The Study On The Sedimentary Microfacies And Diagenesis Of Shahejie Formation Of West Slope Of Shulu Depression

The article had studied the sedimentary microfacies and diagenesis in the period of the second-third member of Shahejie Formation in Che Cheng Oilfield which lies in the west slope of Shulu depression, by analyzing the relevant information such as drilling core description, well-log ,seismic data and analysis of information-based with the direction of sedimentological theory and seiscic stratigraphy.Based on the analysis of lithologic character, grainsize analysis, thin section identification well-log and seismic data, combining with the correlations of single well facies and profile facies, the systemic studies of sedimentary characterization, diagenesis, spacial spreads of sandbodies and controlling factors of Es2-Es3 of Che Cheng Oilfield are done. The result indicates that the beach and bar develops Es2-Es3 of Che Cheng Oilfield, because of the Shulu depression was smaller, the terrain of west slope was gentle, the source was sufficient, the lake level fluctuation was frequent, the influence of lake current was strong. Bar sand mainly fine sandstone and silt-fine sandstone, sand thickness larger which parallel to the praya, it reflect powerful hydrodynamic pressure. And the grain size accumulation curve was composed of bouncing population and suspended population. Bar subfacies divide into three microfacies: key bar, side-portion of bar and between-portion of bar. Beach sand mainly siltstone and argillaceous siltstoue, sand sandstone thickness less frequent among sand layer, divide into three microfacies: key beach, side-portion of beach and between-portion of beach. And the grain size accumulation curve was two-section pattern, but the content of suspended population was high.In the study area, beach bar is mainly associated with storm deposit. Sedimentary structures in tempestites are mainly surface erosion, storm mud gravel, shear structures, outlet structures and bioturbation structures, etc. Size probability curve is mainly the suspension population and the bouncing population displays the features of high slope. On the basis of sedimentary characteristics and their relationship with the source, the tempestites in the study area can be further divided into autochthonous tempestites and near source tempestites. The autochthonous tempestites are characterized by muddy gravel. There are three types of near source tempestites, which are developed above normal wave base and have the block layers developed in common, reflecting the more rapid accumulation of a strong role in storm flow.The main diagenesis types in the studied area include compaction, cementation, metasomatism, and dissolution, and divided into fine kinds of diagenetic facies are. The most important reservoir space in the studied area was secondary intergranular emposieu which the feldspar and carbonate cement was dissolved . The reservoir physical property of Es2 was poorer than Es3, because of during the Es2, the lake level declined, and the hydrodynamic pressure was weaker which lead to higher mud content and the plugging of pores and deterioration of the permeability. The reservoir physical property of key bar of Es3 was better , key beach and side-portion of bar of Es3 and the key bar were best. These microfaces can be treated as the point of the exploratory development in the future.