Browsing by Subject "Polymer"
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Item Accounting for reservoir uncertainties in the design and optimization of chemical flooding processes(2012-08) Rodrigues, Neil; Delshad, Mojdeh; Pope, Gary A.Chemical Enhanced Oil Recovery methods have been growing in popularity as a result of the depletion of conventional oil reservoirs and high oil prices. These processes are significantly more complex when compared to waterflooding and require detailed engineering design before field-scale implementation. Coreflood experiments that have been performed on reservoir rock are invaluable for obtaining parameters that can be used for field-scale flooding simulations. However, the design used in these floods may not always scale to the field due to heterogeneities, chemical retention, mixing and dispersion effects. Reservoir simulators can be used to identify an optimum design that accounts for these effects but uncertainties in reservoir properties can still cause poor project results if it not properly accounted for. Different reservoirs will be investigated in this study, including more unconventional applications of chemical flooding such as a 3md high-temperature, carbonate reservoir and a heterogeneous sandstone reservoir with very high initial oil saturation. The goal of the research presented here is to investigate the impact that select reservoir uncertainties can have on the success of the pilot and to propose methods to reduce the sensitivity to these parameters. This research highlights the importance of good mobility control in all the case studies, which is shown to have a significant impact on the economics of the project. It was also demonstrated that a slug design with good mobility control is less sensitive to uncertainties in the relative permeability parameters. The research also demonstrates that for a low-permeability reservoir, surfactant propagation can have a significant impact on the economics of a Surfactant-Polymer Flood. In addition to mobilizing residual oil and increasing oil recovery, the surfactant enhances the relative permeability and this has a significant impact on increasing the injectivity and reducing the project life. Injecting a high concentration of surfactant also makes the design less sensitive to uncertainties in adsorption. Finally, it was demonstrated that for a heterogeneous reservoir with high initial oil saturation, optimizing the salinity gradient will significantly increase the oil recovery and will also make the process less sensitive to uncertainties in the cation exchange capacity.Item Acid Diversion in Carbonate Reservoirs Using Polymer-Based In-Situ Gelled Acids(2012-07-16) Gomaa, Ahmed Mohamed MohamedDiversion in carbonates is more difficult than in sandstones because of the ability of acid to significantly increase the permeability in carbonates as it reacts in the pore spaces and flow channels of matrix. In-situ gelled acids that are based on polymers have been used in the field for several years and were the subject of many lab studies. An extensive literature survey reveals that there are conflicting opinions about using these acids. On one hand, these acids were used in the field with mixed results. Recent lab work indicated that these acids can cause damage under certain conditions. There is no agreement on when this system can be successfully applied in the field. Therefore, this study was conducted to better understand this acid system and determine factors that impact its performance. Lab test of polymer-based in-situ gelled acids reveal that polymer and other additives separate out of the acid when these acids are prepared in high salinity water. In coreflood tests, in-situ gelled acid formed a gel inside 20? long core samples, and the acid changed its direction several times. Unexpectantly, the core's permeability was reduced at low shear rate. Wormhole length increased as the shear rate was increased; while the diameter of the wormhole increased as the acid cumulative injected volume was increased. CT scan indicated the presence of gel residue inside and around the wormhole. Gel residue increased at low shear rates. Material balance on the cross-linker indicated that a significant amount of the crosslinker was retained in the core. Based on the results obtained from this study the in-situ gelled acids should be used only at low HCl concentrations (5 wt percent HCl). Acid should be prepared in low salinity water and the acid injection rate should be determined based on the expected shear rate in the formation. A core flood experiment is recommended to confirm optimum injected rate. Well flow back is needed to minimize the residual gel inside the formation. The data obtained in this study can be used as a guideline for injection rate selection.Item Analytical and Experimental Assessment of an AASHTO I-girder Type I Prestressed with AFRP Tendons(2014-12-12) Cummings, Wesley DavidCorrosion induced deterioration is one of the main reason for repair and rehabilitation programs in conventional steel reinforced concrete bridge decks. Of all bridges in the United States, over 50 percent are constructed of conventional reinforced or prestressed concrete (NACE, 2013), where one in three bridges are considered structurally deficient or functionally obsolete due to corrosion of the steel reinforcement. According to NACE International (2013) the annual cost of corrosion-related maintenance for highway bridges in the U.S. is estimated at $13.6 billion. Over the past couple of decades, fiber reinforced polymer (FRP) bars have been noted by researchers and engineers as a corrosion-resistant alternative for either conventional reinforcing steel or prestressing strands. High strength-to-weight ratio, corrosion resistance, ease in placement of the bars and accelerated implementation due to light weight are the special characteristics that make these bars an appealing alternative. Up to this end, extensive research has been conducted on the structural performance of FRP reinforced concrete beams and slabs; however, less