Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

The rheology of polymer solutions is important in a wide variety of applications. In particular, solutions of high-molecular-weight, flexible polymers exhibit an increase in their apparent extensional viscosity with strain rate under extensional flow conditions. This extension thickening is due to formation of transient entanglements of polymer molecules. Certain commercial fluids contain both polymers and surfactants that might interact at the molecular level. These interactions affect the conformation of the polymer chain and, therefore, the rheological behavior of the solution. For instance, addition of anionic surfactants to solutions of nonionic polymers is known to induce increases in the shear viscosity of aqueous solution. This work investigates the behavior of aqueous solutions of a high-molecular-weight poly(ethylene oxide) (PEO), a nonionic, flexible polymer, and the anionic surfactants sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) and a commercial alpha-olefin sulfonate (AOS) in extensional flows. The extensional rheology of polymer/surfactant solutions is studied in an opposed-jets device, which generates a flow field close to uniaxial extension. For PEO/SDS mixtures, the results show that formation of micellar aggregates of SDS along the PEO chains results in an increase in the strength of extension thickening of PEO solutions by promoting intermolecular interactions between polymer chains. The minimum PEO concentration required to form intermolecular entanglements is substantially reduced in the presence of micellar aggregates. In solutions containing NaCl, intramolecular interactions are observed at low PEO concentrations. These reduce the strength of extension thickening. Addition of a co-solvent is investigated. The presence of alcohols in the aqueous solutions affects their rheology by changing the solvent nature for both PEO and SDS. In particular, n-octanol promotes aggregation of SDS along the PEO chains, enhancing intermolecular network formation in extensional flow. Results with mixtures of PEO with sulfonated surfactants (SDBS and AOS) show that both intermolecular and intramolecular interactions are promoted by these surfactants, depending on PEO concentration and molecular weight. The effect of ageing on these polymer/surfactant systems was studied. In extensional flows, extension thickening is suppressed in solutions of PEO with SDBS or AOS over a few-day period, whereas PEO and PEO/SDS solutions show no change.

This thesis discusses an experimental study involving sorption studies using methane, carbon dioxide, and a multicomponent gas mixture representative of in situ gas composition. Using the isotherms for pure methane and carbon dioxide, isotherm and variation in gas composition with desorption for gas mixture were established using a numerical technique. When using gas mixture, composition of the desorbing gas at each pressure level was monitored. Results indicate that during desorption, methane concentration decreased as the pressure was decreased while carbon dioxide concentration increased. Experimental results for sorption and variation in gas composition of the gas mixture compare very well with the theoretically obtained results. It is, therefore, possible to establish the sorption isotherm, Langmuir constants for gas mixtures and estimate the variation in gas composition with desorption theoretically, if the sorption isotherms for individual component gases are available and the in situ gas composition is known.

<p> Capturing carbon dioxide (CO₂) from stationary sources and injecting it into deep underground geologic formations has been identified as a viable method for reducing carbon emissions to the atmosphere. Sedimentary rocks, such as sandstones overlain by shales or evaporites, are the preferred formations because their morphology and structure provide pore space, and containment for the long term storage of CO₂. Sandstone formations have also served as repositories to migrating hydrocarbons, and are the sites of many oil recovery operations. For many depleted oil reservoirs, secondary waterflooding recovery methods are no longer efficient or economically viable, hence the application of tertiary CO₂ enhanced oil recovery (CO₂-EOR) followed by CO₂ storage is an attractive and cost effective business plan. </p><p> Citronelle Oil Field, located in southwest Alabama, is the largest and longest producing sandstone oil reservoir in the state, having produced more than 170 million barrels of oil from its estimated 500 million barrels of original oil in place, since its discovery in 1955. The field is in the later stages of secondary recovery by waterflooding and daily oil production has declined considerably. The field is comprised of the Upper and Lower Donovan hydrocarbon bearing sandstones, which are separated by the saline-water-bearing sandstones of the Middle Donovan. The Ferry Lake Anhydrite, which overlies the three sections, serves as their caprock. </p><p> The present work is focused on an investigation of the feasibility of a CO₂-EOR project for the Citronelle Oil Field and the use of the Middle Donovan for long term CO₂ storage. A set of static calculations, based on estimation methods which were retrieved from publications in the field, was followed by computer simulations using MASTER 3.0, TOUGH2-ECO2N, and TOUGHREACT. Results using MASTER 3.0, for simulation of CO₂-EOR, indicated that nearly 50 million barrels of additional oil could be produced by tertiary recovery. Results using TOUGH2-ECO2N and TOUGHREACT, for the simulations of CO₂ storage, indicated that 159 million metric tons (175 short tons) of CO₂ could be stored in the Middle Donovan formation. An investigation into possible CO₂ leakage from the reservoirs indicated that the Ferry Lake Anhydrite serves as a very reliable long term storage seal.</p><p> The present work can serve as a template for preliminary assessment of tertiary oil recovery and CO₂ storage of similar oil reservoirs and saline-water formations.</p>

