Abstract：The bottom simulating reflection (BSR) characteristics of reflected seismic waves are an important sign of gas hydrate. Although they can indicate the bottom of hydrate,they can hardly be used for quantitative interpretation of hydrate content. The rapid development of the gas hydrate exploration technology in recent years results in an understanding that the "blank" zone of seismic amplitude above BSR,directly related to the absorption and attenuation of seismic waves,can be used as an indicator of gas hydrate distribution and quantification. This paper reviews the seismic wave absorption and attenuation characteristics of various hydrate exploration areas around the world (the Mallik permafrost area in Canada,the Nankai Trough in Japan,the Makran accretionary wedge in the Arabian Sea,the Gulf of Mexico,and the Shenhu area in the South China Sea) and artificial hydrate-bearing rock samples. The results show that for different hydrate exploration areas,hydrate-bearing samples,and data used,seismic waves show diffe-rent attenuation characteristics. Then,the possible attenuation mechanisms and related petrophysical theories are summarized for hydrate reservoirs,mainly including global flow attenuation (the Leclaire model),squirt flow (the improved Leclaire model,the hydrate effective grain (HEG) model for submicron hydrate particle squirt,or the hydrate-bearing effective sediment (HBES) model for micron flow squirt),skeleton friction attenuation (the improved Leclaire model). At present,the main problem is that although the hydrate-bearing strata in many areas demonstrate obvious absorption and attenuation characteristics,the relationships of absorption and attenuation variation with hydrate saturation remain unknown due to the varied hydrate formation conditions and geological environments and different occurrence states of hydrate in sediments of different areas. In addition,the frequency band ranges of the current measured observation data and those petrophysical experiments test are limited,so the characteristics of attenuation variation with frequency are not fully reflected. Therefore,petrophysical experimental studies need to be further conducted,and available data from actual exploration areas and the making and experimental measurement results of artificial cores shall be well utilized,thereby studying the additional effect of the microstructure of the hydrate reservoir on the attenuation mechanism in depth. After the reasons of seismic wave attenuation in hydrate reservoirs are clarified,a quantitative seismic interpretation method for hydrate saturation can be developed.
武存志, 张峰, 李向阳. 天然气水合物储层吸收衰减机制及岩石物理理论研究进展[J]. 石油地球物理勘探, 2022, 57(4): 992-1008.
WU Cunzhi, ZHANG Feng, LI Xiangyang. Research progress of absorption and attenuation mechanism and petrophysical theory for gas hydrate reservoir. Oil Geophysical Prospecting, 2022, 57(4): 992-1008.
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