1. No.10 Oil Production Plant of Changqing Oilfield Branch, PetroChina, Qingyang 745100, Gansu, China;
2. Key Laboratory of Sedimentary Basin and Oil and Gas Resources, Ministry of Land and Resources, Chengdu 610081, China;
3. Chengdu Center, China Geological Survey. Chengdu 610081, China

In this study, the authors discuss the diagenetic controlling factors on reservoir development of the Chang-8 section, Huaqing area, on the basis of systematic studies of petrology and reservoir properties, using mi-cro-area, in-situ isotope analysis, homogenization temperature measurement, X-ray diffraction mineral analysis, cathode luminescence observation and coupled with regular thin-section analysis. The results indicate that the early compaction exerting on the low-maturity sandstone of the study area results in dramatic primary porosity decrease. Wide occurrence of two-stage carbonate cementation largely decreases reservoir property, and thin-film chlorite does not protect primary porosity effectively, authigenic clay mineral cementation also contributes to porosity loss. The authigenic quartz filling in dissolution micropores or coating to particle surface causes porosity decrease at certain extent. Moreover, the dissolution of grains or cement does not occur widely due to lack of flowing pathways for dis-solving fluids, which is another major cause for low reservoir quality in the study area.