Abstract: An antenna, and method for forming the same, is provided that receives or transmits three (3) components of low frequency magnetic fields while having physical dimensions that can be easily housed inside a slim borehole tool. The antenna includes a permeable core and a plurality of sets of windings of conductive wire surrounding the permeable core, with each set of plurality of sets having a cross-sectional area associated therewith, with the cross-sectionals of the remaining sets. Typically, the cross-sectional area of each of the plurality of cross-sectional areas extends orthogonally to the cross-sectional areas of the remaining cross-sectional areas of the plurality of cross-sectional areas.

Abstract: Provided is a technique, including a method and a computer program product, to dynamically measure characteristics of geologic formations while hydrocarbons are being extracted therefrom. Specifically, the present invention allows measuring the resistivity of geologic formations in which a borehole has been formed therein and encased with a conductive casing, such as a conductive liner. This has been achieved by providing a method and computer program product that compensates for the effects of a conductive liner by measuring the characteristics of the geologic formation as a function of a ratio of two magnetic fields sensed by a receiver disposed in one of the boreholes.

Abstract: A borehole magnetic sensor includes a plurality of primary detector coils, aligned along parallel axes, and connected in series with each other. A corresponding plurality of feedback coils, each associated with a respective detector coil, are arranged to cooperate with an amplifier system to provide negative feedback and null the magnetic field through the detector coils. The feedback coils are connected in parallel.