Inverting distributed acoustic sensing data using energy conservation principles

Abstract

Distributed acoustic sensing (DAS) technologies are now becoming widespread, particularly in vertical seismic profiling (VSP). Being a spatially densely sampled recording of the seismic wavefield, DAS data provide an extended measurement compared with point geophone VSP. We have developed a basic theory that enables an intuitive geophysical understanding of DAS data amplitudes using the concepts of kinetic and potential energy and their fluxes. We start by relating DAS and geophone measurements to potential energy and kinetic energy, respectively. We use this relationship and energy balancing along the well to construct a scheme for inverting DAS and geophone wavefields for density and velocity simultaneously. Then, recognizing that it may be impractical to have geophones and DAS, we adopt a second inversion scheme that eliminates the need for geophones and uses up- and downgoing DAS wavefields instead. There is no need for first-break picking or windowing the data, and the full-length DAS records can be used in both inversion schemes. We test these inversion schemes on 2D elastic synthetics.