摘要
<span id="EnChDivSummary" name="EnDivSummary">The lower interval of Oligocene Xiaganchaigou Formation is an important prospecting object in the central areas of northern Qaidam Basin.Finding out the factors controlling the reservoir property is prospecting basis.Based on the normal thin sections,cast thin sections and drilling data,the rocks characteristics of No.7 Lenghu and Nanbaxian structure were analyzed in this paper.Study shows that the mixed deposits such as terrigenous clastic,carbonate and anhydrite are found very common in this area.But because of different salinity,the content of anhydrite is high in shore shallow lake facies peperite of No.7 Lenghu structure.Particles are mainly base type cementation.The salinity of Nanbaxian structure located in delta front facies belt is lower because of the great amounts of water input by the rivers and there is little anhydrite in peperite.Particles are mainly pore type-base type calcium cementation.The initial porosity in Nanbaxian is much higher than that of No.7 Lenghu,which is in favour of the later dissolution of acidic fluid.Because the initial porosity and pore throat evolution model for two types of peperites are different,there is great difference in the oil and gas abundance of two areas.span>