The Pore Structure Of Tight Sandstone Of Shanxi Formation In Daning-Jixian Area

With the further development of oil and gas geological theory and exploration and development methods,great progress has been made in the scientific research of unconventional oil and gas geology in recent years.Taking Daning-Jixian area of Shanxi formation tight sandstone as the research target,this essay analyze the main control factors of the group sandstone through the Shanxi formation of tight sandstone sample wafer composition,structure,fill the international characteristic experiment,petrological characteristics,such as using mercury intrusion method of reservoir pore structure of the system research,which lays a solid foundation for future exploration.（1）Through microscopic observation to the tight sandstone chips in Shanxi,we found that the main sandstone are debris sandstone,the highest content of metamorphic rock debris,moderately sorting,main way round-time round edges.The cementation type is mainly in the pore cementation,and the contact type is gradually transferred to the line contact type by the point contact type.The content of interstitial material was the highest in quartz.The pores are mainly intergranular pores,and the throat type is mainly lamellar or curved flaky throat and tube bundle throat.（2）Mercury injection test shows that with the increase of mercury saturation,the correlation between pore throat radius and porosity and permeability increases.The overall separation coefficient of pore and throat in the study area is large,and the separation performance of samples is poor.The correlation between displacement pressure,median pressure and mean throat radius and permeability is good.According to the capillary pressure curve and permeability as the main classification factor,the pore and throat characteristics of the sample can be divided into two categories:Ⅰis given priority to with medium grained sandstone pore structure of reservoir,reservoir sandstone pore types are mainly large aperture of intergranular pore and intergranular dissolved pore and throat are mainly sheet and bent sheet,permeability is generally greater than 0.1×10^-3μm²,porosity is generally greater than 6%.The displacement pressure is low,both of which are less than 0.7MPa.The grain of the sandstone with typeⅡpore structure is mainly fine grain,and the intergranular micropore is the main pore type of this kind of sandstone.The permeability is moderate,located between 0.01×10^-3μm² and 0.1×10^-3μm².The displacement pressure is larger than 0.8 MPa,and the throat is dominated by tube-bundle throat.（3）The pore structure of dense sandstone in Shanxi formation is controlled by sedimentation and diagenesis.The properties of unstable minerals change,and some feldspar may also undergo secondary enlargement.When the clastic particles are compacted,the contact mode between them changes,which affects the pore structure space.With the deepening of diagenesis,cementation,acidic fluid production of dissolved in the sandstone easily dissolved constituents,denudation,secondary porosity raised,so that the study area reservoir property better.