The Geological Research Of Reservoir In Shao 4 Block

The Shao 4 Block locates in the northeast of the Shaojia Oil Field.The regional structural location of Shao 4 Block belongs to the northern slope belt in the Shaojia Depression.The clastic and carbonate reservoirs develop well in the research region since the Ordovician.However,the reservoirs develop strong anisotropy with complex control factors as the reservoirs experience multi-stage and complex tectonic evolution.The distribution of reservoirs is difficult to predict.Therefore,this research reconstructs the sedimentary model and reservoirs developing model to identify the reservoir types and predict its distribution based on the stratigraphic correlation ? sedimentary and reservoirs characteristics.With the researches above,this research mainly achieves the following results and understandings:(1)The dolomite,limestone,diabase dominate the Shao 4 Block during the first member of Shahejie formation.The argillaceous limestone,sandy limestone and calcareous sandstone develops from west to the east during the second member of Shahejie Formation.The fourth member of Shahejie Formation can be divided into two period based on the lithology.The gray,dark grey limestone and mudstone dominates the region.The grey plaster rock mainly develops in the early period.In the late period,the biogenic limestone and arenaceous limestone develops well with some dolomite.(2)During the fourth member of Shahejie formation,the reservoir mainly develops in the limestone which deposited in the shore-shallow lake environment.The granular bank,marginal bank and shallow cement limestone facies are recognized based on the characteristics of lithology,sedimentary structure and geophysics.Furthermore,the carbonate sedimentary model are constructed with the constrains of paleogeomorphology,palaeosource and paleowater depth.(3)During the fourth member of Shahejie formation,the lithology of reservoir is the biolithite limestone which deposits with large thickness and wide distribution.The secondary pores develops well in the reservoir.The main pore types are intergranular dissolved pores,biological dissolved pores and casting membrane pores.Fractures arealso visible.Some of fractures are filled with calcite veins.The reservoir has strong heterogeneity.(4)The rock type,sedimentary facies and diagenesis controls the development and distribution of reservoir during the fourth member of Shahejie Formation.The reservoir physical properties have great differences among different lithofacies.Biological limestone has the best physical property,followed by arenaceous limestone.The compact limestones and marlites develop the lowest physical properties.Based on the lithology,sedimentary microfacies and reservoir physical properties,the carbonate reservoirs of the upper fourth member of Shahejie formation are divided into three types:class I,class II and class III.The three type reservoirs develop in the east-west direction and parallel to the shorelines.