Method for marine electrical survey of oil-and-gas deposits

A method for marine electrical survey of hydrocarbon deposits in a researched profile of sea-bottom, said method comprising the steps of:

• providing a generator of electric current, associated with a generator clock;
• providing a generator line, wherein said generator is capable of generating a predetermined electric current in the generator line, said electric current is generated in the form of alternative-sign pulses with a generator signal frequency associated with a predetermined duration and a predetermined on-off time ratio of said pulses, said generator line is capable of exciting an electric field;
• providing a tow means capable of towing the generator line;
• providing a plurality of sea-bottom stations capable of measuring signals of said electric field, each said sea-bottom station is associated with a station clock;
• synchronizing the generator clock and the station clocks of said plurality of sea-bottom stations;
• mounting said sea-bottom stations at predetermined points, including a first point and a last point, along a predetermined profile line extending through and beyond said researched profile;
• positioning said tow means at a predetermined distance from the first point beyond said researched profile;
• towing said generator line by the tow means along said predetermined profile line to a point located at said predetermined distance from the last point beyond said profile;
• switching said generator on and causing said generator line of exciting the electric field;
• measuring time series of the electric current signals of said generator line, and measuring time series of the signals of said electric field by the sea-bottom stations during both the on and off periods of said electric current pulses;
• recording signal values of the signals of said measured time series;
• for each said sea-bottom station forming:
• a plurality of space-domain data arrays for dependencies of said signal values upon offsets during the movement of said tow means wherein the dependencies are formed for said generator signal frequency, and for a predetermined number of higher odd harmonics frequencies nearest to said generator signal frequency;
• and
• a plurality of time-domain data arrays for selected offsets based on said signal values, the time domain data arrays are formed for dependencies of the signal values upon time, wherein the dependencies are formed for time intervals of signal growing or decay after switching on or off the current in said generator line;
• providing a step for joint inversion of data for each said sea-bottom station for the time-domain data arrays and for the space-domain data arrays;
• and
• determining both a bottom strata resistivity for a predetermined depth of said researched profile and polarization characteristics of said researched profile based on the results of said step for inversion of data.