Refinement of sensitivity and resolution at marine CSEM survey using fictitious wave domain

Abstract:

Marine controlled-source electromagnetic (CSEM) survey is considered as a technique in practice for the exploration of resistive hydrocarbon resources. Although CSEM could provide additional information to seismic surveys, the improvement of its resolution is one of the great issues for hydrocarbon exploration. We demonstrate the improvement of the resolution of CSEM data with our method. 

Recently, the interpretation of marine controlled-source electromagnetic (CSEM) data in the fictitious wave domain has been developed by analytically transforming Maxwell equations from the diffusive domain to the fictitious wave domain. However, the resolution of CSEM data in the fictitious wave domain has not been well exploited.

In the present study, we conduct numerical simulations using a three dimensional resistivity model as a sub-seafloor structure including resistive anomalies such as gas hydrate by using finite-difference time-domain (FDTD) method. First, we compare the waveforms in the diffusive and fictitious wave domains. Since electromagnetic propagates like seismic wave in the fictitious wave domain, the response of anomalies are separated from other waves such as direct one and the sensitivity of anomalies becomes higher compared with the data in the diffusive domain. In order to discuss with the resolution, we have developed a gradient-based 3D full waveform inversion of CSEM data in the fictitious wave domain. From our numerical results, we conclude that a high resolution result is obtained by analyzing in the fictitious wave domain. In future work, we planned to examine applying the real observed data of marine CSEM survey.