Diagenetic Fields and Their Controls on Reservoir Diagenesis Framework of Lower Tertiary, Nanpu Depression, North China

Key words: 
• diagenetic field /
• diagenesis framework /
• reservoir /
• Nanpu depression

Abstract: Diagenetic field analysis have rapid and valid guide significance for regional reservoir prediction and evaluation. The Nanpu de-pression (continental area) is separated into two grade-2 fault blocks. The upbip block (Gaoshanpu-Liuzhan) have undergone twotimes of inorganic-organic diagenesis processes, in relation to two times of evident subsidence burial, and is characterized by abnor-coal high pressure ( compartment) in intermediated-deep burial ( 2700~3450m), as well as indirect freshening alteration in theshallow part resulted from meteoric infiltration. On the other hand, the downthrown block (Beipu-Laoyiemiao) is characterized bycontinual subsidence burial, which provided available conditions for thermo-fluid flow and related abnormal high pressure compart-went development in deep burial part(> 3400m). The diagenetic field separation between the two fault blocks has important controls on reservoir diagenesis framework and se-quences of the Lower Tertiary, in which some relations are discussed and applied to quantitative and semi-quantitative prediction ofburial depths of reservoir diagenesis belts in the blocks. It was found that reservoir burial depth in the downthrown block is gener-ally 200~500m larger than one in the updip block for the same diagenesis belt. In addition, it is also discussed that diagenetic sequences, characterized by chlorite-carbonate-analcime authigenetic assemblagein the Gaoshanpu and carbonate illite-quartz authigenetic assemblage in the Beipu, were related to cation-rich and cation-poor typesof primary sediment and pore water chemistry, respectively.