南堡凹陷成岩场及其对下第三系储层成岩格架的控制

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

成岩场分析对区域储层预测和评价具有快速、有效的指南作用。南堡凹陷(陆上部分)下第三系由于高柳断裂而分割成两个二级断块。断裂上升盘(高柳地区)具有二次埋藏和相应的二次无机—有机成岩过程,发育中深部(2700～3450m)异常高压,同时局部存在大气水明显的淡化改造;下降盘(北堡老爷庙)则以持续深埋藏为特征,具有存在深部(>3400m)热流体活动和异常高压囊的条件。本文据此讨论了成岩场及沉积物分异对下第三系储层成岩格架及成岩序列的控制机理,定量—半定量预测了断裂两盘成岩带埋藏深度的差异。

Diagenetic field analysis have rapid and valid guide significance for regional reservoir prediction and evaluation.The Nanpu depression (continental area) is separated into two grade-2 fault blocks.The updip block(Gaoshanpu-Liuzhan) have undergone two times of inorganic-organic diagenesis processes,in relation to two times of evident subsidence burial,and is characterized by abnormal high pressure(compartment) in intermediated-deep burial(2700～3450m),as well as indirect freshening alteration in the shallow part resulted from meteoric infiltration.On the other hand,the downthrown block(Beipu-Laoyiemiao) is characterized by continual subsidence burial,which provided available conditions for thermo-fluid flow and related abnormal high pressure compartment development in deep burial part(> 3400m). The diagenetic field separation between the two fault blocks has important controls on reservoir diagenesis framework and sequences of the Lower Tertiary,in which some relations are discussed and applied to quantitative and semi-quantitative prediction of burial depths of reservoir diagenesis belts in the blocks.It was found that reservoir burial depth in the downthrown block is generally 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 assemblage in the Gaoshanpu and carbonate illite-quartz authigenetic assemblage in the Beipu,were related to cation-rich and cation-poor types of primary sediment and pore water chemistry,respectively.