attention has been paid to FRP reinforced concrete bridge girders in composite action with the bridge deck. Accounting for the effect of composite action between the bridge girder and deck can significantly impact the structural performance of the girder including the load and deformation capacities as well as the failure mode. Therefore, separate tests of the FRP concrete beams and slabs may not be sufficient to study the structural behavior and to provide design guidelines for engineers. This thesis presents the experimental and analytical investigations on structural performance of a full-scale AASHTO I-girder Type I, reinforced and prestressed with aramid fiber reinforced polymer (AFRP) bars, where the bridge girder is composite with the deck. The major objectives of this research were to develop a reliable prestressing anchorage system, examine the constructability of the full-scale specimen, study the load and deformation capacities, determine whether or not the design criteria per AASHTO LRFD were met, and improve the performance of the specimen by adjusting the prestressing layout. The specimen was constructed at a prestressing plant in San Marcos, Texas and tested at the High Bay Structural and Material Testing Laboratory on the campus of Texas A&M University. The cross-section of the bridge girder was composed of self-consolidating concrete with a total of 24 prestressed and 8 non-prestressed AFRP bars. The bridge deck consisted of a 203 mm (8 in.) conventional steel reinforced concrete slab. A flexure test was conducted to determine the moment-curvature relationship, flexure load capacity, and failure mode. The test was conducted as a simply supported, four point bending test in order to create a region of constant moment at the center of the beam. Two shear tests were conducted to determine the shear capacity, failure mode, maximum strain in the web, and moment-curvature relationship. The shear tests were conducted as a simply supported, three point bending test with varying load placement. The results of these tests were compared to a similar study which investigated the structural performance of a conventional steel reinforced AASHTO I-girder Type I with topping deck (Trejo et al. 2008). The specimen was also analyzed analytically to determine the effect on performance of varying the prestressing ratio of the separate layers in the bottom flange of the girder. The goal of this analysis was to determine an optimal prestressing layout to improve the performance at the ultimate state, while still satisfying serviceability limits. The prestressing ratio of the layers were varied from 0 to 50 percent in 5 percent increments to study the moment and curvature at both the cracking and ultimate states, along with the available compressive stress due to prestressing at the bottom of the girder. The results of this research confirms that the experimental specimen showed adequate strength and deformation capacities, satisfying the AASHTO LRFD design criteria. Additionally, the experimental specimen showed significantly greater cracking when compared to the conventional steel reinforced specimen, which is an early warning of impending failure. It was also determined that reducing the prestressing ratio of the AFRP bars in the lower layers improves the ductility of the specimen. The moment capacity can also be improved depending on the prestressing layout. However, reducing the prestressing ratio of the bottom layers causes the cracking moment and available compressive stress at the bottom of the girder to diminish. In order to compensate for this loss, the non-prestressed bars in the web can be prestressed. The optimal prestressing layout features the bottom three layers of the specimen prestressed to 35, 40, and 45 percent of their ultimate capacity, and two of the three layers of middle bars prestressed to 50 percent of their ultimate capacity.Item Catalysis and materials development for photolithography(2014-08) Mesch, Ryan Alan; Willson, C. Grant, 1939-; Keatinge-Clay, Adrian; Ellison, Christopher; Rose, Michael; Stevenson, KeithIn recent years the microelectronics industry as found itself at an impasse. The tradition pathway towards smaller transistors at lower costs has hit a roadblock with the failure of 157 nm lithography and the continued delays in 13.5 nm extreme ultra violet light sources. While photolithography has been able to keep pace with Moore’s law over the past four decades, alternative patterning technologies are now required to keep up with market demand. The first section of this dissertation discusses the new resolution enhancement technique develop in the Willson lab termed pitchdivision. Through the incorporation of specifically tailored photobase generators (PBGs) into commercially available resists, the resolution of current 193 tools may be doubled. Special two-stage PBGs were designed and synthesized to increase the image fidelity of pitchdivision patterns. The next project deals with the design, synthesis, and evaluation of resists that find amplification through unzipping polymers. An aromatizing polyester polymer that acts as dissolution inhibitor in novolac and is inherently sensitive to 13.5 nm exposure is discussed. Initial results show excellent sensitivity and promise towards a new class of EUV resists.Item CFD-based representation of non-Newtonian polymer injectivity for a horizontal well with coupled formation-wellbore hydraulics(2010-12) Jackson, Gregory Thomas, 1983-; Balhoff, Matthew T.; Huh, ChunDuring injection of a high-viscosity, non-Newtonian polymer into a long horizontal well, a significant pressure drop occurs along the well length. Computational Fluid Dynamics (CFD) modeling of the shear-thinning flow of polymer in the wellbore, coupled with the viscoelastic flow in composite gravel-pack/near-well formation zone, was carried out to develop convenient correlations for axial pressure values of both Newtonian and non-Newtonian fluids along the well length, for use in chemical EOR simulations. The detailed CFD modeling of the non-Newtonian flow behavior of polymer