Method and apparatus for reducing the effects of parasitic and galvanic currents in a resistivity measuring tool

An apparatus for reducing undesirable currents flowing in an induction tool for measuring the properties of a geological formation adjacent a bore hole comprising:

• a tool body for traversing a bore hole formed in a geological formation;
• a transmitter coil wound on a single form and housed in the induction tool body for transmitting an electromagnetic field into the geological formation further comprising a split coil electrically split into sections with equal windings;
• a feed through current carrying conductive pipe and conductors running between the sections of the electrically split transmitter coil, the conductive feed though pipe housing electrical conductors;
• and
• a receiver coil for sensing electromagnetic fields induced in the formation by the transmitted magnetic field.

A logging tool for measuring the properties of a geological formation adjacent a bore hole comprising:

• a tool body for traversing a bore hole formed in a geological formation;
• a receiver coil wound on a single form and housed in the tool body for sensing a magnetic field from the geological formation further comprising a coil electrically split into coil winding sections with an equal number of windings symmetric with respect to a tool's longitudinal axis, each coil winding section wound in a same angular direction with respect to a coil axis;
• a feed through conductive pipe carrying current and conductors in a hollow center between circuitry above and below an induction tool body surrounding coils, further comprising conductors connecting the sections of the receiver coil, conductors connecting receiver and transmitter coils to a respective receiver and transmitter circuitry routed outside the feed through conductive pipe or a feed through pipe hollow center;
• and
• a transmitter coil for transmitting electromagnetic fields into the formation.