Seismic Low-Frequency Shadow beneath Gas Hydrate in the Shenhu Area Based on the Stereoscopic Observation System

Abstract

Spectral analysis shows a low-frequency shadow under the BSR interface. Traditional low-frequency shadow analysis is based on stacked data. In order to understand the BSR low-frequency shadow more clearly, a frequency division analysis on stereoscopic observation seismic data based on the adaptive optimal-kernel (AOK) frequency analysis method is presented. It includes ocean-bottom seismometer (OBS) data (common receiver point data including vertical and horizontal components), vertical cable data (common receiver point data) and horizontal cable data (stacked section of different offsets). The OBS data frequency analysis gets a conclusion that vertical component has a significant effect on the low-frequency shadow, but the horizontal component did not. The vertical cable data shows that the low frequency band of vertical cable is wider than OBS. And then the horizontal cable data frequency analysis points out that the bigger the angle of incidence is, the more obvious the low-frequency shadow will be. The low-frequency shadow feature is shown in the stereoscopic observation field and the visual effect on common reception point data is better. The lateral reservoir distribution characteristics are predicted from low-frequency shadow feature analysis of the hydrate BSR based on stereoscopic observation.

Keywords

hydrate / BSR / stereoscopic observation / low-frequency shadow

References

[1] Castagna J. P., Sun S. J., Siegfried R. W. Instantaneous Spectral Analysis: Detection of Low-Frequency Shadows Associated with Hydrocarbons. The Leading Edge, 2003, 22(2): 120-127.

[2] Chapman M., Liu E. R., Li X. Y. The Influence of Fluid-Sensitive Dispersion and Attenuation on AVO Analysis. Geophysical Journal International, 2006, 167(1): 89-105.

[3] Chen F., Su X., Zhou Y. Late Miocene–Pleistocene Calcareous Nannofossil Biostratigraphy of Shenhu Gas Hydrate Drilling Area in the South China and Variations in Sedimentation Rates. Earth Science—Journal of China University of Geosciences, 2013, 38(1): 1-9.

[4] Chen X. H., He Z. H., Wen X. T., . Numerical Simulation and Detection of Low-Frequency Shadow. Petroleum Geophysical Prospecting, 2009, 44(3): 298-303.

[5] Chen X. H., Tian L. X., Huang R. Research Progressing on Frequency Dependent AVO Analysis. Marine Origin Petroleum Geology, 2009, 14(4): 60-66.

[6] Chen X. H., He Z. H., Zhong W. L. Numeric Simulation in the Relationship between Low Frequency Shadow and Reservoir Characteristic. Journal of China University of Mining & Technology, 2011, 40(4): 584-591.

[7] Ebrom D. The Low-Frequency Gas Shadow on Seismic Sections. The Leading Edge, 2004, 23(8): 772-772.

[8] Fu S. Y., Lu J. A. The Characteristics and Origin of Gas Hydrate of Gas Hydrate in Shenhu Area, South China Sea. Marine Geology Letters, 2010, 26(9): 6-10.

[9] Goloshubin G. M., Bakulin A. V. Seismic Reflectivity of a Thin Porous Fluid Saturated Layer versus Frequency. 68th Annual Meeting, Society of Exploration Geophysicists, 1998, 976-979.

[10] Goloshubin G. M., Korneev V. A. Seismic Low-Frequency Effects from Fluid Saturated Reservoir. 70th Annual Meeting, Society of Exploration Geophysicists. Expanded Abstracts, 2000, 2000: 1671-1674.

[11] Gong Y., Yang S. X., Wang H. B., . Gas Hydrate Reservoir Characteristics of Shenhu Area, North Slope of the South China Sea. Geoscience, 2009, 23(2): 210-216.

[12] Jones D. L., Baraniuk R. G. An Adaptive Optimal-Kernel Time-Frequency Representation. IEEE Transactions on Signal Processing, 1995, 43(10): 2361-2371.

[13] Korneev V. A., Goloshubin G. M., Daley T. M., . Seismic Low-Frequency Effects in Monitoring Fluid-Saturated Reservoirs. Geophysics, 2004, 69(2): 522-532.

[14] Lan F., Li M., Li Y. D., . Numerical Simulation Analysis of Low Frequency Shadow of Earthquake. Xinjiang Petroleum Geology, 2014, 35(4): 408-413.

[15] Odebeatu E., Zhang J. H., Chapman M., . Application of Spectral Decomposition to Detection of Dispersion Anomalies Associated with Gas Saturation. The Leading Edge, 2006, 25(2): 206-210.

[16] Sheriff R. E. Encyclopedic Dictionary of Applied Geophysics (Fourth Edition), 2002

[17] Sun S. J., Castagna J. P., Siegfried R. W. Examples of Enhanced Spectral Processing in Direct Hydrocarbon Detection, 2002, 457-460.

[18] Taner M. T., Koehler F., Sheriff R. E. Complex Seismic Trace Analysis. Geophysics, 1979, 44(6): 1041-1063.

[19] Wang X. J., Wu S. G. Sedimentary and Migration Characteristics of Slope Gorge in Baiyun Depression and Its Influence on Gas Hydrate Accumulation. Marine Geology and Quaternary Geology, 2014, 34(3): 105-113.

[20] Wu S. G., Yao G. S., Dong D. D., . Geological Structures for Forming Gas Hydrate Reservoir in the Huge Deep Water Gas Field of the Northern South China Sea. Acta Petrolei Sinica, 2008, 29(3): 324-328.

[21] Wu S. G., Zhang G. X., Guo C. S., . Geological Constraint on the Distribution of Gas Hydrate in the Dongsha Continental Slope of South China Sea. Acta Petrolei Sinica, 2004, 25(4): 7-12.

[22] Wu X. Y., Chapman M., Li X. Y., . Quantitative Gas Saturation Estimation by Frequency-Dependent Amplitude-versus-Offset Analysis. Geophysical Prospecting, 2014, 62(6): 1224-1237.

[23] Yin C., He Z. H., Huang D. J. The Research and the Application of the Seismic Attenuation Theory Based on the Wave Equation. Computing Techniques for Geophysical and Geochemical Exploration, 2008, 30(5): 353-356.

[24] Yin C., He Z. H., Huang D. J. The Analysis of Seismic Attenuation and Time Delay Based on the Diffusivity Viscosity Wave Equation. Chinese Journal of Geophysics, 2009, 52(1): 187-192.

[25] Zhao L. X., Han D. H., Yao Q. L., . Seismic Reflection Dispersion due to Wave-Induced Fluid Flow in Heterogeneous Reservoir Rocks. Geophysics, 2015, 80(3): D221-D235.