Abstract: With the development of petroleum exploration and exploitation，the proportion of deeply buried tight siliciclastic
reservoirs is increasing significantly. The key to successful exploration in tight siliciclastic reservoirs is usually to find the
growing law of the efficient reservoirs. However，there is a close relationship between formation mechanism and diagenetic
clay minerals. Kaolinite，chlorite，mixed-layer illite-smectite and illite are common clay minerals in tight siliciclastic reservoirs.
Formation mechanism and distribution of clay minerals can be studied by thin section，SEM and BSE，with consideration of
sedimentary facies and sequence stratigraphy. The results show that formation of clay minerals are influenced by framework
grains composition，climate，depositional environment，temperature，and so on. Clay minerals formed in early diagenesis
can be controlled by sea level changes，however，which can influence late diagenetic clay minerals. Formation mechanism
and distribution of clay minerals of deeply buried tight siliciclastic reservoirs can be predicted by integrating framework grain
composition，depositional setting and sequence stratigraphic study.

Key words: siliciclastic rocks, tight reservoirs, diagenesis, clay minerals, kaolinite, chlorite