Patent ID: 7529627

Claim:
A method for sea electrical survey of hydrocarbons deposits under seabed in a survey zone, comprising the steps of: arranging a plurality of bottom systems on the seabed in the survey zone, said bottom systems register electromagnetic signals reflected from the seabed and measure their characteristics; providing electromagnetic field excitation means, said excitation means generate a fixed in time series of alternating-sign electromagnetic pulses of rectangular form with a duration and an on-off time ratio controlled by a preprogrammed computer; synchronizing the operation of said excitation means and said bottom systems; providing a dipole connected to the excitation means and vertically positioned in the survey zone, said dipole having an upper end situated at no more than 200 meters from the sea surface and a lower end situated at no more than 100 m from the seabed, said dipole, being in the vertical position; excitation of the series of said alternating-sign electromagnetic pulses through the dipole during a predetermined time; repeatedly moving said dipole horizontally within the survey zone from a first point to a second point situated at a distance equal at least the sea depth in the first point, thereafter the second point considered as a new first point; operatively registering changes of predetermined electromagnetic field parameters during the predetermined time by said bottom systems; measuring the predetermined electromagnetic field parameters for both the excitation field and the reflected field by said bottom systems both during the generation of said electromagnetic pulses and in absence thereof; determining the environment resistivity and strata polarization characteristics of the seabed based on said measuring of the predetermined electromagnetic field parameters; and compiling a prognosis on presence or absence of the hydrocarbons deposits in the survey zone based at least on anomalies of said resistivity and strata polarization characteristics.