Browsing by Subject "Foam"
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Item Characteristics of foamed asphalt binders for warm mix asphalt applications(2014-08) Arega, Zelalem Alebel; Bhasin, Amit; Li, Wei, doctor of mechanical engineering; Prozzi, Jorge A; Zhang, Zhanmin; Juenger, Maria GAn increase in environmental awareness and energy concerns had recently prompted efforts to make pavement construction cheaper and more environmentally friendly. Warm mix asphalt (WMA) is an asphalt mixture production technology that promises to reduce production costs and greenhouse gas emissions. Foamed asphalt binder is increasingly being used to produce WMA. This dissertation addresses several issues related to the use of foamed asphalt binder for WMA applications. The first objective of the research presented in this dissertation is to develop a method and metrics to precisely quantify the characteristics of asphalt binder foams. Laboratory measurements were obtained using the newly developed method to evaluate the extent and stability of foams produced using different asphalt binders at different water contents and laboratory foaming devices. Results demonstrate that the method developed is promising in terms of its ability to provide a detailed history of the behavior of foamed asphalt binder as the foam collapses. In addition, results indicate that the method is sensitive to distinguish between foaming characteristics of different asphalt binders as well as different water contents and foaming devices. The second objective of this study was to relate intrinsic properties of the asphalt binder to its foaming characteristics. A physical model was developed for expansion of asphalt binder foam based on foam physics and fluid mechanics of micro-droplets. The model relates foamant water and asphalt binder mixing efficiency with the surface tension of the asphalt binder. The model can be used to predict which binder can be effectively foamed and used, and whether any chemical modification to the binder is necessary to achieve the same. Results indicate that only a small percentage of water is effective in foaming the asphalt binder. The last objective of this research was to evaluate the influence of foaming on asphalt binder residues and mixture workability and coatability. The influence of foaming process on the rheological properties of asphalt binder residue was investigated. In addition, the significance of foamed asphalt binder characteristics on mixture workability and coatability was evaluated. Results from this last part of the study can be used to optimize binder foaming such that the resulting mixture is coated and compacted without compromising performance.Item Compressibility of nanoparticle stabilized foams for foamed cement applications(2014-12) Salas Porras, Ricardo Federico; Bryant, Steven L.; Bommer, Paul MichaelFoamed cement is widely used in the oil and gas industry to provide zonal isolation. Foamed cement provides various advantages vs. pure cement. The primary purpose of foamed cement is to reduce the density of the cement mixture. Consequently, foamed cement can be used in weak formations were reduced exerted hydrostatic pressure is needed to prevent/control cement circulation loss into the formation. However, Due to gas compressibility, foamed cement’s gas injection rate has to be constantly adjusted in order to create a constant density slurry through the height of the cement column. Furthermore, foamed cement’s properties include higher ductility, constant pressure exertion to the formation during cement transition time (gelling) and lower thermal conductivity. The ability of solid silica nanoparticles to generate stable gas/water foams was researched for foamed cement applications. Solid nanoparticles have been shown to permanently stabilize foams by assembling into layers at the gas/water interface. A potential decrease in compressibility of the gas phase by the presence of these armoring bubble layers was investigated. Enhancement of cement’s splitting tensile strength and compressive strength by silica nanoparticles was also investigated. The addition of uncoated silica nanoparticles at various concentrations did not appear to enhance neither cement’s splitting tensile or compressive strength. In most tests with varying silica nanoparticles concentrations, the samples with nanoparticles exhibited a slightly reduced splitting tensile and compressive strength. The exception being the compressive strength of the samples mixed with the highest nanoparticle concentration tested. However, the strength improvement was small vs. its pure cement counterpart. An apparatus to test the compressibility of nanoparticle stabilized foams was built for this research. The functionality of the apparatus was validated using various test fluids. The validation process allowed for the establishment of a compressibility benchmark to compare the compressibility of nanoparticle stabilized foams. A vital conclusion of this process was that generating the particle stabilized foams under pressure would allow for greater discernment between the existence of the armored bubble effect and gas dissolution into the water phase. A type of nanoparticle was identified as having the capacity to generate long term stable foams without the need of surfactant. Partially hydrophobic surface treated silica nanoparticles were utilized to generate gas/water foams under pressure and subsequently their compressibility was measured. The compressibility of these foams did not appear to show the armored bubble effect behaving as an equivalent ideal gas + water mixture. An additional surfactant and particle stabilized foam recipe was tested and displayed the same results. It was concluded that either the particle layers were not fully forming in the foam or in the case they were forming; either foam geometry was not conductive to the distribution of forces or they likely had limited rigidity and buckled when compressed. If the latter was true, the apparatus was not sensible enough to measure the limited rigidity.Item The compressive response of open-cell foams(2005) Gong, Lixin; Kyriakides, S.The compressive response of many cellular materials is characterized by a nearly linear elastic regime, which terminates into a limit load. This is followed by an extensive load plateau that is responsible for their excellent energy absorption characteristics. The end of the plateau is usually followed by a second branch of stiff response. This study uses experiment and analysis to illustrate how the cell microstructure and the properties of the base material govern these mechanical characteristics for a class of foams. The experiments are conducted on polyester urethane open-cell foams of several cell sizes. They include: measurement of the