榆林气田主力气层山西组2段为一套辫状河三角洲沉积,储集岩主要为石英砂岩、岩屑石英砂岩。该储层砂岩是典型的低孔低渗储集岩。以岩芯观察为基础,结合对薄片鉴定、扫描电镜、阴极发光和物性等资料分析后认为,榆林气田山西组2段砂岩经历了压实作用、胶结作用、交代作用、溶解作用和粘土杂基的充填作用等多种成岩作用,目前已达到了晚成岩阶段A期。山2 段储集砂岩孔隙中,原生粒间残余孔隙占44.7% ,各类次生孔隙占5 5 .3% ,可见成岩作用是控制该区储层物性特征的一个关键因素。孔隙演化经历了原生孔隙的破坏、次生孔隙的形成和次生孔隙的破坏3个阶段,其中压实、胶结作用起主要破坏性作用,溶解作用起建设性作用.

Member 2 in Shanxi formation of Permian system in Yulin  gasfield is the mainly gas reservoir,was deposited in a braided river of delta  enviroment.The reservoir sandstone mainly is quartzose sandstone, lithic quartzo se sandstone and little lithic sandstone,The reservoir sandstone is typical of l ow porosity and low permeability.This article was based on core observation,and  use thin section observation,scanning transmission electron microscope observati on,cathodoluminesconce and physical property,takes research and analysis,indicat es that the sandstone of member 2 in Shanxi formation in Yulin gasfield went thr ough the compaction,cementation,metasomasis,solution and fillition of clayimpuri ty during the diagenesis,and now it is in the late diagenesis stage. The porosit y of the reservoir sandstone of member 2 in Shanxi formation,its statistical por osity composition being protogenetic intergranular remainder porosity of 44.7%,s econdary porosity of 55.3%,which indicates that the diagenesis has the greatest.