Polymer flooding is one of the most used chemical methods for enhanced oil recovery(EOR). However, laboratory studies and field applications of polymer injections often encounter polymer-induced clogging due to polymer transport and entrapment, leading to permeability reduction and diminished recovery performance. In this work, we focus on understanding polymer flow behavior using microfluidics devices and fluorescence microscopy. Microfluidic devices were designed to mimic and replicate the pore-network structures of oil-bearing conventional reservoir rocks. We present various flow experiments to study polymer transport and the underlying mechanisms of polymer retention in porous media. We assess the polymer-induced clogging of partially hydrolyzed polyacrylamides - HPAMs, using tracers. Afterward, we use a commercially available fluorescent polymer with microfluidics and single-molecule microscopy to give insights into individual molecule dynamics. Furthermore, we perform numerical simulations to replicate and extend the experimental work. As these experiments were conducted using commercially fluorescent polymer of low molecular weight and due to limitations of tracers to track polymers, we extended this work to investigate the transport of HPAMs, which is the most used polymer for EOR, at molecule-scale. However, existent methods in the literature are not suitable for fluorescently labeling ultra-high molecule weight polymers. Therefore, we present a novel method for synthesis of dye-labeled polymers that successfully tagged the HPAMS. Finally, we assessed the conformation and flow dynamics of the fluorescently labeled HPAM molecules. The findings highlight a limitation in some polymer screening workflows in the industry that suggest selecting the candidate polymers based solely on their molecular size and the size distribution of the rock pore-throats. Moreover, we present, for the first time, direct visualization of the three main mechanisms underlying polymer retention in porous media. We bring the first molecular evidence of polymer pore-clogging and permeability reduction reversibility, which sheds light on the controversy in the literature. In addition, we propose a new method for fluorescent labeling water-soluble ultra-high molecular weight polyacrylamides-based polymers that preserves their viscosifying properties. The method can be extended to any polymers containing carboxyl groups or groups that can be functionalized into carboxyls, and therefore, the applicability covers any fields that employ polymers.

This study demonstrated the presence of hyperthermophilic organisms in the upper Jurassic Smackover formation in Womack Hills, AL. Evidence for the presence of these organisms was shown by the cultivation of an aerobic and an anaerobic, oil-degrading hyperthermophilic culture from the cuttings of an oil well in the Jurassic Smackover at 90¢ªC. Viability of microorganisms in the formation was established through electron microscopy, by carbon dioxide production, and by protein production during incubation in medium at 90¢ªC. Not only was the presence of viable microorganisms in the reservoir established, but as a result of this study, new cultivation methods were also developed that may prove useful in future studies of these types of organisms.

Multi-phase fluid systems are an important concept in fluid mechanics, seen every day in how fluids interact with solids, gases, and other fluids in many industrial, medical, agricultural, and other regimes. In this thesis, the development of a two-dimensional digital microfluidic device is presented, followed by the development of a two-phase microfluidic diagnostic tool designed to simulate sandstone geometries in oil reservoirs. In both instances, it is possible to take advantage of the physics involved in multiphase flows to affect positive outcomes in both. In order to make an effective droplet-based digital microfluidic device, one must be able to precisely control a number of key processes including droplet positioning, motion, coalescence, mixing, and sorting. For planar or open microfluidic devices, many of these processes have yet to be demonstrated. A suitable platform for an open system is a superhydrophobic surface, as suface characteristics are critical. Great efforts have been spent over the last decade developing hydrophobic surfaces exhibiting very large contact angles with water, and which allow for high droplet mobility. We demonstrate that sanding Teflon can produce superhydrophobic surfaces with advancing contact angles of up to 151° and contact angle hysteresis of less than 4°. We use these surfaces to characterize droplet coalescence, mixing, motion, deflection, positioning, and sorting. This research culminates with the presentation of two digital microfluidic devices: a droplet reactor/analyzer and a droplet sorter. As global energy usage increases, maximizing oil recovery from known reserves becomes a crucial multiphase challenge in order to meet the rising demand. This thesis presents the development of a microfluidic sandstone platform capable of quickly and inexpensively testing the performance of fluids with different rheological properties on the recovery of oil. Specifically, these microfluidic devices are utilized to examine how shear-thinning, shear-thickening, and viscoelastic fluids affect oil recovery. This work begins by looking at oil displacement from a microfluidic sandstone device, then investigates small-scale oil recovery from a single pore, and finally investigates oil displacement from larger scale, more complex microfluidic sandstone devices of varying permeability. The results demonstrate that with careful fluid design, it is possible to outperform current commercial additives using the patent-pending fluid we developed. Furthermore, the resulting microfluidic sandstone devices can reduce the time and cost of developing and testing of current and new enhanced oil recovery fluids.