compressive response of the foams, characterization of the foam microstructure, and measurement of the mechanical properties of foam ligaments. It was found that for such materials the onset of instability and the subsequent localization occur due to buckling of the microstructure. The foam is idealized to be periodic using the space-filling Kelvin cell assigned the major geometric characteristics found in the foams tested. Several modeling levels are used to analyze the different aspects of this complex mechanical behavior. Beam-type models are used to develop closed form expressions for the initial elastic moduli. The onset of instability is established numerically using models involving either a single or stacks of fully periodic characteristic cells. Large scale models are used to reproduce all aspects of the compressive response including crushing. In the rise direction the prevalent instability exhibits a long wavelength mode that leads to a limit load, an indication that localization is possible. By contrast, in the transverse direction the buckling mode is local to the characteristic cell and has a stable postbuckling response. For more general loadings the Bloch wave method is employed to establish the onset of instability. For such general loadings a rich variety of buckling modes are identified that are affected by the anisotropy and the multiaxiality of the loads. The crushing response is simulated by considering finite size microsections that allow localized deformation to develop. Ligament contact is approximated by limiting the amount a cell can collapse in the direction of the applied load. This arrests local collapse and causes it to spread to neighboring material at a nearly constant stress level as in the experiments. The crushing stress and the extent of the stress plateau can be evaluated by using this pseudo-contact scheme.Item Development of a four-phase flow simulator to model hybrid gas/chemical EOR processes(2015-05) Lotfollahi Sohi, Mohammad; Pope, Gary A.; Delshad, Mojdeh; Sepehrnoori, Kamy; Mohanty , Kishore K; Johnston, Keith PHybrid gas/chemical Enhanced Oil Recovery (EOR) methods are such novel techniques to increase oil production and oil recovery efficiency. Gas flooding using carbon dioxide, nitrogen, flue gas, and enriched natural gas produce more oil from the reservoirs by channeling gas into previously by-passed areas. Surfactant flooding can recover trapped oil by reducing the interfacial tension between oil and water phases. Hybrid gas/chemical EOR methods benefit from using both chemical and gas flooding. In hybrid gas/chemical EOR processes, surfactant solution is injected with gas during low-tension-gas or foam flooding. Polymer solution can also be injected alternatively with gas to improve the gas volumetric sweep efficiency. Most fundamentally, wide applications of hybrid gas/chemical processes are limited due to uncertainties in reservoir characterization and heterogeneity, due to the lack of understanding of the process and consequently lack of a predictive reservoir simulator to mechanistically model the process. Without a reliable simulator, built on mechanisms determined in the laboratory, promising field candidates cannot be identified in advance nor can process performance be optimized. In this research, UTCHEM was modified to model four-phase water, oil, microemulsion, and gas phases to simulate and interpret chemical EOR processes including free and/or solution gas. We coupled the black-oil model for water/oil/gas equilibrium with microemulsion phase behavior model through a new approach. Four-phase fluid properties, relative permeability, and capillary pressure were developed and implemented. The mass conservation equation was solved for total volumetric concentration of each component at standard conditions and pressure equation was derived for both saturated and undersaturated PVT conditions. To model foam flow in porous media, comprehensive research was performed comparing capabilities and limitations of implicit texture (IT) and population-balance (PB) foam models. Dimensionless foam bubble density was defined in IT models to derive explicitly the foam-coalescence-rate function in these models. Results showed that each of the IT models examined was equivalent to the LE formulation of a population-balance model with a lamella-destruction function that increased abruptly in the vicinity of the limiting capillary pressure, as in current population-balance models. Foam models were incorporated in UTCHEM to model low-tension-gas and foam flow processes in laboratory and field scales. The modified UTCEM reservoir simulator was used to history match published low-tension-gas and foam coreflood experiments. The simulations were also extended to model and evaluate hybrid gas/chemical EOR methods in field scales. Simulation results indicated a well-designed low-tension-gas flooding has the potential to recover the trapped oil where foam provides mobility control during surfactant and surfactant-alkaline flooding in reservoirs with very low permeability.Item Development of a four-phase thermal-chemical reservoir simulator for heavy oil(2014-12) Lashgari, Hamid Reza; Sepehrnoori, Kamy, 1951-Thermal and chemical recovery processes are important EOR methods used often by the oil and gas industry to improve recovery of heavy oil and high viscous oil reservoirs. Knowledge of underlying mechanisms and their modeling in numerical simulation are crucial for a comprehensive study as well as for an evaluation of field treatment. EOS-compositional, thermal, and blackoil reservoir simulators can handle gas (or steam)/oil/water equilibrium for a compressible multiphase flow. Also, a few three-phase chemical flooding reservoir simulators that have been recently developed can model the oil/water/microemulsion equilibrium state. However, an accurate phase behavior and fluid flow formulations are absent in the literature for the thermal chemical processes to capture four-phase equilibrium. On the other hand, numerical simulation of such four-phase model with complex phase behavior in the equilibrium condition between coexisting phases (oil/water/microemulsion/gas or steam) is challenging. Inter-phase mass transfer between coexisting phases and adsorption of components on rock should properly be modeled at the different pressure and temperature to conserve volume balance (e.g. vaporization), mass balance (e.g. condensation), and energy balance (e.g. latent heat). Therefore, efforts to study and understand the performance of these EOR processes using numerical simulation treatments are quite necessary and of utmost importance in the petroleum industry. This research focuses on the development of a robust four-phase reservoir simulator with coupled phase behaviors and modeling of different