Imaging of offset VSP data acquired in complex areas with modified reverse‐time migration

Abstract

A B S T R A C TA modified reverse-time migration algorithm for offset vertical seismic profiling data is proposed. This algorithm performs depth imaging of target areas in the borehole vicinity without taking into account the overburden. Originally recorded seismograms are used; reliable results can be obtained using only the velocity profile obtained along the well. The downgoing wavefield emitted from a surface source is approximated in the target area using the transmitted P-wave, recorded by the receivers deployed in the well. This is achieved through a reverse-time extrapolation of the direct transmitted P-wave into the target area after its separation in offset vertical seismic profiling seismograms generated using a finite-difference scheme for the solution of the scalar wave equation.The proposed approach produces 'kinematically' reliable images from reflected PPand PS-waves and, furthermore, can be applied as a salt proximity tool for salt body flank imaging based on the transmitted PS-waves. Our experiments on synthetic data demonstrate that the modified reverse-time migration provides reliable depth images based on offset vertical seismic profiling data even if only the velocity profile obtained along the borehole is used.

3D Reverse-Time Migration Imaging for Multiple Cross-Hole Research and Multiple Sensor Settings of Cross-Hole Seismic Exploration

“…Subsequently, to provide richer and more effective information for a better understanding of the geological characteristics between wells, the researchers derived the first-order velocity-stress elastic wave equation of longitudinal and transverse wave decoupling based on an inhomogeneous medium and obtained 2D cross-hole longitudinal and shear wave imaging sections [38]. However, current research is limited to 2D cross-hole RTM imaging and does not utilize information from multiple wells, so it is impossible to obtain the entire 3D geological structure [39,40].…”

A joint imaging method of vertical seismic profiling data by generalized radon transform migration

“…Each wavefield component contributes to the final image to varying degrees, especially the primaries and surface‐related multiples. Conventional imaging methods for VSP data mostly rely on the upgoing primary‐only wavefield, which is a natural application of primary migration method from SSP to VSP data, for instance, Kirchhoff migration (Keho, 1984; Wiggins, 1984; Dillon, 1988; Gherasim et al ., 2005; Lou and Simpson, 2019), reverse time migration (Chang and Mcmechan, 1986; Xiao and Leaney, 2010; Du et al ., 2018), interferometric migration (Hornby and Yu, 2006; He et al ., 2008; Xiao and Schuster, 2008; Neklyudov and Borodin, 2009) and Gaussian beam migration (Protasov and Tcheverda, 2012). These types of VSP migration methods mainly consider imaging the upgoing primary reflections.…”

The issues of prestack reverse time migration and solutions with Graphic Processing Unit implementation

“…In recent years, due to the fast development of computer technology and increasing demand of accurate imaging for a complex structure reservoir, RTM has regained attention in the seismic community. RTM has been developed from post‐stack to prestack migration, from 2D to 3D migration (McMechan 1990), from acoustic to elastic wave equation migration (Chang and McMechan 1994) and from streamer data to VSP data migration (Neklyudov and Borodin 2009); from isotropic to tilted transversely isotropic (TTI) media migration (Zhang, Rector and Hoversten 2005; Du, Bancroft and Lines 2007; Fletcher, Du and Fowler 2009; Duveneck and Bakker 2011; Zhang, Zhang and Zhang 2011). But like any other imaging methods, RTM does have some limitations.…”