The Lowry Method of Protein Assay is an effective alternative to point count or culture methods to determine the relative abundance of microorganisms in geologic samples. Results of this project show that the outcome of the Lowry assay is not affected by the constituents of a sandstone reservoir and that a relationship exists between microbes and clay minerals. Core samples were taken from the Carter sandstone at the North Blowhorn Creek Unit in Lamar County, Alabama. Samples were chosen based on mineralogic heterogeneity. The samples were placed in an anaerobic glove bag and given nutrients to induce the growth of in situ microorganisms. Samples were then assayed. Results of the protein assays show that the Lowry Method of Protein Assay is effective in determining protein concentrations in geologic samples with varying mineralogies. The assays also indicated that samples with abundant clay minerals show the greatest amount of microbial growth.

[pt] Evidências experimentais demonstram o potencial da injeção de emulsões no aumento do fator de recuperação de óleo. O mecanismo responsável por esta melhor varredura do reservatório é a redução da mobilidade da água em regiões do reservatório já varridas por água. Esta redução pode ser associada ao bloqueio parcial de gargantas do meio poroso por gotas da fase dispersa da emulsão. A eficiência deste bloqueio parcial depende fortemente da geometria do poro, das características morfológicas e propriedades físicas da emulsão injetada. A utilização eficiente deste método de recuperação é limitada pela falta de entendimento fundamental de como emulsões escoam através de um meio poroso. Este trabalho tem como objetivo estudar o escoamento de emulsões através de gargantas de poros, que são modeladas fisicamente por micro- capilares com garganta nos experimentos desenvolvidos nesta pesquisa. Os resultados mostram como a permeabilidade varia com as propriedades e características morfológicas da emulsão e parâmetros geométricos do micro-capilar. Estes dados definem as propriedades necessárias de emulsões em função das características do reservatório para a obtenção do efeito de bloqueio parcial desejado e servem de entrada de dados para modelo de rede de capilares de escoamento de emulsões em meios porosos. / [en] Experimental evidences show the potential of emulsion injection in the improvement of oil recovery factor. The responsible mechanism for this better reservoir sweep is the water mobility reduction in regions already swept by water. This reduction can be associated with partial blockage of porous media throats by droplets of emulsion dispersed phase. The efficiency of this partial blockade strongly depends on pore geometry, morphological characteristics and physical properties of the injected emulsion. The efficient use of this recovery method is limited by the lack of fundamental understanding of how emulsions flow through a porous medium. This work aims to study the flow of emulsions through pores throats, which are physically modeled by constricted micro- capillaries in the experiments presented here. The results show how permeability varies with geometrical parameters of micro-capillaries, emulsion properties and morphological characteristics. These data define the necessary properties of emulsions according to the reservoir characteristics to obtain the desired blocking effect and serve as input data to capillaries network model of flow of emulsions in porous media.