within the horizontal wellbore, completion zone and the near-well formation, not only allows accurate accounting of pressure distribution along the long horizontal well, but also can be employed for screening diagnosis for possible injectivity inefficiencies resulting from non-uniform pressure values. At both high and low injection rates, CFD modeling predicts non-uniform pressure distributions for highly viscous fluids. The inclusive pressure correlation was implemented into UTCHEM, a University of Texas at Austin research simulator, to determine the importance of including pressure drop in polymer injections. Early times (i.e., less than 100 days) yielded a significant oil recovery deviation from a uniform pressure wellbore. However, at later times the recovery loss generated by the pressure decrease was deemed negligible; therefore, the traditional assumption regarding uniform pressure in horizontal wellbores was still reasonable for highly viscous non-Newtonian flow. This CFD study is the first mechanistic investigation of the polymer injectivity with detailed description of the wellbore, completion zone and near-well formation, and with full accounting of the shear-thinning rheology for pipe flow and the viscoelastic rheology of polymer in porous media. With increased use of very high molecular-weight polymers for chemical EOR processes for mobility control, the latter mechanism is known to be critical.Item Complex Nanoscopic Objects from Well-defined Polymers that Contain Functional Units(2012-08-29) Li, Ang 1982-The construction of nanoscale polymeric objects with complex, well-defined structures and regiochemical functionalities is of great importance, because it enables the fabrication of soft materials with tunable properties. Direct polymerization of macromonomers through covalent bond formation and self-assembly of block copolymers via non-covalent interactions are two typical strategies to afford nanoscopic structures. Molecular brush polymers are composed of densely-grafted side chains along a polymeric backbone. Due to the significant steric repulsion from the side chains, they tend to adopt bottle-brush like conformations, as opposed to linear polymers. "Grafting through" synthesis of molecular brush polymers can provide precise control over the dimensions and functionalities of brush polymers. Shell crosslinked knedel-like nanoparticles (SCKs) are constructed by assembling from amphiphilic block copolymers into micelles, followed by covalent shell crosslinking to further stabilize the nanoparticles and introduce additional functional moieties. SCKs are attractive nanocarriers because of their variable morphologies, compositions and functionalities, which allow for the development of platforms for therapeutic or diagnostic purposes. By utilizing the orthogonal reactivity of the norbornene group and methacrylate group, two distinctly different reactive well-defined linear polymers, and a facile, one-pot synthesis of well-defined molecular brush polymers were studied by selective, orthogonal controlled radical polymerizations (CRPs) and ring-opening metathesis polymerization (ROMP). The living and high efficient characteristics of "grafting-through" strategy were further investigated for the preparation of topology-controlled brush polymers with tunable dimensions of both backbone and side chain lengths. Apart from the fundamental investigation of molecular brush polymers, a series of poly(carboxybetaine) (PCB)- and poly(ethylene glycol) (PEG)-grafted degradable SCKs were developed to evaluate their in vivo pharmacokinetics and biodistributions, aiming to achieve novel therapeutic and diagnostic platforms that may surpass the performance of the conventional PEGylated analogs.Item Critical Analysis and Review of Flash Points of High Molecular Weight Poly-functional C, H, N, O Compounds(2011-08-08) Thomas, DerrickThe research focuses on the critical review and prediction of flash points of high molecular weight compounds used mainly in the specialty chemical area. Thus far this area of high molecular weight specialty chemicals has not been thoroughly reviewed for flash point prediction; therefore critical review for accuracy of experimental values is difficult. Without critical review, the chance of hazards occurring in the processing and handling of these compounds increases. A reliable method for making predictions is important to efficiently review experimental values since duplicate experimentation can be time consuming and costly. The flash point is strongly correlated to the normal boiling point (NBP) but experimental NBP is not feasible for chemicals of high molecular weight. The reliability of existing NBP prediction methods was found inadequate for our compounds of interest therefore a new NBP prediction method was developed first. This method is based on ten simple group contributions and the molecular weight of the molecule. The training set included 196 high molecular weight C, H, N and O compounds. It produced an average absolute error (AAE) of 13K, superior to any other model tested so far. An accurate NBP is essential for critical review and new method development for flash point. A preliminary data analysis based on chemical family analysis allowed for detection of erroneous data points. These compounds were re-tested at a Huntsman facility. With a predicted normal boiling point, a new FP method that differentiates strong and iv weak hydrogen bonding compounds was developed. This was done because of the differences in entropy of vaporization for hydrogen bonding compounds. The training set consisted of 191 diverse C, H, N, O compounds ranging from 100 to 4000 g/mol in molecular weight. The test set consisted of 97 compounds of similar diversity. Both data sets produced an AAE of 5K and maximum deviation of 17.5K. It was also found that no substantial decomposition was found for these compounds at flash point conditions. These compounds appear to follow the same physical trends as lower molecular weight compounds. With this new method it is possible to critically review this