ELECTROMAGNETIC METHOD ON SHALLOW WATER USING CONTROLLED SOURCE Russian patent published in 2013 - IPC G01V3/12 

FIELD: physics.

SUBSTANCE: invention relates to geophysical measurements made in a sea (4) over a seafloor (1) with rock formations (3) having relatively low resistivity for detecting a possibly underlying petroleum bearing reservoir formation (2) having relatively high resistivity. A low frequency electromagnetic transmitter (5) is placed in the sea (4). An electromagnetic field with frequency lower than 1 Hz is emitted and propagates in the sea (4), in the rocks (3, 2) and in the air (0) above the sea. Sensors (6) are arranged with desired offsets (x) in the sea. The electrical component of the field is measured for at least one large offset (x_L) from the transmitter (5) where the field essentially only has its origin from the field propagating as a field through the air. The field measured at the large offset (x_L) is recalculated back to one or more offsets (x) shorter than the large offset (x_L). The recalculated field is subtracted from the measured field at offsets (x) for highlighting a field arising due to the possibly petroleum bearing reservoir formation (2).

EFFECT: possibility of use on shallow water with a higher signal level, possibility of measuring only the electrical component of the field.

8 cl, 22 dwg