| On basis of regional geological data and relevant literature information,this paper is guided by fundamental theories and techniques of sedimentology,reservoir geology,petroleum geology,and supported by core,mud logging,logging data etc.By utilizing the lab analysis and assay data of microscopic thin section,grading analysis,SEM,X-ray diffraction and mercury injection experiment,this paper researched the petrologic characteristics,pore structure characteristics,physical characteristics,diagenesis characteristics of study area reservoir.Combined with depositional microfacies and reservoir essential features,the paper ultimately conducted reservoir classification and favorable zone prediction.The reservoir research shows that the rock type is mainly lithic feldspathic sandstone,followed by feldspathic lithic sandstone.The particle sorting of reservoir ranges from medium to preferable,while the psephicity ranks from sub-angular to sub-rounded,among which the sub-rounded is the majority.The primary contact form between particles is point-line,while the particles are supported by each other.The form of cementation is contact-type.The reservoir space is mainly secondary pore,with general existed intragranular dissolved pores.The diagenesis and sedimentary facies are the dominant factors to affect the reservoir physical property.The pore structure is mainly micro pore and micro throat,while micro pore and thin throat is developed locally.The diagenesis types of target stratum include compaction(pressolution),replacement,cementation,dissolution,and the reservoir is situated in the late diagenetic stages.On this basis,this paper conducted classification of reservoir.The Chang 8 reservoir of Yanchang Formation mainly develops II type reservoir,while I type reservoirs are less developed and III type reservoirs are least.In the Chang 8~1 reservoir,there are more I type reservoirs,while II type reservoirs are mainly developed in the Chang 8~2 reservoir. |
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