class of chemicals as well as update NBP and other physical property data.Item Development of ASP formulations for reactive crude oil in high clay, high temperature reservoirs(2012-08) Tipley, Kyle Andrew; Pope, Gary A.; Weerasooriya, Upali P.Surfactant formulations consisting of surfactant, alkali, polymer, and electrolyte have been developed using well defined screening processes established through experimentation in labs around the world. Due to recent advances in chemical enhanced oil recovery, surfactants can be used to extend the life of mature reservoirs with increasingly diverse conditions. High temperatures, complex geochemistry, or high clay content can provide significant challenges when developing formulations for chemical flooding. Through careful selection and screening of surfactants and chemicals, oil recovery of greater than 90% can be achieved in laboratory corefloods despite these difficulties. The objective of this research was to determine the ideal surfactant formulation using a sulfate surfactant for a reservoir with high clay content at 85 ºC. Advances in our laboratory have shown sulfate surfactants to be stable under specific conditions at elevated temperature. In addition, new methods of synthesizing surfactants have yielded a vast array of structures and iterations of novel surfactants to test for EOR applicability. Experiments contained within include surfactant screening both with and without the presence of crude oil and evaluation of polymer and microemulsion viscosity. From these results, a series of corefloods were performed in Berea and reservoir corefloods that yielded oil recovery of 90% and above with low surfactant retention.Item Development of improved ASP formulations for reactive and non-reactive crude oils(2010-12) Yang, Hyun Tae; Huh, Chun; Pope, Gary A.; Weerasooriya, UpaliThe ability to select low-cost, high-performance surfactants for a wide range of crude oils under a wide range of reservoir conditions has improved dramatically in recent years. Surfactant formulations (surfactant, co-surfactant, co-solvent, alkali, polymer, and electrolyte) were developed by using a refined phase behavior approach. Such formulations nearly always result in more than 90% oil recovery in core flood when good surfactants with good mobility control are used. The advances that have improved performance, reduced cost, increased robustness, and extended the range of reservoir conditions for these formulations are described in this work. There are thousands of possible combinations of the chemicals that could be tested for each oil and each chemical combination requires many observations over a long time period at reservoir temperature for proper evaluation. It would take too long, cost too much and in many cases not even be feasible to test all combinations. In practice the scientific understanding is used to match up the surfactant/co-surfactant/co-solvent characteristics with the oil characteristics, temperature, salinity, hardness and so forth. Synthesized and new surfactants with much larger hydrophobes and more branching than previously available were tested. New classes of co-solvents and co-surfactants with superior performance were test to improve aqueous solubility. These new developments resulted in improved ASP formulations for both oils that react with alkali to make soap and oils that do not. Many of these developments are synergistic and taken together represent a breakthrough in reducing the cost of chemical flooding and thus its commercial potential.Item The effect of synthesis route and ortho-position functional group on thermally rearranged polymer thermal and transport properties(2013-05) Sanders, David Finley; Freeman, B. D. (Benny D.); Paul, Donald R.This dissertation discusses the effect of synthesis route and ortho-position group on the thermal and transport properties of thermally rearranged polymers. Thermally rearranged polymers are polybenzoxazoles formed via the solid state rearrangement of ortho-functional polyimides. In this study, polymers were derived from 3,3'-dihydroxy-4,4'-diamino-biphenyl and 2,2'-bis-(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (HAB-6FDA). These HAB-6FDA polymers were synthesized using chemical and thermal imidization, and hydroxyl, acetate, propanoate, or pivalate ortho-position groups were considered. In these polymers, gas permeability increases as a function of conversion for all samples. The polyimide synthesis route does not affect the thermal or transport properties. However, the precursor ortho-position group strongly influences the thermal and transport properties of TR polymers. Additionally, it was determined that an increase in gas diffusivity was the primary cause of increased permeability as a function of thermal rearrangement.Item Enhanced Oil Recovery in High Salinity High Temperature Reservoir by Chemical Flooding(2012-02-14) Bataweel, Mohammed AbdullahStudying chemical enhanced oil recovery (EOR) in a high-temperature/high-salinity (HT/HS) reservoir will help expand the application of chemical EOR to more challenging environments. Until recently, chemical EOR was not recommended at reservoirs that contain high concentrations of divalent cations without the need to recondition the reservoir by flooding it with less saline/ less hardness brines. This strategy was found ineffective in preparing the reservoir for chemical flooding. Surfactants used for chemical flooding operating in high temperatures tend to precipitate when exposed to high concentrations of divalent cations and will partition to the oil phase at high salinities. In this study amphoteric surfactant was used to replace the traditionally used anionic surfactants. Amphoteric surfactants show higher multivalent cations tolerance with better thermal stability. A modified amphoteric surfactant with lower adsorption properties was evaluated for oil recovery. Organic alkali was used to eliminate the water softening process when preparing the chemical solution and reduce potential scale problems caused by precipitation due to incompatibility between