mechanisms pertaining to thermal and chemical recovery methods. Development and implementation of a four-phase thermal-chemical reservoir simulator is quite important in the study as well as the evaluation of an individual or hybrid EOR methods. In this dissertation, a mathematical formulation of multi (pseudo) component, four-phase fluid flow in porous media is developed for mass conservation equation. Subsequently, a new volume balance equation is obtained for pressure of compressible real mixtures. Hence, the pressure equation is derived by extending a black oil model to a pseudo-compositional model for a wide range of components (water, oil, surfactant, polymer, anion, cation, alcohol, and gas). Mass balance equations are then solved for each component in order to compute volumetric concentrations. In this formulation, we consider interphase mass transfer between oil and gas (steam and water) as well as microemulsion and gas (microemulsion and steam). These formulations are derived at reservoir conditions. These new formulations are a set of coupled, nonlinear partial differential equations. The equations are approximated by finite difference methods implemented in a chemical flooding reservoir simulator (UTCHEM), which was a three-phase slightly compressible simulator, using an implicit pressure and an explicit concentration method. In our flow model, a comprehensive phase behavior is required for considering interphase mass transfer and phase tracking. Therefore, a four-phase behavior model is developed for gas (or steam)/ oil/water /microemulsion coexisting at equilibrium. This model represents coupling of the solution gas or steam table methods with Hand’s rule. Hand’s rule is used to capture the equilibrium between surfactant, oil, and water components as a function of salinity and concentrations for oil/water/microemulsion phases. Therefore, interphase mass transfer between gas/oil or steam/water in the presence of the microemulsion phase and the equilibrium between phases are calculated accurately. In this research, the conservation of energy equation is derived from the first law of thermodynamics based on a few assumptions and simplifications for a four-phase fluid flow model. This energy balance equation considers latent heat effect in solving for temperature due to phase change between water and steam. Accordingly, this equation is linearized and then a sequential implicit scheme is used for calculation of temperature. We also implemented the electrical Joule-heating process, where a heavy oil reservoir is heated in-situ by dissipation of electrical energy to reduce the viscosity of oil. In order to model the electrical Joule-heating in the presence of a four-phase fluid flow, Maxwell classical electromagnetism equations are used in this development. The equations are simplified and assumed for low frequency electric field to obtain the conservation of electrical current equation and the Ohm's law. The conservation of electrical current and the Ohm's law are implemented using a finite difference method in a four-phase chemical flooding reservoir simulator (UTCHEM). The Joule heating rate due to dissipation of electrical energy is calculated and added to the energy equation as a source term. Finally, we applied the developed model for solving different case studies. Our simulation results reveal that our models can accurately and successfully model the hybrid thermal chemical processes in comparison to existing models and simulators.Item Development of compositional three-phase relative permeability and hysteresis models and their application to EOR processes(2016-12) Mohammad Reza Beygi, Mohammad Reza; Delshad, Mojdeh; Wheeler, Mary F. (Mary Fanett); Pope, Gary A; Sepehrnoori, Kamy; Mohanty, Kishory K.; Arbogast, ToddEnhanced oil recovery (EOR) techniques have the potential to improve hydrocarbon recovery and project economics substantially. Characterizing fluid displacement and the relevant multiphase flow properties are essential to modeling EOR processes to reliably forecast the performance and economics. The spatial-temporal distribution of fluids spans a broad spectrum of composition and saturation spaces. In addition, a fundamental understanding of characteristic parameters of interphase mass-transfer in various EOR applications is crucial to capture and model fluid displacement. Relative permeability is a critical characteristic petrophysical property for modeling fluid displacement in porous media. Also, hysteresis phenomena govern physics of fluid flow in many subsurface applications such as multicyclic EOR processes, geological CO2 sequestration, and natural gas storage. Capillary trapping is the essence of hysteresis to trap fluids. In this research, we developed a high-fidelity computational tool for integrating compositional three-phase relative permeability and hysteresis to assist in accurate modeling of multicycle and compositional EOR methods. This viable tool can be implemented into general-purpose reservoir simulators to model field-scale projects. It consists of an integrated compositionally-consistent three-phase relative permeability and three-phase hysteresis models. The developed three-phase relative permeability model is valid on entire saturation and composition spaces, is simple with one free parameter for each phase, and is versatile for all phases and wettability states. The general model is saturation-path dependent and adopts a linear saturation-weighted interpolation scheme for calculation of relative permeability parameters. For the compositional relative permeability modeling, we developed a general framework applicable to hydrocarbon and non-hydrocarbon phases. The developed framework provides a pragmatic approach for adding the direct impact of composition, pressure, and temperature and is independent of the conventional phase-labeling method. The proposed framework unifies thermodynamics, petrophysics, and geochemistry to enhanced relative permeability modeling. Relative permeability parameters are calculated based on a mapping scheme of current-state bulk and interphase Gibbs free energy onto corresponding initial-state values. We applied the developed framework to modeling lowsalinity waterflood and complex fluid displacement of near-critical fluids. The three-phase hysteresis model provides a general and straightforward approach for calculation of capillary trapping in multicyclic processes. The developed hysteresis model provides a set of cycle-dependent relative permeability curves and applies to any three-phase relative permeability model by incorporating the free-saturation concept. We implemented the developed toolbox into two in-house compositional reservoir simulators (i.e., IPARS and UT-DOECO2). Several synthetic field cases are discussed to