Research On Reservior Characteristics And Favorable Area Prediction Of Chang7in Caijiamiao-bazhu Area

Ordos basin is one of the earliest basins found that contains oil in China, and it is alsothe second largest basin containing rich oil and gas. Yanchang Formation of Ordos basin iskind of subsiding and clastic inland lake basin. With progress in exploration and developmentin Erdos, new wells is drilled with oil and the rich data obtained from wells make it possibleto study in-depth Yanchang Formation Chang7oil-bearing,and based on the data, it isrealized that Yanchang Formation Chang7oil-bearing is not only the main source rock,butalso good reservoir and it contains good conditions favorable to self-generation andself-storage. The turbidites existing in deep water region as oil reservoir break the regularnotion that deep water region is not suitable to be explored.Marker and base level cycle converted point hierarchical strategy are adopted to analyzethe region structural feature and no obvious evidence can be found that the developednose-like structure in the region can control oil and gas well. Based on core type, heavyminerals feature, ancient river direction and previous research results, it is regarded that thesource material of Chang7oil-bearing of Yanchang Formation mainly comes from Southwestand Northeast. Systematic research of sedimentary system in Chang7is studied based onanalyzing source material in the region, it is regarded that the target region in research area isdeep-lake and turbidites sedimentary system developed, in which Chang73to74historyperiod is contained, and lake-basin area was decreasing, lake shoreline was shrinking, andChang71to72had wide turbidites and fine reservoir had formed. In the research area,microscopic-analysis on casting thin sections and SEM method is used to show that reservoirlithology is main mine feldspar, and the porosity type is mainly intergranular. In total, thephysical properties is not good, belonging to ultra-low porosity ultra-low permeability, and bycomparing with the change trend of permeability and porosity, permeability and porosity hasgood correlation relationship. The reservoir is seriously heterogeneous in macroscopic andmicroscopic aspect, and the interlayer frequency is decreasing from71to73, and in planegraph it is clustered distributed. The reservoir feature of lithology，physical properties， oiliness，electrical property are established and the porosity,permeability and oil saturationare recognized. Then reservoir evaluation is done and the formation is classified into5levelswhich provides basis for predict favorite oil and gas-bearing regions. Besides, sedimentaryenvironment and diagenesis are the main factors affecting reservoir physical property and thewidely developed fissures provide good channels for oil and gas migration.According to the research, good featured turbidite submerged fan is good place for oiland gas accumulation. Meanwhile, Chang7turbidite lies close to lake-basin center, and it hasgood source-reservoir-cap assemblage, and the sand depth at turbidite submerged fan is high.With the combination method of oil production, oil production oil test data andcomprehensive reservoir evaluation, favorable target area prediction is selected and the nextdirection of exploration is suggested.