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为了解致密油储层的微观特征及成因机理,通过薄片、扫描电镜、阴极发光、岩心物性等资料,详细分析了陇东地区长7段砂岩岩石学特征、成岩作用、孔隙类型及物性控制因素,认为长7段致密油砂岩成岩作用与常规储层具一定差异,整体上储层物性是大地构造背景、沉积条件、岩石学特征、埋藏过程及成岩作用等多因素共同作用的结果.研究结果表明:研究区目的层主要为细砂-粉砂级长石岩屑砂岩和岩屑长石砂岩,平均孔隙度10.1%,平均渗透率0.18mD.成岩特征表现为早期快速埋藏,压实强烈,但由于紧邻主力烃源岩,后期仍具有一定的溶蚀作用,溶孔是主要孔隙类型之一.对物性影响最大的胶结作用为伊利石、铁方解石和铁白云岩胶结,其中伊利石主要形成于早期沉积,云母水化,中后期黑云母蚀变、蒙脱石转化,杂基蚀变及长石溶蚀和钠长石化等,含铁碳酸盐大量出现于有机酸溶蚀之后,是中晚期孔隙继续损失的主要原因.
In order to understand the microscopic characteristics and genetic mechanism of tight oil reservoirs, the lithology characteristics, diagenesis, pore types and physical controlling factors of sandstone in Chang 7 section of Longdong area are analyzed in detail by means of thin slices, scanning electron microscopy, cathodoluminescence and core material properties. , It is considered that the diagenesis of the Chang 7 Member tight oil sandstone is different from that of conventional reservoirs, and the reservoir physical properties as a whole are the result of multi-factors such as tectonic setting, sedimentary conditions, petrological characteristics, burial processes and diagenesis. The results show that the study area is mainly composed of fine sand-silt grade feldspathic lithic sandstone and lithic feldspathic feldspar sandstone with an average porosity of 10.1% and an average permeability of 0.18mD.The diagenetic characteristics are characterized by early rapid burial, strong compaction, However, due to its close proximity to the main source rocks, dissolution still has some dissolution effect in the later period, and the dissolution pores are one of the major pore types.The cementation that has the most influence on the physical properties is the cementation of illite, iron calcite and iron dolomite, Early sedimentation, mica hydration, alteration of biotite in the middle and later stages, montmorillonite transformation, alteration of alluvial base and dissolution of feldspar and albite, a large number of iron-bearing carbonates appeared in After dissolution acids, it is the main reason for losses continue advanced pores.