Multiscattering illumination in blended acquisition design

In traditional seismic surveys the firing time between shots is such that the records do not interfere in time. However, in the concept of blending the records do overlap, allowing much denser and wider geometries in an economic way. The blending parameters are the locations of the involved sources and their time delays (or a more complex code). A denser shot sampling and a wider aperture make that each subsurface gridpoint is illuminated from a larger number of angles and will therefore improve the image quality in terms of resolution and signal-to-noise ratio. In a next step, the illumination can be further improved by utilizing the surface-related multiples. This means that multiples can be exploited to improve the incident wavefield, e.g., by filling angle gaps in the illumination, or extending the range of angles. In this way the energy contained in the multiples now contributes to the image, rather than making it noisy. To study the illumination roperties of blended primaries and multiples, the incident wavefield at subsurface gridpoints is assessed. The incident wavefield at a specific gridpoint is a dispersed time series with a ‘complex code’, even with very simple blending parameters like time delays. This paper introduces a framework that quantitavely connects the blended source configuration at the surface with the properties of the incident wavefield in the subsurface. The spectral properties of the ‘complex code’ in the subsurface form the basis for our acquisition geometry analysis and design. In addition, the contribution of surface-multiples as illuminating wavefields is included in the design.