Apparatus and method for determination of subsurface permittivity and conductivity

摘要

The disclosure is directed to an apparatus and method for determining dielectric constant and/or conductivity of earth formations surrounding a borehole. Electromagnetic energy is generated at a first location in the borehole. The relative attenuation of the electromagnetic energy is detected at a second location in the borehole. The detection is preferably performed using a first or "close" differential receiver arrangement. The relative phase of the electromagnetic energy is detected at a third location in the borehole, the third location being spaced farther from the first location than is the second location; in other words, the second location is between the first and third locations. The relative phase shift of the electromagnetic energy is measured by a second or "far" differential receiver arrangement located at the third location in the borehole. Means are provided for determining the dielectric constant and/or the conductivity of the formations as a function of the detected relative attenuation and relative phase. The dielectric constant and/or conductivity are determined with improved accuracy as compared to prior art techniques, since the attenuation and relative phase information is representative of the effects of formations of substantially the same volume and extent. In a further embodiment of the invention, the attenuation of the electromagnetic energy is also detected at the third location and then combined with the other information to obtain an "ultra deep" conductivity value.