Extending illumination using all multiples: application to 3D acquisition geometry analysis

Abstract

Recent advances in survey design have led to conventional common-midpoint-based analysis being replaced by subsurface-based seismic acquisition analysis, with emphasis on advanced techniques of illumination analysis. Among them is the so-called focal beam method, which is a wave-equation-based seismic illumination analysis method. The objective of the focal beam method is to provide a quantitative insight into the combined influence of acquisition geometry, overburden structure, and migration operators on the resolution and angle-dependent amplitude fidelity of the image. The method distinguishes between illumination and sensing capability of a particular acquisition geometry by computing the focal source beam and the focal detector beam, respectively. Sensing is related to the detection properties of a detector configuration, whereas illumination is related to the emission properties of a source configuration. The focal source beam analyses the incident wavefield at a specific subsurface grid point from all available sources, whereas the focal detector beam analyses the sensing wavefield reaching at the detector locations from the same subsurface grid point. In the past, this method could only address illumination by primary reflections. In this paper, we will extend the concept of the focal beam method to incorporate the illumination due to the surface and internal multiples. This in fact complies with the trend of including multiples in the imaging process. Multiple reflections can illuminate a target location from other angles compared with primary reflections, resulting in a higher resolution and an improved illumination. We demonstrate how an acquisition-related footprint can be corrected using both the surface and the internal multiples.

Numerical Method for Horizontal and Vertical Spatial Resolutions of Seismic Acquisition Geometries in Complex 3D Media

“…Note that only the focal beam of primary waves is discussed above with multiple reflections being ignored. To consider the effect of multiple reflections on the spatial resolution, the primary-wavefield focal beam can be extended to a full-wavefield focal beam that can include multiple waves in the manner of iterative modeling [30]. The full-wavefield focal beam can be used to analyze the nonlinear effect of complex media (e.g., highvelocity anomalies) on the horizontal and vertical resolutions, which will be discussed in the example section.…”

“…The theory of focalbeam analysis in a homogeneous medium [25] has been extended to complex media [26] with a fast multifrequency focal-beam analysis [27] used to investigate the effect of acquisition geometries on the horizontal resolution in complex 3D media [28]. Recent researches extend the focalbeam analysis to account for surface waves [29] and surface/internal multiples [30]- [31]. Most the studies of focal-beam analysis address the horizontal resolution of acquisition geometries for seismic imaging.…”

Order‐controlled closed‐loop focal beams and resolution comparison of primary and multiple reflections for seismic acquisition geometries

“…Based on this, Kumar et al . (2015) extended the focal beam theory to incorporate the illumination of the surface by multiples and then discussed the enhanced illuminating effects of multiples on filling coverage holes (Kumar et al ., 2016). However, as a practical matter, it is still difficult to design proper acquisition geometries in the case of complex media, especially considering the contradictory effects of multiples being considered as either potential signal or additional noise depending on the imaging technology used.…”

“…Compared with open-loop migration, closed-loop migration not only balances amplitudes and reduces crosstalk noise, but it also has the flexibility to migrate the full-wavefield seismic data with full control over the order of surface and internal multiples taken into consideration. Based on this, Kumar et al (2015) extended the focal beam theory to incorporate the illumination of the surface by multiples and then discussed the enhanced illuminating effects of multiples on filling coverage holes (Kumar et al, 2016). However, as a practical matter, it is still difficult to design proper acquisition geometries in the case of complex media, especially considering the contradictory effects of multiples being considered as either potential signal or additional noise depending on the imaging technology used.…”

“…For this reason, we extend the full-wavefield focal beams (Kumar et al, 2015(Kumar et al, , 2016 to an order-controlled closed-loop focal beam method, which provides the flexibility to analyse migration operators and resolution functions with the ordercontrolled surface and internal multiples in the process of iterative inversion-based migration. In the frameworks of both open-loop and closed-loop focal beams, we compare the temporal and spatial resolution of primary and different-order multiple reflections in simple-layered and complex-structured velocity models.…”