Marine oil and gas exploration system using telluric currents as a natural electromagnatic energy source

Abstract

A marine oil and gas exploration system used for measuring telluric currents as a natural electromagnetic energy source flowing beneath an ocean and sea floor. The marine exploration system includes a towed fish adapted for being pulled behind a survey ship. The coordinates of the ship and the towed fish can be controlled by a GPS satellite and time data. The fish includes an aerodynamic waterproof housing, somewhat reminiscent of a shape of a fish. Metal sheet electrodes of electric field sensors are mounted on the surface of a tubular nose extending outwardly from the housing. The electric field sensors are in direct contact with the sea water. Typically, the fish is towed approximately 100 feet above the sea floor. The positioning of the fish is maintained by the use of an acoustic 'pinger' on the fish. The pinger transmits signals up a towed cable to the survey ship. The fish can also include a cesium magnetometer connected to the electric field sensors. The magnetometer provides for detecting low frequency magnetic components of the electromagnetic fields generated by the telluric currents flowing under the sea floor. A filtering of the magnetic component signals is used to provide a phase and amplitude references for the electric fields. The amplitudes of the electric field at each frequency are ratioed against the amplitudes of similarly filtered components of the magnetometer.