Study On Reservoir Diagenesis Of Middle Sub-member Of Es3 In Niuzhuang Sag Of Dongying Depression

Reservoirs in middle sub-member of Es3 is a low-porosity and low-permeability reservoir.The low-permeability reservoir has strong heterogeneity,and the physical properties of the reservoir vary greatly.Other scholars have researched the diagenesis of middle Sub-member of Es3 in Niuzhuang Sag,However,no specific diagenetic evolution studies have been carried out on the different physical properties of the turbidite sand reservoirs.Previous studies on the diagenetic facies of study area have only focused on the overall composition of the middle Sub-member of Es3 in Niuzhuang Sag.Aim at these points,this paper using many technical methods in this study.Firstly,the reservoir characteristics of turbidite sand bodies in middle sub-member of Es3in the study area were studied by means of core description,casting thin section analysis and particle size analysis and testing.The turbidite sandstone reservoirs in middle sub-member of Es3 Formation in the study area are widely distributed throughout the region,and are typical low-porosity and low-permeability reservoirs.The types of reservoir porosity are mainly low porosity and ultra-low porosity.The types of permeability are mainly low permeability,ultra-low permeability and ultra-low permeability,and the correlation between porosity and permeability is good.The turbidite sandstone reservoirs are dominated by secondary pores.The pore types mainly include intergranular pores,dissolved pores,and intercrystalline pores.Most of them are dissolved pores,and the pore diameters are of different sizes,generally less than100?m.Based on the sedimentary characteristics of study area middle sub-member of Es3,this paper through the core analysis,thin slice observation,scanning electron microscope observation,X-ray diffraction,clay mineral content and other data to analysis reservoir mineral diagenesis characteristics,research shows that there are 4 types of diagenesis in study area middle sub-member of Es3 reservoirs,these reservoirs mainly in the diagenetic stage A₂ to B.The carbon and oxygen isotope analysis shows that the reservoir diagenetic fluid is mainly derived from the lower hydrocarbon source rocks,caused reservoirs in middle sub-member of Es3 experienced 4 times diagenetic environmental changes.Further 7 diagenetic facies are distinguished by the diagenesis with the greatest influence on reservoir quality,and then combined with single-well facies analysis,well logging,and logging data,the diagenetic facies plane distribution was analyzed based on the plane distribution of sedimentary facies.Through the analysis of physical properties of turbidite sand bodies and observation of microflake,6 dense zones and 4 pore zones were identified in the turbidite sand bodies of the middle sub-segment in the study area.And based on the background of diagenetic evolution,combined with core observations,microscopic observation of casting thin sections,logging data,well logging data,and physical property statistics,the formation and evolution of various physical belts of turbidite sand bodies are discussed,and the formation and evolution of each physical belt are analyzed in detail.Finally,the porosity evolution process of each physical zone was recovered through calculations,and the main reasons for the densification and porosity improvement of turbidite sand bodies in reservoirs in middle sub-member of Es3 in the study area were analyzed.