Abstract:

The 3D seismic data were firstly acquired to explore gas hydrates in permafrost area in Muli of Qinghai. According to the features of permafrost thickness, formation lithology, the pore type and hydrate-bearing depth of reservoir, the scheme of 3D seismic data acquisition and processing was designed, and a satisfied result was gained. Based on the analysis of these seismic data it is found that the structure and seismic response characteristics of the formation in this area are obviously different from aboard hydrate-bearing permafrost zones. The gas hydrate in Muli area is mainly filled in fractures of reservoirs, occasionally in the pores; in addition, the hydrate formation is also controlled by the depth and lithology of permafrost. As a result, the characteristics of seismic responses, such as amplitude, frequency and speed have some unique features. Combined with the geological data of the study area, it is revealed that the seismic responses of hydrate-bearing intervals manifest low frequency and disorderly medium oscillation amplitude. These characteristics can provide valuable proof to recognize gas hydrates in the study area.

Key words: Muli area, 3D seismic profile, natural gas hydrate, respond characteristic