Abstract
Seismic properties of hydrate-bearing reservoirs that are affected significantly by the hydrate distribution are key for quantitative assessment of the reservoir. The knowledge of hydrate distribution in fractured reservoirs remains poorly understood. To obtain such knowledge, we measured and analyzed five anisotropic velocities needed to fully characterize the seismic anisotropy in an artificial sandstone with aligned fractures during hydrate formation associated with varying distribution. We showed that while the formation of hydrate improved the velocities, the improvement was more significant for hydrate saturation above 10%. We also showed that the increasing trends varied among the anisotropic velocities when hydrate saturation was above 10%. Specifically, the compressional wave velocity travelling vertical to the bedding plane and the shear wave velocity with polarization perpendicular to the bedding plane increased more rapidly than the other compressional and shear wave velocities, respectively. Interpretation of the anisotropic seismic results suggested that the hydrate tends to bind to the grains in the fractures at low hydrate saturation, and becomes to bridge the fracture surfaces when the hydrate saturation exceeds 10%. The results have provided new insights into the hydrate distribution and its resulting anisotropic seismic properties in fractured reservoirs. This will pave the way for the successful assessment of hydrate in fractured reservoirs.
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Acknowledgements
We are grateful to the scientific editor and the anonymous reviewers for their constructive comments that significantly improved the manuscript. This work was supported by the National Natural Science Foundation of China (Grant Nos. 41821002, and 41874151), the Fundamental Research Funds for the Central Universities (Grant No. 18CX05008A), and the Postgraduate Innovation Project of China University of Petroleum (East China) (Grant No. YCX2020002).
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Liu, S., Han, T. & Fu, LY. Distribution of gas hydrate in fractured reservoirs: Insights from anisotropic seismic measurements. Sci. China Earth Sci. 64, 744–752 (2021). https://doi.org/10.1007/s11430-020-9725-0
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DOI: https://doi.org/10.1007/s11430-020-9725-0