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The properties of foam fluid are substantially determined by its interfacial dynamics changes during foam transport. In this research, a foam flow simulation model based on the level set method and the N–S equation with surface tension term is established to simulate the dynamic interface evolution mechanism of group foam and individual foam from various aspects such as drainage process and foam migration in porous media, coalescence and Jamin effect. The results show that the foam life decreases linearly with the logarithm of the surface tension and enhances linearly with the liquid viscosity. For foam transport in porous media, both flowing foam and trapped foam exist, and the pressure fluctuates at a certain pressure value and the best foam structure is achieved at the optimum conditions with the optimum values of gas-liquid ratio, surface tension, and porosity being 1:1˜3:2, 0.1˜0.3, and 44.4%, respectively. Besides, the temporary blocking effect of foam has been verified. During the foam coalescence, foam gradually evolves towards minimum interfacial energy with oscillating and gradually decreasing foam volume. During the process of the foam passing through the throat, the maximum pressure occurs when the front end of the foam reaches the narrowest point, and the minimum pressure occurs when half of the foam passes through the narrowest point. The maximum pressure elevates linearly with the surface tension and the inverse of the throat radius. [ABSTRACT FROM AUTHOR]

Highlights • Dual energy CT measurements are performed. • Three phase distributions in the foam displacement process are obtained. • Obvious entrance effect is observed in CO 2 foam flooding process. • Parameter studies are performed on foam quality, comparison with N 2 foam, system back pressure and the rock permeability. • Mechanisms for the foam flow inlet behavior are investigated based on stochastic bubble population balance model. Abstract In relation with the potential applications of CO 2 foam technology on Enhanced Oil Recovery and CO 2 geological storage, the foam assisted CO 2 displacement process in a surfactant solution and oil pre-saturated porous medium is experimentally investigated with special attention on the dynamic foam propagation behavior in the entrance region of porous media. Computational Tomography (CT) imaging is employed to visualize the transient CO 2 foam sweep process and the dual-energy CT measurement is performed to obtain the dynamic three phase saturation distributions along the sample core. Studying parameters include the comparison with N 2 foam, system backpressure and the porous medium permeability. It is found foam could push most of the liquid phase in the latter part of the porous media but leaves the forepart of the sample less flooded, showing a clear entrance effect of foam flooding process. Compared to CO 2 foam, N 2 foam displacement process shows higher liquid phase saturation in the entrance section and presents less oil recovery rate. Elevating system backpressure to 1.0 MPa leads to less pressure drop for CO 2 foam flooding process without compromising the oil phase sweep efficiency. The CO 2 foam flooding process in lower permeable medium shows higher pressure drop and higher oil recovery rate. The mechanisms for the inlet behavior of the foam displacement processes have been scrutinized based on good qualitative and quantitative agreement of the experimental and numerical results with the stochastic bubble population balance model. [ABSTRACT FROM AUTHOR]

Foam fluid has found wide applications in oilfield development, such as profile control, water plugging, gas channeling control, fracturing, and so on. As a non-Newtonian fluid, the successful application of foam is significantly influenced by its structure. The foam texture, however, is complex and irregular, and becomes even more complicated in porous media by the boundary effects. Therefore, the description of dynamic foam structure is crucial and a quantitative description method for foam fluid is worth exploring. In this paper, the fractal characteristics of foam in porous media are verified and combined with foam microdisplacement experiment, and the fractal rule of foam is found. The relationship between fractal dimension and pressure is also discussed. The results show that foam has dynamic fractal characteristics during transport in porous media and the box-counting fractal dimension ranges from 1 to 2. Furthermore, the dynamic change of foam fractal dimension during transport in porous media could be divided into three stages. In the first stage when no foam forms, the fractal dimension is about 2; in the second unsteady foam stage, the fractal dimension is reduced from 1.9 to 1.6; the last one is the steady stage and the fractal dimension is almost constant (about 1.6). Besides, the fractal dimension of foam fluid is closely related to displacement pressure. Low pressure corresponds to higher fractal dimension, and high pressure corresponds to lower fractal dimension. Pressure is negatively linearly correlated with fractal dimension. These results are expected to enrich the understanding of the foam dynamic characteristics in their advanced applications. [ABSTRACT FROM AUTHOR]

