Knowledge of viscosity of flow streams is essential for the design and operation of production facilities, drilling operations and reservoir engineering calculations. The determination of the viscosity of a reservoir fluid at downhole conditions still remains a complex task due to the difficulty of designing a tool capable of measuring accurate rheological information under harsh operational conditions. This dissertation presents the evaluation of the performance of a novel device designed to measure the viscosity of a fluid at downhole conditions. The design investigated in this study addresses several limitations encountered in previous designs. The prototype was calibrated and tested with fluids with viscosities ranging from 1 to 28 cp under temperatures ranging from 100 to 160oF. Viscosity measurements were validated with independent measurements using a Brookfield viscometer. We proposed a mathematical model to describe the performance of the device for Power-law fluids. This model describes the response of the device as a function of the rheology of the fluid and the physical dimensions of the device. Experimental data suggests the validity of the model to predict the response of the device under expected operating conditions. This model can be used to calculate optimal dimensions of the device for customized target applications.

Estimation of viscosities of naturally occurring petroleum gases provides the information needed to accurately work out reservoir-engineering problems. Existing models for viscosity prediction are limited by data, especially at high pressures and high temperatures. Studies show that the predicted viscosities of natural gases using the current correlation equations are about 15 % higher than the corresponding measured viscosities at high pressures and high temperatures. This project proposes to develop a viscosity prediction model for natural gases at high pressures and high temperatures. The project shows that commercial gas viscosity measurement devices currently available suffer from a variety of problems and do not give reliable or repeatable results. However, at the extremely high pressures encountered in high pressure and high temperature reservoirs, the natural gases consist mainly of methane as the hydrocarbon constituent and some non-hydrocarbon impurities. Available viscosity values of methane were used in the development of a correlation for predicting the viscosities of naturally occurring petroleum gases at high pressures and high temperatures. In the absence of measurements, this correlation can be used with some confidence.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 228-233). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.S.)--Middle East Technical University, 2003. / Keywords: Ethyl methacrylate, atom transfer radical polymerization, gamma irradiation, free radical polymerization, viscosity.

In this thesis, we establish the asymptotic analysis of the singularly perturbed reaction diffusion equation [cataloger unable to transcribe mathematical equations].... Our results establish the specific dependency on the coefficients of this equation and the size of the parameter [delta] with respect to [epsilon]. The analyses include equation subject to Dirichlet and Neumann boundary conditions. In both cases, the solutions u[superscript epsilon] converge locally uniformally to the equilibria of the reaction term f. We characterize the limiting behavior of the solutions through the viscosity solution of a variational inequality. To construct the coefficients defining the variational inequality, we apply concepts developed for the homogenization of elliptic operators. In chapter two, we derive the convergence results in the Neumann case. The third chapter is dedicated to the analysis of the Dirichlet case. / text

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published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

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