| The evolution of petroleum reservoir is more complicated in superimposed petroliferous basindue to the multiple source strata and tectonic events during geological history. As a dynamic andcontinue process in a time zone, its evolution can be divided into three relatively independentstages from formation to destruction, as "pre-reservoir", "reservoir" and "post-reservoir",respectively. The former two are normal in petroleum geology and result in the formation of oilpool with a unified oil-water interface. While the stage of "post-reservoir" is always accompaniedby the destruction of palaeo-oil pool, and forms new oil pool with a tilting oil-water interfacewhich is strongly controlled by the adjustment of palaeo-oil pool. In this dissertation, wepresented the research of pool-forming mechanism of Hadexun oilfield in Tarim basin to show the influence of "post-reservoir" stage on the formation and distribution of petroleum reservoirs.With about 100 millions of tons of reserve, the Hadexun Oilfield, located in the north Tarim basin, is the first marine-sourced, large-scale oilfield in sandstone sequence discovered to date in China. Integrations of geological and geochemical data showed that the Hadexun oilfield was composed of a group of secondary oil reservoirs which were strictly controlled by the palaeo-oil pool. Hydrocarbon generation and accumulation history suggested that the palaeo-oil pool in Hadexun region was formed before Hereynian orogeny with a source of Cambrian-lower Ordovician rocks, With the Himalayan orogeny making the reversion of structural layer, the pre-reservoir was adjusted to three post-reservoirs (the layered and the massive lithology -anticline composite Donghe sandstone reservoir, and thin sand bed structure reservoirs along the zones of Well Hade 1 and Hade 10). The successful exploration in the Hadexun region suggested that the "post-reservoir" stage was one of the key factors controlling the exploration potential in superimposed petroliferous basin.
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