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I'd first like to thank Dr. Bryant, whom I first met as a sophomore when he taught me how to program in excel. With his guidance I believe I am finally closer to being 90% right 100% of the time. Dr. Huh, for helping me through countless edits of my papers and a calm approach toward research has made my time here that much more enjoyable. I would also like to thank is Dr. Bommer, who advised me to go to graduate school where I became a better engineer; and Glen Baum for not just being a lab supervisor, but being the person I call no matter how badly I screwed up an experiment. You are like a father figure of the petroleum labs who always gets us out of trouble. Lastly, Arletta for being the best advisor I could have, more like a mother away from home. My lab-mate Federico Caldelas, who provided the example for me as an engineer. My lab-mate Nic Huerta for being a great lunch partner and friend, and helping me stumble onto the tests for critical shear rate. I would also like to thank the other members of the nanoparticle group, Tina Zhang, Ki Youl Yoon, and Matt Roberts for your added input on presentations, experiments, and making the meetings exciting with your findings too.

Nanoparticles, when synthesized in a specific size range and with a special surface coating tailored to achieve certain desired functionalities, exhibit unique properties. This is because they are almost of molecular size but still retain many useful colloidal characteristics. Recent developments on novel potential upstream applications of nanoparticles are reviewed with focus on research at our laboratory. Oil-water emulsions and CO2 foams that have long-term stability under harsh downhole conditions could be employed as alternatives to surfactant-stabilized emulsions and foams for drilling and other applications. Nanoparticles that show minimal retention can be employed as sensing-capability carrier to detect fluid and rock properties of the producing zone. For example, paramagnetic nanoparticles delivered to the target formation could evaluate fluids saturations there, with application of magnetic field and measurement of response. Emulsions stabilized with surface-coated silica nanoparticles remain stable for months at high temperatures. By designing the hydrophilic/hydrophobic nature of surface coating, either oil-in-water or water-in-oil emulsions can be generated, with droplet size approaching uniform ~5 micron diameter, and with strongly shear-thinning rheology. Stable foams of supercritical CO2-in-water have been generated by co-injecting CO2 and silica nanoparticle aqueous dispersion through a glass-bead pack. The domain of foam stability and the apparent foam viscosity (which were 10 to 100 times more viscous than CO2) reveals threshold values of critical shear rate, particle concentration and phase ratio. An extensive series of sand-pack column and core-plug flow experiments revealed the mechanisms controlling retention of silica and paramagnetic iron-oxide nanoparticles in porous media. A wide range of particle loadings (0.1~18 wt%) and different rock samples were employed. With proper coating, retention was below 10% of the injected amount even in low permeability rock and with large particle concentrations. Potential for various novel upstream applications of engineered nanoparticles is demonstrated. Introduction Novel nanoscale structured materials, in the form of solid composites, complex fluids, and functional nanoparticle-fluid combinations, are bringing major technological advances in many industries. A few examples are the extraordinary material strength, elasticity and thermal conductivity of nano-based metal and polymer composites; targeted and programmed delivery of drugs and enhanced imaging of human organs in medicine; and chemical/physical properties of nano sensors. These and many other novel advances are due to the orders-of-magnitude increase in interfacial area and associated excess stress and chemical potential for the nano-structured materials; and some chemical and physical properties that are unique to nanoscale. In the petroleum/geosystems engineering discipline, research and applications of nanotechnology have been very limited. This is because subsurface formations have heterogeneity of all length scale and any treatments have to be carried out through boreholes, so that process control is generally difficult with significant uncertainties. And any process application requires a large volume treatment so that the material/process cost has to be small. Despite the difficulties, the current advances in nanotechnology are such that a judicious choice of potential applications, and carrying out focused research to bring those potentials to practical maturity, will result in quantum benefits to the oil and gas industry. The recent surge of interest on nanotechnology applications in upstream oil industry, as evidenced by the search of the SPE literature, shows that the important potential of the nanotechnology is beginning to be recognized.

With a number of advantages hitherto unrecognized, nanoparticle-stabilized emulsions and foams have recently been proposed for enhanced oil recovery (EOR) applications. Long-distance transport of nanoparticles is a prerequisite for any such applications. The transport of the particles is limited by the degree to which the particles are retained by the porous medium. In this work, experiments that quantify the retention and provide insight into the mechanisms for nanoparticle retention in porous media are described. Sedimentary rock samples (Boise sandstone and Texas Cream limestone) were crushed into single grains and sieved into narrow grain size fractions. In some cases, clay (kaolinite or illite) was added to the Boise sandstone samples. These grain samples were packed into long (1 ft–9 ft) slim tubes (ID = 0.93 cm) to create unconsolidated sandpack columns. The columns were injected with aqueous dispersions of silica-core nanoparticles (with and without surface coating) and flushed with brine. The nanoparticle effluent concentration history was measured and the nanoparticle recovery was calculated as a percentage of the injected nanoparticle dispersion. Fifty experiments were performed in this fashion, varying different experimental parameters while maintaining others constant to allow direct comparisons between experiments. The parameters analyzed in this work are: specific surface area of the porous medium, lithology, brine salinity, interstitial velocity, residence time, column length, and temperature. Our results indicate that retention is not severe, with an 8% average of the injected amount, for all our experiments. Of the parameters analyzed, specific surface area was the most influential, with a linear effect on nanoparticle retention independently of lithology. Larger salinity increased nanoparticle retention slightly and delayed nanoparticle arrival. Velocity, residence time and sandpack length are coupled parameters and were studied jointly; they had a minor effect on retention. Temperature had a marginal effect, with two percentage points greater retention at 80°C compared to 21°C. Both surface coated and bare silica nanoparticles were successfully transported, so surface coating is not a prerequisite for transport for the particle and rock systems studied.