Abstract Not Available.

The object of the present work has been to study the adsorption of hydrocarbon vapors on various types of clays, and to learn from this adsorption study the relative importance of various factors, both chemical and physical, which determine the adsorptive phenomena. The initial work was designed to learn the relative magnitude and flexibility of adsorption due to the following factors: (1) The atomic structure of the mineral grain. (2) The degree of dispersion of the clay grains, and the relative importance of the external surfaces. (3) The relative importance of the spacing of secondary aggregates, i.e., spaces between the clay grains. (4) The effect of exchangeable ions within the clay grains. (5) The effect of intra particle spaces, or channels of near molecular sizes in the primary grain structure.

One of the technical challenges in deviated drilling is the transport of drill bit cuttings to the surface. The complexity arises due to the narrow settling clearance for the cuttings and the presence of a cuttings bed on the low side of the bore hole. Fluid rheology is the determining factor in the efficiency of this operation. Drilling fluid selection for possible field use is the focus of this dissertation. The problem has been treated with a two-pronged strategy: (i) macroscopic studies that involve numerical models for the prediction of effects of rheology on drilling fluid flow through deviated bore holes; and (ii) microscopic experimental studies that provide physical insights into the fluid forces and relevant rheological parameters in cuttings resuspension. The objective of this study is to propose guidelines for fluid selection and rheological characterization of drilling fluids for the industry. The numerical study demonstrates that power law index is a significant parameter in determining the local flow regime in the different regions of the annulus and hence accurate control of power law index is critical in optimizing bore hole flow. In laminar flow, the shear thinning nature of a fluid does not aid flow through the narrow regions. Turbulence in the wider regions of the annuli aids flow through the narrow regions. The wall shear stresses are dependent only on the pressure drop, gap width and the local flow regimes. Eccentricity is found to hinder flow through the narrow regions of the annuli and certain combinations of rheology and eccentricity can cause stationary 'plug like' zones inside the annuli. The experimental study combined with microscopic calculations identified lift force as the limiting force in particle mobilization and put in perspective the possible importance of normal stresses due to the viscoelastic behavior of the fluid. It is shown that viscous characterization of the fluid is inadequate to predict the particle mobilization velocities even for very simple situations. Characterization of the fluid viscoelastic properties can provide qualitative information on the importance of fluid rheology for particle mobilization. The parameters of interest identified are the magnitude and strain sensitivity of linear viscoelastic moduli.

