Analysis Of The Physical Properties And Heterogeneity Of Chang7 And Chang8 Reservoir In Dingbian Kangliang Area,ordos Basin

The combined oil and gas exploration has witnessed great development in Yanchang group on Dingbian Kangliang area in Ordos basin.However,several factors have hampered its further exploration: the large burial depth of oil layer in Chang7 and Chang8(Chang7/8),the limited research on the reservoir and the unclarity of the reservoir properties and distribution.Thus it is necessary for the oil and gas exploration to make further studies on the physical properties and controlling factor of Chang7/8 reservoir in Dingbian Kangliang area.Based on the theory of petroleum geology and reservoir sedimentology,I collected statistics of drilling,logging,rock core and experimental files;and applied thin section analysis,scanning electroscope,mercury penetration etc.Then we studied the microstructure,reservoir heterogeneity,distribution regularity and controlling factors of Chang7/8 sandstone reservoir in Dingbian Kangliang area and drew the following conclusion.Delta front is distributed in the whole area of the studied Chang7/8 reservoir,while shallow lake facies develops in the lower part of Chang7 reservoir.The major pore types of Chang7/8 reservoir comprises intergranular solution pore,residual intergranular pore and intragranular solution pore.The concentrated distribution interval of reservoir porosity ranges from 4-12%,vastly between 6-10%.The concentrated distribution of permeability ranges from 0.03-3m D with 0.43 m D in average,belonging to low-ultra low permeability reservoir and type IIb,IIIa-IIIb reservoir mainly.Chang 7/8 reservoir shows strong interlayer and intralayer heterogeneity in general,while Chang8 reservoir shows the strongest interlayer heterogeneity.The porosity and permeability also reveal strong heterogeneity in Chang7/8 sublayer in studied area.In general,sections with thicker sandstone allow for better permeability,and vice versa for sections with high oil-saturability and thin sandstone.The physical properties of Chang7/8 reservoir in Yanchang group in the studied area are determined by sedimentation and diagenesis.Underwater distributary channel of delta front dominates the reservoir distribution and physical properties,while diagenesis has a large effect on reservoir physical properties and pore characteristics.The reservoir favorable area is in Sand-body distribution area of Underwater distributary channel microphase,central and northwest section of Chang71.