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| | Abstract | | Marine controlled-source electromagnetic (CSEM) survey is considered as a technique in practice for the exploration of resistive hydrocarbon resources. Although CSEM survey could provide additional information to seismic surveys, the improvement of its resolution is one of the great issues. In this study, we focus on the fictitious wave domain to improve the resolution of CSEM survey. Electromagnetic (EM) field in the fictitious wave domain can be derived by transforming Maxwell equations from the diffusive wave domain (Mittet, 2010), mainly with the aim of faster numerical time-domain calculations. However, the resolution to the resistive hydrocarbon in the fictitious wave domain has not been well exploited. We conduct several tests of numerical simulations using the finite-difference time-domain (FDTD) method and a 3D resistivity model of a sub-seafloor structure. The sensitivity of resistive anomalies in fictitious wave domain becomes higher compared with the raw data in the diffusive domain, since the responses of anomalies are separated from other waves. For discussion on the resolution, we develop 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 can be achieved by our inversion analysis in the fictitious wave domain. |
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