FORMING MECHANISM OF CONVENTIONAL CRUDES IN NORTH TARIM BASIN

There are two genetic types of conventional oils in the northern area of the Tarim Basin. The conventional oils related to the types and maturity of source rocks include continental conventional oils related to Mesozoic moderate-mature source rocks whose source-regions are mainly distributed in Kuqa Depression and whose products are mainly light-conventional oils, marine conventional oils related to Carboniferous mOderate-mature source rocks which have less resource scale and low concentric extent and in which oil and gas fields (pools) have not been discovered so far, and conventional Oils related to Ordovician source rocks in upwelling and slope regions whose middle and upper series though with the low abundance of organic material have widespread distribution and large thickness and whose degraded products are conventional-light oils and the oil-bearing potential of the late stage is worth paying attention to.Conventional oils related to pool-forming stages and epigenetic changes include residual oils formed by epigenetic recreation and conventional oils formed by reassemblage from hydrocarbons pool-fOrmed at early (Hercynian) epoch and conventional oils formed by hydrocarbons pool-formed at middle (Indosinian-Yanshan, latest Middle Himalayan Movements) epoch because of untightly enclosed system in pool-forming periods.Different source rocks, different evolutionary stages and corresponding hydrocarbon products in North Tarim area have gone through the recreation and changes of different stages, times and extent , and formed at last the hydrocarbon pools with different properties, including a large number of conventional oil pools formed by epigenetic recreation.