ANTENNA STRUCTURES AND APPARATUS FOR DIELECTRIC LOGGING

摘要

This disclosure describes a dielectric logging tool for evaluating the earth formation using at least one transmitter antenna disposed in a cavity on a pad engaged with a borehole wall. The logging tool may comprise at least one power driver in electrical communication with the at least one transmitter antenna and configured to modulate a phase of output current of the at least one power driver. The logging tool may enforce symmetric current on both feeds of the at least one transmitter antenna causing a point of symmetry of the current to align with an axis of geometric symmetry of the at least one transmitter antenna. A parameter of interest of the formation may be estimated by using the attenuation and phase difference between the received and transmitted signals or between received signals from spaced receivers.

主权项

1. An apparatus for evaluating an earth formation, the apparatus comprising:
a carrier configured for conveyance in a borehole intersecting the earth formation; a logging tool disposed on the carrier, the logging tool comprising:
a pad having at least one face configured to engage the borehole wall, the face comprising a surface defining a cavity,at least one transmitter antenna disposed in the cavity of the face, the at least one transmitter antenna receiving an electrical signal from an excitation source, andat least one power driver in electrical communication with the at least one transmitter antenna and configured to modulate a phase of output current of the at least one driver.