Patent ID: 7728596

Claim:
A method for sea electrical survey of hydrocarbons deposits, situated under seabed strata in a transit shelf zone with a depth not exceeding 10 meters, comprising the steps of: providing a plurality of multi-channel bottom systems placed onto the seabed in the survey zone and in proximity thereof, said bottom systems equipped with receiving lines each having at least three electrodes located at a predetermined substantially equal distance from each other, said bottom systems capable to register and measure electromagnetic signals; providing excitation means for excitation of electromagnetic signals, said excitation means capable to generate a fixed-period series of alternating-sign electromagnetic pulses substantially of a rectangular shape with a duration and an on-off time ratio controlled by a preprogrammed computer; providing a dipole generating means associated with the excitation means and substantially horizontally positioned; synchronizing the operation of said excitation means and said bottom systems; submerging and placing said bottom systems upon the seabed along a predetermined survey profile direction; aligning said receiving lines with the electrodes at a predetermined angle relatively to the survey profile direction; moving said dipole means substantially horizontally within the survey zone in a predetermined excitation direction, substantially along the sea surface; controllable excitation of the series of said pulses within said excitation means and said dipole means during said moving; registering electromagnetic signals by the receiving lines; measuring the potentials difference and the spatial derivatives of said registered signals both during the current pulses passage and during the pauses and recording the measured data substantially by the bottom systems; analyzing said data taking into account the fields behavior in time and in space simultaneously; determining both the environment resistivity and environment polarizability characteristics based on the data analysis, and utilizing a predetermined mathematical model of the strata profile; and compiling prognosis on the hydrocarbons deposits presence based at least on anomalies of said resistivity and strata polarizability characteristics.