbon chain lengths in the laboratory. The test results of foaming agents for its properties showed that when the concentration of foaming agent was over 0.5%, the initial foaming volumes of the two foaming agent systems were more than 500mL, and the foam half-life of GFPA-2 was about 3.5 hours, obviously longer than that of GFPA-1. Therefore, GFPA-2 was selected as the foaming agent for air foam flooding. The experimental results of static adsorption, plugging and core displacement performance of GFPA-2 foaming agent showed that the initial foaming volume of GFPA-2 foaming agent could still maintain 500mL after 48 hours of adsorption at a concentration of 0.5%, and when the ratio of gas to liquid was 1: 1, the resistance factor was more than 50. When a 0.4% foaming agent was injected with 0.35 PV slug, the displacement efficiency of air foaming flooding was 17.4% higher than that of water flooding.

Experimental study and field demonstration of air-foam flooding for heavy oil EOR

Foam flooding is an effective oil displacement technique to improve fluid sweep efficiency and increase oil recovery. The objective of this study is to investigate the application of air-foam for heavy oil recovery under heterogeneous reservoir conditions. The paper first investigated the air-foam flow behavior in porous media and identified the effects of different factors such as gas-liquid ratio, injection rate, and crude oil saturation on air-foam resistance. Then, dual-tube sand-packs were used to evaluate the performance of air-foam for heavy oil recovery from heterogeneous reservoir conditions. The results indicated that the air-foam could divert the fluid from the high-permeability zone to the low-permeability zone, decrease the water cut and improve the oil recovery. Further studies revealed that there existed an optimal reservoir permeability contrast ratio in air-foam flooding for heavy oil recovery. The air foam performance for oil recovery would be reduced beyond or below this permeability contrast ratio. Finally, field tests on air-foam for heavy oil recover demonstrated that air foam flooding could increase heavy oil production rate and decrease the production water cut.

Study on property evaluation and numerical simulation of air-foam flooding in low permeability reservoir

ABSTRACT Comprehensively considering the migration law of air and foam in porous media, various physical and chemical phenomena, and the change of gas phase mobility are researched, then mathematical models of air-foam flooding are established. Based on air-foam flooding experiments, the relevant parameters of empirical model for numerical simulation of air-foam flooding were obtained. Matching of parallel core displacement experiment and air foam test flooding in Wuliwan Oilfield is completed with total fitting degree of more than 90%, and the reliability of empirical model of numerical simulation for air-foam flooding is verified.

Exploration of Air Foam Oxygen Reduction Fracturing Technology

Air is a source of gas that is widely and easily obtained. Air fracturing is an ideal technology for reservoir stimulation in the future, and is also the best way to solve the pollution problem of oil and natural gas exploitation. The technology of air foam flooding and air drilling has achieved good results in oil fields at home and abroad. The feasibility of air foam fracturing technology is explored through studying the safety conditions for deflagration of air medium in gas reservoirs and the requirements of air foam fracturing technology. The results of preliminary laboratory study: at 100°C and 1MPa, the mixture of methane and air is safe when oxygen concentration is not higher than 11% in air, while the safety boundary is 5% for oxygen reduction requirement in air foam flooding. The viscoelastic properties of the developed air foam fracturing fluid can meet the requirements of conventional fracturing construction.

Study on the EOR experiment and field test of air foam flooding in Wuliwan oilfield

In order to solve the problems of oil wells in ZJ53 well area of Wuliwan oilfield, such as premature water breakthrough, rapid rise in water cut, obvious plane conflict, low reserve utilization degree and the difficulty in tapping remaining oil with conventional treatment methods, the laboratory experiment and field test of air foam flooding were performed. The results of laboratory experiment of air foam flooding revealed that the crude oil in Wuliwan oilfield was able to effectively consume oxygen in low temperature oxidation reaction. When the gas/liquid ratio was 1:1∼5:1, the oxidation rate was 0.5∼6.252×10-5mol O2/hr-ml[oil]. After low temperature oxidation reaction, the viscosity of crude oil and the number of long carbon chains increased, but the main peak carbon of crude oil remained unchanged, which was still C10. The foam system with foaming agent of AES and foam stabilizer of HPAM had good foam performance. In the oil displacement experiment of sand pack, when the water cut was close to 100%, the recovery factor could reach 52.8% after water flooding, then it could enhance by 7.4% and 4.9% through foam flooding and subsequent water flooding, respectively. The field test of the ZJ53 well block in Wuliwan District 1 oilfield showed that air foam flooding was able to significantly increase the water absorption thickness of single well, enhance reserve utilization degree of water flooding and improve development effect.

Oil-Recovery-Parameter Optimization by Air—Foam Injection into a Low-Permeability Light-Oil Reservoir

The physical mechanism of air-foam flooding that was proposed earlier by other authors was studied using NB-95 foaming agent as an example. The parameters for air-foam injection in the T9 block of SY oilfield were simulated numerically optimized using the STARS module of the CMG reservoir simulation software. The experimental results demonstrate that the optimal injection-volume-to-production ratio for air-foam flooding in the T9 block is 0.8-1; gas-to-liquid ratio, 0.8-1; foaming agent concentration, 0.5-0.75%; and injection slug, 0.18-0.22 of the pore volume. Experimental physical simulation shows that air-foam flooding can enhance oil recovery by 25.85% and can be used to develop a theory of oil displacement by air-foam flooding.

