The Study Of Gas Hydrate’s Gas Sources In The Qiangtang Basin,Northern Tibet

With the rapid development of national economy, more and more attentions have been paid to the energy security. As a new type energy, Natural gas hydrate is always hosted in submarine sedinment or Permafrost land. Because of its huge reserves, it is considered as an alternative energy that can replace the petroleum and natural gas. Qiangtang Basin,which is located in Tibet Plateau, is accepted as the most promising region to find the gas hydrate. But,there has found nothing so far,even an evidence directly related to the hydrate. A recent study shows that the key to find the gas hydrate in this basin is seeking the gas source.In this paper, I studied the samples from a couple of drillings which were serving for seeking natural gas hydrate. With the help of the organic geochemical analysis, I research the source rocks’ characteristic of the Late Triassic Tumen Gela formation, the Early Jurassic Quse formation, the Middle Jurassic Buqu formation and Xiali formation, the Late Jurassic Bailongbinghe formation.The result of the study shows the following:(1)there is a dark mudstone source rock in the Late Triassic Tumen Gela formation which has reached the medium to good source rocks, its kerogen type is Ⅲ, it is at a high maturity stage.(2) The mudstone and oil shale of Quse formation has the highset organic matter abundance in this research, the type of the organic is Ⅱ which is beneficial to the formation of oil and gas, but it is at the maturity stage.(3)The type of Middle Jurassic Buqu formation’s kerogen is also II, the formation has a high degree of thermal evolution,but its TOC is too low.(4)Middle Jurassic Xiali formation contain some mudstones, its kerogen type is Ⅲ, the organic in it is at a high maturity stage, it has reached the standard of poor to medium source rocks.(5) The source rocks of Late Jurassic Bailongbinghe formation is at the maturity stage, its organic matter abundance is higher, its kerogen type is II.The study also shows that (1)the organic matter which is isolated from the dolostone of Buqu formation present a close relationship with source rocks in Buqu formation. The phenomenon implies that the organic matter which is stored in dolomite may be derived from source rocks in Buqu formation.(2)The liquid seepage found in Quse formation has an extremely good affinity with source rocks in Quse formation, this also prove that Quse formation has an outstanding hydrocarbon generation potential.(3) The bituminous veins doesn’t show a good relationship with the limestone of Late Jurassic Bailongbinghe formation, but there is some relation with the mudstone in this formation. We need further research to find out the question.Combining the above research results with the distribution of source rocks and the thickness of the formations and so on, this paper believes that source rocks of the Early Jurassic Quse formation, the Late Triassic Tumen Gela formation, and the Late Jurassic Bailongbinghe formation are the best in Qiangtang Basin, they have the great potential of hydrocarbon generation. They can provide sufficient gas source for the formation of natural gas hydrate. Considering the three parts of the gas hydrate geological, Qiangtang Basin is favorable for the formation and accumulation of gas hydrate. And we can consider the source rocks mentioned above as the most important target strata when we start our next work for natural gas hydrate.