The Seismic Sedimentology Study Of Lower Pliocene For Wunan-Lvcaotan Tectonic Zone

This dissertation takes sequence stratigraphy, sedimentology, seismic sedmentology and Geophysics as instruction, and focus on the seismic sedimentary study of the lower Pliocene(N21) formation in Wunan-Lvcaotan Zone. Based on the analysis of well logging and core, combine with the technics of seismic sedmentology, we carry out the sedimentological study, and the seismic sedimentary technics make the findings more realiable. The study area locates in the western depression of Qaidam Basin, the integral structure is an anticline inclined to NW, the general depositional migrate direction is from west to east, but in the study area, under the effect of local tectonic activities, there are two provenance directions: W-NW and S-SE.We established the sequence stratigraphic framework, the N21 formation is a third-order sequence unit, and divided into 7 fourth-order sequences(SQⅠ-SQⅦ), 174 fifth-order sequences. We created the general sedimentary facies model, the principal facies in the study area is beach, bar and delta front in shore-shallow lake. Through the time, the water depth of the depositional environment become shallow.By the means of seismic sedmentology (90°-phase shift, frequency conversion and stratal slicing), we make a series of stratal slices. The properties extracted from these slices represent the sedimentary facies, so we draw microfacies maps for every fourth-order sequence refer to the stratal slices, and maps for the fifth-order sequences to study the evolution of the sedimentary system.On the microfacies maps, there are 7 microfacies types: bar, beach, lake mudstone, submarine distributary channel, interchannel, mouth bar, distal bar. The sand in delta front, beach and bar of the shore-shallow lake are the favorable reservoir rocks of the study area.