The drainage of horizontal thin liquid films produced from aqueous solutions of ionic surfactants was studied experimentally, using videomicroscopy and interference techniques, for several surfactants in a wide range of concentrations. Two types of drainage were observed: asymmetric and symmetric. The film drainage was found to be much faster in the asymmetric case. First, axisymmetric drainage was investigated. In this case, a numerical model was developed to simulate the entire drainage process, including the film formation. The condition for the transition from a nearly "plane-parallel" film to a dimpled film in the absence of disjoining pressure was determined. The ratio of the minimum to maximum thickness in the film and a dimensionless rate of drainage was correlated with the ratio of the maximum possible curvature in the dimple to the curvature in the meniscus. The presence of disjoining pressure makes a qualitative difference in film drainage. Low electrolyte concentrations in a film containing ionic surfactants produce a repulsive disjoining pressure that inhibits formation of the thin barrier ring and thus of the dimple itself. The film drains rapidly to its equilibrium thickness. For high electrolyte concentrations, disjoining pressure is dominated by van der Waals attraction. As a result a thin annular film forms that forces the dimple into a lens with a finite contact angle. These types of behaviors were observed experimentally. Then, the mechanisms of asymmetric thin film drainage were investigated. A simple linear stability analysis and a two dimensional numerical model were developed and showed that asymmetric drainage is caused by a hydrodynamic instability that is produced by a surface-tension-driven flow and stabilized by surface viscosity, surface diffusivity and system length scale. A criterion for the onset of instability causing asymmetric drainage was determined. Experiments performed on aqueous solutions of SDS and SDS:1-dodecanol showed the strong dependence of the drainage type on the surface shear viscosity. Experimental results were found to be in good agreement with the stability predictions.

Using simple structural and hydrodynamic models, a parametric study is made of the effect of the various parameters that influence the dynamic response of a compliant offshore structure in 2,000 ft of water. The parameters examined include the effects of different sea states, the stretching scheme used to approximate the near surface fluid kinematics, the horizontal variation of fluid kinematics; the effects of fluid-structure interaction and current; and the number of modes considered in the computation of the response. The dynamic responses of the structure, including maximum displacements, shears, and bending moments, are presented both in tabular and graphic forms. The sensitivity of the responses to the various parameters involved is examined and the practical implication of the results is discussed.

Pitzer et al. (1955) three-parameter (T$\sb{\rm c}$, P$\sb{\rm c}$,$\omega$) corresponding states principle (CSP) correlations for saturated properties are extended to long-chain n-alkanes and to other classes of compounds by use of n-alkane reference fluid properties. New vapor pressure measurements, a critical review of the n-alkane literature, and numerous correlational studies are described. Direct vapor pressure measurements of zone-refined n-alkanes (decane, dodecane, tetradecane, hexadecane, octadecane, nonadecane, eicosane, docosane, tetracosane, and octacosane) are reported in the 0.1 to 1400 kPa and 323 to 588$\sp\circ$K pressure and temperature ranges. These results allow the evaluation of existent data and the subsequent development of accurate correlations for vapor pressures and heats of vaporization. Wagner equation fits, which are scaled using the T$\sb{\rm c}$ and P$\sb{\rm c}$ correlations of Twu (1984) for the longer n-alkanes, are given for representing vapor pressures of n-alkanes over the liquid-vapor coexistence range. The scarcity of low-pressure data in the vicinity of the triple point is addressed by use of two-real-fluid CSP techniques (Ambrose & Patel, 1984) to extrapolate data available at higher pressures. Observations of triple point corresponding states in the long-chain n-alkanes suggest an alternative approach for fitting vapor pressure equations at low-pressures. Extensions of Pitzer-type CSP correlations to long-chain n-alkanes (C$\sb{36+}$) are achieved in two ways. First, a second-order perturbation term in Pitzer's acentric factor expansion of In(P$\sb{\rm r}$) is included. This approach is referred to as the PERT2 model. In a second method, parameters (P$\sb{\rm c}$, $\omega$) for a two-fluid CSP model based on methane and n-octane, C$\sb1$/C$\sb8$, are determined by regression of vapor pressures. The two models are compared with experimental data and literature correlations. Applications of the n-alkane-based correlations to other classes of compounds, such as model compounds derived from coals, are given. Extensions of Pitzer-type CSP correlations to associated fluids are briefly considered by applying two- and three-fluid CSP models.