Abstract:

The first discovery of gas hydrate reservoir in middle-latitudes zone was made in the Qilian Mountain permafrost zone. To evaluate the geochemical exploration method for gas hydrate in middle-latitudes zone, Muli area was chosen as the test area. Soil headspace gas, acid extracted hydrocarbon, carbon isotope of methane and carbonate were tested. The results reveal that geochemical anomalies were consistent with the gas hydrate reservoir underneath. The carbon isotope of methane and hydrocarbon composition analysis of the surface geochemical anomaly zone indicated a thermo-pyrogenation origin, suggesting the gas source of the potential gas hydrate reservoir in this area may contribute by oil gas and coal-formed gas. The origin model was also studied for the gas hydrate reservoir. An integrated exploration project which targets at gas hydrate, oil and coal bed methane altogether was recommended as the next step in Muli area.

Key words: natural gas hydrate, middle-latitude permafrost zone, Qilian Mountain, geochemical index, gas hydrate origin model