Studying And Significance Of Sequence Stratigraphy Of Silurian In The Tarim Basin

Based on the theory of sedimentology, sequence stratigraphy and petroleum geology, this dissertation take typical marine clastic reservoir- the Silurian strata in the Tarim Basin, northwest China, as its study object and sophisticated researches have been done for the depositional system, sequence stratigraphy and its study significance.These achievements would provide important basic information for further petroleum exploration in the basin.Based on the data collected from field outcrops, cores, logs and indoor tests, the depositional systems, including barrier shore system, open shore system and braided channel dominated deltaic system, are recognized in the Silurian strata of the basin. The barrier shore depositional system is further divided into supratidal, intertidal and subtidal facies, the open shore system into foreshore and shoreface facies, and the deltaic system into delta plane, delta front and prodelta facies. Thereby, with the aid of seismic data, we systematically studied the lateral and vertical transitional characteristics of the depositional systems of the Kepingtage Formation, the Tataaiertage Formation and the Yimugantawu Formation. Consequently, the depositional models of the Silurian in the Tarim basin have been established, which comprises the shore-shelf open marine model and the tidal flat-shelf barrier coast model.According to the facies characteristics, key surfaces that bound the systems tracts, such as weathering crusts, condensed sections, onlap-offlap surfaces, erosional surfaces and transitional surfaces of different lithologies are recognized. Then, the Silurian in the Tarim basin is divided into 12 third-order sequences. By comparison with seismic profiles, the regional sequence stratigraphic framework has been established.With respect to the established depositional systems and sequence stratigraphic framework, It was the first time to carry out the systematical study on the relationships between stratigraphic key surfaces and tectonics, conduits of oil and gas movement, and favorable traps.Then, the contacting relationships between the Silurian formations in the Tarim basin are presented.On the basis of the distributing pattern of systems tracts for the forst time, we sum up the corresponding relationships between the sequence stratigraphic framework and the depositional systems of Silurian in the Tarim basin as follow: (1) TST>HST sediment infilling pattern mainly develops in littoral zones with or without barrier; (2) TSTHST–TSTHST-TST= HST-TST