validate the implemented models conceptually. Using the enhanced simulators, we demonstrated accurate modeling of multiphase fluid displacement and trapping in EOR processes such as water-alternate-gas injection scheme, low-tension gas flood (i.e., foam), and carbon capture, utilization, and storage (CCUS).Item Dynamical refinement in loop quantum gravity(2015-08) Hassan, Syed Asif; Matzner, Richard A. (Richard Alfred), 1942-; Dicus, Duane A; Freed, Daniel S; Morrison, Philip J; Weinberg, StevenIn Loop Quantum Gravity, a quantum state of the gravitational field has a semiclassical interpretation as a three-dimensional lattice discretization of space. We explore the possibility that the scale of the lattice is only as fine as it needs to be in order to carry the dominant frequency excitations of the auxiliary fields living on the lattice, by considering graph-changing transition amplitudes in the context of a pure gravity quantum theory. We define regular graphs that correspond to closed spatial slices of FLRW spacetime in a novel way, with coherent state labels that correspond to physical observables. This correspondence is obtained using the novel concept of a pseudoregular polyhedron which affords a dimensionless volume to surface area ratio in terms of the number of faces of the polyhedron. We normalize these regular graph states using a new method, employing a saddle point approximation based on the valence of the nodes rather than the large-scale semiclassical limit to obtain a result that holds in the quantum limit. Finally we employ the EPRL spin foam model to obtain a transition amplitude between single-node graphs of arbitrary valence that is valid in both the semiclassical and quantum regimes, using an improved method of normalizing the amplitude. We find that if we fix the scale factor and the fiducial volume of space the amplitude favors final states with infinitely large valence.Item Dynamics of foam mobility in porous media(2013-05) Balan, Huseyin Onur; Nguyen, Quoc P.; Balhoff, Matthew T.Foam reduces gas mobility in porous media by trapping substantial amount of gas and applying a viscous resistance of flowing lamellas to gas flow. In mechanistic foam modeling, gas relative permeability is significantly modified by gas trapping, while an effective gas viscosity, which is a function of flowing lamella density, is assigned to flowing gas. A complete understanding of foam mobility in porous media requires being able to predict the effects of pressure gradient, foam texture, rock and fluid properties on gas trapping, and therefore gas relative permeability, and effective gas viscosity. In the foam literature, separating the contributions of gas trapping and effective gas viscosity on foam mobility has not been achieved because the dynamics of gas trapping and its effects on the effective gas viscosity have been neglected. In this study, dynamics of foam mobility in porous media is investigated with a special focus on gas trapping and its effects on gas relative permeability and effective gas viscosity. Three-dimensional pore-network models representative of real porous media coupled with fluid models characterizing a lamella flow through a pore throat are used to predict flow paths, threshold pressure gradient and Darcy velocity of foam. It is found that the threshold path and the pore volume open above the threshold pressure are independent of the fluid model used in this study. Furthermore, analytical correlations of flowing gas fraction as functions of pressure gradient, lamella density, rock and fluid properties are obtained. At a constant pressure gradient, flowing gas fraction increases as overall lamella density decreases. In the discontinuous-gas foam flow regime, there exists a threshold pressure gradient, which increases with overall lamella density. One of the important findings of this study is that gas relative permeability is a strong non-linear function of flowing gas fraction, opposing most of the existing theoretical models. However, the shape of the relative gas permeability curve is poorly sensitive to overall lamella density. Flowing and trapped lamella densities change with pressure gradient. Moreover, analytical correlations of effective gas viscosity as functions of capillary number, lamella density and rock properties are obtained by up-scaling a commonly used pore-scale apparent gas (lamella) viscosity model. Effective gas viscosity increases nonlinearly with flowing lamella density, which opposes to the existing linear foam viscosity models. In addition, the individual contributions of gas trapping and effective gas viscosity on foam mobility are quantified for the first time. The functional relationship between effective gas viscosity and flowing lamella density in the presence of dynamic trapped gas is verified. A mechanistic foam model is developed by using the analytical correlations of flowing gas fraction and effective gas viscosity generated from the pore-network study and a modified population balance model. The developed model is successful in simulating unsteady-state and steady state flow of foam through porous media. Moreover, the flow behaviors in high- and low-quality flow regimes are verified by the experimental studies in the literature. Finally, the simulation results are successfully history matched with two different core-flood data.Item Experimental and simulation study of foam in porous media(2006) Shen, Chun; Rossen, William RichardThis dissertation comprises two studies of foam in porous media. The first part is an experimental study of the effect of polymer on the properties of foam in porous media. Addition of polymer has been proposed as a way to stabilize foam, especially in the presence of oil. This study probes the possible stabilizing effect of polymer on foam in terms of steady-state properties. Specifically, we tested the effect of polymer addition on the two steady-state foam regimes identified by Alvarez et al. (2001). For the two polymers (Xanthan and partially hydrolyzed polyacrylamide), two oils (decane and 37.5°API crude oil), and surfactant (an alpha-olefin sulfonate surfactant (AOS)) tested, it appears from coreflood pressure gradient that polymer destabilizes foam modestly. The increased viscosity of the aqueous phase with polymer mitigates the effects of destabilization of foam. For the same polymers and surfactant, polymer does not stabilize foam in the presence of decane or 37.5°API crude oil relative to foam without polymer. Surface-tension measurements with these polymers and surfactant likewise showed no evidence of presence of polymer at the air-water interface that might stabilize foam lamellae between bubbles. This suggests that, for similar polymers and surfactants, addition of polymer would not give stronger foams in field