Browsing by Author "Hirasaki, George"
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Item A Multi-scale Study of Carbonate Wettability Alteration: A Route to “Smart Water”(2019-12-05) Song, Jin; Hirasaki, George; Biswal, Sibani Lisa“Smart water” refers to the low-salinity brine that can alter wettability and enhance oil recovery. The injection of “smart water” as a low-cost enhanced oil recovery (EOR) approach has drawn increasing attentions in the oil and gas industry. Particularly, the “smart water” EOR has promising applications in oil-wet, naturally fractured carbonate reservoirs where capillary imbibition is extremely important. Successes of “smart water” in carbonate systems have been reported in both laboratory flooding experiments and a field-scale pilot. However, underlying mechanism of the “smart water”-induced wettability alteration in carbonates remains unclear. Therefore, this dissertation systematically investigates the wettability alteration process of carbonate rocks in “smart water”. The first objective of this work is to understand the electrostatic interactions between carbonate rocks and oils. In particular, the surface charge of carbonate minerals in brines has been a focus of literature research because it is generally believed to govern the surface wettability. To model the formation of surface charge, surface complexation models (SCM) are developed based on rock-ion complexations. A SCM was first developed for pure calcite, the primary component of carbonate rocks, in Chapter 3. Divalent ions Ca2+, Mg2+, CO32-, and SO42- are found to bind much more strongly to the calcite than monovalent ions. The equilibrium constants for binding reactions are also found to negatively correlate to the hydrated ion radius for ions of the same charge. Moreover, the weak potential determining ion Na+ is found to significantly contribute to the positive charge of calcite in high-salinity brines (5M NaCl). The synthetic calcite SCM was then extended to work for natural carbonates with surface impurities in Chapter 4. Three carbonate rocks, Iceland spar, Indiana limestone, and “SME” reservoir rock, were investigated. The effects of inorganic impurity silica and organic impurities are examined individually in the model calculation. Both the silica surface binding reactions and the organic acids surface coverage (%) are included in the extended model. The SCM successfully fits all 63 zeta potential data of synthetic calcite and three natural carbonates in various mixed-electrolyte brines with varying ionic strengths and CO2 partial pressures. The organic impurities are found to play the dominant role in making the natural carbonates more negatively charged than synthetic calcite. Humic acids extracted from a humus sample were used to treat the synthetic calcite sample in an experiment. The treated calcite had a significantly more negative zeta potential, demonstrating the effect of organic impurities on the carbonate surface charge. The second objective of this work is to experimentally evaluate the carbonate wettability alteration in “smart water”. Spontaneous imbibition was chosen over contact angle to characterize wettability alteration due to the poor reproducibility of contact angle measurements. The effects of brine chemistry, especially Mg2+, SO42-, and salinity, were investigated in a model oil system in Chapter 5. Both the reduction in Na+ and addition of SO42- are found to contribute to wettability alteration. Mg2+ is found to be unfavorable for wettability alteration. Ca2+ is believed to facilitate SO42- with wettability alteration. Rock/brine and oil/brine zeta potentials are measured, and the electrostatic component of disjoining pressure is calculated to understand the role of electrostatics in this process. The surface concentration of charged species on the Indiana limestone surface is also analyzed based on the SCM developed in Chapter 4. The reduction of the Na+ surface complexation (>CaOH…Na+0.25) in low salinity brines is believed to be a critical mechanism responsible for wettability alteration based on the SCM calculations. In Chapter 6, the effect of oil physicochemical properties on carbonate wettability alteration was also investigated by spontaneous imbibition measurements. The results were also used to evaluate two possible wettability alteration mechanisms: rock/oil electrostatic repulsion and microdispersion formation. Seven oils were fully characterized and used in spontaneous imbibition measurements in