Browsing by Author "Ma, Kun"

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    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.
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    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.
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    Measuring in-situ capillary pressure of a flowing foam system in porous media
    (Elsevier, 2022) Vavra, Eric; Puerto, Maura; Bai, Chutian; Ma, Kun; Mateen, Khalid; Biswal, Lisa; Hirasaki, George
    Hypothesis: Capillary pressure (Pc) is an intrinsic property of aqueous foams that has been demonstrated to play an important role in lamella rupture. Thus, directly measuring in-situ capillary pressure of a foam flowing through porous media has potential to greatly improve understanding of this complex process. Experiments: A capillary pressure probe was constructed and validated. Direct measurements of capillary pressure were made at ambient conditions during foam quality scan experiments in a transparent 1.41 × 10−10 m2 (143-Darcy) homogenous sand pack conducted at constant gas velocity. The foam texture was simultaneously visualized at the wall of the sand pack via microscope. Findings: In the low-quality regime, a plateauing trend in Pc was identified. In-situ microscopic visualization of the flowing foam revealed that gas bubbles were convecting with a fine discontinuous texture while Pc is at the plateau value Ppc. In the high-quality regime, the measured capillary pressures first decreased with increasing quality before increasing again at the driest qualities. These changes in Pc correlated with foam bubbles becoming coarser with increasing injected gas fractional flow before transitioning to continuous-gas flow at the slowest and driest injection conditions. These findings have been previously unreported for steady-state flow conditions and shall have significant implications for the general physical description of foam flow in porous media.
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    Transport of Surfactant and Foam in Porous Media for Enhanced Oil Recovery Processes
    (2013-09-16) Ma, Kun; Hirasaki, George J.; Biswal, Sibani Lisa; Miller, Clarence A.; Gonnermann, Helge M.
    The use of foam-forming surfactants offers promise to improve sweep efficiency and mobility control for enhanced oil recovery (EOR). This thesis provides an in depth understanding of transport of surfactant and foam through porous media using a combination of laboratory experiments and numerical simulations. In particular, there are several issues in foam EOR processes that are examined. These include screening of surfactant adsorption onto representative rock surfaces, modeling of foam flow through porous media, and studying the effects of surface wettability and porous media heterogeneity. Surfactant adsorption onto rock surfaces is a main cause of foam chromatographic retardation as well as increased process cost. Successful foam application requires low surfactant adsorption on reservoir rock. The focus of this thesis is natural carbonate rock surfaces, such as dolomite. Surfactant adsorption was found to be highly dependent on electrostatic interactions between surfactants and rock surface. For example, the nonionic surfactant Tergitol 15-S-30 exhibits low adsorption on dolomite under alkaline conditions. In contrast, high adsorption of cationic surfactants was observed on some natural carbonate surfaces. XPS analysis reveals silicon and aluminum impurities exist in natural carbonates, but not in synthetic calcite. The high adsorption is due to the strong electrostatic interactions between the cationic surfactants and negative binding sites in silica and/or clay. There are a number of commercial foam simulators, but an approach to estimate foam modeling parameters from laboratory experiments is needed to simulate foam transport. A one-dimensional foam simulator is developed to simulate foam flow. Chromatographic retardation of surfactants caused by adsorption and by partition between phases is investigated. The parameters in the foam model are estimated with an approach utilizing both steady-state and transient experiments. By superimposing contour plots of the transition foam quality and the foam apparent viscosity, one can estimate the reference mobility reduction factor (fmmob) and the critical water saturation (fmdry) using the STARS foam model. The parameter epdry, which regulates the abruptness of the foam dry-out effect, can be estimated by a transient foam experiment in which 100% gas displaces surfactant solution at 100% water saturation. Micromodel experiments allow for pore-level visualization of foam transport. We have developed model porous media systems using polydimethylsiloxane. We developed a simple method to tune and pattern the wettability of polydimethylsiloxane (PDMS) to generate porous media models with specific structure and wettability. The effect of wettability on flow patterns is observed in gas-liquid flow. The use of foam to divert flow from high permeable to low permeable regions is demonstrated in a heterogeneous porous micromodel. Compared with 100% gas injection, surfactant-stabilized foam effectively improves the sweep of the aqueous fluid in both high and low permeability regions of the micromodel. The best performance of foam on fluid diversion is observed in the lamella-separated foam regime, where the presence of foam can enhance gas saturation in the low permeable region up to 45.1% at the time of gas breakthrough. In conclusion, this thesis provides new findings in surfactant adsorption onto mineral surfaces, in the methodology of estimating foam parameters for reservoir simulation, and in micromodel observations of foam flow through porous media. These findings will be useful to design foam flooding in EOR processes.
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    Visualizing oil displacement with foam in a microfluidic device with permeability contrast
    (The Royal Society of Chemistry, 2014) Conn, Charles A.; Ma, Kun; Hirasaki, George J.; Biswal, Sibani Lisa
    Foam mobility control and novel oil displacement mechanisms were observed in a microfluidic device representing a porous media system with layered permeability. Foam was pre-generated using a flow focusing microfluidic device and injected into an oil-wet, oil-saturated 2-D PDMS microfluidic device. The device is designed with a central fracture flanked by high-permeability and low-permeability zones stratified in the direction of injection. A 1 : 1, 1% blend of alpha olefin sulfonate 14-16 (AOS) and lauryl betaine (LB) surfactants produced stable foam in the presence of paraffin oil. The oil saturation and pressure drop across the microfluidic device were measured as a function of time and the injected pore volume, indicating an increase in apparent viscosity for foam with an accompanying decrease in oil saturation. In contrast to the control experiments, foam was shown to more effectively mobilize trapped oil by increasing the flow resistance in the fracture and high-permeability zones and by diverting the surfactant solution into adjacent low-permeability zones. The foam was observed to separate into gas-rich and aqueous-rich phases depending on matrix permeability, suggesting that it is not appropriate to treat foam as a homogeneous dispersion of gas and liquid.