Abstract:

The organic geochemical indicators were analyzed emphatically on the hydrocarbon (gas) source rocks of the Middle Jurassic and the Upper Triassic in gas hydrate occurrence interval in Sanlutian area of Muli,Qinghai. Results showed that the organic matter contents are at high levels in hydrocarbon (gas) source rocks of the Middle Jurassic and the Upper Triassic in the study area. Most TOC contents are more than 0.6%, that is medium, good and very good source rocks.The main organic matter is typed II₂ and Ⅲ. The vitrinite reflectance of most samples are between 0 .7% to 1.3% and only a small part of the vitrinite reflectances are less than 0.7%. So the organic matter in most samples are at mature levels, or at condensate levels, not reach the level of wet to dry gas.This kind of gas source rocks may not produce large amounts of hydrocarbon gases to meet the prerequisite formation conditions for gas hydrate in the study area.The maturity of organic matter in the Upper Triassic is not high, even lower than that in the Middle Jurassic in the study area, which is probably caused by ground or shallow occurrence of the Upper Triassic reversed by faults.

Key words: gas hydrate, gas source rock, organic geochemical characteristic, Sanlutian, Muli,Qinghai