Reservoir Evaluation Of Chang 4+5 Formation In C270 Well Area,Ordos Basin

The C270 well block is located in Fengdi keng^Majiashan Town,Dingbian County,Shanxi Province.Included in the study area development Triassic,Jurassic oil-bearing layer,the Triassic Chang 4+5 reservoir group is"low permeability lithologic reservoir",geological condition is relatively complex,has not yet formed the scale development,the above problem is the main reason for the reservoir recognition.Starting from the study of sequence,sedimentation and reservoir,the paper aims at solving the actual needs of exploration and development in the research area,digests and assimilates predecessors'research achievements,and fully utilizes the drilling log data to carry out geological study of 4+5 reservoir.The main achievements of the studies are as follows:Based on the principle of"focusing on the standard layer,the sedimentary cycle as the auxiliary and the thickness as the reference",the paper divides the Chang 4+5 oil layers into Chang 4+5₁ and Chang 4+5₂ sand groups,and further subdivides them into Chang 4+5₁¹,Chang 4+5₁²,Chang 4+5₂¹,Chang 4+5₂²4 small layers,with little change in the thickness of each layer.The whole shape is a single diagonal that's going down from east to west.Through the analysis of the lithologic features,sedimentary structure,grain size distribution characteristics and logging data of the target strata in the research area,the paper determined that the study area was located in the delta front subfacies in the period of Chang4+5,identifying the underwater underwater distributary channel,the frontal sheet sand,channel mouth bar and interdistributary bay the four main sedimentary microfacies.By studying the stratigraphic features,sedimentary features,and reservoir features of the research district,it is clear that the target area Chang 4+5 is mainly pink and fine-grained arkose;Intergranular pores and feldspar dissolved pores are mainly the pore types in the research area.The main distribution range of porosity is8%to 13%,and the permeability is mainly distributed in 0.3×10^-3?m²⁰.7×10^-3?m²,and the average is 0.41×10^-3?m².The reservoir type is mainly low-porosity and ultra-low permeability.And the reservoir has a strong reservoir heterogeneity.By analyzing the sedimentary characteristics,physical characteristics and reservoir feature,heterogeneity,interstitial content,pore type,logging interpretation and other favorable parameters were selected,and the reservoir in the study area was classified into 4 types.?categories in the study area reservoir distribution limited,mainly in the distributary channel micro phase;?,?reservoir is the main reservoir type in the research area,with large area,wide distribution and good linking.?kind of reservoir are mainly distributed in sheet sand and distributary bay in the thin layer of powder sandstone.By comparison,the dominant reservoir in the research area is mainly concentrated in Chang4+5₂,and Chang 4+5₂² is better than Chang4+5₂¹.