延安南部地区山西组成岩作用特征研究

Study on the Diagenesis Characteristics of Shanxi Formation in the Southern Part of Yan’an Area

为明确延安南部地区山西组成岩作用类型及其特征,从建设性作用和破坏性作用两个角度对其进行了深入分析。研究表明:储层砂岩中杂基、长石、岩屑、碳酸盐、石英常发生了溶蚀作用,形成残余粒间孔、粒内溶孔、粒间溶孔等;压实作用使刚性颗粒发生破裂、塑性颗粒发生变形、碎屑颗粒接触紧密(线接触);储层砂岩普遍经历了强烈的压溶作用,表现在颗粒受压溶处的形态由点接触演化为线接触、凹凸接触和缝合接触;胶结作用主要包括盐酸盐胶结作用和硅质胶结作用,碳酸盐胶结物以方解石为主,少量菱铁矿、白云石充填在砂岩孔隙、裂缝、溶蚀孔隙内部。硅质强胶结使岩石致密、坚硬,孔隙结构遭到严重破坏,若有构造运动则易产生裂缝。

In order to clarify the types and characteristics of the diagenesis in Shanxi formation in the southern part of Yan ’an, an in-depth analysis on them was carried out from the perspectives of constructive action and destructive action. The results showed that the dissolution of heterobase, feldspar, detritus, carbonate and quartz occured frequently in the reservoir sandstone, and the residual intergranular pores and intragranular dissolved pores were formed in the reservoir sandstone. The compaction caused the rigid particles break, the plastic particles deform, and the clastic particles contact closely(line contact). The reservoir sandstone generally experienced strong pressure dissolution, and the morphology of the pressure dissolution of the particles evolved from point contact to line contact,concavo-convex contact and suture contact. Cementation mainly included carbonate cementation and siliceous cementation, carbonate cementation was dominated by calcite, and a small amount of siderite and dolomite was filled in the pores, cracks and dissolution pores of sandstone. The strong cementation of silica made the rock compact and hard, and the pore structure was seriously damaged.