Alexander Druzhinin

A Practical Approach to P-SV Prestack Time Migration And V Elocity Analysis For Transverse Isotropy

We present an accurate double-square-root (DSR) migration equation for P-SV (C-) waves in transversely isotropic media. It is expressed in terms of the migration velocity, P/S velocity ratio, and Thomsens parameters. These parameters are estimated using both migration velocity analysis and correlation stacking procedure. We show the results of prestack time migration applied to the Valhall data and compare the isotropic and VTI images produced with C-waves.

Prestack depth imaging via model-independent stacking

Most seismic reflection imaging methods are confronted with the difficulty of accurately knowing input velocity information. To eliminate this, we develop a special prestack depth migration technique which avoids the necessity of constructing a macro-velocity model. It is based upon the weighted Kirchhoff-type migration formula expressed in terms of model-independent stacking velocity and arrival angle. This formula is applied to synthetic sub-basaltic data. Numerical results show that the method can be used to successfully image beneath basalts.

Data-driven Multi-mode Interval Velocity Analysis In Terms of P-Q Wavefront Attributes

We study a data-driven approach to multi-mode interval velocity analysis in laterally inhomogeneous and anisotropic media. We obtain a simple model-independent description of long-spread reflection moveout versus offset for both symmetric and asymmetric wave modes. It resolves a trade-off between anisotropy and lateral heterogeneity. This is done using offset-dependent arrivalangle and wavefront-curvature (P-Q) attributes. These attributes are estimated by transforming common-shot (CS) or common-receiver (CR) data with local slant and beam stacks for various offsets. The relationship between interval parameters and the P-Q attributes is provided by the generalized Dix-type layer-stripping formula. This formula is implemented as a recursive CS or CR wave-equation downward continuation process. The process is performed without reference to an a priori seismic model. We operate with CS or CR gathers without model-based common midpoint (CMP) or common conversion-point (CCP) binning. Our method is robust in that it offers options of wavefield separation and multiple removal in the P-Q Radon-type domain during downward continuation. Examples show that the method is numerically accurate even for large offset-to-depth ratios and in the presence of substantial lateral velocity gradients.

Multi‐scale fracture characterization using fractal frequency‐power‐law attenuation models

We have investigated wave scattering by chaotic fractured systems of fractal geometry with random spatial variation. Specifically, we have examined simple closed-form solutions in fractal poroelastic media. These solutions may be characterized by their frequency-power-law (FPL) signature caused by wave dispersion and attenuation. Numerical results show that the fractal dimension can be estimated from the FPL dependence of the scattered wavefield. It appears that finite-bandwidth signals are delayed with respect to the wavefront in comparable elastic media. Applications to fracture characterization are considered.