Characteristics And Main Controlling Factors Of Ordovician Carbonate Rock Reservoir In Tazhong Area Of Tarim Basin

Tarim Basin is largest inland petroliferous basin in China.The forming,development mechanism,quality and spatial distributionof reservoir is one of the key factors to achieve the breakthrough of oil and gas exploration inTarim Basin.This article is mainly explore the geology and development factors of reservoir in deep carbonate rocks of Lower Ordovician in Tarim Basin through geology,geochemistry,geophysics,principles and methods.We also predicted good hydrocarbon accumulation area.It is importance of next oil exploration in Tarim basin.Different levels of sequence boundary has an important role in controlling the development of carbonate reservoir.We identified fourTrd level sequence in Yingshan group of Tazhong area.Supergene karstification under T₇⁴ interfaceis the most obvious in this formation.Advantageous area belt of weathering crust karst system is mainly distributed in karst surface monadnock,karst slope area and Karst Upland edge.High-frequency sequence interfaces lead cyclic carbonate exposure which formed karst multi period development section.The large unconformity surface corresponding sequence boundaries is the key to control of the carbonate karst reservoir in Tarim Basin.Carbonate sequence affected by the change of base level cycles is favorable location of karst reservoir.The comprehensive use of the structural stress field and the distribution of lithologic distribution of Yingshan formation in Tazhong area could make prediction of tectonic fracture.The tectonic fractures main high angle fracture in the strata are.Through rock mechanics experiment,we found that lithology of rock layers directly control the development degree of cracks in the carbonate reservoir.Based on the rock mechanics parameters of carbonate rocks in Yingshan formation,combined with the distribution of tensile stress and the Trd sequence,we predicted the favorable areas of fracture zone.The prediction results are in good agreement with the drilling results.The feasibility of this method is high.Permian magmatic activities have obvious effects on the carbonate reservoir.Porosity in the reservoir is defined by fractures and secondary pores and there is a notable increase in porosity of the carbonate reservoirs with proximity to magmatic intrusion,particularly about a certain distance from the intrusive rocks.The development of secondary pores was controlled by lithofacies and corrosion by various fluids.The formation of clay minerals such as illite and montmorillonite caused a decrease in porosity.In the condition of high temperature thermal diffusion,A large number of pore water and magmatic fluid mixed,this make local chemical field changed significantly.Hydrothermal convection system makethe corrosion and transformation in carbonate rocks.