靖安油田Q1区空气泡沫驱用起泡剂的优选与应用

靖安油田Q1区空气泡沫驱用起泡剂的优选与应用

A study on oxygen consumption mechanism of air-foam flooding in low-temperature oil reservoir

Air flooding/air-foam flooding recovery technology has been attracting attention in oilfield development. The key point to the application of this technology is to ensure that the oxygen injected with the air can be fully dissipated inside the reservoir to lower the explosion risk in production wells and reduce the oxidation of the pipeline. It is generally believed that the oxygen and crude oil can react more in low-temperature-oxidation (LTO) reactions above 80 °C. As a large amount of oxygen would be spontaneously consumed at this temperature, this technology is mainly used in reservoirs where the temperature is greater than 80 °C. In the fractured low-permeability reservoir of China's Yanchang oilfield, where the reservoir temperature is only approximately 30 °C, a wide range of crude oil LTO would not be triggered theoretically. However, we found that the oxygen content of the associated gas in the gas channeling wells is significantly lower than that in the air. This phenomenon suggests that, there are other factors that could consume oxygen apart from the LTO reaction. To verify this assumption, an oxygen dissipation core flooding experiment at 30 °C and 80 °C was carried out to evaluate the oxygen consumption at different temperatures. At the same time, in order to determine the main controlling factors and dissipation mechanisms of oxygen dissipation, theoretical analyses and experimental studies were carried out from the aspects of reductive mineral oxidation reaction in the rock surface and formation water, the physical absorption of the micropore and the dissolution of the reservoir fluid. The results show that at the same experimental conditions, the oxygen consumption at 30 °C is 38.14% lower than that at 80 °C. The oxygen consumption factors in the low-temperature reservoir mainly include the chemical reactions between the oxygen and reducing minerals, dissolution and retention of formation water and oil, adsorption of Van der Waals forces in the reservoir and physical electronic adsorption of the hydrogen-sulfur bonds and carbon-sulfur bonds. In Chang 6 Reservoir of Ganguyi oilfield, formation water could theoretically consume 56 mg/L (1.75 mmol/L) oxygen through dissolved Fe2+. The dissolution by formation water could absorb 11.85 mmol/L oxygen (experimental value). The dissolution by oil could absorb 69.25 mmol/L oxygen (experimental test value), and the oxygen physical adsorption rate of rock pore surface was 1.26 mmol/L. Together with the pilot test data, the results show that the LTO reaction of the stratum crude oil barely occurs in the reservoir at low temperature (30 °C). However, a large amount of oxygen dissipation could still be achieved. This study demonstrates that air-foam flooding could break the applicable limit temperature and could also be applied in low-temperature reservoirs.

Corrosion behavior study of oil casing steel on alternate injection air and foam liquid in air-foam flooding for enhance oil recovery

The effect of air and foam liquid alternating injection frequency on corrosion of oil casing steel in air-foam flooding process for enhanced oil recovery (EOR) was investigated in an autoclave. The characteristics of alternating corrosion in air-foam flooding were different from the conventional corrosion. The surface micro-topography of corrosion scale was observed by scanning electron microscopy (SEM) at various alternating injection frequencies (F = 0, 1, 2, 4 and 6). In addition, energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) were used to analyze the composition of the corrosion product when alternating injection frequency was F = 0, 1 and 6. The results showed that the corrosion rate was increased significantly with the increase of alternating injection frequency. Meanwhile, pitting gradually developed into localized corrosion, which then slowly led to general corrosion. Moreover, the main corrosion products were Fe(OH)3, FeOOH, and Fe3O4 with alternating injection frequency for F = 0, F = 1 and F = 6, respectively. In this study, the alternating corrosion in air-foam flooding was investigated systematically, which would provide theoretical guidance for further research of air-foam corrosion.

Enhanced oil recovery by air-foam flooding system in tight oil reservoirs: Study on the profile-controlling mechanisms

A one-dimensional long core displacement experiment was designed based on injection of pure foam liquid, air, and air-foam system into the tight matrix core and fracture core. This aimed to verify the individual injection capacity of these materials in the ZenPing well area in a typical tight oilfield, China. The results indicate that the air-foam system cannot be injected directly into the tight matrix core. However, because some of the foaming agent is absorbed by the reservoir rock, causing foam collapse, the defoamed liquid and separated air can flow into the tight matrix core, which results in stable displacement. Three-core parallel displacement experiments were designed, including two matrix cores (with permeability difference ratios of 10) and one fractured core. The results indicated that the air-foam system mostly flows into the fractured core and blocks the fractures. Thereby, some of the defoamed liquid and separated air could flow into the matrix core to displace the residual oil. The residual oil saturation and the oil displacement efficiency were 21.12% lower and 32.89% higher, respectively, than those of water flooding. We also analyzed the profile-controlling mechanisms, which indicated the air-foam system flooding is capable of improving performance following water flooding. We recommend that water flooding should be switched to air-foam system flooding as early as possible before the water cut reaches around 90%. Our findings were successfully used to guide a pilot test of the ZenPing well area. The results indicate that air-foam flooding is a feasible means for improving oil recovery in tight oil reservoirs.

Experimental study of air foam flow in sand pack core for enhanced oil recovery

Abstract As an innovative way of Enhancing Oil Recovery (EOR), the air foam flooding technique comprises the merits of air flooding and foam flooding, which not only has the double effects on profile controlling and oil displacement, but also avoids the gas channeling weakness. In this paper, a series of flow experiments of the simultaneous injection of air and air foam through artificial sand pack core was conducted to investigate changes in gas and oil composition and oil displacement efficiency. The effects of foaming agent concentration and slug were investigated. The results show that in low temperature oxidation process, oxygen content decreases, and carbon dioxide content increases. Aromatic hydrocarbon content decreases, while resins and asphaltene content increases. Oil displacement efficiency of air foam flooding is much higher than air flooding. The Foam blocking ability and the function of profile controlling of the foam, significantly prolongs gas breakthrough. The displacement efficiency was dropped due to the decrease of foaming agent concentration or the decrease of the foam slug.