Abstract: The sandstone reservoirs are broadly found in south area in western Qaidam basin, in which existing diagenetic phenomena such as the secondary outgrowth of quartz and the replacement of calcite, dolomite and anhydrite are of great effects on the reservoir petrophysical property. This paper presents the effects of the secondary outgrowth pattern and the replacement intensity on the reservoir petrophysical property. The study shows that the deep strata in Wunan-Lvcaotan area are of developed quartz secondary outgrowth, where the reservoir property is poor; while the replacement of calcite, dolomite and anhydrite reaches strong or extremely strong, the property becomes poor obviously.

Key words: Qaidam basin, secondary outgrowth, replacement, reservoir, petrophysical property