Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisor: Yan Jin, Dept. of Plant & Soil Sciences. Includes bibliographical references.

There have been significant advances in the research of nanoparticle technologies for formation evaluation and reservoir engineering operations. The target applications require a variety of different retention characteristics ranging from nanoparticles that adsorb near the wellbore to nanoparticles that can travel significant distances within the porous medium with little or no retention on the grain substrate. A detailed understanding of the underlying mechanisms that cause nanoparticle retention is necessary to design these applications. In this thesis, experiments were conducted to quantify nanoparticle retention in unconsolidated columns packed with crushed Boise sandstone and kaolinite clay. Experimental parameters such as flow rate, injected concentration and sandpack composition were varied in a controlled fashion to test hypotheses concerning retention mechanisms and enable development and validation of a mathematical model of nanoparticle transport. Results indicate nanoparticle retention, defined as the concentration of nanoparticles remaining attached to grains in the porous medium after a volume of nanoparticle dispersion is injected through the medium and then displaced with brine, is a function of injected fluid velocity with higher injected velocities leading to lower retention. In many cases nanoparticle retention increased nonlinearly with increasing concentration of nanoparticles in the injected dispersion. Nanoparticle retention concentration was found to exhibit an upper bound beyond which no further adsorption from the nanoparticle dispersion to the grain substrate occurred. Kaolinite clay was shown to exhibit lower retention concentration [mg/m2] than Boise sandstone suggesting DLVO interactions do not significantly influence nanoparticle retention in high salinity dynamic flow environments. / text

The flow, reactions and current in a porous rotating disk electrode (PRDE) is studied experimentally and theoretically. A PRDE is an electrochemically active porous disk mounted on a classic rotating disk electrode (RDE). For the oxidation of iodide, the measured current from a PRDE as a function of rotation rate shows much richer behavior than the flat RDE, including a sigmoidal dependence on the rotation rate that specifically depends on the geometry of the disk, its permeability, porosity and the fluid and reactant transport properties. It is found that when the complex behavior of the current is explained in terms of the ratio of the effective electrochemical reaction time to the residence time of the fluid in the porous disk all the data can be plotted onto a universal curve at high rotation rates. With this knowledge the PRDE is modeled analytically where the reactant transport is dominated by either advection or diffusion. When advection is dominant the current can be expressed in a simple algebraic form involving the dimensionless reaction time. The diffusion dominated regime is modeled utilizing a boundary layer theory. The current is found as a function of the rotation rate, reaction rate, permeability, diffusion coefficients, kinematic viscosity, and geometry of the disk. Combined with finite effects analysis, the two analytic models accurately describe the PRDE for the full range of its operation regardless of the geometry of the disk. Also, the dominant mass transfer mode transition point is identified. Additional experiments with ferrocenemethanol are carried out using PRDEs constructed by mounting various sized carbon fiber disks onto glassy carbon RDEs to complement previous experiments using iodide. The results validate the theories for the operation of the PRDE in the regimes of advection or diffusion dominated transport. A possible application of the PRDE system for measuring rock acidization and permeability is explored by developing analytic and numerical models for a nonconductive porous disk. This system exhibits regimes limited by different processes: diffusion, advection, and reaction. It is found that a one-dimensional analytic model incorporating the finite thickness of the porous disk and the surface reaction rate suffices to describe the system. / text

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Not available / text

Not available / text

Not available / text

The goal of this research was to determine relationships between post-coarsening processing conditions and the microporous morphology of membranes. Specifically, the processes of matrix solidification in liquid -- liquid thermally induced phase separation (L−L TIPS), the drying of the microporous structure, and the uni-axial elongation of a simple microporous structure were examined. Additionally, the effect uni-axial elongation has on pore shape was included in a sieve filtration model to look at the impact on performance. A deterministic approach was taken to predict membrane morphologies resulting from the matrix solidification step that occurs in L–L TIPS. Many studies have examined the growth rate of droplets in the coarsening stage of membrane formation, but few have attempted to extend this information into the subsequent processing steps of matrix solidification, diluent extraction/exchange, and drying. The modeling of matrix solidification utilized Monte-Carlo routines to provide quantitative information on cell size and cell size distribution for a representative polymer -- diluent system. The predicted structures were in agreement with experimentally formed membranes. The information gained from matrix solidification modeling was used to make finite element (FE) simulations in ABAQUS CAE to model the drying of the microporous morphology, with capillary forces being the dominant force driving shrinkage and collapse of the structure. These FE simulations predicted no permanent deformation arising from only capillary forces, which was confirmed through experimental evidence showing no correlation to surface tension. For polar polymers an additional heuristic was proposed: use extractants that are more alkane-like, regardless of surface tension, to reduce the collapse of the structure. FE simulations were used to model the uni-axial elongation of track-etch membranes in an effort to change performance characteristics. The FE simulations accurately predicted pore shape changes comparable to experimental values. The pore shape change information was used to modify standard sieve filtration models. The modified sieve filtration models show that a relatively modest strain of 35% can double the initial flux of track-etch membranes. / text

This study investigates peculiarities of the filtration combustion (FC) of the gaseous fuel-air mixtures in a porous inertia media (PIM). Combustion wave velocities and temperatures were measured for hydrogen-air, propane-air and methane-air mixtures in the PIM at different mixture filtration velocities. It is shown that the dependences of the combustion wave velocities on the equivalence ratio are V-shaped, It was further confirmed that the FC in the PIM has more contrasts than similarities with the normal homogeneous combustion. One of the interesting observations in the present study, which is not common in normal homogenous combustion, is the shifting of the fuel-air equivalent ratio at the minimum combustion wave velocity from the stoichiometric condition (¢ = 1). For a hydrogen-air mixture, the fuel-air equivalence ratio at the minimum combustion velocity shifts from the stoichiometric condition to the rich region, while for the propane-air and methane-air mixtures the fuel-air equivalence ratio at the minimum combustion velocity shifts toward fuel-leaner conditions. The measured maximum porous media temperatures in the combustion waves are found to be weakly dependent on the mixture filtration velocities. In general, the effects of the mixture filtration velocities on the measured maximum porous media temperatures are not significant.

In the mantle section of many ophiolite sequences, dunite dikes are present. Around dunite dikes at the Josephine and Trinity ophiolite, a sequence of lithologies consisting of plagioclase lherzolite, lherzolite, and harzburgite is present. This sequence of rocks has been interpreted to be the result of reactive porous flow. From trace element data, the mafic melt has been interpreted to flow both into and out of the dunite dikes. Whether the melt emanates from the dunite bodies or is collected by them has implications for the mechanisms of melt extraction beneath ridge systems. The determination of the flow direction based on tracer distributions is difficult and therefore additional constraints are important. Reactive transport theory predicts that lithological zonations around dunite bodies can indicate the direction of flow. To date no reactive transport model has been developed to test these hypotheses, and therefore I have built a reactive transport model using COMSOL v. 4.1. I developed a model for an orthopyroxene dissolution front based on the model of Chadam et al. (1986, Reactive infiltration instabilities, IMA Journal of Applied Mathematics, v. 36, p.207-221). This model includes the strong nonlinearity feedback that has been invoked to lead to the channelization of melt flow. The instability leads to the formation of elongated regions where orthopyroxene is depleted. This model predicts that the melt is focused into the dunite bodies, most flow is parallel to the dunite boundaries, and exits the fingers at the tip of the column. / text