Reservoir Characteristics And Optimal Selection Of Yanchang 6 Reservoir In Dalugou Area Jing’an Oilfield

Ordos Basin is rich in oil and gas resources.After years of oil and gas exploration and development,great exploration achievements have been made.In this paper,Yanchang Chang 6 reservoir in Dalugou area of Ordos Basin is taken as the research object.The sedimentary microfacies characteristics,sand body distribution characteristics and reservoir characteristics of Yanchang Chang 6 reservoir in Dalugou area are studied,and the reservoir classification evaluation and favorable area prediction are carried out,which provides a theoretical basis for the future oil and gas exploration in the study area.The main understanding is as follows:（1）Through stratigraphic division and correlation,the stratification standard and correlation scheme of Yanchang 6 oil formation are unified.Taking K1,K2 and K3 as the main marker beds and K4 as the auxiliary marker beds,the Chang 6 reservoir group is divided into three small layers,namely Chang6₁,Chang6₂ and Chang6₃,by combining with the lithology characteristics.Chang6₁ was further subdivided into Chang 6₁¹,Chang 6₁^2-1,Chang6₁^2-2and Chang 6₁^2-3 sub-layers,Chang 6₂ was subdivided into Chang6₂¹,Chang6₂² and Chang6₂³ sub-layers,and Chang6₃ was subdivided into Chang6₃¹ and Chang6₃² sub-layers.（2）Through the study of sedimentary microfacies,the delta-front subfacies are developed in the Chang 6 oil formation in the Dalugou area,and the sedimentary microfacies include underwater distributary channel microfacies and underwater interdistributary bay microfacies.The main part is underwater distributary channel microfacies,and the distribution of channel sand body presents a strip extending from northeast to southwest.（3）The Chang 6 reservoir in the study area is a low porosity and ultra-low permeability reservoir.The reservoir rock type is mainly feldspar sandstone.The pore type of Chang 6 reservoir in the study area is mainly intergranular pores,followed by feldspar dissolved pores.The cement is composed of chlorite,iron calcite,silica and turbidite.The pore structure of Chang 6 reservoir in the study area is divided into three types:classⅠ,classⅡand classⅢ.According to the analysis,long6₁^2-2 small layer has the best physical properties.（4）The favorable area of Chang 6reservoir in the study area is predicted,and it is considered that the Chang 6₁^2-2 reservoir in the favorable area of Chang 6₁ is better on the whole,and the favorable area of ClassⅠis widely distributed,among which there is one favorable area of classⅠwith reserves of 8.251,000 tons,and that of ClassⅡwith reserves of 2.218,000 tons;The middle Chang 6₂²reservoir in Chang 6₂ favorable area is good as a whole,and the remaining reserves of ClassⅠarea are 200,000 tons,and the remaining reserves are mainly classⅢ.In Chang 6₃ favorable areas,Chang 6₃¹ was better,with 1 favorable area of classⅡand 3 favorable areas of classⅢ.