Applications of multiscale waveform inversion to marine data using a flooding technique and dynamic early-arrival windows

Abstract

A recently developed time-domain multiscale waveform tomography (MWT) method is applied to synthetic and field marine data. Although the MWT method was already applied to synthetic data, the synthetic data application leads to a development of a hybrid method between waveform tomography and the salt flooding technique commonly use in subsalt imaging. This hybrid method can overcome a convergence problem encountered by inversion with a traveltime velocity tomogram and successfully provides an accurate and highly resolved velocity tomogram for the 2D SEG/EAGE salt model. In the application of MWT to the field data, the inversion process is carried out using a multiscale method with a dynamic early-arrival muting window to mitigate the local minima problem of waveform tomography and elastic effects. With the modified MWT method, reasonably accurate results as verified by comparison of migration images and common image gathers were obtained. The hybrid method with the salt flooding technique is not used in this field data example because there is no salt in the subsurface according to our interpretation. However, we believe it is applicable to field data applications.

Plane-wave least-squares reverse-time migration

“…The migration velocity is obtained by waveform inversion (Boonyasiriwat et al, 2010). Figure 2 shows: (a) the shotdomain reverse time migration image, (b) the plane-wave domain reverse time migration image and (c) the plane-wave LSRTM image.…”

Acceleration strategies for elastic full waveform inversion workflows in 2D and 3D

“…1 is typically an irregular surface, and hence, finding a global minimum can be challenging if not impossible. In this context, multi-scale techniques [4,9,32,35,40,48], combined with gradient preconditioning and regularization methods, have been developed to sequentially incorporate higher wavenumber information into the inverted model. This results in a reduction of local minima effects by means of either selecting increasing individual frequency samples (in frequency domain) or broadening a low-pass filter by increasing its corner frequency (in time domain).…”

Interferometric full-waveform inversion of time-lapse data

“…Multiscale full waveform inversion (FWI) can be used to resolve both the low-and high-wavenumber characteristics of the inverted models (Boonyasiriwat et al, 2010;Fichtner et al, 2013). This makes FWI an ideal choice for inverting for timelapse changes in the subsurface medium.…”