Study On The Response Of Marine Controlled-source Electromagnetic

Marine electromagnetic method is one of the most important methods for exploding marine resoure. It uses artificial source,measuring the amplitude of the elctromagnetic field,in order to make up the low frequency signal missing at the seabed.This method can detect electrical distribution underground by calculating the apparent resistivety and apparent phase, or by the electric and magnetic filed directly. It is difficult to obtain the electromagnetic spectrum curve, the same as it on land, because of efficiency and construction condition. So numerical simulation may be an effective way to deal with CSEM data, and provide technical target for marine CSEM instruments. In this paper, we use frequency domain axial electric dipole-dipole devices, design a model with different parameters, use INTEM3D_V2 that based on the integral equation method to process one-dimensional or three-dimensional forward, and draw some curves to study on the response of marine controlled-source electromagnetic.1. Study on the response of one-dimensional forward model: the greater impact by sea water on electric filed than the magnetic, but range of the best observing window is larger than electric filed component at the same conditions.2. For Towing method, study on the response of three-dimensional forward model: the maximum detecting depth is almost the same size as the offset; the respond to the edge of this method is more sensitive than Fixed method. The location of curve's extreme positions is corresponding to the edge of the abnormal body.3. Towing method is the way of profiling. Study on the curve of amplitude and Normalized amplitude at the diffident line reveals that the respond of abnormal body is very clear. However,the offset and frequency limit the depth of exploration.4. Transmitting and receiving systems move simultaneously, lateral resolution is very strong. We can infer from the response of model's electric filed, which have two abnormal bodies, that we can locate the edges even if two plats apart 200m with each other.