Abstract:

The oil and gas exploration began in the 1940s in the Xujiahe Formation,Upper Triassic, Sichuan Basin, of which the second, the fourth and the sixth members are not only main aim strata, but also one of the most favorable horizons in search for new gas sources. According to core of drilling observation, the actual measurement of field section, the identification and analysis of microscope thin sections, and combined the research of sedimentary facies marks with petrology, well logging and seismology, it is indicated that fan delta, braid river delta and lakes are developed in the Xujiahe Formation, largescale Central Sichuan,and further are divided into several subfacies and microfacies. Through the theory and technology of high resolution sequence stratigraphy, we identify two super longterms and five longterms of datum baselevel cycles sequences in the Xujiahe Formation. Using the sedimentary theory as a guidance, we choose the longterm baselevel cycle sequences as isochronal stratigraphic units to map sequencelithofacies paleogeography of Sichuan basin. The result of maping diagram makes it clear that five longterm lithofaciespaleogeographic subsidence center, migration direction and the distribution rule of sedimentary facies are strictly controlled by the Longmen orogenic belt and Micang Mountains with the nonsynchronous tectonic framework.

Key words:
largescale Central Sichuan, Xujiahe Formation, sedimentary facies, sequencelithofaciespalaeogeography