Chemical enhanced oil recovery (cEOR) aims to increase the oil recovery of mature oil fields, using aqueous solutions of surfactants and polymers, to mobilize trapped oil and maintain production. The interfacial tensions (IFTs) between the injected aqueous solution, the oil droplets in reservoirs, and other possible phases formed (e.g., a “middle phase” microemulsion) are important for designing and assessing a chemical formulation. Ultralow IFTs, less than 10^-2 mN·m^-1, are needed to increase the capillary number and help mobilize trapped oil droplets. Despite this fact, phase behavior tests have received more attention than IFTs for designing and evaluating surfactant formulations that result in high oil recovery efficiencies, because incorporating reliable IFTs into such evaluation process is avoided due to difficulties in obtaining reliable values. Hence, the main thrusts of this dissertation are to: (a) develop robust IFT measurement protocols for obtaining reliable IFTs regardless of the complexity of water and oil phase constituents and (b) improve the existing surfactant polymer formulation evaluation and screening processes by successfully incorporating the IFT as one of the critical parameters.<br>First, two robust tensiometry protocols using the known emerging bubble method (EBM) and the spinning bubble method (SBM) were demonstrated, for determining accurately equilibrium surface tensions (ESTs) and equilibrium IFTs (EIFTs). The protocols are used for measuring the dynamic surface tensions (DSTs), determining the steady state values, and establishing the stability of the steady state values by applying small surface area perturbations by monitoring the ST or IFT relaxation behavior. The perturbations were applied by abruptly expanding or compressing surface areas by changing the bubble sizes with an automated dispenser for the EBM, and by altering the rotation frequency of the spinning tube for the SBM. Such robust tension measurement protocols were applied for Triton X-100 aqueous solutions at a fixed concentration above its critical micelle concentration (CMC). The EST value of the model solution was 31.5 ± 0.1 mN·m^-1 with the EBM and 30.8 ± 0.2 mN·m^-1 with the SBM. These protocols provide robust criteria for establishing the EST values.<br>Second, the EIFTs of a commercial single chain anionic surfactant solution in a synthetic brine against a crude oil from an active reservoir were determined with the new protocol described earlier. The commercial surfactant used here has an oligopropoxy group between a hydrophobic chain and a sulfate head group. The synthetic brine has 9,700 ppm of total dissolved salts, which are a mixture of sodium chloride (NaCl), potassium chloride (KCl), manganese (II) chloride tetrahydrate (MnCl₂·4H₂O), magnesium (II) chloride hexahydrate (MgCl₂·6H₂O), barium chloride dihydrate (BaCl₂·2H₂O), sodium sulfate decahydrate (Na₂SO₄·10H₂O), sodium bicarbonate (NaHCO₃), and calcium chloride dihydrate (CaCl₂·2H₂O). The DSTs curves of the surfactant concentrations from 0.1 ppm to 10,000 ppm by weight had a simple adsorption/desorption equilibrium at air/water surface with surfactant diffusion from bulk aqueous phase. Such a mechanism was also observed from the tension relaxation behavior after area perturbations for the oil/water interfaces while DIFT measurements. The CMC of the commercial surfactant was determined to be 12 ppm in water and 1 ppm in the synthetic brine used. From the initial tension reduction curves from DST and DIFT measurements, the equilibrium timescales were shorter with brine than with water, because the adsorbed surfactant on the oil/water interfaces were partitioned into oil phases. For both DST and DIFT results suggest that the adsorbed surfactant layer at interfaces were typical adsorbed soluble monolayers.<br>Third, the phase and rheological behavior of a commercial anionic surfactant in water and in brine are important for large scale applications. A phase map of the surfactant at 25 °C at full range of surfactant concentration was obtained. The supramolecular structures of the various phases were characterized by dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM), conductimetry, densitometry, and x-ray scattering. The identified phases evolved as the surfactant concentration was increased; they were a micellar solution phase, a hexagonal liquid crystalline phase, and a lamellar liquid crystalline phase. In addition, the characterization results provided detailed information about supramolecular structure parameters such as micellar sizes and their aggregation numbers, and liquid crystal spacings. The phase and rheological behavior trends identified here were of great importance because the trend was similar to that of single chain monoisomeric surfactant. Thus, this study provides a potential universality of phase behavior trends of surfactant-water systems despite of the multicomponent nature of surfactants.