APPLICATION OF THE MECHANISM OF HYDROCARBON REGENERATION TO EVALUATION OF SOURCE ROCKS OF HIGH MATURITY IN MIDDLE AND LOWER YANGTZE REGION

Mechanism of hydrocarbon regeneration, on the basis of geologic research in field, hydrocarbon geochemistry and sampling, was applied to evaluation of source rocks potential of high maturity in Middle and Lower Yangtze region. Through simulating, it is shown that there is obvious time lag in the performance of hydrocarbon regeneration and also there is peak of hydrocarbon generation. Relationship among the hydrocarbon regeneration quantity, first and second generation quantity and one-time successive generation relies on the degree of initial maturity of hydrocarbon regeneration that is the key factor to evaluate potential of hydrocarbon regeneration of source rocks of high maturity. In Mesozoic-Paleozoic, the Lower and Middle Yangtze region gave birth to six sets of source rocks, of which three sets(lower Cambrian Series, lower Silurian Series and lower Permian Series)are great in width, high in richness and potent in hydrocarbon generation, being the most important hydrocarbon source rocks in the region. The lower Paleozoic source rocks have high thermal evolutionary degrees,and very early enter the period of hydrocarbon generation. Against the background of intensive tectonic movements, the early period of lower Paleozoic(the thermal evolutionary hydrocarbon generation)did not have adequate conditions for hydrocarbon preservation. The upper Paleozoic source rocks have relatively lower thermal evolutionary degrees, did not enter oil generation stage until Indo-Chinese-Yenshan epoch, and reached the oil generation peak in Yenshan epoch, thus such area is the major supply area for hydrocarbon regeneration. So the lower Paleozoic stable platform and the upper Paleozoic source rocks have high potential of hydrocarbon regeneration.