chemical slug containing alkali and formation brine. Using organic alkali helped in minimizing softening required when preparing an alkali-surfactant-polymer (ASP) solution using seawater. Solution prepared with organic alkali showed the least injectivity decline when compared to traditional alkalis (NaOH and Na2CO3) and sodium metaborate. Adding organic alkali helped further reduce IFT values when added to surfactant solution. Amphoteric surfactant was found to produce low IFT values at low concentrations and can operate at high salinity / high hardness conditions. When mixed with polymer it improved the viscosity of the surfactant-polymer (SP) solution when prepared in high salinity mixing water (6% NaCl). When prepared in seawater and tested in reservoir temperature (95?C) no reduction in viscosity was found. Unlike the anionic surfactant that causes reduction in viscosity of the SP solution at reservoir temperature. This will not require increasing the polymer concentration in the chemical slug. Unlike the case when anionic surfactant was used and more polymer need to be added to compensate the reduction in viscosity. Berea sandstone cores show lower recovery compared to dolomite cores. It was also found that Berea cores were more sensitive to polymer concentration and type and injectivity decline can be a serious issue during chemical and polymer injection. Dolomite did not show injectivity decline during chemical and polymer flooding and was not sensitive to the polymer concentration when a polymer with low molecular weight was used. CT scan was employed to study the displacement of oil during ASP, SP, polymer and surfactant flooding. The formation and propagation oil bank was observed during these core flood experiments. ASP and SP flooding showed the highest recovery, and formation and propagation of oil bank was clearer in these experiments compared to surfactant flooding. It was found that in Berea sandstone with a permeability range of 50 to 80 md that the recovery and fluid flow was through some dominating and some smaller channels. This explained the deviation from piston-like displacement, where a sharp change in saturation in part of the flood related to the dominated channels and tapered front with late arrival when oil is recovered from the smaller channels. It was concluded that the recovery in the case of sandstone was dominated by the fluid flow and chemical propagation in the porous media not by the effectiveness of the chemical slug to lower the IFT between the displacing fluid and oil.Item Enhanced oil recovery of heavy oils by non-thermal chemical methods(2013-05) Kumar, Rahul, active 2013; Mohanty, Kishore KumarIt is estimated that the shallow reservoirs of Ugnu, West Sak and Shraeder Bluff in the North Slope of Alaska hold about 20 billion barrels of heavy oil. The proximity of these reservoirs to the permafrost makes the application of thermal methods for the oil recovery very unattractive. It is feared that the heat from the thermal methods may melt this permafrost leading to subsidence of the unconsolidated sand (Marques 2009; Peyton 1970; Wilson 1972). Thus it is necessary to consider the development of cheap non-thermal methods for the recovery of these heavy oils. This study investigates non-thermal techniques for the recovery of heavy oils. Chemicals such as alkali, surfactant and polymer are used to demonstrate improved recovery over waterflooding for two oils (A:10,000cp and B:330 cp). Chemical screening studies showed that appropriate concentrations of chemicals, such as alkali and surfactant, could generate emulsions with oil A. At low brine salinity oil-in-water (O/W) emulsions were generated whereas water-in-oil (W/O) emulsions were generated at higher salinities. 1D and 2D sand pack floods conducted with alkali surfactant (AS) at different salinities demonstrated an improvement of oil recovery over waterflooding. Low salinity AS flood generated lower pressure drop, but also resulted in lower oil recovery rates. High salinity AS flood generated higher pressure drop, high viscosity emulsions in the system, but resulted in a greater improvement in oil recovery over waterfloods. Polymers can also be used to improve the sweep efficiency over waterflooding. A 100 cp polymer flood improved the oil recovery over waterflood both in 1D and 2D geometry. In 1D geometry 1PV of polymer injection increased the oil recovery from 30% after waterflood to 50% OOIP. The tertiary polymer injection was found to be equally beneficial as the secondary polymer injection. It was also found that the combined application of AS and polymer did not give any major advantage over polymer flood or AS flood alone. Chemical EOR technique was considered for the 330cp oil B. Chemical screening studies showed that microemulsions could be generated in the system when appropriate concentrations of alkali and surfactant were added. Solubilization ratio measurement indicted that the interfacial tension in the system approached ultra-low values of about 10-3 dynes/cm. The selected alkali surfactant system was tested in a sand pack flood. Additionally a partially hydrolyzed polymer was used to provide mobility control to the process. The tertiary injection of ASP (Alkali-Surfactant-Polymer) was able to improve the oil recovery from 60% OOIP after the waterflood to almost 98% OOIP. A simple mathematical model was built around viscous fingering phenomenon to match the experimental oil recoveries and pressure drops during the waterflood. Pseudo oil and water relative permeabilities were calculated from the model, which were then used directly in a reservoir simulator in place of the intrinsic oil-water relative permeabilities. Good agreement with the experimental values was obtained. For history matching the polymer flood of heavy oil, intrinsic oil-water relative permeabilities were found to be adequate. Laboratory data showed that polymer viscosity is dependent on the polymer concentration and the effective brine salinity. Both these effects were taken into account when simulating the polymer flood or the ASP