Hydrocarbon Accumulation Regularity In Member One Of Nantun Formation Of Tanan Depression

Using comprehensive knowledge of petroleum geology, sedimentary petrology, geochemistry and geophysics, and combining materials of research area, and also based on the regional geological situation of depression, we have made the studies as follows:research on types and distribution of reservoir in K1n1, determination of hydrocarbon source, analysis of the main factors controlling hydrocarbon accumulation, and study on period and mode of accumulation. And then, according to the above analysis, we can finally predict the favorable area of hydrocarbon accumulation.Based on lots of research, we regarded Tanan depression as a broad dustpan-shaped rift with small size which was fractured in its easten part and overlapped in its western part. And the evolution process of the basin can be divided into three stages, such as intermontane residual basin, passive rift basin and active rift basin which includes rift structure, fault-depression transformation and depression synthem. The main types of hydrocarbon reservoir include antithetic fault screened reservoir, unconformity screened reservoir, miniature anticline reservoir, lithology updip pinchout reservoir, fault-lithology reservoir and structure-lithology reservoir. The hydrocarbon distribution in the plane shows characteristics as follows:the main hydrocarbon accumulation focus on the middle sub-sag, next is the western sub-sag, and then is the eastern sub-sag. In vertical distribution, oil is mainly in the special lithologic section, second is in the composite cycle section, and the least is the flooding mudstone section. The source of hydrocarbon in K1n1 is mainly from flooding mudstone section and special lithologic section, moreover, due to wide cover area and large thickness, the source rock is conducive to the formation of rich hydrocarbon resources. The hydrocarbon accumulation are mainly under the cotroll of source rock, fault, sedimentary cover, structure and reservoir, that is, source rock controlls the range of accumulation, fault provides screened conditions, sedimentary cover determines the strata of accumulation, and structure controlls the position of accumulation together with reservoir. Homogenization temperature of fluid inclusion measured from reservoir samples mainly changes from 80 to 100 centigrade in Tanan dpression, the accumulation age determined by K-Ar isotop ranges from 111.6Ma to 89.1Ma. After combining the stratigraphic burial history, thermal history, hydrocarbon generation and expulsion history of source and faulting history recovery, it was shown that the accumulation period of K1n1 was mainly in late stage of Yimin formation. The main accumulation models include antithetic fault tilting combination traps,depressionmedian...