Browsing by Author "Farajzadeh, Rouhi"
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Item A 2-D simulation study on CO2ᅠsoluble surfactant for foam enhanced oil recovery(Elsevier, 2019) Zeng, Yongchao; Farajzadeh, Rouhi; Biswal, Sibani L.; Hirasaki, George J.This paper probes the transport of CO2ᅠsoluble surfactant for foaming in porous media. We numerically investigate the effect of surfactant partitioning between the aqueous phase and the gaseous phase on foam transport for subsurface applications when the surfactant is injected in the CO2ᅠphase. A 2-D reservoir simulation is developed to quantify the effect of surfactant partition coefficient on the displacement conformance and CO2ᅠsweep efficiency. A texture-implicit local-equilibrium foam model is embedded to describe how the partitioning of surfactant between water and CO2ᅠaffects the CO2ᅠfoam mobility control when surfactant is injected in the CO2ᅠphase. We conclude that when surfactant has approximately equal affinity to both the CO2ᅠand the water, the transport of surfactant is in line with the gas propagation and therefore the sweep efficiency is maximized. Too high affinity to water (small partition coefficient) results in surfactant retardation whereas too high affinity to CO2ᅠ(large partition coefficient) leads to weak foam and insufficient mobility reduction. This work sheds light upon the design of water-alternating-gas-plus-surfactant-in-gas (WAGᅠ+ᅠS) process to improve the conventional foam process with surfactant-alternating-gas (SAG) injection mode during which significant amount of surfactant could possibly drain down by gravity before CO2ᅠslugs catch up to generate foam in situ the reservoir.Item Distinguishing the Effect of Rock Wettability from Residual Oil on Foam Generation and Propagation in Porous Media(American Chemical Society, 2021) Amirmoshiri, Mohammadreza; Wang, Xinglin; Bai, Chutian; Tewari, Raj Deo; Xie, Sheena Xina; Bahrim, Ridhwan Zhafri Kamarul; Singer, Philip M.; Farajzadeh, Rouhi; Biswal, Sibani Lisa; Hirasaki, George. J.One of the common challenges of applying foam for enhanced oil recovery is the foam instability in the presence of crude oil and nonwater-wet surfaces. In this experimental study, we systematically distinguish the effect of rock surface wettability from that of crude oil saturation on foam rheology under reservoir conditions. Neutral-wet Berea and reservoir sandstone cores are prepared by aging with crude oil, followed by the wettability index measurements. Transient foam generation and steady-state foam quality scans are conducted in neutral-wet cores, with/without water-flood residual oil. Nuclear magnetic resonance imaging is also utilized to measure the remaining oil saturation at the end of the foam-flood. It is shown that strong foam can be generated in a neutral-wet core with no residual oil because of the solubilization of the adsorbed crude oil components and the wettability alteration toward more water-wet conditions. However, in a neutral-wet core containing residual oil, foam generation is initially hindered. Foam generation occurs after injecting several pore volumes of surfactant solution and increasing the superficial velocity to overcome the minimum pressure gradient required for in situ foam generation. The findings from this study suggest that surface wettability in the presence of bulk oil saturation significantly affects transient foam generation. The final steady-state foam strength becomes comparable to the water-wet and oil-free case once the residual oil saturation is adequately reduced.Item Effect of Surfactant Partitioning Between Gaseous Phase and Aqueous Phase onᅠCO2ᅠFoam Transport for Enhanced Oil Recovery(Springer, 2016) Zeng, Yongchao; Ma, Kun; Farajzadeh, Rouhi; Puerto, Maura; Biswal, Sibani L.; Hirasaki, George J.CO2 flood is one of the most successful and promising enhanced oil recovery technologies. However the displacement is limited by viscous fingering, gravity segregation and reservoir heterogeneity. Foaming the CO2 and brine with a tailored surfactant can simultaneously address these three problems and improve the recovery efficiency. Commonly chosen surfactants as foaming agents are either anionic or cationic in class. These charged surfactants are insoluble in either CO2 gas phase or supercritical phase and can only be injected with water. However, some novel nonionic or switchable surfactants are CO2 soluble, thus making it possible to be injected with the CO2 phase. Since surfactant could be present in both CO2 and aqueous phases, it is important to understand how the surfactant partition coefficient influences foam transport in porous media. Thus, a 1-D foam simulator embedded with STARS foam model is developed. All test results, from different cases studied, have demonstrated that when surfactant partitions approximately equally between gaseous phase and aqueous phase, foam favors oil displacement in regard with apparent viscosity and foam propagation speed. The test results from the 1-D simulation are compared with the fractional flow theory analysis reported in literature.Item Insights on Foam Transport from a Texture-Implicit Local-Equilibrium Model with an Improved Parameter Estimation Algorithm(American Chemical Society, 2016) Zeng, Yongchao; Muthuswamy, Aarthi; Ma, Kun; Wang, Le; Farajzadeh, Rouhi; Puerto, Maura; Vincent-Bonnieu, Sebastien; Akbar Eftekhari, Ali; Wang, Ying; Da, Chang; Joyce, Jeffrey C.; Biswal, Sibani L.; Hirasaki, George J.We present an insightful discussion on the implications of foam transport inside porous media based on an improved algorithm for the estimation of model parameters. A widely used texture-implicit local-equilibrium foam model, STARS, is used to describe the reduction of gas mobility in the state of foam with respect to free gas. Both the dry-out effect and shear-dependent rheology are considered in foam simulations. We estimate the limiting capillary pressure Pc* from fmdryvalues in the STARS model to characterize foam film stability in a dynamic flowing system. We find that Pc* is a good indicator of foam strength in porous media and varies with different gas types. We also calculate Pc* for different foaming surfactants and find that foam stability is correlated with the Gibbs surface excess concentration. We compare our improved parameter estimation algorithm with others reported in literature. The robustness of the algorithm is validated for various foam systems.Item Role of Gas Type on Foam Transport in Porous Media(American Chemical Society, 2016) Zeng, Yongchao; Farajzadeh, Rouhi; Eftekhari, Ali Akbar; Vincent-Bonnieu, Sebastien; Muthuswamy, Aarthi; Rossen, William R.; Hirasaki, George J.; Biswal, Sibani L.We present the results of an experimental investigation of the effect of gas type and composition on foam transport in porous media. Steady-state foam strengths with respect to three cases of distinct gases and two cases containing binary mixtures of these gases were compared. The effects of gas solubility, the stability of lamellae, and the gas diffusion rate across the lamellae were examined. Our experimental results showed that steady-state foam strength is inversely correlated with gas permeability across a liquid lamella, a parameter that characterizes the rate of mass transport. These results are in good agreement with existing observations that the foam strength for a mixture of gases is correlated with the less soluble component. Three hypotheses with different predictions of the underlying mechanism that explain the role of gas type and composition on foam strength are discussed in detail.