Schlumberger

Technical Paper: A Broadband Full-Azimuth Land Seismic Case Study from Saudi Arabia: Interpretation and Inversion Lessons Learned

Society: SEG
Paper Number: 2012-933
Presentation Date: 2012
 

Abstract

Interpretation of conventional wide azimuth 3D seismic data over deep reservoirs in Saudi Arabia has reached its limits. Impedance calculated from these data and long used as a predictive tool is low in both resolution and fidelity from the standpoint of reservoir properties. Further seismic reprocessing and recalculation of inversion is considered to yield limited upside.

A state-of-the-art, high-density full azimuth seismic dataset was acquired over a producing field in eastern Saudi Arabia to attempt to address these issues. The southern one-third of the total volume was selected with well control to develop, optimize, and quality control processing workflows. This “pilot” volume was processed through anisotropic prestack time migration followed by poststack spatially-adaptive wavelet processing and spectral balancing. Analysis of the new reflection seismic data volume shows an increase in bandwidth with improved signal-to-noise ratio when compared with legacy 3D data.

Colored inversion was prepared from the pilot volume and compared with the legacy colored inversion conventional 3D volume. The increase in signal bandwidth significantly improves the relative impedance resolution when compared with the legacy inversion. Use of colored inversion simplifies the process of horizon picking and was used to generate horizon control for use in calculation of absolute impedance.

Seismic data-driven relative inversion compares favorably with the well-log-derived low frequency model. Acoustic impedance inversions were computed from the new data and benefited significantly from the increase in low frequency signal. In the final absolute acoustic impedance inversion, a portion of the bandwidth typically reserved for well-generated models was replaced by seismic low frequencies.

As the methodology for incorporating seismic low frequency into the inversion process improves, so will the prediction of reservoir properties and geometry. Extraction of geobodies at this time varies among the several inversion results and this variability reflects uncertainty in methodology. Additional work will be required to determine which methodology produces the most accurate predictive capability.

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