Research On Tight Oil Enrichment Regularity Of Chang 9 In Huanxian-Zhengning Area

This paper investigates the chang 9 oil-bearing Intervals of the sriassic YanChang formation in Huanxian-Zhengning area,using SEM,cathodoluminescence,and casting thin-section analysis,discussed it from four aspects,Such as field profiles,well core,log informations and sample tests,mainly studied sedimentary system,reservoir characters and main controlling factors of hydrocarbon accumulation.Based on the above jobs,this paper made the following results and understanding:1.The sedimentary systems of chang 9 of Huanxian-Zhengning area is delta deposition,mainly develops delta front facies.2.The rock types of Chang 9 in this region are mostly lithic feldspathic sandstone.The Chang 9 reservoir types include both low permeability reservoirs and tight reservoirs.The porosity distribution range is 0.32%~20.8%,the average value is 10.47%,.The permeability distribution range is 0.001mD~261.71 mD,the average value is 3.2mD.The pore types include residual intergranular pores and feldspathic intragranular dissolved pores.Compaction,cementation,metasomatism and denudation are the dominant diagenesis in the study area.3.This paper focuses on the research of the controlling factors of hydrocarbon accumulation in Huanxian-Zhengning area.The control effect of local structure on oil and water distribution is weak;Oil source characteristics control the distribution of oil and gas,firstly,Chang9 reservoir filling degree is not high?oil shortage;Second,the study area Chang 7 reservoir source rocks Hydrocarbon-generation strength is mainly distributed in(100-500)×104t/km2?The main hydrocarbon source rocks in Chang 7;Chang 9 reservoir is located in the lower,Chang 7 reservoir hydrocarbon source rocks generated oil downward migration through the Chang 8 reservoir into Chang 9 reservoir;Chang 7 hydrocarbon source rocks control the generation and distribution of Chang 9 reservoir.The combination of reservoir and caprock controls the gas distribution;The lithology combination of Chang8 sandstone and mudstone?the ratio of sand and formation in Chang 8 control the downward movement and distribution of oil.