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Broadband Land Seismology

The reef-flat facies reservoirs in carbonate are dominantly developed along the Eastern Edge of the Pre-Caspian Basin. Due to the influences of salt domes and strong heterogeneity, the pre-salt stratigraphy-controlled traps cannot be well imaged with the conventional source, geometry, and processing methods. The narrow-azimuth and low-fold geometry cannot provide high S/N data and image salt-domes and pre-salt reef-flat bodies distinctively; the lack of low frequencies and the loss of high frequencies severely affect the resolution of seismic data and inversion quality. The broadband vibrator, LFV3 which enhances low frequency energy from 3Hz, has been developed and was deployed in AMG 3D project, Kazakhstan in 2013. A Wide-azimuth, Broadband, and High-density (WBH) data volume was acquired. Following the acquisition, a WBH processing and inversion flow was set up, and the imaging accuracy of the salt dome boundaries and pre-salt reflections and resolution were greatly improved.
Key techniques
1. Low frequency vibrator
2. Source wavelet constrained low frequency recovery
3. Adaptive data-driven ground roll removal
Application in Kazakhstan
• Pre-salt strata cannot be well imaged with conventional seismic data.
• The boundary of reef-shoal is not clear.
• Low resolution data fails to characterize thin carbonate reservoirs with strong heterogeneity.
• The dominant frequency of conventional seismic data is within 25~30Hz, only recognizing layers of 45m~60m.
1. High-density data can be used to increase the spatial sampling density and reduce the impact of spatial aliasing. The adaptive data-driven ground roll noise suppression method can improve data fidelity and maintain low frequency components.
2. High-density data combined with extensive near-surface upholes can create a more accurate near-surface model and improve field statics. The iterative process of the azimuthal velocity analysis and residual statics can improve the accuracy of statics.
3. The acquisition with the low-frequency vibrator can obtain abundant low frequency components. The low-frequency recovery and high-frequency compensation techniques can whiten the frequency band of seismic data effectively.
4. Wide azimuth acquisition improves the illumination of targets. Wide azimuth data processing in the COV domain eliminates the effect of azimuth anisotropy and improves the imaging accuracy of targets.
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