Abstract: A system for measuring magnetic fields outside a ferromagnetic container from inside the same container is described. The invention uses magneti circuits to direct the flow of magnetic flux to a magnetic field detector. By using magnetic fields for detection, this invention is able to measure the properties of magnetic materials outside the ferromagnetic container, such as a geologic formation, electric or magnetic parameters, or log well and drill holes that have been cased.

Abstract: A magnetic method is disclosed that can be used to map, track and monitor the progress of secondary oil recovery during water or steam floods. An electric current is injected directly into the water hydrocarbon system to be monitored. The electricity that flows in the water creates a magnetic field, which can be monitored. Monitoring the changes in the magnetic field monitors the changes in the water flooding the subsurface hydrocarbon zone. The resulting surface magnetic field is measured at various time intervals. Variation in magnetic field is used to interpret and determine the status of the hydrocarbon recovery zone.