Date of Award
Spring 1996
Document Type
Thesis - Restricted
Degree Name
Master of Science (MS)
Department
Electrical and Computer Engineering
First Advisor
Josse, Fabien
Second Advisor
Freedman, Robert
Third Advisor
Ishii, Thomas K.
Abstract
Azimuthally propagating microwaves were predicted by theoretical calculations in 1990. These calculations were solutions of a theoretical model consisting of a longitudinally oriented magnetic dipole transmitter on the surface of a metallic cylinder situated in a lossy dielectric medium. Computer simulations, using the new solutions, showed the existence of azimuthally propagating electromagnetic (EM) waves with properties analogous to those of the longitudinally propagating waves measured by conventional microwave tools used in hydrocarbon exploration. Previous theoretical models for the prior microwave tools assumed that the antennas were situated on an infinite metallic plane adjacent to a lossy half space. These models are not applicable to the study of azimuthal waves. On the basis of the theoretical predictions, it was recognized that a new microwave logging tool that measured both longitudinally and azimuthally propagating microwaves might provide the oil exploration industry new capabilities for formation evaluation. These new capabilities include: ( 1) the identification of vertical fractures, (2) vertical resolution substantially better that achievable with conventional longitudinal wave measurements, and (3) a method for borehole dielectric imaging and ·anisotropy measurements .This thesis describes experiments in which azimuthally propagating microwaves have been observed. A cylindrical metallic fixture on which standard endfire slot antennas were mounted was designed and constructed for the experiments. Initial experiments were conducted in a 150-gallon container with brine solutions of various salinities. The experiments measured the travel times and attenuations of both longitudinal and azimuthal waves propagating between pairs of receivers. The azimuthal waves were observed by displacing receivers at different azimuthal positions relative to the transmitters. These were followed by experiments in a set of well characterized test formations consisting of brine saturated porous rocks penetrated by boreholes of several differentsizes. The measured travel times and attenuations of the azimuthal waves in the brine solutions and .test formations are in excellent agreement with the predictions of the theoretical model. For certain receiver positions, which are predicted by the modeling, the azimuthal wave propagation is analogous to plane wave propagation except for spreading losses that are weakly dependent on the properties of the medium. The signal strength at the azimuthally displaced receiver locations is significantly greater than that for longitudinally displaced receivers due to the predominantly transverse radiation pattern of the endfrre antennas. The results of the experiments confirm the accuracy of the theoretical model.
Recommended Citation
Schaaf, Stuart, "Measurements of Azimuthally Propagating Microwaves for Applications in Petrophysical Measurements" (1996). Master's Theses (1922-2009) Access restricted to Marquette Campus. 4058.
https://epublications.marquette.edu/theses/4058