Current researches about the evolution process of diagenesis-porosity

the burial-thermal history

and the hydrocarbon charging history of tight sandstone reservoirs are still in a static stage in China.Apparently

less attention has been paid to the relevance between hydrocarbon charging and tightening process caused by the petrological components of sandstones and its differential diagenetic evolution process.In order to better understanding the dynamic evolution history of burial-diagenesis-hydrocarbon charging-porosity of tight sandstone

samples from the 8

th

Member of Xiashihezi Formation (He8) of the Upper Paleozoic in eastern Ordos Basin were studied in detail through the identification and quantitative statistics of cast sections

together with various analysis methods such as SEM

CL

homogenization temperature and chemical composition of fluid inclusions etc.Furthermore

the differences of the timing of densification process and hydrocarbon charging among different sandstone layers were discussed.The results indicate that the diagenesis-hydrocarbon charging evolution processes of both the calcium-cemented sandstone and high plastic lithic sandstone are relatively simple.The former became tightened after carbonate cementation in the stage A of middle diagenesis phase

which confirms that hydrocarbon charging was early than tightening; while the latter became tightened after compaction in the early diagenetic stage

which confirms that tightening occurred before hydrocarbon charging.In contrast

the quartz sandstone and lithic quartz sandstone are complicated in diagenetic-charging evolution process and their tighenging and hydrocarbon charging synchronous.