METHOD OF ELECTROMAGNETIC GEOPHYSICAL SURVEY OF UNDERWATER ROCK STRATA Russian patent published in 2010 - IPC G01V3/17 

FIELD: mining.

SUBSTANCE: one tows sources (s₁, s₂) emitting the first and the second variable fields (E₁, E₂) at the first and the second depth below the sea level. The first field (E₁) has the first phase (ϕ₁) while the second variable filed (E₂) has the second phase (ϕ₂) different from the first one(ϕ₁). The sources (s₁, s₂) form an emitting phased antenna grid directed for emitting most of the total electromagnetic energy downwards. The grid may include vertical and horizontal element shifts. The first and the second fields (E₁, E₂) partly penetrate downwards through the sea bottom (3) and are reflected and/refracted on the rock strata (1) and partly penetrate backwards through the sea bottom (3). The first and the second fields (E₁, E₂) are joined into a total field which is measured with the help of electromagnetic field receptors (r₁ r₂, …, r_n) registering the corresponding field readings (E_r1(t), E_r2(t), E_r3(t), …, E_rn(t).

EFFECT: possibility of transfer of a stronger signal downwards from the emitting antenna through the sea bottom for better detection of oil-bearing strata, reduction of undesirable air waves, possibility to suppress reflections from the sea bottom surface and repeated waves in the sea.

22 cl, 7 dwg