陕北子长长4+5砂岩储层成岩作用及孔隙演化

Reservoir diagenesis and pore evolution of Chang 4+5 of Yangchang formation in Shaanbei Zichang Area

目的探讨鄂尔多斯盆地子长地区长4+5储层的成岩作用特征、孔隙演化及其分布与变化规律。方法运用岩石薄片、铸体薄片、扫描电镜、X衍射等资料对储层进行分析研究。结果该区储层砂体主要为长石砂岩,具有成分成熟度低、结构成熟度高的特点,储层砂岩的成岩处于中成岩A期;压实作用、碳酸盐胶结作用是使物性变差和孔隙度降低的主要原因,而溶蚀作用,特别是长石的溶蚀是储层物性变好的重要成岩控制因素。结论长4+5段储层砂岩为典型的低孔低渗储集岩,成岩作用对本区砂岩储层孔隙演化起着重要的控制作用。

Aim To study the diagenesis,pore evolution,distribution and variation of Chang 4＋5 reservoir of Zichang Area in Ordos Basin.Methods To analyze the reservoirs by using the analysis of casting lamella,scan electron microscope and x-ray diffractions.Results Feldspar sand stone is the main sandstone type,with low composition maturation and high fabric maturation,diagenesis reaches A-period of middle diagenesis stage.Compaction and carbonate cementation are the main causes for bad reservoirs and porosity losses.Physical properties of sandstone reservoirs can be improved especially by dissolution of feldspar.Conclusion Chang 4＋5 is the typical low porosity and low permeability sandstone reservoir,diagenesis is an important power of controlling the pore evolution of this area.