Study On The Characteristics And Main Control Factors Of Chang6 Reservoirs Of Wuqi Area In Ordos Basin

The Chang 6 reservoir of Wuqi area in Ordos Basin is rich in oil and gas resources.The exploration and development practice over the years has shown that ultra-low permeabilitytight reservoirs are relatively developed.Pore-throat structure directly affects the quality and recovery degree of the reservoir.Therefore,it is of great scientific significance for further exploration to clarify the micro-geological characteristics,fluid flow capacity,and the main influencing factors of high-quality reservoirs.Based on the cores,the cast thin section and scanning electron microscope techniques have been used to study the basic geological characteristics.The pore throat quality and the fluid flow capacity also have been comprehensively analyzed by combining the physical property test,mercury injection experimental,nuclear magnetic resonance test and oil-water phase infiltration.The main control factors and the classification of the reservoir has been studied.The analysis results show that the sedimentary facie in the area is delta front facie,and the oil-enriched sandstones are mainly distributed in underwater distributary channels and mouth bar in the delta front.Feldspar sandstone and lithic feldspar sandstone are the main rock types.The interstitial material mainly consisted of matrix and cements,with an average of 21.05 %.Ultra-low permeability and extra-low permeability reservoirs with poor physical properties.The main reservoir space of oil and gas is the combination of intergranular pores and dissolved pores,and the average total face rate is 3.05%.The curves of high pressure mercury injection can be classified into 4 categories,and the maximum pore throat radius from 1 to 4 categories is respectively 2.5?m,1.56?m,0.78?m and 0.48?m.The constant rate mercury injection experiment shows that the throat radius of different samples is greatly different,and the overall heterogeneity of pore throat is strong.The size of throat directly affects the fluid flow capacity.The difference of pore throat structure is also an important factor affecting the occurrence of movable fluid in the reservoir.According to the parameters of oil-water movement obtained from the relative permeability curve,the percolation capacity is divided into 4 categories,and the corresponding displacement efficiency becomes worse in turn.Four factors,sedimentary process,diagenesis,micro pore throat structure and micro fracture,play an important role in controlling reservoir physical properties.Finally,the reservoir is classified and evaluated reasonably,which provides scientific suggestions for later oilfield development.