Tarim Basin Gas Accumulation Conditions

This thesis belongs to the tenth five-year-plan state key-critical scientific research projects. Under the guidance of petroleum system,, the systematic researches on the condition of gas reservoir formation in cratonic area in Tarim Basin were made by means of petroleum geochemistry, petroleum geology and gas reservoir formation geochemistry. Based on the research results, the main contoliing factors for middle-large scale gas reservoir in cratonic area was suggested and the prediction was made to guide the exploration of middle-large scale gas reservoir.There are many difficulties and problems encountered in the study: (l)Cambrian and lower Ordovician source rock are old history and have experienced a long period of geological history. During Caledonian period, the source rocks were buried quickly and a great deal of oil/gas were generated quickly. Owing to so much difference in the local structure evolution, there are different models of generation, migration and accumulation of oil/gas in different region.(2)The gases in cratonic basin have complex genesis. The oil-cracking gas is dominant. Up to now, there have not been a good suit of index to distinguish between oil-cracking gas and kerogen-cracking gas and a good means to calculate the mixing proportion of these two kinds of natural gases.(3)There are many type of natural gases in cratonic basin, including condensate gas, dry gas and wet gas. The content of the non-hydrocarbon in these gases is high, and the models of the reservoir formation is incompletely clear.(4)If the oil-cracking gas is the main genesis, what are the main important control factors?(5)The distribution of the gas and the good exploration direction is still incompletely clear.There were much new creation made in research methods in this thesis that the hydrocarbon compound condenstated in the gas reservoir was applied to gas-source correlation, and the inclusions and reservoir bitumen as well as tectonic evolution...