Study On The Reservoir Property Of The Chang4+5,Chang6₁ In The Area Of Majiashan-Buziwan

Based on the research of sedimentary facies ,The author has synthetically analyzed the Chang4+5, Chang6₁ oil-bearing formation zone of the reservoir of Yanchang formation of Upper Triassic of the Majiashan-Wangwazi area in Ordos Basin, effectively utilizing the first data of well logging, core observation, geological borehole log and using the techniques of modern laboratory analysis.Starting with the characteristics of the reservoir petrology, the author also has analyzed the porosity structure and the reservoir capability of the Chang4+5, Chang6₁ sandstone formation of the reservoir of Yanchang formation of Upper Triassic, and probed into the controlling factors to the quality of the reservoir, such as diagenesis, original elements of mineral, crack, heterogeneity;The author has expounded both the geological characteristics of low permeability reservoir and the reasons which cause low permeability of reservoir, divided the diagenetic facies and analysed the distribution of favorable reservoir.Through the research of diagenesis, the author thought that the main reasons which make the physical characteristic of the Chang4+5, Chang6₁ sandstone formation weaker are mechanical squeezing action of the early diagenetic stage and carbonate cementation action of the late diagenetic stage. besides the crack caused by the tectonic stress, the crack caused by squeezing action during the stage of diagenesis also plays an important role.Macroscopic heterogeneity of the reservoir is mainly controlled by Sedimentary Facies and Diagenesis, the interlayer heterogeneity from bottom to top has a trend of decrease, Pore structure of the sandstone is a main reason which results in the micro- heterogeneity of the reservoir. The result of real-sandstone micro-model experimentation indicated that there are two types of oil displacement: crack one and pore-crack one, the later efficiency of oil displacement is better than the former.Diversity analysis of the capability of reservoir indicated the factors which improve the performance of reservoir in researching region includes: the Submarine distributary channel and the sandstone-body primary intergranular pore of the mouth bar preserved well, thus the reservoir property is better;Solution function is growing;Each kind of cracks caused by the tectonic movement in Various stages made the reservoir property improved;The high heterogeneity of low permeability reservoir indicated that there was sandstone with relatively high permeability .In view of the practice of Chang6₁, Chang4+5 reservoirs in the Majiashan-Wangwazi area, the author has established the synthetic evaluative standard and thought that the Chang4+5₂ is the favorable reservoir, Chang 6₁ is inferior, Chang4+5₁ is worse than another ones in the region. The favorable reservoir mainly distributes in the delta-front submarine distributary channel .The researching effort of the project has been applied and validated in petroleum exploration in Changqing Oilfield, and has achieved good economic profit.