low-salinity water. For the first time, the effectiveness of low-salinity water is found to positively correlate with the oil interfacial tension in low-salinity water. Oils with higher interfacial activity are found to respond more positively to low-salinity water. Moreover, cryogenic transmission electron microscopy (Cryo-TEM) images suggest that microdispersion is essentially macroemulsion, and its formation is an effective indicator – but not the root cause – of wettability alteration. Rock/oil electrostatic repulsion based on zeta potentials is found to be an insufficient condition for wettability alteration in carbonate minerals. Finally, low-salinity water coreflooding was performed using a crude oil that responded positively to low-salinity water in spontaneous imbibition. 41% of original oil in-place (OOIP) was recovered after the initial high-salinity water flooding. An additional 12% (of OOIP) is observed after the injection of low-salinity water. The reduction of NaCl concentration is confirmed to effectively improve oil recovery in the forced displacement experiment.Item Diffusion phenomena in oil-water-surfactant systems(1983) Raney, Kirk H.; Miller, Clarence A.; Zygouakis, Kyriacos; Dyson, Derek; Hirasaki, GeorgeThe diffusional processes which occur when oil contacts an aqueous surfactant solution have been investigated. These are important in enhanced oil recovery by surfactant flooding, where the rate of phase equilibration can affect recovery efficiency. Also, they are pertinent to certain mechanisms of detergency. Experimentally, systems containing anionic surfactants and alcohol cosurfactants were studied by optical microscopy. A microscope which utilized a vertical sample orientation was specifically designed for this purpose. As a result, an Improved and detailed viewing of intermediate phase growth, interface velocities, and spontaneous emulsification was achieved. The conditions of interest ranged from low salinities at which the surfactant is water-soluble to high salinities at which it is oil-soluble. At low salinities, the initial aqueous solution was a dilute dispersion of liquid crystals in brine. After oil was gently brought into contact, an intermediate oil-in-water microemulsion began to form. Also, an increase in liquid crystal concentration was observed at the microemulsion interface. At intermediate salinities, where the surfactant solution was mostly liquid-crystalline, a brine phase and a middle-phase microemulsion were both formed. It was in this salinity range that spontaneous emulsification of brine drops in the oleic phase began to occur. At high salinities, only a brine phase formed between the initial phases. Myelinic projections slowly developed at the liquid crystal-brine interface and changed in size and shape as diffusion proceeded. These salinity conditions produced vigorous spontaneous emulsification of brine in oil. In some systems, the brine phase formed by diffusion was more dense than the liquid-crystalline phase below it. Brine would channel to low points and push liquid crystal up to the' oil interface. The points at which liquid crystal contacted the oil produced volcano-like instabilities where mass transfer was enhanced. Not unexpectedly, these systems equilibrated much more rapidly than those in which diffusion predominated. The theory of diffusion paths, extended to allow for diffusion in a dispersed-phase region, was used to solve the diffusion equations for a model, pseudo-ternary system. As a result, the calculated diffusion paths and interface velocities were used to qualitatively explain the various phenomena observed experimentally.Item Foam rheology of zwitterionic anionic blends in porous media(2016-03-30) Muthuswamy, Aarthi; Hirasaki, George; Miller, Clarence; Verduzco, Rafael; Biswal, Lisa; Tomson, MasonBlending of certain types of surfactants is known to promote synergism as studied by bulk measurements. This study analyzes if such synergistic interactions are beneficial for foam rheology in porous media. Foam experiments were conducted systematically in porous media, at different ratios of zwitterionic and anionic surfactants, both in the presence and absence of crude oil. Interfacial studies were conducted to explain the behavior of surfactant mixtures with respect to foam rheology in porous media. The zwitterionic surfactants used in this study were C12 straight chain betaine- Lauryl betaine (LB), C12 straight chain sultaine- Lauryl sultaine (LS), C18 tailed amido betaine (Rhodia