Study On The Characteristics Of Chang 7 Dense Reservoir In Hebi Area Of ​​Ordos Basin

The chang7formation of Ordos basin was regarded as source rock previously; with the increase of exploration and improvement of technology in recent years, a variety of industrial oil wells are found in chang7formation of Heshui area, and the reservoir permeability are generally less than0.3mD, which belong to typical tight oil. Therefore, it is very important to strengthen the study of reservoir characteristics in the area.Taking the petroleum geology, reservoir geology, ore geology, logging geology and other advanced theories and methods as the guidance, on the basis of core observation description, combining with the logging data, the thesis research the distribution characteristics of different sand body; by using casting thin sections, scanning electron microscope, mercury injection and other advanced testing means, the thesis analyze systematically reservoir property characteristics, diagenesis, main control factors and the relation between reservoir property and oil-bearing in the chang7formation of study area, and obtain the following conclusions.The scale of sand body is controlled by sedimentary microfacies, along the provenance the sand body is relatively thick and the connectivity is better; at the vertical provenance direction the sand body is relatively thin and the connectivity is poor.The lithology in study area is mainly feldspar lithic sandstone and lithic feldspar sandstone, the clastic particle size is smaller and sorting is medium, and roundness is mainly subangular. The chang7reservoir property is relatively poor on the whole, which have characteristics of chang71reservoir property is best, chang72is better, chang73is worst. The pore types are mainly intergranular pore, dissolved pore and micropore, the throat is relatively small, the distribution characteristics of throat have an important impact on reservoir permeability.Thediagenesis in study area are mainly occurred in the late diagenetic stage A, the types of diagenesis are mainly compaction, dissolution, illite cementation, carbonate cenmentation and chlorite cementation. The most favorable diageneticfacies in study area are cementation-micropore and intergranular pore phase and dissolution-dissolved pore and micropore phase.Deposition, diagenesis and tectonization play an important controlling role on reservoir. The diagenesis in study area are mainly occurred in the late diagenetic stage A, compaction and pressure solution make the reservoir become more tight. The pores are filled by chlorite, illite and carbonate cement, and the reservoir property is greatly decreased, but chlorite membrane on the surface of particles increase particle compaction resistance, which plays an important role in the original reservoir protection. Dissolution and tectonic microfracture have great impact on the improvement of reservoir space and seepage ability. Therefore, the content of interstitial material, content of quartz, sorting, dissolution and degree of fracture development play an important controlling role in formation of local relatively high permeability reservoir.Not only the reservoir property has an important influence on reservoir oil-bearing, but also has good correlation with production capacity of reservoir. The reservoir property is better, the production is higher. So the reservoir property has great impact on hydrocarbon accumulation.On the basis of the above analysis, in combination with the actual situation of study area, the reservoir in the study area are divided into four classes, class Ⅰ and class Ⅱ reservoirs are the good reservoir of study area, which are favorable for hydrocarbon enrichment; class Ⅲ and class IV reservoirs are the poor reservoir of study area, which are not favorable for hydrocarbon enrichment.