flood. The filtration theory developed by Soo and Radke (1984) was used to simulate the dilute oil-in-water emulsion flow in the porous media when alkali-surfactant flood of the heavy oil was conducted. The generation of emulsion in the porous media is simulated via a reaction between alkali, surfactant, water and heavy oil. The theory developed by Soo and Radke (1984) states that the flowing emulsified oil droplets clog in pore constrictions and on the pore walls, thereby restricting flow. Once captured, there is a negligible particle re-entrainment. The simulator modeled the capture of the emulsion droplets via chemical reaction. Next, the local water relative permeability was reduced as the trapping of the oil droplets will reduce the mobility of the water phase. This entrapment mechanism is responsible for the increase in the pressure drop and improvement in oil recovery. The model is very sensitive to the reaction rate constants and the oil-water relative permeabilities. ASP process for lower viscosity 330 cp oil was modeled using the UTCHEM multiphase-multicomponent simulator developed at the University of Texas at Austin. The simulator can handle the flow of three liquid phases; oil, water and microemulsion. The generation of microemulsion is modeled by the reaction of the crude oil with the chemical species present in the aqueous phase. The experimental phase behavior of alkali and surfactant with the crude oil was modeled using the phase behavior mixing model of the simulator. Oil and water relative permeabilities were enhanced where microemulsion is generated and interfacial tension gets reduced. Experimental oil recovery and pressure drop data were successfully history matched using UTCHEM simulator.Item Exciton behaviour at organic solar cell interfaces(2015-12) Dinica, Olivia; Henkelman, Graeme; Rossky, Peter J; Vanden Bout, David A; Makarov, Dmitrii E; Mullins, Charles BOrganic photovoltaics (OPVs) have emerged as a promising class of materials in the production of flexible and cheap solar cells. Polymer OPVs are typically composed of a blend of a semiconducting electron donating poly- mer with an electron accepting fullerene derivative. This blend leads to a high donor-acceptor interfacial surface area where excitons are split apart to create free charges. The generation of free charges after photo-excitation is a main factor influencing solar cell efficiency. However, the mechanisms of charge transfer and the competing process of charge recombination at the interface are not completely clear. The understanding of these processes is essential for the rational design of materials that can maximize photovoltaic conversion efficiencies. The focus of this dissertation is on the influence that electric fields and chemical structure have on exciton dissociation and recombination at the interface of donor-acceptor materials. In particular, we use mixed quantum/classical dynamical simulations and electronic structure calculations to investigate several oligomer-fullerene systems. In order to study the potential energy surfaces guiding the dynamics of electron transfer, the nuclear and electron dynamics of large systems need to be simulated. To make these calculations computationally feasible, a mixed quantum classical molecular dynamics (MQCMD) approach was taken. This technique is based on the QCFF/PI formalism first described by Warshel and Karplus and was further developed by Lobaugh and Rossky for the simulation of betaine-30. This approach divides the conjugated system into a classical and a quantum subsystem. The quantum treatment is reserved for the π electronic system described by the Pariser-Parr-Pople (PPP) Hamiltonian. The classical potential describes a fully flexible molecular backbone and is modeled using an empirical molecular mechanics force field. In the first part of the dissertation we are examining the effect of an external electric field on charge transfer pathways and rates at sexithiophene/fullerene interfaces. In the second part, we develop a rigorous parametrization technique that allows us to model push-pull polymers. These polymers include PCDTBT and KP115 which have a more complex molecular structure than homo-polymers like the one considered in the first part. We use the QCFF/PI method as well as electronic structure calculations to investigate the influence of molecular structure and donor-acceptor orientation on charge transfer and recombination. The pathways linking exciton formation, charge transfer and thermal relaxation are explored, particularly in the context of dependence in the morphology of the donor molecules as well as the non-adiabatic coupling between excited states.Item Experimental and Numerical Study of Polymer Scratch Behavior(2010-10-12) Jiang, HanAs part of a larger effort to understand the fundamental knowledge of polymer scratch behavior, this dissertation is focused on both experimental study and numerical analysis of scratch deformation of a broad range of polymers, with an emphasis on the mechanical understanding of how the scratch-induced damage is formed. An instrumented progressive load scratch method recommended by ASTM/ISO standards was adopted for the experimental work. The commercial finite element (FE) method package ABAQUS was employed as a numerical simulation tool to describe the stress-strain fields, and it analyzes the deformation mechanisms during the scratch process. A thorough parametric study has been performed to assess the influence of material parameters and surface properties, such as Young's modulus, yield strength, and friction coefficient, on the polymer scratch behavior. Upon investigation of the scratch behaviors of a broad range of polymer materials, various kinds of scratch damage features are identified and correlated with the mechanical characteristics of the polymers. A generalized scratch damage mechanism map for polymers is presented. Correlation between different material types and scratch damage mechanisms is made. It is found that both the material characteristics and the stress state exerted on the scratched