application or stabilize foam against the presence of crude oil. Complex behavior, some of it in contradiction to the expected two steady-state foam regimes, was observed. At the limit of, or in the place of, the high-quality regime, there was sometimes an abrupt jump upwards in pressure gradient as though from hysteresis and a change of state. In the low-quality regime, the pressure gradient was not independent of liquid superficial velocity, but decreased with increasing liquid superficial velocity, as previously reported and explained by Kim et al. (2004). The second part of this dissertation is a simulation study of gravity segregation during injection of shear-thinning foam in a homogenous reservoir. A useful model for gravity override with Newtonian flow is Stone’s model (1982), which describes gravity override during simultaneous water-gas flow. Shi and Rossen (1998) extend the model to foam processes with Newtonian rheology. However, foams are non-Newtonian, often in the high-quality regime, and always in the low-quality regime. In this study we examined the ability of shear-thinning foam to overcome gravity segregation in homogeneous reservoirs with different foam properties. In the limited range of conditions tested, we extended Stone's model to non-Newtonian flow using the estimated mobility at a representative "average" location which depended on the degree of shear-thinning behavior. We then developed a method to estimate the segregation distance for nonNewtonian foams that required iterative calculation but not computer simulation. The estimates were qualitatively, but not quantitatively, correct.Item Experimental evaluation of foam in environmental remediation(2002-05) Rong, Jiann Gwo; Liljestrand, Howard M. (Howard Michael); Rossen, William RichardGround water is the major source of drinking water for many people around the world. Two challenges in subsurface remediation are the removal of nonaqueous phase liquids (NAPL) located in the capillary fringe above the water table and at the bottom of an aquifer. Although several innovative technologies have demonstrated the ability to remove NAPL from source zones, geologic heterogeneities can cause significant NAPL to remain after remediation. The effect of heterogeneity can be mitigated by the application of a mobility-control fluid such as foam. The use of foam as a means of improving remediation efficiency has unique advantages. (1) Foams are inherently stiffer in region of higher permeability. (2) Foams can reduce gravity effects. (3) Foams collapse in the presence of hydrocarbon contaminants. It was found that foam has two different flow regimes in porous media: (a) the high-quality regime and (b) low-quality regime. Steady-state experiments were conducted to study the two foam-flow regimes under low pressure gradient conditions typical of subsurface remediation and identify the effect of various factors on the two regimes. Gas and surfactant solution were co-injected through sandpacks of permeability ranging from 5 to 210 darcy (hydraulic conductivity: 2x10-3 to 5x10-5 cm/sec) in vertical columns. The results confirm that the two foam-flow regimes are present in both the absence and presence of oil in porous media. In the high-quality regime, two factors weakened the foam, decreasing surfactant concentration and the presence of oil. These require an increase of liquid flow rate to maintain a given pressure gradient. In the low-quality regime, as predicted by the fixed-bubble-size model, increasing permeability requires higher gas flow rate to maintain a given pressure gradient. Shear-thinning foam behavior was consistently found in the lowquality regime, while the shear-thinning, Newtonian and shear-thickening foam behavior was observed in the high-quality regime. Lower apparent relative gas permeability was also obtained in higher-permeability porous media.Item Fabrication and characterization of open celled micro and nano foams(2013-08) Srinivas Sundarram, Sriharsha, 1985-; Li, Wei, doctor of mechanical engineeringOpen celled micro and nano foams fabricated from polymers and metals have attracted tremendous attention in the recent past because of their applications in numerous areas such as catalyst carriers, filtration media, ion exchange membranes and tissue engineering scaffolds. In this study open celled polymer micro- and nano foams with controllable pore size and porosity were fabricated via solid state foaming of immiscible blends. The polymer foams were used as templates for fabricating nickel foams using an ethanol based electroless plating process. Thermal conductivity of micro- and nano foams was studied as a function of pore size and porosity using finite element and molecular dynamics based models. The effect of pore size and porosity on performance of phase change material infiltrated metal foams for thermal management was investigated via numerical models. Open celled micro foams were fabricated via solid state foaming of ethylene acrylic acid (EAA) and polystyrene (PS) co-continuous blends. Blending temperature was the main parameters affecting the formation of co-continuous structure. Gas saturation and foaming studies were performed to determine ideal processing conditions for the blend. The results indicated that saturation pressure and foaming temperature were major process parameters determining the porosity of the foamed samples. Open celled polymer templates were obtained by selective extraction of PS phase using dichloromethane (DCM). Foaming resulted in faster extraction of PS and also in a higher porosity. Open celled nano foams were fabricated via solid state foaming of polyetherimide (PEI) and polyethersulfone (PES). The effect of process parameters namely saturation pressure and temperature, desorption time, and foaming temperature and time on porosity and pore size was studied. A high gas concentration and foaming temperature were required to obtain nano pore-sized foams. Throughout the cross section there existed regions with varying pore size and porosity and solid skins at the surface regions of the foam. A solvent surface dissolution process using dimethylformamide (DMF) was employed to access the internal porous structure. Micro- and nano cellular nickel foams were fabricated from EAA and PES templates via electroless plating. The structure of the nickel foams was an inverse of the polymer templates. Ethanol based electroless plating solutions were used to ensure infiltration into the porous structure because of the small pore sizes. Finite element and molecular dynamics based models were developed to predict thermal conductivity of polymer foams as a function of pore size and porosity. Pore sizes ranging from 1 nm to 1 mm were studied. Models were partially validated using experimental data. The results showed