Validation of Seismic Methods to Detect Natural Gas Hydrates in Permafrost

The physical samples of natural gas hydrate were obtained first by drilling in permafrost region of Qilian Mountain of China in 2008. Permafrost area in Qilian Mt. is located in lower latitudes at high altitude, and the samples form in the Jurassic stratum under hard rock environment, rather than in unconsolidated soil layer. The environment of the Gas hydrate discovered is different from in the Arctic region. The validity experimental study of seismic reflection method at Muli region in Qinghai province was carried out for detecting natural gas hydrate in 2010. High-precision seismic reflection method is used in the experimental study. Under the environment of high altitude and permafrost, the seismic survey is very difficult. The seismic data to be able to interpret is obtained through the hard work of field staff. It is considered preliminary that reflections formed from natural gas hydrate media on seismic profile possess low velocity and low amplitude, high frequency characteristics, through comprehensive analyzing and interpreting the seismic and well logging and geological data. According to the dynamic features of the reflections and logging results, anomaly segments of natural gas hydrate found in the DK-4 and crystal segments of gas hydrate revealed by the DK-3 borehole are analyzed. The analysis results do not support natural gas hydrate drilled in the DK-4. Combined with borehole data, the enrichment zones of the natural gas hydrate are inferred.