<br>Fourth, the EIFTs of the pre-equilibrated mixtures of surfactant, brine, and oil were determined and compared to the EIFTs prior to pre-equilibration, in order to systematically identify the most relevant IFT for oil recovery. The EIFT between surfactant solutions and oil without any pre-equilibration prior to tension measurements is defined as the un-pre-equilibrated EIFT (EIFT_up). The EIFT between oil and water phases after the pre-equilibration of surfactant, brine, and oil is defined as pre-equilibrated EIFT (EIFT_p). The EIFT_p’s were generally higher than EIFT_up’s. In addition, the effects of three mixing methods and the water-to-oil volume ratio (WOR) on the EIFT_p were evaluated. Out of three mixing methods, (A) mild mixing, (B) magnetic stirring, and (C) shaking vigorously by hand, method C produced mixtures which are the closest to the equilibrium state. The mixtures produced by method C had the largest decrease of the surfactant concentration during pre-equilibration due to the surfactant partitioning into oil phases. Moreover, the WOR affects the EIFT_p significantly due to the preferential partitioning of surfactant components into oil phases. More specifically, the WOR and the EIFT_p were found to be inversely correlated, because the amount of partitioned surfactant increased as the oil volume fraction increased. The EIFT_p’s were different from the EIFT_up’s at the same total surfactant concentrations in the aqueous layer evidently because of preferential partitioning of the various surfactant components.<br>Finally, the effect of surfactant losses due to adsorption into the rock surface on the pre-equilibrated EIFT (EIFT_p) were evaluated to improve surfactant formulation protocols. Here, five types of EIFTs were identified, along with robust protocols for determining them. These are: (I) the un-pre-equilibrated equilibrium IFT (EIFT_up); (II) the un-pre-equilibrated EIFTs in the presence of rock (EIFT_up,rock); (III) the pre-equilibrated EIFTs (EIFT_p) in the presence of oil; (IV) the pre-equilibrated EIFT in the presence of rock and oil (EIFT_p,rock); and (V) the effluent EIFT (EIFT_eff). The EIFT_up is the EIFT of the aqueous surfactant/brine solution against an oil drop without any pre-equilibration. The EIFT_up,rock is the EIFT between an oil drop and the surfactant solution after pre-equilibration with a rock sample to account for adsorption losses. The EIFT_p is the EIFT between the pre-equilibrated water and the oil phases from surfactant/brine/oil mixtures. The EIFT_p,rock is the EIFT between the pre-equilibrated water and the oil phases from surfactant/brine/oil/rock mixtures. The EIFT_eff is the EIFT from an effluent sample mixture of a laboratory-scale core flood test. Among the five types of EIFTs, the EIFT_p,rock was found to be the most important for the highest oil recovery performance in core flood tests, because it captures the most important surfactant partition processes, the partitioning to the oil phase and the partitioning by adsorption on the rock surface. Among three surfactant formulations tested with core flood experiments, the one with the lowest EIFT_p,rock (~0.01 mN·m^-1) had the highest oil recovery ratio (78%), and the one with the highest EIFT_p,rock (~0.2 mN·m^-1) had the lowest oil recovery ratio (55%). The other EIFTs correlated less with the oil recovery performance. Identifying surfactant formulations that have low or ultralow EIFTs, especially ultralow EIFT_p,rock’s, are critical for screening formulations appropriate for core flood tests and target field applications, and for predicting oil recovery performance. These works are a significant contribution for improving (a) the surfactant formulation evaluation protocols, and (b) the utilization of reliable IFTs and phase behavior test protocols for oil recovery and many other surfactant and colloid sciences applications.<br>

As easy target reservoirs are depleted around the world, the need for intelligent enhanced oil recovery (EOR) methods increases. The first part of this work is focused on modeling aspects of novel chemical EOR methods for naturally fractured reservoirs (NFR) involving wettability modification towards more water wet conditions. The wettability of preferentially oil wet carbonates can be modified to more water wet conditions using alkali and/or surfactant solutions. This helps the oil production by increasing the rate of spontaneous imbibition of water from fractures into the matrix. This novel method cannot be successfully implemented in the field unless all of the mechanisms involved in this process are fully understood. A wettability alteration model is developed and implemented in the chemical flooding simulator, UTCHEM. A combination of laboratory experimental results and modeling is then used to understand the mechanisms involved in this process and their relative importance. The second part of this work is focused on modeling surfactant/polymer floods using a fully implicit scheme. A fully implicit chemical flooding module with comprehensive oil/brine/surfactant phase behavior is developed and implemented in general purpose adaptive simulator, GPAS. GPAS is a fully implicit, parallel EOS compositional reservoir simulator developed at The University of Texas at Austin. The developed chemical flooding module is then validated against UTCHEM. / text

