Seismic Imaging of Complex and Steep Structures in the Kuqa Depression

Author:

FU Li-Yun  XIAO You-Jun  SUN Wei-Jia  WU Chao  GUAN Xi-Zhu and ZHANG Jing-Zhou  

Journal:

Chinese Journal of Geophysics

Issue Date:

2013

Abstract(summary):

Seismic imaging generally relies on data quality, velocity reliability, and migration operator performance. Complex near-surface geological conditions in Kuqa depression cause extremely low signal-to-noise (S/N) ratios of seismic data. Salts penetrating into overthrust structures are widely distributed, vary in thickness and shape of complex geometries, and distort the imaging of subsalt faults, leading to complicated imaging problems. This article studies three key issues. In the preprocessing of prestack data, some innovative techniques combined with commercial techniques are employed by three levels to improve data quality and reconstruct the reflections from depths. Three-stage migration velocity analyses, subtle DMO velocity analysis, prestack time-migration, and prestack depth-migration velocity analyses are implemented to build a topology-preservation prestack-migration velocity model. The time-depth conversion of the prestack time-migration velocity model is performed based on the Kuqa-depression modeling of salt-related overthrust complex structures combined with the velocity-varying mapping technique. The well-constrained seismic inversion for low-frequency velocities is conducted to handle the syncretization of the well-building and migration-building velocity fields. Finally, prestack time and depth migrations are performed by a semi-analytic degenerate Fourier migrator that improves the imaging of high-wavenumber components. Applications to the Dabei, Bozi, Quele, Xiqiu10, and Xiqiu4 structures result in well-positioned images for salt-related overthrust complex structures.

Page:

310-327