High frequency induction log for determining resistivity and dielectric constant of the earth

Patent · Tue Jul 14 04:00:00 EDT 1981

OSTI ID:5723396

Freedman, R

A method and apparatus for logging rock formations penetrated by a borehole to determine both the resistivity and dielectric constant of the formations. The apparatus comprises an induction logging tool having at least a transmitting coil and two receiver coils and operating in the radio frequency range from 20 to 60 megahertz. The method utilizes both the in-phase and out-of-phase , with respect to the transmitter current, voltage components which are measured at each receiver. The in-phase and out-of-phase voltage components are used to compute the phase shift between the voltage signals and the relative attenuation of the voltage amplitudes between the receivers. The phase shifts and relative attenuations are relatively insensitive to the borehole (E.G., borehole radius and drilling mud resistivity) and can be used as inputs into theoretically constructed nomograms to determine both the resistivity and dielectric constant of the formation. If the invasion of the drilling mud into the formation is not negligible then a tool with four spatially separated receiver coils is employed and the phase shifts and relative attenuations between the three adjacent pairs of receiver coils are computed from the in-phase and out-of-phase voltage components measured at each receiver. These data are used to determine the resistivity and dielectric constant of the invaded zone, the radius of the invaded zone, and the resistivity and dielectric constant of the non-invaded formation.

• Assignee: Shell Oil Co
• Patent Number(s): US 4278941
• OSTI ID: 5723396
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580203* -- Geophysics-- Geophysical Survey Methods-- (1980-1989)
BOREHOLES
CAVITIES
DIELECTRIC PROPERTIES
DRILLING FLUIDS
ELECTRIC COILS
ELECTRIC CONDUCTIVITY
ELECTRIC LOGGING
ELECTRICAL EQUIPMENT
ELECTRICAL PROPERTIES
EQUIPMENT
FLUIDS
INDUCTION LOGGING
MEASURING METHODS
MECHANICS
OIL WELLS
PHYSICAL PROPERTIES
ROCK MECHANICS
ROCKS
WELL LOGGING
WELLS