RESEARCH ON THE METHOD FOR GAS HYDRATE IDENTIFICATION BASED ON BROADBAND SEISMIC IN DEEP WATER AREAS

In the deep water areas of the Qiongdongnan Basin, it is difficult to make clear the occurrence of gas hydrate only with the seismic reflection data of BSR, which influences gas hydrate exploration. Based on the drilling data and the characteristics of the elastic parameters of gas hydrate bearing rocks in the basin, the physical properties of gas hydrate are clarified. Seismic forward modeling is adopted to distinguish the seismic reflection characteristics of the pore type hydrate from the chimney type hydrate. Then based on the AVO forward modeling, it is confirmed that the gas hydrate bottom interface (BSR) has the class Ⅲ AVO anomaly, while the MTD bottom interface, similar to the BSR reflection, shows the class Ⅳ AVO anomaly. Broadband seismic data and 3D seismic velocity volume are used for broadband deterministic inversion under the velocity model. With high velocity and high impedance anomalies, the occurrence and development status of gas hydrate are described. Integrating the methods of seismic reflection characteristics analysis, AVO characteristics analysis, well free broadband seismic inversion analysis and other means, various types of gas hydrate are discovered in the deep water area of the Qiongdongnan Basin, indicating the effectiveness of the broadband seismic method.