The Microscopic Heterogeneity Of Chang 8₁ Reservoir In Xi-feng Area

The Xifeng oilfield in the Ordos Basin is the largest integrated oil and gas field discovered in China in the past decade.The Chang-8 reservoir is a typical tight sandstone reservoir.In this paper,through the reservoir rock characteristics,micro-pore throat characteristics,seepage characteristics,etc.of the Chang 8₁ reservoir,the methods and techniques of casting thin section,core analysis,mercury intrusion technology,and water flooding infiltration experiments are applied to the chief of the study area.The microscopic heterogeneity of reservoir8₁ was studied and the following knowledge was obtained:The reservoir of the Chang 8₁ reservoir in the study area is a delta front sub-facies deposit.The reservoir rocks are mainly characterized by gray-light gray powder-fine lithic feldspar sandstone,feldspathic lithic sandstone,and fine-grained grain size.Fine-fine-grained sandstone,followed by fine-grained,medium-grained,unequal-grained;fine-grained sandstone content of 54.20%,very fine sandstone content of 40.25%;sandstone compositional maturity is low,sorting,etc.-good;The degree is mainly sub-angular,accounting for 82.9%,and the particle contact mode is point-line contact and line contact.Higher levels of heterojunctions and cements.The content of interstitials was 16.06%,clay minerals were6.62%,carbonate cements accounted for 5.95%,siliceouss accounted for 1.37%;pore types were intergranular pores 73%,feldspar dissolved holes 23%,rock cuttings 4%;diagenesis is mainly compaction and pressure dissolution,followed by cementation and dissolution.The micro-characteristics of pore throat,the average pore radius is 56um,and the throat radius is less than 0.6um.The pore throat distribution is generally good,the pore throat distribution is uniform,and the throat type is mainly flake or curved throat.The constant rate mercury injection experiment shows that the smaller the permeability,the narrower the throat radius distribution and the smaller the peak value.On the contrary,the larger the permeability,the wider the throat radius distribution range and the larger the peak value.All the Chang8₁ reservoirs in the study area reflected by the NMR experiments belong to the medium reservoirs,and there are also a few good reservoirs.