|
| | Abstract | | Marine controlled-source electromagnetic (CSEM) survey is considered as a technique in practice for the exploration of resistive hydrocarbon resources below seafloor. However, the improvement of its resolution is one of the great issues for hydrocarbon exploration. Electromagnetic (EM) field in the fictitious wave domain can be derived by the analytically transforming Maxwell equations from the diffusive wave domain, mainly with the aim of faster numerical calculations of time-domain EM propagation. In the present study, we hypothesize that the transformation from the diffusive to the fictitious wave domain could be utilized to improve the response of resistive anomaly and conduct several tests of numerical simulations using the finite-difference time-domain (FDTD) method and a 3D resistivity model of a sub-seafloor structure, which includes resistive anomaly. From our numerical results, the sensitivity of anomalies in fictitious wave domain becomes higher compared with the raw data in the diffusive domain. We apply a gradient-based 3D full waveform inversion of CSEM data in the fictitious wave domain and high resolution can be achieved. In addition, marine CSEM data collected in offshore New Zealand can be transformed to the fictitious wave domain. We conclude that EM signals from sub-seafloor can be estimated from the transformed data. |
|
|
|
| |
|