碎屑岩储层碳酸盐胶结物成因研究进展

Research status of the genesis of carbonate cementation in clastic reservoirs

在对国内外相关文献充分调研的基础上,对碎屑岩储层碳酸盐胶结物的基本特征、物质来源、成因机制进行系统梳理和论述,总结了不同机制下碳酸盐胶结物的分布规律,并强调了几个需要注意的问题。碳酸盐胶结物具有多类型、多期次和多种分布形式的特征,其物质来源可分为内源和外源2种类型。碳酸盐胶结物可以由砂泥岩协同成岩作用、蒸发作用、生物碎屑溶解再沉淀作用、沉积速率控制作用、热对流作用、深部热流体作用等机制形成。在陆相碎屑岩储层中,砂泥岩协同成岩作用是形成碳酸盐胶结的最重要机制;但在海陆过渡相—海相地层中,除了砂泥岩协同成岩作用外,生物碎屑溶解再沉淀作用、沉积速率控制作用也是重要的碳酸盐胶结物形成机制。不同成因机制下形成的碳酸盐胶结物的矿物类型及特征、控制因素和分布规律存在差异。碳酸盐胶结物成因分析应注意利用δ13C值判断物质来源的不确定性;应重视层序地层和沉积环境在海陆过渡相—海相地层中对碳酸盐胶结的作用;应注意相同的矿物类型(如"铁白云石")或相似的分布特征(如"顶钙")成因的多解性。

On the basis of a thorough review of the up-to-date relevant literatures, the characteristics, material sources,and genetic mechanisms of carbonate cements in clastic reservoirs are systematically examined and discussed;the distribution laws under different mechanisms are summarized;and several issues that should be paid attention to are emphasized. Carbonate cements in clastic reservoirs are characterized by multiple mineral types, multiple formation phases and heterogeneous distribution. The material sources of carbonate cements include both endogenous and exogenous sources. Carbonate cements in clastic reservoirs can be formed by the synergistic diagenesis of sandstones and mudstones, evaporation, bioclast dissolution and re-precipitation, sedimentation rate controlling effect, thermal convection, deep hydrothermal fluid intrusion and other mechanisms. In the continental clastic reservoirs, the synergistic diagenesis of sandstones and mudstones is one of the most important mechanisms for the formation of carbonate cementation. But in marine-transitional strata, bioclastic dissolution and re-precipitation and sedimentation rate controlling effect are also important mechanisms for the formation of carbonate cementation besides the synergistic diagenesis of sandstones and mudstones. The mineral types and characteristics, controlling factors and distribution laws of carbonate cements under different mechanisms can vary significantly. Given the current status in carbonate cementation in clastic reservoirs, it is emphasized that particular attention needs to be paid to the uncertainty of the material sources proxied by δ13 Cvalue, the effect of high-frequency sequence stratigraphy and sedimentary environments on carbonate cementation in the transitional depositional settings and marine facies, and the non-unique interpretation of the origin of the same mineral type(such as "ankerite") or the same distribution(such as "top carbonate cementation layers") when it comes to determine the genesis of carbonate cements.