地质力学学报2025，Vol.31Issue(4)：704-719,16.DOI:10.12090/j.issn.1006-6616.2025054
鄂尔多斯盆地延川东地区本溪组储层特征与成岩过程
Reservoir characteristics and diagenetic processes of the Benxi Formation in the East Yanchuan Block,Ordos Basin
摘要
Abstract
[Objective]The Benxi Formation in the East Yanchuan Block of the southeastern Ordos Basin has emerged as a significant exploration target for tight gas reservoirs.Despite its strategic importance,the sandstone reservoirs in this interval are typically characterized by low porosity,poor permeability,strong heterogeneity,and complex diagenetic histories.These characteristics limit their development potential and make accurate reservoir prediction challenging.This study aims to thoroughly investigate the reservoir characteristics and diagenetic evolution of the Benxi Formation sandstones,with the goal of clarifying how multi-stage diagenetic processes control pore evolution and reservoir quality differentiation.[Methods]An integrated analytical approach was applied,including casting thin section petrography,scanning electron microscopy(SEM),and high-pressure mercury intrusion(HPMI).These techniques were used to examine pore types,mineral assemblages,diagenetic alterations,and pore-throat distributions,allowing for a detailed reconstruction of the diagenetic evolution and its influence on petrophysical properties.[Results]The study reveals:(1)The Benxi Formation sandstones have undergone a multi-stage diagenetic evolution involving three principal phases:mechanical compaction,cementation enhancement,and dissolution modification.Each stage had a distinct influence on the pore structure and reservoir performance.(2)Quartz-rich sandstones showed relatively high resistance to mechanical compaction but experienced substantial porosity loss during the middle diagenetic stage due to the pervasive precipitation of quartz and carbonate cements.This stage led to the formation of a rigid framework,where the intergranular pores were severely occluded,significantly reducing effective porosity and permeability.(3)Lithic quartz sandstones exhibited a much more favorable diagenetic trajectory.These rocks experienced strong dissolution of unstable components,such as feldspar and lithic fragments,resulting in the formation of secondary intragranular and intergranular pores.This process markedly improved pore connectivity and storage capacity,making this lithofacies the most favorable for tight gas accumulation.(4)Lithic sandstones suffered from intense early-stage compaction and cementation,which drastically reduced both primary and secondary porosity.As a result,these rocks exhibit extremely poor reservoir quality and are considered the least favorable reservoir type.(5)Based on the observed differences in diagenetic intensity and pore evolution characteristics,four distinct diagenetic facies types were identified.[Conclusion](1)The reservoir quality of the Benxi Formation sandstones is primarily controlled by the intensity and sequence of compaction,cementation,and dissolution.(2)Different mineral compositions lead to divergent diagenetic pathways and contrasting pore evolution patterns.(3)Lithic quartz sandstones hold the highest potential due to extensive dissolution,while quartz sandstones are more susceptible to cementation.(4)Lithic sandstones,dominated by early-stage densification,represent poor-quality reservoirs.(5)The proposed four-type diagenetic facies framework effectively reflects the reservoir heterogeneity and offers practical criteria for facies-based reservoir prediction.[Significance]This study advances the understanding of diagenetic control on pore structure in tight sandstone reservoirs and provides a robust geological foundation for classifying and predicting reservoirs and targeting sweet spots in future exploration efforts.关键词
致密砂岩/成岩作用/成岩相/本溪组/鄂尔多斯盆地Key words
tight sandstone/diagenesis/diagenetic facies/Benxi Formation/Ordos Basin分类
能源科技引用本文复制引用
高雅宁,张少华,于淼,高其宇,郭海洋,张龙..鄂尔多斯盆地延川东地区本溪组储层特征与成岩过程[J].地质力学学报,2025,31(4):704-719,16.基金项目
国家自然科学基金项目(42102128) （42102128）
陕西延长石油集团科研项目(KTKTB0822SFW0032) This research is financially supported by the National Natural Science Foundation of China(Grant No.42102128)and the Scientific Research Project of Shaanxi Yanchang Petroleum(Group)Co.,Ltd,(Grant No.KTKTB0822SFW0032). （KTKTB0822SFW0032）
