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Hydrate identification based on hydrate indicator |
DENG Wei1,2( ), LIANG Jin-Qiang1,3, ZHONG Tong1, HE Yu-Lin3, MENG Miao-Miao3 |
1. Guangzhou Marine Geological Survey,CGS,Guangzhou 510075,China 2. Key Laboratory of Marine Mineral Resources,Guangzhou Marine Geological Survey,Guangzhou 510075,China 3. Natural Gas Hydrate Engineering Technology Center,CGS,Guangzhou 510700,China |
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Abstract Compared with the post-stack inversion,coupling features in impedance are complex.The pre-stack inversion can make full use of the information such as the amplitude and travel time and frequency of the prestack seismic data,more diverse logging data and geology,and yields geophysical parameters that are highly correlated with hydrate saturation.Seismic rock physics modeling of hydrate reservoirs is the basis for hydrate-oriented prestack inversion.Considering the microscopic pore structure and composition characteristics of hydrate reservoir rocks,this paper introduces SCA-DEM rock physics modeling methods.The influence of physicochemical parameters on the elastic characteristics of rock and its role in AVO characteristics are analyzed.The geophysical response of hydrates is discussed and a new hydrate seismic indicator is constructed.Seismic rock physics analysis shows that the indicator has a high correlation with hydrate saturation.Then,the seismic reflection equation based on hydrate indicator is derived and the feasibility analysis of the inversion is carried out. Finally, based on geological prior, we get the indicator using the actual pre-stack data and logging data in the Qiongdongnan sea of South China Sea.The real data application shows that the method has certain practicability and scientificity.
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Received: 13 November 2019
Published: 01 March 2021
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Log data of a typical hydrate-bearing well in Qiongdongnan area of South China Sea
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Modeling results with corresponding hard porosity
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Velocity corresponding to different gas saturation and hydrate saturation when porosity is 45% a—P-velocity corresponding to different gas saturation and hydrate saturation;b—S-velocity corresponding to different gas saturation and hydrate saturation
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Velocity corresponding to different gas saturation and porosity a—P-velocity corresponding to different gas saturation and porosity;b—S-velocity corresponding to different gas saturation and porosity
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Velocity corresponding to porosity at different gas saturations a—P-velocity corresponding to different porosity;b—S-velocity corresponding to different porosity
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Typical high saturation hydrate and P-velocity corresponding to porosity with a no hydrate-bearing well in Qiongdongnan area of South China Sea a—P-velocity corresponding to porosity in w1 well;b—S-velocity corresponding to porosity in w2 well
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Modeled AVO at the hydrate top and bottom a—AVO at the hydrate top;b—AVO at the hydrate bottom
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AVO at the hydrate top and bottom in w3 well a—AVO at the hydrate bottom;b—AVO at the hydrate top
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Relation between hydrate saturation and porosity a—relation between hydrate stauration and porosity in w2 well;b—relation between hydrate stauration and porosity in w3 well
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Crossplots of Fp and P-velocity and P-impedance in w2 well a—crossplot of Fp and P-velocity;b—crossplot of Fp and P-impedance
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Flow chart of hydrate indicator inversion
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The target seismic section in Qiongdongnan area a—small angle partial angle stack seismic data(1°~10°);b—middle angle partial angle stack seismic data(11°~20°);c—big angle partial angle stack seismic data(21°~30°)
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Inverted results of porosity
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v?p(a) and (b) ">
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Inverted results of (a) and (b)
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Inverted results of Fp
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Relation between P-impedance and porosity reflection coefficient in Qiongdongnan area of South China Sea a—relation between P-impedance and porosity in w1 well;b—relation between P-impedance and porosity in w2 well
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Inverted porosity in w1 well
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Inverted porosity in w2 well
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