that pore size has significant effect on thermal conductivity even for microcellular and conventional foams. When the pore size is reduced to the nanometer scale, the thermal conductivity of the nano foam dramatically reduces and the value could be lower than that of air for certain porosity levels. The extremely low thermal conductivity of polymer nanofoams is possibly due to increased phonon-phonon scattering in the solid phases of the polymer matrix in addition to low thermal conductivity of gas trapped in nano sized pores. Finite element based models were also developed to study the effect of pore size and porosity on performance of phase change material infiltrated metal foams for thermal management applications. The results showed that foams with smaller pore sizes can delay the temperature rise of the heat source for an extended period of time by rapidly dissipating heat in the phase change material. The lower temperatures resulting from the use of a smaller pore size metal foam could significantly increase the lifetime of IC chips.Item Foam assisted low interfacial tension enhanced oil recovery(2010-05) Srivastava, Mayank; Nguyen, Quoc P.; Pope, Gary A.; Johns, Russel T.; Srinivasan, Sanjay; Bonnecaze, Roger T.Alkali-Surfactant-Polymer (ASP) or Surfactant-Polymer (SP) flooding are attractive chemical enhanced oil recovery (EOR) methods. However, some reservoir conditions are not favorable for the use of polymers or their use would not be economically attractive due to low permeability, high salinity, or some other unfavorable factors. In such conditions, gas can be an alternative to polymer for improving displacement efficiency in chemical-EOR processes. The co-injection or alternate injection of gas and chemical slug results in the formation of foam. Foam reduces the relative permeability of injected chemical solutions that form microemulsion at ultra-low interfacial tension (IFT) conditions and generates sufficient viscous pressure gradient to drive the foamed chemical slug. We have named this technique of foam assisted enhanced oil recovery as Alkali/Surfactant/Gas (ASG) process. The concept of ASG flooding as an enhanced oil recovery technique is relatively new, with very little experimental and theoretical work available on the subject. This dissertation presents a systematic study of ASG process and its potential as an EOR method. We performed a series of high performance surfactant-gas tertiary recovery corefloods on different core samples, under different rock, fluid, and process conditions. In each coreflood, foamed chemical slug was chased by foamed chemical drive. The level of mobility control in corefloods was evaluated on the basis of pressure, oil recovery, and effluent data. Several promising surfactants, with dual properties of foaming and emulsification, were identified and used in the coreflood experiments. We observed a strong synergic effect of foam and ultra-low IFT conditions on oil recovery in ASG corefloods. Oil recoveries in ASG corefloods compared reasonably well with oil recoveries in ASP corefloods, when both were conducted under similar conditions. We found that the negative salinity gradient concept, generally applied to chemical floods, compliments ASG process by increasing foam strength in displacing fluids (slug and drive). A characteristic increase in foam strength was observed, in nearly all ASG corefloods conducted in this study, as the salinity first changed from Type II(+) to Type III environment and then from Type III to Type II(-) environment. We performed foaming and gas-microemulsion flow experiments to study foam stability in different microemulsion environments encountered in chemical flooding. Results showed that foam in oil/water microemulsion (Type II(-)) is the most stable, followed by foam in Type III microemulsion. Foam stability is extremely poor (or non-existent) in water/oil microemulsion (Type II (+)). We investigated the effects of permeability, gas and liquid injection rates (injection foam quality), chemical slug size, and surfactant type on ASG process. The level of mobility control in ASG process increased with the increase in permeability; high permeability ASG corefloods resulting in higher oil recovery due to stronger foam propagation than low permeability corefloods. The displacement efficiency was found to decrease with the increase in injection foam quality. We studied the effect of pressure on ASG process by conducting corefloods at an elevated pressure of 400 psi. Pressure affects ASG process by influencing factors that control foam stability, surfactant phase behavior, and rock-fluid interactions. High solubility of carbon dioxide (CO₂) in the aqueous phase and accompanying alkali consumption by carbonic acid, which is formed when dissolved CO₂ reacts with water, reduces the displacement efficiency of the process. Due to their low solubility and less reactivity in aqueous phase, Nitrogen (N₂) forms stronger foam than CO₂. Finally, we implemented a simple model for foam flow in low-IFT microemulsion environment. The model takes into account the effect of solubilized oil on gas mobility in the presence of foam in low-IFT microemulsion environment.Item Foam drilling simulator(Texas A&M University, 2007-04-25) Paknejad, Amir SamanAlthough the use of compressible drilling fluids is experiencing growth, the flow behavior and stability properties of drilling foams are more complicated than those of conventional fluids. In contrast with conventional mud, the physical properties of foam change along the wellbore. Foam physical and thermal properties are strongly affected by pressure and temperature. Many problems associated with field applications still exist, and a precise characterization of the rheological properties of these complex systems needs to be performed. The accurate determination of the foam properties in circulating wells helps to achieve better estimation of foam rheology and pressure. A computer code is developed to process the data and closely simulate the pressure during drilling a well. The model also offers a detailed discussion of many aspects of foam drilling operations and enables the user to generate many comparative graphs and tables. The effects of some important parameters such as: back-pressure, rate of penetration, cuttings concentration, cuttings size, and formation water influx on pressure, injection rate, and velocity are presented in tabular and graphical form. A discretized heat transfer model is formulated with an energy balance on a control volume in the flowing fluid. The finite difference model (FDM) is used to write the governing heat transfer equations in discretized form. A detailed discussion on the determination of heat transfer coefficients and the solution approach is presented. Additional research