Rheological properties of supercritical CO 2 (ScCO 2 ) foam fluids are essential to understand foam displacement mechanisms in the research & development of efficient CO 2 -EOR and CO 2 geological storage technologies. In this paper, a systematic laboratory study concerning non-Newtonian ScCO 2 foam flow characteristics in a straight tube was carried out under different gas-liquid ratios. Through modifying experimental pressure and temperature conditions, comparative studies on liquid phase CO 2 and gaseous CO 2 foam rheology were also carried out. The experimental results show obvious shear-thickening behavior for the scCO 2 foam (45 °C and 8.0 MPa) with flow behavior index increasing from 1.03 to 1.76 with increasing foam quality. And the apparent viscosity of scCO 2 foam could reach up to 140 times of the single-phase water. The liquid phase CO 2 foam (25 °C and 8.0 MPa) also exhibits clearly the shear-thickening characteristics with flow behavior index ranging from 1.56 to 1.88. The gaseous CO 2 foam, on the other hand, behaves in a shear-thinning or pseudo-plastic manner with flow behavior index of 0.70 < n < 0.76. Due to the decreased interfacial tension and less bubble coalescence rate, much finer foam textures are observed for ScCO 2 and liquid CO 2 bulk foam, which mainly contributes to the shear thickening behavior for ScCO 2 and liquid CO 2 foam fluid. [ABSTRACT FROM AUTHOR]

A numerical analysis employing the stochastic population balance (SPB) model is presented on foam displacement behavior in a water saturated heterogeneous porous media consisted of two parallel layers of medium with different permeabilities. Detailed parameter studies of the two key parameters of the SPB model, bubble generate rate K g and maximum bubble density n ∞ , are carried out to understand foam flow behavior and mechanisms in the heterogeneous porous media. Numerical results indicate variation of Kg and n ∞ values could significantly affect the ongoing foam flooding process and lead to obviously different pressure drops and sweep efficiencies. The parameter of K g stands for the formation rate of foam, therefore determines the distance and time for foam fluid reaching equilibrium in the displacement process. Higher Kg values result in higher pressure drop and lower water saturation after foam sweeping through the heterogeneous porous media. The parameter of n ∞ , on the other hand, determines directly the magnitude of foam apparent viscosity through defining the maximum bubble density of the flooding foam fluid. Larger n ∞ values lead to higher pressure drops and higher foam sweep efficiencies of the heterogeneous porous media. Reasonable numerical results indicate the SPB model could adequately describe foam displacement process in the heterogeneous media, therefore supplies an important alternative for foam mechanistic studies to promote essentially the foam field applications. [ABSTRACT FROM AUTHOR]

Stochastic Bubble Population (SBP) balance model has been widely applied on investigation of surfactant foam flow characteristics in porous media, while its application on predict nanoparticle (NP)-stabilized foam behavior has not been well refined. There are two empirical parameters in the SBP model, namely, the bubble generation rate K g and the maximum bubble density n max. To qualify the SBP model on prediction of the transient NP-stabilized foam propagation behavior, we make the efforts to calibrate the parameters of K g and n max based on the literature reported systematic experimental results. Through five sets of simulations in correspondence to the experimental works, it is found K g has little effect on the pressure drop along the core, while the n max increases from 200 mm−3 to 8000 mm−3 with the addition of NPs and the increment of NP concentration. Larger n max values at higher NP concentrations indicates the foam stabilized by NPs has stronger foam structure and therefore leads to a better displacement result. It is concluded that based on the simple but carefully calibrated parameters, SBP model could provide accurate predictions of NP-stabilized foam flow characteristic in porous media. [ABSTRACT FROM AUTHOR]

In relationship with the potential application of nanoparticle (NP) foam technology in CO2 enhanced oil recovery (EOR) and greenhouse geological storage in tight reservoirs, the rheological properties of the NP-stabilized CO2 foam with surfactant (α-olefin sulfonate-AOS) solution were experimentally investigated. The foam was treated as a power-law non-Newtonian fluid, and the relationships between the shear stress and shear rate as well as the apparent viscosity of foam and foam quality were determined under influential parameters including the NP additive, internal gas type, salinity, and oil presence. Critical foam quality values in the range 91–96% were observed for the NP-stabilized foam, whereas no such values were obtained for the corresponding AOS-CO2 foam. The results show the NP-AOS-CO2 foam has lower viscosity compared to the NP-AOS-N2 foam, and the solution salinity decreases the viscosity of the NP-AOS-CO2 foam, whereas oil presence has no obvious effect on the foam viscosity. • Rheological properties of Nanoparticle (NP) stabilized CO2 foam are comprehensively investigated. • Effects of internal gas phase, salinity and oil presence are studied. • Critical foam quality is clearly observed. • Oil presence doesn't show negative effect on NP stabilized CO2 foam strength. [ABSTRACT FROM AUTHOR]