surface are responsible for the observed scratch damage mechanisms. The phenomenological deduction of the scratch damage process based on the stick-slip mechanism is established. A more realistic material law for the scratch analysis is also provided. To evaluate the polymer resistance against scratch visibility quantitatively, an entirely new automated on-set scratch visibility determination methodology is developed based on typical visual characteristics of human eyes. Its application on the evaluation of mar and abrasion of polymer is also explored. This new methodology can quantify polymer scratch resistance consistently and reliably regardless of the sample surface characteristics and color.Item An experimental and simulation study of the effect of geochemical reactions on chemical flooding(2010-12) Chandrasekar, Vikram, 1984-; Delshad, Mojdeh; Pope, Gary A.The overall objective of this research was to gain an insight into the challenges encountered during chemical flooding under high hardness conditions. Different aspects of this problem were studied using a combination of laboratory experiments and simulation studies. Chemical Flooding is an important Enhanced Oil Recovery process. One of the major components of the operational expenses of any chemical flooding project, especially Alkali Surfactant Polymer (ASP) flooding is the cost of softening the injection brine to prevent the precipitation of the carbonates of the calcium and magnesium ions which are invariably present in the formation brine. Novel hardness tolerant alkalis like sodium metaborate have been shown to perform well with brines of high salinity and hardness, thereby eliminating the need to soften the injection brine. The first part of this research was aimed at designing an optimal chemical flooding formulation for a reservoir having hard formation brine. Sodium metaborate was used as the alkali in the formulation with the hard brine. Under the experimental conditions, sodium metaborate was found to be inadequate in preventing precipitation in the ASP slug. Factors affecting the ability of sodium metaborate to sequester divalent ions, including its potential limitations under the experimental conditions were studied. The second part of this research studied the factors affecting the ability of novel alkali and chelating agents like sodium metaborate and tetrasodium EDTA to sequester divalent ions. Recent studies have shown that both these chemicals showed good performance in sequestering divalent ions under high hardness conditions. A study of the geochemical species in solution under different conditions was done using the computer program PHREEQC. Sensitivity studies about the effect of the presence of different solution species on the performance of these alkalis were done. The third part of this research focused on field scale mechanistic simulation studies of geochemical scaling during ASP flooding. This is one of the major challenges faced by the oil and gas industry and has been found to occur when sodium carbonate is used as the alkali and the formation brine present in situ has a sufficiently high hardness content. The multicomponent and multiphase compositional chemical flooding simulator, UTCHEM was used to determine the quantity and composition of the scales formed in the reservoir as well as the injection and production wells. Reactions occurring between the injected fluids, in situ fluids and the reservoir rocks were taken into consideration for this study. Sensitivity studies of the effect of key reservoir and process parameters like the physical dispersion and the alkali concentration on the extent of scaling were also done as a part of this study.Item Experimental development of a chemical flood and the geochemistry of novel alkalis(2012-08) Winters, Matthew Howard; Pope, Gary A.; Weerasoriya, UpaliSurfactant-Polymer (SP) and Alkaline-Surfactant-Polymer (ASP) floods are tertiary oil recovery processes that mobilize residual oil to waterflood. These Chemical EOR processes are most valuable when the residual oil saturation of a target reservoir to waterflood is high. The first steps of designing a SP or ASP flood are performed in a laboratory by developing a surfactant formulation and by performing core flood experiments to assess the performance of the flood to recovery residual oil to waterflood. The two criteria for a technically successful laboratory SP or ASP core flood are recovering greater than 90% of residual oil to waterflood leaving behind less than 5% of residual oil and accomplishing this at a field scalable pressure gradient across the porous medium of approximately 1 psi per foot. This thesis documents the laboratory development of SP and ASP core floods for a continental Unites States oil reservoir reported to contain the minerals anhydrite and gypsum. The significance of these minerals is that they provide an infinite acting source of calcium within the reservoir that makes using the traditional alkali sodium carbonate unfeasible using conventional Chemical EOR methods. This is because sodium carbonate will precipitate as calcite in the presence of free calcium ions. Secondly, this thesis investigates two novel alkalis that are compatible with free calcium ions, sodium acetate and tetrasodium EDTA, for their viability for use in ASP floods for reservoirs containing anhydrite or gypsum.Item Experimental investigation of the effect of increasing the temperature on ASP flooding(2011-12) Walker, Dustin Luke; Pope, Gary A.; Weerasooriya, UpaliChemical EOR processes such as polymer flooding and surfactant polymer flooding must be designed and implemented in an economically attractive manner to be perceived as viable oil recovery options. The primary expenses associated with these processes are chemical costs which are predominantly controlled by the crude oil properties of a reservoir. Crude oil viscosity dictates polymer concentration requirements for mobility control and can also negatively affect the rheological properties of a microemulsion when surfactant polymer flooding. High microemulsion viscosity