鄂尔多斯盆地正宁地区延长组长6、长8砂岩储层成岩作用特征

鄂尔多斯盆地正宁地区主要储集岩——三叠系延长组长6、长8砂岩，是典型的低孔低渗储集岩，具有粒径细、成分成熟度低、磨圆度较差、分选性差的特点。运用铸体薄片、X衍射、电镜扫描、镜质体反射率测定及物性分析等资料，研究了延长组长6、长8段的成岩作用特征，分析了它们对储层物性的影响状况，确定了储层砂岩的成岩作用阶段．成岩阶段普遍达到晚成岩A期；成岩作用对本区砂岩储层孔隙演化起着重要的控制作用，成岩早期浅埋藏阶段的机械压实作用和成岩晚期的铁方解石和铁白云石胶结作用是储层孔隙度降低和物性变差的主要原因。

Reservoir Diagenesis of Chang 6-8 in Yangchang Formation of Zhengning Area in Ordos Basin

Reservoir sandstone of chang 6 and chang 8 in Yanchang Formation of Zhengning area in Ordos basin is typical of low porosity and low permeability, which has the characteristics of fine grain size, low compositional maturity, poor roundness and sorting. Based on casting slice identification of sandstone, scanelectron microscope, X-ray diffraction, reflection of vitrinite and physical property, we studied diagenetic characteristics of Yanchang Formation chang 6 and chang 8, analyszed their effect on reservoir physical property, and determined diagenetic stage of reservoir sandstone, diagenetic stage of reservoir sandstone is mainly the late diagenetic phase A. Our study shows that mechanical compaction and late cement of carbonate are the main factor causing the loss of porosity and reducing the reservoir quality of the sandstones.