Abstract:

The types of reservoir and secondary pores of Lower Cretaceous in Tanzhuang sag were studied on the basis of core observation, thin section analysis, statistics and analysis of core porosity and permeability. The results show that the clastic rocks of Lower Cretaceous in Tanzhuang sag have undergone early and middle diagenetic stages and the present diagenetic stage  is at a period of the middle A stage. Primary and secondary pores developed in sandstone, which evolved from primary to secondary pores, pore evolution levels and diagenetic stages have different characteristic in different wells blocks. There are three secondary pore zones developed of Lower Cretaceous in the study area, secondary pore closely related to the dissolution of feldspar, debris, quartz, the dehydration of clay minerals and the filling of oil and gas, which has different reasons in different wells and depth，and the dissolution of feldspar, debris were the mainly cause, quartz and clay of interparticles mixed base were followed.

Key words: southern North China basin, Tanzhuang sag, Lower Cretaceous, reservoirs, secondary porosity