Foam technology has shown great potentials not only on enhancing oil recovery (EOR) but also on the Carbon Capture Storage Utilization (CCUS) applications. In this paper, the foam three phase displacement characteristics in the porous media is investigated based on the mechanistic Stochastic Bubble Population Balance (SBPB) model. With taking the foam generation rate K g and maximum bubble density n max as the key influential parameters, the dynamic distributions of the water, oil and gas phase saturations as well as the bubble densities along the foam flow direction are successfully obtained. Firstly, the overall computation frame is validated based on good agreements between the numerical and the reported experimental results on the foam displacement efficiency on water and oil phases. Then, the parameter studies are thoroughly performed concerning the two key factors of K g and n max in the SBPB model. Numerical results show the parameter of K g dominates the foam flow behavoir in the inlet region of the porous media therefore doesn't show significant effect on the final oil and gas phase recovery rates. On the other hand, it is found larger n max could lead to higher oil and water recovery ratio, which indicates to increase the n max values of the foam fluid could act as the favorable means in oil recovery enhancement practices. • The SBPB model is validated on simulating foam three phase displacement process in porous media. • The parameter studies on model factors of K g and n max are thoroughly performed. • The dynamic foam behavior as well as the recovery efficiency for water and oil phase is reported. • It is revealed higher n max is the favorable mechanism in foam oil recovery enhancement. [ABSTRACT FROM AUTHOR]

Foam technology has shown great potential in enhancing oil recovery as well as fulfilling carbon geological storage practices in mature and low permeability reservoirs. To reveal the mechanism of the foam quality effect on foam displacement behavior in underground formations, numerical studies on three-phase foam flow characteristics in porous media have been carried out based on the Stochastic Bubble Population Balance (SBPB) model. Through modifying the injection gas and liquid rate ratio, various foam qualities between 40% and 90% have been set, and the effect of foam quality was taken into account with higher foam quality corresponding to the larger maximum bubble density parameter in the SBPB model. Comprehensive numerical results, including the dynamic distribution curves of the oil, water, and foam phase saturation, oil phase pressure, and the foam bubble density along the flow direction, were obtained under different foam quality cases. Parameter investigations on the bubble generation rate and the oil viscosity were carried out as well. It is observed the pressure drop and water recovery rate of the foam flooding process increases monotonously with the increasing foam quality, while the ultimate oil recovery rate shows the highest value at the intermediate foam quality of 70%. The numerical results on the foam quality effect agree well with reported experimental observations, indicating the SBPB model could characterize in mechanism the three phase foam displacement behavior in porous media. [Display omitted] [ABSTRACT FROM AUTHOR]

Adding nanoparticles (NPs) into surfactant solution has been widely employed in improving foam stability in CO 2 Enhanced Oil Recovery (EOR) applications. To help understand the foam flow characteristics in porous media, the rheology behavior of the NP-stabilized CO 2 foam is experimentally investigated in this paper. The foam fluid is treated as a non-Newtonian fluid obeying the power law constitutive equation, and the effect of CO 2 phase state, oil presence as well as solution salinity on the power law index, and the apparent viscosity of the NP-stabilized foam is scrutinized. Different rheology behavior between the NP-stabilized gaseous CO 2 foam and the supercritical CO 2 (ScCO 2) foam is revealed in the both power law index and the apparent viscosity results. The NP-stabilized gaseous CO 2 foam shows the rheology transition behavior from shear thickening to shear thinning with increasing shear rates and supplies maximal foam apparent viscosity of 27.7 mPa s, whereas the NP-stabilized ScCO 2 foam shows the universal shear thickening behavior in the studied shear rate range with much higher maximum apparent viscosity of 95.8 mPa s. It is found the apparent viscosity of the NP-stabilized ScCO 2 foam could reach up to 210.9 mPa s under the oil presence conditions, while 5 wt% NaCl existence in the aqueous solution could result in slightly lower apparent viscosity of 80.3 mPa s. • Systematic studies on NP-stabilized CO 2 foam rheology are performed focusing on the phase state, oil and salt effects. • The rheology transition from shear thickening to shear thinning is observed for NP-stabilized gaseous foam. • NP-stabilized ScCO 2 foam shows shear thickening behavior and much higher viscosity than gaseous CO 2 foam. • Effect of oil and salt presence on NP-stabilized ScCO 2 foam rheology is revealed. [ABSTRACT FROM AUTHOR]