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碳酸盐岩的胶结作用直接和孔隙发育、油气分布以及成岩环境的恢复有着十分密切的关系。 桂西北地区二迭系碳酸盐岩的胶结作用类型,除了R·C·Lindholm所提出的纤维状——粒状和刃状——粒状两种外,还具有以下的四种类型:微粒状——粒状,纤维状——刃状——粒状,纤维状——柱状——粒状以及纤维状——泥晶——粒状,上述的胶结作用类型,可以归成两大类;即具有两个世代方解石的和有三个世代方解石的。不同的胶结作用类型反映了不同的成岩环境。 根据室内的鉴定,本区二迭系碳酸盐岩中发育多种储集空间类型,尤以原生的粒间孔隙为数最多。在那些亮晶方解石胶结的颗粒灰岩中,原生的粒间孔隙,有的高达33％,而绝大多数也不低于10％。但根据地表露头样品分析,已全部被方解石所胶结,几乎没有什么残留孔隙。大量的粒状亮晶方解石的沉淀充填,加上分散的白云石晶体和硅化作用,表明堵塞孔隙的成岩作用过程主要发生在地表下而不是原始沉积中。 碳酸盐岩的胶结作用过程是有时间间隔的,各不同世代晶体间的大小和结晶习性上的明显差异,本身证明它的沉积和成岩作用是不连续的。“渗流粉砂”的出现,介壳碎屑在压实时期破碎了,从破碎前后不同世代的胶结物分布特点以及不同剖面、不同世代贫铁和富铁方解石的出现等均能说明胶结作用过程的阶段性。油气生成、运移时期将与某一些阶段有着明显的联系,因而有效孔隙空间将是油气动移时的孔隙空间的总和。所以不仅要研究岩石的沉积环境,恢复沉积历史,而且还要注意尽可能地逐步恢复成岩作用及成岩以后的孔隙充填、溶解又充填的历史。
The cementation of carbonate rocks is directly related to pore development, oil and gas distribution and the restoration of diagenetic environments. The type of cementation of Permian carbonate rocks in northwestern Guangxi has the following four types in addition to the fiber-granule and blade-granule proposed by RC Lindholm: particulate- - Granular, fibrous - Blades - Granular, fibrous - Columnar - Granular and fibrous - Granular - Granular, the above types of cementation can be grouped into two broad categories; that is, Calcite and three generations of calcite. Different types of cementation reflect different diagenetic environments. According to the indoor identification, a variety of reservoir space types are developed in the Permian carbonate rocks in this area, especially the largest number of primary intergranular pores. In those luminescent calcite-bound grain limestones, native intergranular pores, some as high as 33%, the vast majority are not less than 10%. However, according to the analysis of the surface outcrop samples, all of them have been cemented by calcite, with almost no residual pores. A large number of granular bright calcite precipitation, coupled with the dispersion of dolomite crystals and silicification, indicating that the plugging pore diagenesis mainly occurs in the subsurface rather than the original deposition. The cementation of carbonate rocks is time-spaced, with significant differences in size and crystallinity between different generations of crystals, evidenced by their discontinuity in sedimentation and diagenesis. The appearance of “seepage silt”, crust crust crushed in the compaction period, the cementation characteristics of different generations before and after crushing and the occurrence of different profiles, different generations of iron deficiency and iron-rich calcite can explain the cementation process Phased. The period of oil and gas generation and migration will be obviously linked with some stages, so the effective pore space will be the sum of the pore space when the oil and gas move. Therefore, it is not only necessary to study the sedimentary environment of the rock and restore the sedimentary history, but also pay attention to gradually recovering the diagenesis and the history of pore filling, dissolution and filling after diagenesis as much as possible.