Diagenesis evolution of fragmental reservoir in alkali sediment environment—taking the Member 4 of Shahejie Formation of steep-slope zone in Dongying sag, Shandong, China for example

Based on the analysis of thin-section analysis, scan electricitymicroscope observation, vitrinite reflectance-diffraction and geochemical analysis, the diagenesis evolution of shahejie formation in dongyingsag has been systematically researched. It is indicated that the original depositional environment of Es4 Member is alkali salt lake, and the calcareous and argillaceous were included in the rock. The diagenesis evolution is controlled by factors including alkali original depositional environment, sequence development, tectonic event, transformation of clay minerals, acid fluid provided by organic matter thermal evolution, which has experiences below stages including cryptocrystalline calcite cementation, early chlorite cementation, quartz dissolution, feldspar dissolution, phase Ⅱquartz increase, phase Ⅲ quartz increase, Fe carbonate cementation, quartz and calcite vein filling. The conclusion has been verified that Es4 Member influenced by the original alkali fluid on early stage, cementation of the crypto-crystal carbonate, quartz solution and feldspar increase were occurred in the reservoir; influenced by the acid-fluid on the advanced stage, quartz increase, carbonate solution and feldspar solution were occurred in the reservoir of member 4 of shahejie formation in dongying sag.