Abstract:

The efficiency test of trace element geochemical exploration was carried out for natural gas hydrates in the Qilian Mountains permafrost region, the study area covered 150 km² and sampling density of 2 sampling sites per km2 was used. Results showed that Ba, V, Fe and Ca in soils presented the apical pattern, and had identical anomalies. Natural gas hydrates could be higher successfully prospected by trace elements. The dry wells ( DK-4, DK-5, DK-6)drilled before this survey were located in background area, and the hydrate wells DK-1, DK-2, DK-3, DK-7 drilled before the survey and DK3-11, DK2-13, DK1-14 drilled after the survey were both located in anomaly area. Two prospective target regions were predicted according to the test results. Test has shown that trace elements were the effective index for prospecting gas hydrate in the Qilan Mountain permafrost region. Combined with permafrost conditions and geological characteristics, the comprehensive interpretation of trace elements and other geochemical index could improve the success rate of prediction for natural gas hydrate in permafrost area.

Key words: Qilian Mountains permafrost, gas hydrate, trace element, apical pattern, mechanism of geogasmigration