Method Of Sea Electrical Survey Of Oil And Gas Deposits And Apparatus Complex For Its Realization 'VesoTem'

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 capable to register electromagnetic signals reflected from the seabed and measure their characteristics;
• providing electromagnetic field excitation means, said excitation means capable to 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 substantially 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 substantially vertical position;
• excitation of the series of said alternating-sign electromagnetic pulses through the dipole during a predetermined time;
• repeatedly moving said dipole substantially 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.

A research complex for sea electrical survey of hydrocarbons deposits under seabed in a survey zone, comprising:

• a sea vessel;
• a generator installed on the vessel;
• an excitation field formation unit installed on the vessel and connected with the generator, said excitation field formation unit capable to 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;
• a dipole associated with the vessel, said dipole substantially connected with the excitation field formation block, said dipole including a lower source electrode and an upper source electrode for submerging into seawater, said dipole capable to irradiate an excitation electromagnetic field acting upon the seabed;
• a plurality of bottom systems each including registering devices capable to register horizontal and vertical components of the excitation electromagnetic field and of a reflected electromagnetic field reflected from the seabed with predetermined accuracy, said bottom systems fixed to the seabed;
• and
• data processing means for registration and processing of data obtained from said excitation field formation unit and said registering devices;
• wherein the research complex characterized in that
• said dipole being positioned substantially vertically, so that the lower electrode situated at a distance not exceeding 100 m from the seabed and the upper electrode situated at a distance not exceeding 200 meters from the sea surface.