is required to analyze the foam heat transfer coefficient and thermal conductivity.Item Foam generation and propagation in homogeneous and heterogeneous porous media(2006) Li, Qichong; Rossen, William RichardItem Laboratory investigation of low-tension-gas (LTG) flooding for tertiary oil recovery in tight formations(2012-12) Szlendak, Stefan Michael; Nguyen, Quoc P.This paper establishes Low-Tension-Gas (LTG) as a method for sub-miscible tertiary recovery in tight sandstone and carbonate reservoirs. The LTG process involves the use of a low foam quality surfactant-gas solution to mobilize and then displace residual crude after waterflood. It replicates the existing Alkali-Surfactant-Polymer (ASP) process in its creation of an ultra-low oil-water interfacial tension (IFT) environment for oil mobilization, but instead supplements the use of foam over polymer for mobility control. By replacing polymer with foam, chemical Enhanced Oil Recovery (EOR) methods can be expanded into sub-30 mD formations where polymer is impractical due to plugging, shear, or the requirement to use a low molecular weight polymer. Overall results indicate favorable mobilization and displacement of residual crude oil in both tight carbonate and tight sandstone reservoirs. Tertiary recovery of 75-95% ROIP was achieved for cores with 2-15 mD permeability, with similar oil bank and other ASP analogous process attributes observed. Moreover, similar recovery was achieved during testing at high initial oil saturation (56%), indicating high process tolerance to oil saturation and potential application for implementation at secondary recovery. In addition, a number of tools and relations were developed to improve the predictive relationship between observed coreflood properties and actual mobilization or displacement mechanisms which impact reservoir-scale flooding. These relations include qualitative dispersion comparison and calculation of in-situ gas saturation, macroscopic mobility ratio at the displacement fronts, and apparent viscosity of injected fluids. These tools were validated through use of reference gas and surfactant floods and indicate that stable macroscopic displacement can be achieved through LTG flooding in tight formations. Furthermore, to better reflect actual reservoir conditions where localized fractional flow of gas can vary substantially depending on mixing or gravity phenomenon, two additional sets of data were developed to empirically model behavior. Through testing of LTG co-injection at a number of discrete fractional flow values over a wide range, recovery was shown to achieve a relative maximum at 50% gas fractional flow which also corresponded with optimal observed mobility control as measured by the previously established tools. Likewise, through testing of surfactant-alternating-gas (SAG) injection cycling, displacement and overall recovery were shown to be improved versus reference co-injection flooding. Finally, by comparing the observed displacement and mobility data among co-injection and surfactant-alternating-gas floods, a new displacement mechanism is introduced to better relate actual displacement conditions with observed macroscopic mobility data. This mechanism emphasizes the role of liquid rate in actual displacement processes and a mostly static gas saturation (independent of gas rate) in altering liquid relative permeability and diverting injected liquid into lower permeability zones.Item Mobility control of chemical EOR fluids using foam in highly fractured reservoirs(2011-05) Gonzaléz Llama, Oscar; Nguyen, Quoc P.; Pope, Gary A.; Mohanty, KishoreHighly fractured and vuggy oil reservoirs represent a challenge for enhanced oil recovery (EOR) methods. The fractured networks provide flow paths several orders of magnitude greater than the rock matrix. Common enhanced oil recovery methods, including gases or low viscosity liquids, are used to channel through the high permeability fracture networks causing poor sweep efficiency and early breakthrough. The purpose of this research is to determine the feasibility of using foam in highly fractured reservoirs to produce oil-rich zones. Multiple surfactant formulations specifically tailored for a distinct oil type were analyzed by aqueous stability and foam stability tests. Several core floods were performed and targeted effects such as foam quality, injection rate, injection type, permeability, gas saturation, wettability, capillary pressure, diffusion, foam squeezing, oil flow, microemulsion flow and gravity segregation. Ultimately, foam was successfully propagated under various core geometries, initial conditions and injections methods. Consequently, fluids were able to divert to unswept matrix and improve the ultimate oil recovery.Item Mobility control of gas injection in highly heterogeneous and naturally fractured reservoirs(2016-05) Cavalcante Filho, Jose Sergio de Araujo; Sepehrnoori, Kamy, 1951-; Delshad, Mojdeh; Mohanty, Kishore; Chin, Lee; Moinfar, AliSince a significant portion of the world's oil reserves resides in naturally fractured reservoirs (NFR), it is important to maximize oil production from these reservoirs. Mobility control EOR techniques, such as water alternating gas (WAG) and foam injection, may be used in NFRs to improve oil recovery. Foam injection may be modeled by empirical or mechanistic models, the latter being capable of representing foam generation and coalescence effects. Numerical models are needed to evaluate EOR techniques in NFR. The Embedded Discrete Fracture Model (EDFM) is capable of representing conductive faults or fractures and describing NFR and unconventional reservoirs as a triple porosity medium (hydraulic fractures, natural fractures, and matrix). This work aims at developing a general EDFM framework to allow the evaluation of different mobility control EOR methods in NFR. The mobility control EOR methods evaluated were the WAG and continuous foam injection. The formulation used to evaluate mobility control by foam injection in NFR was the population balance assuming local equilibrium and the Pc* models. Nanoparticle transport models (Two Site and Two Rate models) were implemented and validated to allow simulation of nanoparticle stabilized foam injection. An EDFM preprocessor was further developed and validated against the in-house fully implicit simulator, unstructured grid models from the literature and fine-grid models using a commercial simulator. Simulation run time was reduced by applying a porosity cut-off in the fracture cells assuming constant fracture conductivity. Validation case studies included multi-fractured wells producing through depletion and a 2D quarter five-spot production scheme (water and miscible gas injection) in NFR. We obtained a good agreement between EDFM, unstructured grid, and