can be reduced with the introduction of an alcohol co-solvent into the surfactant formulation, but this increases the cost of the formulation. Experimental research done as part of this study combined the process of hot water injection with ASP flooding as a solution to reduce both crude oil viscosity and microemulsion viscosity. The results of this investigation revealed that when action was taken to reduce microemulsion viscosity, residual oil recoveries were greater than 90%. Hot water flooding lowered required polymer concentrations by reducing oil viscosity and lowered microemulsion viscosity without co-solvent. Laboratory testing of viscous microemulsions in core floods proved to compromise surfactant performance and oil recovery by causing high surfactant retention, high pressure gradients that would be unsustainable in the field, high required polymer concentrations to maintain favorable mobility during chemical flooding, reduced sweep efficiency and stagnation of microemulsions due to high viscosity from flowing at low shear rates. Rough scale-up chemical cost estimations were performed using core flood performance data. Without reducing microemulsion viscosity, field chemical costs were as high as 26.15 dollars per incremental barrel of oil. The introduction of co-solvent reduced chemical costs to as low as 22.01 dollars per incremental barrel of oil. This reduction in cost is the combined result of increasing residual oil recovery and the added cost of an alcohol co-solvent. Heating the reservoir by hot water flooding resulted in combined chemical and heating costs of 13.94 dollars per incremental barrel of oil. The significant drop in cost when using hot water is due to increased residual oil recovery, reduction in polymer concentrations from reduced oil viscosity and reduction of microemulsion viscosity at a fraction of the cost of co-solvent.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 Fire retardant polyamide 11 nanocomposites/elastomer blends for selective laser sintering(2016-05) Ortiz, Rogelio; Bourell, David Lee; Koo, Joseph H.Additive manufacturing (AM) had previously been used solely for prototyping and visualization purposes, but in recent years, this technique has shifted to the idea of producing end-use parts. This has already been successfully done in some areas via selective laser sintering (SLS). Unfortunately, current polymeric materials for processing via SLS do not meet the requirements of the majority of commercial applications. Hence, this thesis presents efforts to develop a multifunctional polyamide 11 (PA11) polymer with enhanced thermal, mechanical, and flammability properties for SLS through the use of nanotechnology.Item Forecasting of isothermal enhanced oil recovery (EOR) and waterflood processes(2011-12) Mollaei, Alireza; Delshad, Mojdeh; Lake, Larry W.; Patzek, Tadeusz W.; Edgar, Thomas F.; Lasdon, Leon S.Oil production from EOR and waterflood processes supplies a considerable amount of the world's oil production. Therefore, the screening and selection of the best EOR process becomes important. Numerous steps are involved in evaluating EOR methods for field applications. Binary screening guides in which reservoirs are selected on the basis of reservoir average rock and fluid properties are consulted for initial determination of applicability. However, quick quantitative comparisons and performance predictions of EOR processes are more complicated and important than binary screening that are the objectives of EOR forecasting. Forecasting (predicting) the performance of EOR processes plays an important role in the study, design and selection of the best method for a particular reservoir or a collection of reservoirs. In EOR forecasting, we look for finding ways to get quick quantitative results of the performance of different EOR processes using analytical model/s before detailed numerical simulations of the reservoirs under study. Although numerical simulation of the reservoirs is widely used, there are significant obstacles that restrict its applicability. Lack of necessary reservoir data and time consuming computations and analyses can be barriers even for history matching and/or predicting EOR/waterflood performance of one reservoir. There are different forecasting (predictive) models for evaluation of different secondary/tertiary recovery methods. However, lack of a general purpose EOR/waterflood forecasting model is unsatisfactory because any differences in results can be caused by differences in the model rather than differences in the processes. As the main objective of this study, we address this deficiency by presenting a novel and robust analytical-base general EOR and waterflood forecasting model/tool (UTF) that does not rely on conventional numerical simulation. The UTF conceptual model is based on the fundamental law of material balance, segregated flow and fractional flux theories and is applied for both history matching and forecasting the EOR/waterflood processes. The forecasting model generates the key results of isothermal EOR and waterflooding processes including variations of average oil saturation, recovery efficiency, volumetric sweep efficiency, oil cut and oil rate with real or dimensionless time. The forecasting model was validated against field data and numerical simulation results for isothermal EOR and waterflooding processes. The forecasting model reproduced well (R2> 0.8) all of the field data and reproduced the simulated data even better. To develop the UTF for forecasting when there is no injection/production history data, we used experimental design and numerical simulation and successfully generated the in-situ correlations (response surfaces) of the forecasting model variables. The forecasting model variables were proven to be well correlated to reservoir/recovery process variables and can be reliably used for forecasting. As an extension to the abilities of the forecasting model, these correlations were used for prediction of volumetric sweep efficiency and missing/dynamic pore volume of EOR and waterflooding processes.