致密砂岩储层差异性成岩演化对孔隙度演化定量表征的影响——以鄂尔多斯盆地华庆地区长6_3储层为例

Quantitative calculation of tight sandstone reservoir porosity evolution based on different diagenesis:A case study of Chang 6_3 reservoir in Huaqing area,Ordos Basin

基于鄂尔多斯盆地华庆地区长63致密砂岩储层三角洲前缘及半深湖的稳定沉积特征,按照碎屑岩成岩演化特征或地质综合效应,建立与孔隙度对应的模拟方程。采用铸体薄片及扫描电镜描述岩石的矿物组分及孔隙类型;图像粒度获取碎屑颗粒的结构特征及分选性;沉积微相、测井、样品取样点常规物性及深度分析获取沉积环境、埋藏深度、物性;同时测试古温度、镜质组反射率、最高热解温度、黏土矿物等数据,开展成岩作用、孔隙演化、相对高渗成因的研究;结合研究区埋藏史研究,为致密砂岩储层油气勘探开发提供理论参考。4类典型样品分析结果表明,目的层主要属于压实型成岩改造类型,差异性成岩演化过程是导致储层物性不同和孔隙结构差异的根本原因。

The Chang 63 tight sandstone reservoirs in Huaqing area of the Ordos Basin was deposited in delta front and stable,semi-deep lake environments. A simulation equation corresponding to porosity was established according to the characteristics of diagenetic evolution or the comprehensive geological effect of a clastic reservoir. Mineral components and porosity types were described by using casting thin section and SEM analyses. Granularity images were applied to get the structural characteristics and sorting features of clastic particles. Sedimentary microfacies,well logging,normal physical characteristics and depth analyses were applied to determine the depositional environment,burial depth and physical characteristics. Simultaneously,we tested paleotemperature,vitrinite reflectance,the highest pyrolysis temperature and clay minerals to study diagenesis,porosity evolution and relatively high permeability formation. Burial history analysis of the study area provided a theoretical reference for oil-and-gas exploration and development of tight sandstone reservoirs. According to the analysis of four typical samples,we considered that the properties were mainly controlled by compaction,and differentiated diagenetic evolution was the root cause that led to different physical characteristics and porosity structures.