ELECTROMAGNETIC METHOD FOR SHALLOWS USING A CONTROLLED SOURCE

摘要

1. The method of processing and analysis of the recorded results of electromagnetic measurements (R) performed at or in the sea (4) above the seabed (1) with rock formations (3) having a relatively low resistivity (ρ3) to detect possible underlying oil and gas bearing rocks -collector (2) having a relatively high resistivity (ρ2),! in which a low-frequency electromagnetic emitter (5) is located in the sea (4) and emits an electromagnetic field (F) propagating in the sea (4), in rocks (3, 2) and in the air (0) above the sea; ! in which the electromagnetic sensors (6) are positioned at specified distances (x) in the sea (4) to measure the electromagnetic field (P (x)) while the field is propagating,! characterized in that! measure one or more components of the electromagnetic field (F) at least one large distance (xL) from the emitter (5), where the field (F) has its origin essentially only as a result of a field propagating as a field (P0) through air ( 0); ! in that one or more components of the electromagnetic field (F) measured at a large distance (xL) is calculated back to recalculate the field (F0 (x)) to one or more offsets (x) smaller than the large offsets (xL) ; ! the fact that the recalculated field (F0 (x)) is subtracted from the field (F (x)) to possibly isolate a field that originates from resistivity anomalies in the underlying rock, such as a possible oil and gas bearing reservoir rock (2) having relatively high resistivity (ρ2). ! 2. The method according to claim 1, in which the specified emitter (5) is towed into the sea and in which these receivers are stationary. ! 3. The method according to claim 1