Wave equation GSP prestack depth migration and illumination

Abstract

Aheterogeneous medium with strong velocity contrast and complex subsurface structures presents a great challenge to seismic imaging. Prestack depth migrations based on the wave equation are accurate but very expensive, thereby limiting their use. However, recent advances in efficient 3D wavefield extrapolators and the continued increase in computing performance are making application of full 3D prestack wave equation depth imaging more affordable. In addition, since PreSDM was first employed for subsalt and carbonate imaging, there have been major advances in efficient and accurate 3D wavefield extrapolation technologies.The generalized screen propagator (GSP) is a one-way wave-equation-based wide-angle propagator that can provide high-resolution and high-fidelity subsurface images. GSP neglects up/down reverberations between heterogeneities and correctly handles forward multiple-scattering phenomena including focusing/defocusing, diffraction, and wave-interference effects. The algorithm alternates between the space-domain and wavenumber-domain via the fast Fourier transform (FFT). The operations within each domain are self-adaptive to the complexity of the medium, making this method robust in the presence of strong velocity contrasts.

Full-wave directional illumination analysis in the frequency domain

“…It has many applications, including survey design ͑e.g., Li and Dong, 2006͒, studying the influences of acquisition geometry and overburden structures on the image ͑e.g., Jin and Walraven, 2003;Wu and Chen, 2006;Xie et al, 2006͒, and image amplitude correction ͑e.g., Wu et al, 2004;Wu, 2005, 2008͒. Traditionally, illumination analyses have used ray-based methods ͑e.g., Schneider and Winbow, 1999;Bear et al, 2000;Muerdter et al, 2001;Ratcliff, 2001a, 2001b;Lecomte et al, 2003͒, in which the directional information is inherently carried by the rays. However, the high-frequency asymptotic approximation and the caustics inherent in ray theory might limit severely its accuracy in complex regions ͑e.g., Hoffmann, 2001͒.…”

Migration Compensation with Plane Wave Illumination

“…The seismic data migration used in current oil-gas exploration is mainly for solving the imaging problems of subsurface structures [1,2] . However, in the complex structural zones, due to the influences of finiteness of the seismic data acquisition system and the complicated subsurface structure, the seismic wave propagation and illumination are inhomogeneous, so the seismic data acquisition system cannot effectively acquire the reflection information from some subsurface targets, and the seismic data migration imaging on these targets will show some migration shadows [3,4] . Seismic wave illumination analysis has been used for the design and appraisement of seismic data acquisition system, especially for the seismic data acquisition under complex conditions [5] .…”

Illumination Compensation for Wave Equation Migration Shadow

“…Dong et al [21] applied seismic wave illumination for the study of seismic data acquisition system design and optimum. Chen and Wu [22] as well as Jin and Walraven [23] used wave equation method to discuss the relationships among prestack depth migration imaging, seismic data acquisition aperture and seismic wave illumination, and pointed out the corresponding relationship between seismic wave illumination shortage and migration imaging shadow. Rickett [24] derived the illumination normalization method for wave equation depth migration by using the wave equation least-squares migration method, applied it to real data and obtained positive results.…”