Extension and application of the full waveform inversion method for seismic imaging in complex geological media
Prof. Dr. Mehrdad Soleimani
Shahrood University of Technology
Conventional seismic imaging methods are no more reliable in solving imaging problems raised from complex geological media. Due to the high demand on obtaining high quality seismic image for various aspects such as exploration studies, gas storage projects, geological hazard, CO2 storage projects in target finding and monitoring and also in geothermal resource, it is required to investigate more on obstacles of obtaining reasonable seismic images and developing reliable imaging methods. Soleimani (2017) performed a study on problems of seismic imaging in Iran and defined reasons of poor seismic images from different regions of Iran. The minor concerns were related to the data acquisition problems due to harsh topography, but the major one rooted in extreme complexity in subsurface media and poor quality in signal to noise ratio (SNR). The former could be resolved by adequate acquisition, however, the later requires deep investigation on developing proper imaging tools. Some of these obstacles were resolved partially by the common reflection surface (CRS) and the NIP tomography method. The reverse time migration (RTM) and the full waveform inversion (FWI) methods, as the latest introduced method deals with a vast majority of problems in seismic imaging. However, these methods are still challenging in application on large field data, poor quality data with shortage in frequency content and low SNR in the low frequency part of the data. Challenges for FWI/RTM land applications are consists of addressing the wavefield propagation from rough topography, low SNR of the low-frequency data and determination of an appropriate source wavelet throughout the iterations by improving the velocities and model parameters. Groos et al. (2017) showed that taking key elements properly into account, FWI produces a reliable high-resolution near-surface model that could not be otherwise recovered through traditional methods. Although few attempts have been reported that incorporate FWI for land studies (Kurzmann et al. 2018), however, they were convincing in providing acceptable seismic image. Therefore, it is supposed that deriving a processing workflow modified for accurate imaging of seismic data from complex regions of Iran would be promising in resolving the problem of low SNR and strong lateral velocity changes due to complexity in wave propagation media. Thus, the aim of the research plan would be modifying and developing the FWI/RTM package of the KIT research group to be applicable on deep reflection seismic data from Iran with the mentioned problems to obtain higher quality seismic images.