Une des méthodes de récupération assistée du pétrole les plus utiliséesest l'injection de polymères. L'efficacité de cette méthode est attribuée principalement à laréduction de la mobilité de la phase aqueuse et à la viscoélasticité des polymères. Cetteefficacité dépend de plusieurs paramètres comme la perméabilité, la température, la salinité,l'hétérogénéité, la mouillabilité, le nombre capillaire, etc. De nombreuses connaissances ontété accumulées s’agissant du rôle des polymères dans la récupération du pétrole. Néanmoins,il subsiste encore des questions importantes:• Quel est le meilleur moment pour l’injection de polymère?• Quel rôle joue la mouillabilité dans la récupération ultime de pétrole?• Comment les effets viscoélastiques influencent-ils la récupération?• Quel est le rôle l’adsorption du polymère dans le processus de récupération?Cette thèse, expérimentale, a pour but de fournir des données concernant ledéplacement diphasique (en conditions de mouillabilité intermédiaire et de mouillabilité francheà l’eau) et d’investiguer l’impact réel de la rhéologie sur l’efficacité de déplacement de l’huile.Des injections de polymères sont réalisées à différents stades de précocité (c’est àdire, à différents moments après l’injection d’eau). Les résultats montrent un impact significatifde la précocité du balayage de polymère sur les taux de récupération finale et apparait commeun facteur déterminant à prendre en compte. D’autre part, on observe une récupération plusfaible pour une mouillabilité franche à l’eau que pour une mouillabilité intermédiaire etl’adsorption et la viscoélasticité de la solution de polymère ne sont pas déterminants dans letaux de récupération (dans nos conditions) alors que nos résultats indiquent un changementde mouillabilité durant l’injection de polymère.Des expériences complémentaires de dispersion diphasique ont ensuite mis enévidence un lien direct entre la dispersivité et le taux de récupération final. / Polymer flooding is one of the most developed chemical enhanced oil recoverymethod that has been used successfully since decades. In this chemical EOR method, thepolymer is adding to a waterflood to decrease its mobility. The resulting increase in viscosityas well as a decrease in aqueous phase permeability improve macroscopic oil sweepefficiency. At the pore scale, viscoelasticity is known to be also a key parameter that controlsthe microscopic sweep efficiency. However this sweep efficiency depends on several factorslike the permeability, temperature, salinity, wettability, capillary number, heterogeneity, etc.Therefore several studies are still necessary to have a better understanding of the behaviourof the polymer inside porous media and to optimize the process.• What is the best moment to inject polymer?• What is the role of wettability in final recovery?• How do viscoelastic effects influence recovery?• What is the role of adsorption of the polymer in the recovery process?In our interest to optimize and to understand polymer flooding process we have analysed thedependence of the sweep efficiency with the moment of the polymer injection duringwaterflooding and wettability (Water wet and intermediate wet). The polymer solution isinjected in the core at different maturity times (0PV, Breakthrough, 1PV, 2PV, 3PV, 4PV and6PV).The main results can be summarized in three points .The results show oil recoveryfinal for water wet corefloods is lower than intermediate wet corefloods. On the other hand, theproduction of oil with the injection of polymer is higher than the injection of water due to afavorable mobility ratio. Finally, the final recovery rates are lower when the polymer injectionis late. These results suggest that the history of sweeping can lead to different distributions ofphases (oil/brine) at the end of the waterflood. The sweep efficiency is related to the ability ofthe polymer to disperse throughout the accessible portal space. We have analysed this aspectfrom the point of view of the diphasic dispersion by showing that the dispersivity of the phasesis different at each time of the water injection. The complementary diphasic dispersionexperiments showed a direct link between dispersivity and the final oil recovery.