A), C 18-22 tailed amido sultaine (Rhodia B), C 18-22 tailed amido betaine - with more C 22 (Rhodia C) and C 18-22 tailed amido betaine -with more C18 (Rhodia D). LB and LS surfactants had a viscosity close to that of water ~1 cP at room temperature. On the other hand 0.5 wt% of Rhodia A, Rhodia B, Rhodia C and Rhodia D were viscoelastic and shear thinning fluids due to the presence of wormlike micelles. Rheological studies which were conducted at room temperature revealed that salinity had a prominent effect on Rhodia A. On increasing salinity from ~ 4% to 12%, the relaxation time of Rhodia A increased by three orders of magnitude, thereby causing the weakly viscoelastic surfactant solution to change to a strongly viscoelastic solution. On the other hand salinity had a negligible effect on Rhodia B, Rhodia C and Rhodia D. When 1 wt% surfactant solutions of Rhodia A, B, C or D were mixed with ~ 35% synthetic crude oil (mass basis), all surfactant solutions lost viscosity and viscoelasticity except Rhodia C. Crude oil had an adverse effect on Rhodia A perhaps due to the conversion of wormlike micelles to spherical micelles. Rhodia B and D had lower elastic and viscous moduli most likely due to the shortening of the wormlike micelles. Additional tests were done to study the flow of these complex fluids in a 100 Darcy silica sand pack. Rhodia A, B and D showed no elongational effects during flow in porous media. Their shear thinning apparent viscosities in porous media were very close to the rheometric data in shear flow. Rhodia C exhibited yield stress behavior and hence could not be injected in a porous medium. Zwitterionic surfactants Rhodia A/LB/LS were blended with anionic Alpha Olefin Sulfonate AOS 14-16 (AOS) surfactant at specific ratios - one with high and one with low bulk mass ratio of zwitterionic to anionic. Rhodia A which was weakly viscoelastic by itself, when blended with AOS in the ratio 9:1 respectively (by mass) produced a strongly viscoelastic solution. Nitrogen foam experiments were conducted in 100 Darcy silica sand at 25° C for Rhodia A and AOS blends and, in Bentheimer sandstone cores at 45° C, for LB/AOS blends and LS/AOS blends. Zwitterionic surfactants of this type have been reported to be “foam boosters” for bulk foams when added to anionic surfactant. Rhodia A betaine was a weak foamer both in the presence and absence of oil. However when blended with AOS (9:1 ratio), its foam strength significantly improved in the absence of oil. In the presence of oil the viscoelastic surfactant helped generate strong foam in fewer pore volumes (PVs- a dimensional unit of time) but took a longer time than AOS to propagate through the sand pack. In the case of LB/AOS and LS/AOS surfactant systems, the zwitterionic (LB, LS) foam by itself was weak, but AOS and the blends of zwitterionic and AOS had strong foam with comparable foam rheology. The regular solution theory approach of Rubingh combined with Rosen’s application to water-air film interfaces and its adaption to oil-water interfaces was applied to understand this behavior, especially the high foam strength observed when the poor-foaming zwitterionics were added to the strong foamer AOS. It was found that the zwitterionic-anionic blends exhibited synergistic interactions. The Gibbs surface excess calculations suggested that the synergistic interactions promoted tighter packing at the interface thereby helping the poorly foaming zwitterionic surfactant to exhibit strong foam rheology in porous media. Interestingly, AOS surfactant by itself had tight packing at the interface. The trends observed in porous media were well explained by the Gibbs surface excess calculations. However, the synergism did not lead to improvement in foam performance in porous media beyond that seen for AOS alone. Additionally foam strength in the presence of water flood residual oil was weak for the pure zwitterionic surfactants, but the blends with higher mole fraction of AOS and pure AOS had comparable foam performance. Again AOS by itself was able to achieve good mobility control in displacing residual oil. The addition of zwitterionic surfactant had apparently not boosted the foam performance of AOS in porous media in the presence of oil as well. Interfacial shear rheology for the LB/AOS and LS/AOS systems were performed and it showed that none of the surfactants possessed interfacial shear viscosity. Qualitative film drainage studies were conducted and it was observed that a small addition of LB to