Study On The Characteristics And Main Control Factors Of Yan10 Reservoir In Beisan Area Of Maling Oilfield,Ordos Basin

Yan10 layer of the Yan'an formation is one of the main developing reservoir of Beisan area in Maling Oilfield,Ordos Basin.According to the practical development experience,due to the lack of systematic understanding of reservoir characteristics in the early period,the controlling factors of the reservoir are not clear enough,so it directly affects and restricts the later exploration and development.This study starts from the characteristics of the reservoir,analyzing the structure and sedimentary characteristics,diagenesis types,micro-pore structure characteristics,and the occurrence and seepage of reservoir fluids.On the basis,summarizing the main controlling factors of high-quality reservoir,then classifing and evaluating the reservoir of the study area.The following results have been achieved:Yan10 layer of Beisan area in Maling oilfield is tilted to the west and is a nasal uplift,which belongs to fluvial deposition.The main rock type is medium-grained feldspar quartz sandstone,which is well sorted.The main roundness is sub-circular.The interstitials are developed,mainly autogenic clay minerals.The main porosity is between 10%?17%,and the main permeability is between 5×10^-3?m²?20×10^-3?m²,which is a typical low porosity and low permeability reservoir.Compaction is the main type of diagenesis,followed by cementation and dissolution.Mechanical compaction is the main reason for the decrease of the reservoir porosity,which decreases by average 18.6%.According to the diagenetic evolution classification criteria,the reservoir diagenetic stage is currently between late stage A and the early stage B of the middle diagenetic stage.According to the observation of casting flakes and scanning electron microscope experiments,the main pore type of the target reservoir is residual intergranular pore,and the main throat type is flaky and spotted throat.Combining high-pressure mercury injection and constant-speed mercury injection experiments,the target reservoir has many large pores with a pore radius ranging from148.5?m to 172.22?m;the throat heterogeneity is strong,and the throat radius ranges from0.741?m to 11.383?m.The microscopic pore structure of the target reservoir can be divided into three types?types?,?,and??.Among them,there are many samples of type?micropore structure,which is the main micropore structure type in the study area.According to nuclear magnetic resonance,Oil-water phase seepage test,and Microscopic water flooding experiment with real sandstone model,target reservoir has high mobile fluid saturation,ranging from 70.17%to 90.3%,and Low water flooding efficiency,ranging from 40.07%to51.2%.Mainly due to the strong heterogeneity of the throat,the microscopic pore structure of the layer in the study area is complicated,and the displacement effect is poor.Overall,the reservoir is affected by sedimentation,diagenesis,and micro-pore structure characteristics.Sedimentation controls distribution of sand bodies and petrographic characteristics,and determines material basis of the reservoir.Diagenesis changes the reservoir space and affects the physical properties.The micro pore structure directly affects the reservoir properties.The cluster analysis method is used to divide the reservoir into 4 types?Type?,Type?,Type?,and Type??.Type?reservoir is the best reservoir type but less distributed.Type?reservoir has lower quality but wider distribution than type?reservoir.Type?and?reservoirs have the lowest quality.In the future,attention should be paid to the development of type?and type?reservoir.