fine-grid models. Application case studies included 3D models under water, miscible gas and WAG injection, which confirmed the efficiency of the EDFM in modeling complex fracture networks. We used the EDFM to simulate multilateral well stimulation and we performed an automated history matching of the production data of a field test. The foam model and the nanoparticle transport models were validated against experimental data from the literature. It is concluded that the effect of fractures on hydrocarbon production depends on fracture network connectivity, which may be modeled using the EDFM preprocessor. Simulation results using mobility control EOR methods show considerable improvements in oil recovery due to a postponement in gas breakthrough.Item Modeling wellbore pressure with application to multi-stage, acid-stimulation treatment(Texas A&M University, 2006-08-16) Ejofodomi, Efejera A.Estimation of bottomhole pressure during a matrix-acidizing treatment provides the information needed to accurately determine the evolution of skin factor during and after the treatment. It could be a very complicated process, especially when compressible fluids, such as foams, are involved. Existing models for estimating bottomhole pressure during a matrix-acidizing treatment ignore the volume reduction of compressible fluids and its effect on the bottomhole pressure. This research developed a model that uses a unique solution to the mechanical energy balance equation, to calculate the bottomhole pressure from known surface measurements during foamed acid stimulation. The model was used to evaluate two stimulation treatments. Field examples are presented which illustrate the application of the model to optimize stimulation treatments. Properly accounting for the flow behavior and tracking the injected volume of the foam diverter used during the treatment resulted in more reliable and accurate bottomhole pressure profile.Item Nanoparticle-stabilized supercritical CO₂ foam for mobility control in CO₂ enhanced oil recovery(2014-08) Aroonsri, Archawin; Bryant, Steven L.Foam has been used as a mobility control technique in CO₂ flooding to improve volumetric sweep efficiency. Stabilizing CO₂ foam with nanoparticle instead of surfactant has some notable advantages. Nanoparticle-stabilized foam is very stable because a large adsorption energy is required to bring nanoparticles to the bubble interfaces. As a solid, nanoparticle can potentially withstand the high temperature in the reservoir, providing a robust foam stability for an extended period of time. The ability of nanoparticles to generate foam only above a threshold shear rate is promising as foam can be engineered to form only in the high permeability zone. These nanoparticles are hundreds of times smaller than pore throats and thus can travel in the reservoir without plugging the pore throats. Surface-modified silica nanoparticle was found to stabilize CO₂ -in-water foam at temperature up to 80 ˚C and salinity as high as 7.2 wt%. The foam was generated through the co-injection of aqueous nanoparticle dispersion and CO₂ into consolidated rock cores, primarily sandstones, with and without an induced fracture in the core. A critical shear rate for foam generation was found to exist in both matrix and fracture, however, this critical rate varied with the experiment conditions. The effects of experimental parameters on the critical shear rate and foam apparent viscosity were also investigated. Additionally, the flow distribution calculation in fractured sandstone cores revealed a diversion of flow from fracture toward matrix once foam was generated, suggesting conformance control potential in fractured reservoirs. In order to study foam rheology, high-permeability beadpack was installed upstream of the core to serve as a foam generator. This allows the foam mobility to be measured solely while being transported through the core, without the complicating effect of transient foam generation in the core. The injection of the pre-generated foam into the core at residual oil condition was found to reduce the residual oil saturation to the same level as CO₂ flood, however, with the advantage of mobility control. The 'coalescence-regeneration' mechanism of foam transport in porous media possibly allowed the foam's CO₂ to contact and mobilize the residual oil. The injection of the foam slug followed by a slug of only CO₂ was also tested, showing similar viscosification as the continuous foam injection, however, required less nanoparticles.Item Novel cationic surfactants for CO₂-foam flooding in carbonate reservoirs(2015-08) Hahn, Ruth Ellen; Mohanty, Kishore Kumar; Sepehrnoori, KamyA majority of oil throughout the world is contained in carbonate reservoirs. Alkaline-Surfactant-Polymer (ASP) floods cannot be applied in many carbonate reservoirs for three main reasons: conventional alkali are not compatible with divalent ions, adsorption of anionic surfactants is high in the absence of alkali, and the permeability of the rock is often low for polymers to pass through the pores. One alternative to ASP flooding is CO₂-foam flooding. Foam flooding reduces the mobility of the CO₂ and increases the sweep efficiency. To overcome the adsorption of surfactant on the carbonate surface, cationic surfactants can be used rather than anionic surfactants. The objective of this research is to study two novel cationic surfactants for foam flooding applications. These surfactants are gemini surfactants, containing two head groups and two tail groups. The bulk foam stability in the presence and absence of oil was studied for these surfactants and compared to conventional surfactants; these gemini surfactants showed comparable bulk foam stability to other cationic surfactants. Corefloods in the absence of oil were performed at reservoir conditions to prove foam formation in porous media and to determine the optimum ratio of CO₂ to surfactant injection ratio. Both water-wet and oil-wet coreflood experiments were performed for the gemini surfactants. The water-wet corefloods for both surfactants recovered 6-16 %OOIP after the waterflood. The pressure drop during the water-wet foam floods was not too high, less than 15 psi/foot which is reasonable for a low permeability carbonate core. The corefloods showed results comparable with a polymer flood, with no injectivity issues, indicating that these surfactants can be used in place of polymer flooding in carbonate reservoirs. The oil-wet experiment also resulted in foam flood recovery of 13% OOIP, despite the poor wettability alteration results seen with calcite chips. With better foam stability in the presence of oil and enhanced wettability alteration, this new class of cationic surfactants could be a viable option for enhanced oil recovery in carbonate reservoirs.