Using a hydrogen donor and a catalyst for upgrading and increasing oil recovery during in situ combustion is a known and proven technique. Based on research conducted on this process, it is clear that widespread practice in industry is the usage of tetralin as a hydrogen donor. The objective of the study is to find a cheaper hydrogen donor with better or the same upgrading performance. Decalin (C10H18) is used in this research as a hydrogen donor. The experiments have been carried out using field oil and water saturations, field porosity and crushed core for porous medium. Four in situ combustion runs were performed with Gulf of Mexico heavy oil, and three of them were successful. The first run was a control run without any additives to create a base for comparison. The next two runs were made with premixed decalin (5 percent by oil weight) and organometallic catalyst (750 ppm). The following conditions were kept constant during all experimental runs: air injection rate at 3.1 L/min and combustion tube outlet pressure at 300 psig. Analysis of the performance of decalin as a hydrogen donor in in-situ combustion included comparison of results with an experiment where tetralin was used. Data from experiments of Palmer (Palmer-Ikuku, 2009) was used for this purpose, where the same oil, catalyst and conditions were used. Results of experiments using decalin showed better quality of produced oil, higher recovery factor, faster combustion front movement and higher temperatures of oxidation. API gravity of oil in a run with decalin is higher by 4 points compared to a base run and increased 5 points compared to original oil. Oil production increased by 7 percent of OOIP in comparison with base run and was 2 percent higher than the experiment with tetralin. The time required for the combustion front to reach bottom flange decreased 1.6 times compared to the base run. The experiments showed that decalin and organometallic catalysts perform successfully in in situ combustion, and decalin is a worthy replacement for tetralin.

The continuous rising of anthropogenic emission into the atmosphere as a consequence of industrial growth is becoming uncontrollable, which causes heating up the atmosphere and changes in global climate. Therefore, CO2 emission becomes a big problem and key issue in environmental concerns. There are several options discussed for reducing the amount of CO2 emitted into the atmosphere. CO2 sequestration is one of these options, which involves the capture of CO2 from hydrocarbon emission sources, e.g. power plants, the injection and storage of CO2 into deep geological formations, e.g. depleted oil reservoirs. The complexity in the structure of geological formations and the processes involved in this method necessitates the use of numerical simulations in revealing the potential problems, determining feasibility, storage capacity, and life span credibility. Field K having 32o API gravity oil in a carbonate formation from southeast Turkey was studied. Field K was put on production in 1982 and produced until 2006, which was very close to its economic lifetime. Thus, it was considered as a candidate for enhanced oil recovery and CO2 sequestration. Reservoir rock and fluid data was first interpreted with available well logging, core and drill stem test data. Monte Carlo simulation was used to evaluate the probable reserve that was 7 million STB, original oil in place (OOIP). The data were then merged into CMG/STARS simulator. History matching study was done with production data to verify the results of the simulator with field data. After obtaining a good match, the different scenarios were realized by using the simulator. From the results of simulation runs, it was realized that CO2 injection can be applied to increase oil recovery, but sequestering of high amount of CO2 was found out to be inappropriate for field K. Therefore, it was decided to focus on oil recovery while CO2 was sequestered within the reservoir. Oil recovery was about 23% of OOIP in 2006 for field K, it reached to 43 % of OOIP by injecting CO2 after defining production and injection scenarios, properly.