FOCUSED CURRENT MARINE GEOELECTRIC PROSPECTING METHOD Russian patent published in 2010 - IPC G01V3/06 

FIELD: physics.

SUBSTANCE: dipole source excites an electromagnetic field inside the examined medium by transmitting thereto rectangular current pulses with pauses in between. Geometric probing is carried out along the given profile during the current pulse and probing on transient process is done during the pauses. Measurements are taken using a measuring apparatus mounted on sea bed, consisting of five electrodes: a central electrode surrounded by four equidistant electrodes lying at the corners of a square, two opposite sides of which are parallel to the axis of the profile. First potential differences between the outer electrodes and the central electrode are measured. When the dipole sources passes through different points, equipotentiality of closed lines passing through the four outer electrodes of the measurement apparatus is provided, thus excluding the horizontal component of current density in each probing point, inside the area bounded by the contour of this line. The values of the measured first potential differences are used to calculate two sets of standardised interpreted electrical parametres which are not susceptible to lateral effect of three-dimensional geological irregularities lying outside the probing point. The obtained parametres are used to find the model of the medium and time sections of this model are built from electroconductivity of elements of the medium, coefficient of induced polarisation and decay time constant of the polarisation induced potential difference.

EFFECT: possibility of complete exclusion of the horizontal component of current density at the probing point and exclusion of the lateral effect, which enables finding and high-contrast delimiting of hydrocarbon accumulation in a deep sea using a relatively simple measurement electrical circuit.

4 cl, 6 dwg