AOS helped in creating very stable black film and substantially increased the longevity of the film more than AOS itself. However all these thin film studies failed to offer any explanation to porous media foam studies but perhaps help develop an understanding on bulk foam studies. In the case of Rhodia A:AOS 9:1 viscoelastic blend, an injection strategy can be proposed where in a small slug of A:AOS 9:1 blend can be injected which can aid in quicker foam generation followed by a large AOS slug which can help in faster propagation and hence more efficient oil recovery. Anionic AOS 14-16 surfactant did not need a foam booster contrary to the opinion in literature that a betaine surfactant (coco amido propyl betaine) is needed to boost the foam strength of an anionic surfactant (AOS 16-18) in the presence and absence of crude oil in porous media.Item High order discontinuous Galerkin methods for simulating miscible displacement process in porous media with a focus on minimal regularity(2015-04-20) Li, Jizhou; Riviere, Beatrice M.; Symes, William; Hirasaki, George; Warburton, Timothy; Heinkenschloss, MatthiasIn my thesis, I formulate, analyze and implement high order discontinuous Galerkin methods for simulating miscible displacement in porous media. The analysis concerning the stability and convergence under the minimal regularity assumption is established to provide theoretical foundations for using discontinuous Galerkin discretization to solve miscible displacement problems. The numerical experiments demonstrate the robustness and accuracy of the proposed methods. The performance study for large scale simulations with highly heterogeneous porous media suggests strong scalability which indicates the efficiency of the numerical algorithm. The simulations performed using the algorithms for physically unstable flow show that higher order methods proposed in thesis are more suitable for simulating such phenomenon than the commonly used cell-center finite volume method.Item 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, GeorgeHypothesis: 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.Item Transport Phenomena(Rice University, 2010-05-24) Hirasaki, GeorgeItem Two-Step Adsorption of a Switchable Tertiary Amine Surfactant Measured Using a Quartz Crystal Microbalance with Dissipation(American Chemical Society, 2019) Chen, Yi-Lin; Zhang, Leilei; Song, Jin; Jian, Guoqing; Hirasaki, George; Johnston, Keith; Biswal, Sibani LisaThe adsorption of a switchable cationic surfactant, N,N,N′-trimethyl-N′-tallow-1,3-diaminopropane (DTTM, Duomeen TTM), at the silica/aqueous solution interface is characterized using a quartz crystal microbalance with dissipation (QCM-D). The adsorption isotherms reveal that changes in the solution pH or salinity affect surfactant adsorption in competing ways. In particular, the combination of the degree of protonation of the surfactant and electrostatic interactions is responsible for surfactant adsorption. The kinetics of adsorption is carefully measured using the real-time measurement of a QCM-D, allowing us to fit the experimental data with analytical models. At pH values of 3 and 5, where the DTTM is protonated, DTTM exhibits two-step adsorption. This is representative of a fast step in which the surfactant molecules are adsorbed with head-groups orientated toward the surface, followed by a slower second step corresponding to formation of interfacial surfactant aggregates on the silica surface.Item Ultra-low-tension compositions and their use in enhanced oil recovery(2018-01-02) Puerto, Maura; Salinas, José Luis López; Miller, Clarence A.; Hirasaki, George; Rice University; United States Patent and Trademark OfficeIn some embodiments, the present disclosure pertains to compositions for enhanced oil recovery. In some embodiments, such compositions include: (1) a first agent, wherein the first agent acts as a foam booster; (2) a second agent, wherein the second agent includes a sulfonated or sulfated anionic surfactant; a (3) a third agent, wherein the third agent includes an alkoxylated and anionic surfactant; and (4) a base liquid. In some embodiments, the compositions of the present disclosure further include a gas, such as nitrogen. Further embodiments of the present disclosure pertain to methods of formulating the aforementioned compositions for enhanced oil recovery. Additional embodiments of the present disclosure pertain to methods of recovering oil from a reservoir by utilizing the aforementioned compositions.