碎屑岩成岩作用及其对储层的影响--以鄂尔多斯盆地镇泾地区为例

Clastic rock diagenesis and its influence on reservoirs:A case study of Zhenjing area in the Ordos Basin

基于岩心观察、铸体薄片、扫描电镜、阴极发光等测试,对鄂尔多斯盆地镇泾地区延长组储层开展了成岩作用类型、成岩序列等研究。结果表明:(1)溶蚀孔的形成不仅有长石溶蚀的贡献,而且还有长石蚀变形成沸石的二次溶蚀贡献;微裂缝的形成是石英在强烈压实作用下导致的硅质微碎裂;晶间孔和粒间孔的形成与成岩早期形成的白云石抑制压实作用的进行密切相关;(2)早期形成的绿泥石膜,因成岩环境的改变,脱出大量的铁和镁离子,并在水解溶蚀作用下与絮凝胶体形成叶片状绿泥石,封堵孔隙;(3)镇泾地区成岩序列演化特征揭示,早期碳酸盐胶结物自形程度比较高;绿泥石膜是成岩初期的产物,第二期绿泥石多呈叶片状产出;早期浊沸石交代斜长石,在后期的溶蚀改造为储层提供了较好的储集空间;长石溶蚀形成书页状高岭石。

The diagenetic types and diagenetic sequences of the Yanchang Formation in Zhenjing area of the Ordos Basin were studied based on core observation, casting thin section, scanning electron microscopy and catho-doluminescence. （1） Dissolution pores were not only from feldspar dissolution, but also the secondary dissolution of the feldspar alteration to form zeolite. Microfractures are siliceous microcracks caused by the strong compaction of quartz. The formation of intracrystalline pores and intergranular pores was closely related to the inhibition of compaction by dolomite formed early in diagenesis. （2） Due to the change of diagenetic environment, the early formed chlorite membranes released a large number of iron and magnesium ions, forming leaf-like chlorites during hydrolytic dissolution, which blocked pores. （3） The evolution characteristics of the diagenetic sequence in Zhenjing area reveal that the early carbonate cement has a high degree of self-formation. Chlorite membranes are the products of initial diagenesis, and leaf-like chlorites generated during the secondary diagenesis. Zeolites replaced plagioclases during the early phase, and then, the dissolution of zeolites provided better reservoir space. Feldspar dissolution yielded page-like kaolinites.