Geophysical surveying apparatus, system and method

A geophysical surveying system, comprising:

• a. a geophysical surveying assembly to be carried by an aircraft, including;
• a time domain electromagnetic transmitter operable to carry transient pulses of electric current to generate a primary controlled electromagnetic field, the pulses of electric current being carried during on times and spaced from one another by off times, and
• an assembly receiver secured to the transmitter, the assembly receiver operable to measure magnetic fields to generate magnetic field data,
• b. a ground receiver at a ground station, the ground receiver operable to measure telluric electrical currents induced by a natural electromagnetic field and/or a magnetic component of the natural electromagnetic field to generate second natural field data;
• and
• c. at least one processor communicatively coupled to the assembly receiver to receive the magnetic field data and communicatively coupled to the ground receiver to receive the second natural field data, the at least one processor operable to:
• i. extract controlled field data from the magnetic field data,
• ii. extract first natural field data from the magnetic field data,
• iii. merge the first natural field data and the second natural field data into combined natural field data;
• and
• iv. extract off-time natural field data from the combined natural field data to suppress interference including from the controlled electromagnetic fields and improve detection of naturally occurring electromagnetic signals from the natural electromagnetic field, and
• v. generate geophysical survey data based on the controlled field data and the off-time natural field data.

A geophysical surveying system for surveying a ground formation, the geophysical surveying system comprising at least one processor operable to:

• a. receive controlled field data generated from a secondary controlled electromagnetic field measured by an airborne receiver, the secondary controlled electromagnetic field resulting from electrical currents induced in the ground formation by a primary controlled electromagnetic field generated by transient pulses of electric current applied to an airborne time-domain electromagnetic transmitter, the pulses of electric current having been applied during on times and spaced from one another by off times;
• b. receive first natural field data generated from a magnetic component of a natural electromagnetic field measured at an above-ground position by the airborne receiver;
• c. receive second natural field data generated from telluric electrical currents induced by the natural electromagnetic field and/or a magnetic component of the natural electromagnetic field measured at a ground position by a ground receiver at a ground station;
• d. merge the first natural field data and the second natural field data into combined natural field data;
• e. extract from the combined natural field data off-time natural field data recorded during the off times to suppress interference from an environment at the above-ground position and improve detection of naturally occurring electromagnetic signals from the natural electromagnetic field;
• and
• f. generate geophysical survey data based on the controlled field data and the off-time natural field data.