Study On Geological Characteristics And Distribution Law Of Chang 8 Reservoir In Maling Area,Ordos Basin

This paper takes Chang 8 reservoir of Yanchang formation in Maling area of Ordos Basin as the analysis object,combined with previous achievements,based on the theory of petroleum geology and reservoir geology,based on core observation,logging data analysis,casting thin sections,physical property data and analytical test data,the geological characteristics and main controlling factors of Chang 8 reservoir in Maling area are studied.The study area as a whole is a westward oblique undeveloped large structure,locally developed nose uplift,with good inheritance,mainly affected by the southwest provenance,the delta front subfacies are developed in the whole area,and the underwater distributary channel microfacies are the dominant facies in the study area.The reservoir rock types are mainly lithic feldspathic sandstone and feldspathic lithic sandstone with high interstitial content.The main diagenesis are compaction,pressure solution,cementation,metasomatism,dissolution and so on.The main pore types are intergranular pores and dissolution pores.The results of physical property analysis show that the average median porosity of Chang 8reservoir is 9.00%,the median average permeability is 0.045 m D,and type III pore structure is mainly developed.The oil and gas rich integrated reservoir in the study area is controlled by many factors.The oil and gas of Chang 8 formation mainly comes from Chang 7 source rock with strong hydrocarbon generation ability,which is mainly lithologic reservoir,the superimposed structure of sand body is complex,and the reservoir boundary is difficult to control.The influence of structure on reservoir formation is weak but is obviously controlled by sedimentary facies,and the development of channel sand body is controlled by underwater distributary channel microfacies.There is a positive correlation between reservoir physical properties and reservoir oil saturation,and it is also related to reservoir pore structure and other factors.Pore throat radius is affected by factors such as displacement pressure and clay content,which leads to the change of reservoir oil saturation.Chang 8 reservoir has no obvious edge and bottom water,insufficient displacement pressure or poor physical properties at the edge of the reservoir are often easy to store retained water,which is not conducive to oil and gas accumulation.