Simultaneous waveform inversion of SWD data for P-wave velocity, density, and source parameters
Jinji Li, Scott Keating, Kristopher A. Innanen, Roman Shor
Full-waveform inversion (FWI), an optimization-based approach to estimating subsurface models, is limited by incomplete acquisition and illumination of the subsurface. Adding data corresponding to new and independent ray paths as input could significantly increase FWI models' reliability. In principle, seismic-while-drilling (SWD) technology can supply these additional ray paths; however, it introduces a new suite of unknowns, namely precise source locations (i.e., drilling path), source signature, and radiation characteristics. Here we formulate a new FWI algorithm in which source radiation patterns and positions join the velocity and density values of the grid cells as unknowns to be determined. We then conduct several numerical inversion experiments with the SWD sources located along a plausible well-trajectory with different source settings through a synthetic model. These SWD sources are supplemented by explosive sources and multicomponent receivers at the surface, simulating a conventional surface acquisition geometry. The subsurface model and SWD source properties are recovered and analyzed. After adding SWD data, both the inversion of physical elastic properties and source mechanisms get considerably enhanced, even in the cases where low frequencies are missing; the inversion also shows preferences on the features of the sequence of SWD sources along the trajectory. This model-source inversion algorithm also indicates the potential to simultaneously estimate the anelastic properties and trajectory deviation while drilling. The analysis suggests that, in principle, SWD participation improves the accuracy of FWI models, and source information can also be acquired. However, further studies are required to provide a more comprehensive representation of the SWD sources.