榆林气田山西组2段砂岩成岩作用及孔隙演化

DIAGENESIS AND POROSITY EVOLUTION OF THE SANDSTONE OF MEMBER 2 IN SHANXI FORMATION,YULIN GASFIELD

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。

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 quartzose sandstone and little lithic sandstone,The reservoir sandstone is typical of low porosity and low permeability.This article was based on core observation,and use thin section observation,scanning transmission electron microscope observation,cathodoluminesconce and physical property,takes research and analysis,indicates that the sandstone of member 2 in Shanxi formation in Yulin gasfield went through the compaction,cementation,metasomasis,solution and fillition of clayimpurity during the diagenesis,and now it is in the late diagenesis stage. The porosity of the reservoir sandstone of member 2 in Shanxi formation,its statistical porosity composition being protogenetic intergranular remainder porosity of 44.7%,secondary porosity of 55.3%,which indicates that the diagenesis has the greatest effects in control of the physical property in this aera.The porosity evolution experienced the destruction of protogenetic porosity,the constitution of secondary and the destruction of secondary pore.In that,the compaction and the cemetation were play of mainly destruction,the solution was paly of construction.