Characteristics Of Reservoir Sedimentology Of Chang9Oil-bearing Layer Of Yanchang Formation In Longdong Area,Ordos Basin

Based on the theory of sedimentology, reservoir sedimentology and petroleum geology, this dissertation take typical tight clastic reservoir Chang9oil-bearing layer of Yanchang Formation in Longdong area, Ordos Basin,as its study object and sophisticated researches have been done for the sedimentary facies、reservoir characteristicse and its controlling factors, so in the end we can predict distribution of the reservoirs. These achievements would provide important basic information for further oil exploration in the area.According to detailed field outcrop profiles and the core drilling observation, combining with the rock color, sedimentary structures, profile structures and log facies, Chang9oil-bearing layer of Yanchang Formation in Longdong area were studied. The results show that distributary channel and underwater distributary channel sandbodies of shallow-water deltas developed. Based on correlations of sedimentary microfacies of single-well and well-to-well,we systematically studied the vertical and lateral transitional characteristics of the depositional systems of each member of Chang9oil-bearing layer of Yanchang Formation in Longdong area. Consequently, the depositional models have been established, which is lake-braided river delta model.Based on the core observation of36wells and casting thin section, scanning electron microscope and other comprehensive analyses of108samples, the types of petrology of Chang9oil-bearing layer of Yanchang Formation reservoir in this area are mainly gray medium-fine-grained lithic arkose sandstone and Follow by feldspathic sandtone and feldspathic lithic sandstone. The technical datas of core measurements and log interpretation showed that the reservoir have medium-low permeability. The overall reservoir physical property is bad because the space mainly includes primary remanent intergranular pores and intragranular dissolved pores. Statistics of mercury injection parameters show that the pore structure of reservoir is poor, which has the characteristics of mini pore throat and mediate sorting. Pore throat and physical parameters are related.Based on the study of sedimentary facies and reservoir characterices, the main controlling factors of reservoir was studied. The reservoirs were mainly controlled by the deposition, sandbody thickness and diagenesis. The sedimentary facies controlled distribution of reservoir sandbodies, and the compaction, cementation and dissolut controlled the pore structure and physical property. Reservoir sandstones of Chang9oil-bearing layer can be classified into four types. The most advantageous microfacies are distributary channels, underwater distributary channels and mouth bars of the shallow-water delta. The research on the characteristics of sandstone reservoir of shallow-water delta in Chang9oil-bearing layer will help further exploration and development in Longdong area.