Abstract:

Up to date, onshore permafrost-associated gas hydrate is just restricted to the area of Sanlutian of Muli in Qinghai in China; drilling holes revealed that gas hydrate distribution was very scattered in this area; then what geological constraints affect such heterogeneity of gas hydrate distribution in this area? Targeting this question, based on past work, the geological data and analytical results of various samples collected from the series of gas hydrate drilling holes invested by Shenhua Corporation are emphatically and comprehensively studied in Sanlutian of Muli in Qinghai, to discuss constraints of the genetic type of gas source, the available supply amount of gas source, the different occurrence and nature of faults on gas hydrate formation and distribution. Study results show that the genetic type of gas source is mainly thermal in the middle to west of the study area of Sanlutian where gas hydrate is found and it is mainly microbial in the east of the study area where gas hydrate is not found, indicating that the genetic type of gas source plays an important role in controlling gas hydrate formation and distribution in the study area. The available supply amount of gas source is the best in the west of the study area, and it is the second in the middle, and it is the worst in the east; this available supply circumstance of gas source directly affects the difference of gas hydrate formation and distribution between the middle to west and the east of the study area. Thrust faults F₁ and F₂ control gas hydrate formation and distribution in the middle to west of the study area. The occurrence and nature of the thrust fault F₁ is various in the east to middle of the study area, which go against gas hydrate formation and distribution. The nature of normal fault F₃₀ locally affects gas hydrate formation and distribution in the west of study area.

Key words: permafrost, gas hydrate, geological constraint, formation and distribution, Sanlutian of Muli in Qinghai