致密砂岩孔隙演化特征及其成岩作用对储层质量的影响——以鄂尔多斯盆地马岭南延长组长8储层为例

成岩演化的差异性是导致储层微观孔喉结构差异、影响致密砂岩储层储集性能及渗流能力的主要原因。通过岩石铸体薄片、扫描电镜、阴极发光、X衍射、高压压汞和核磁共振等多种测试手段，对鄂尔多斯盆地马岭南地区长8储层的成岩作用和孔隙演化历史进行定量研究。长8砂岩岩石类型相近，成分成熟度低而结构成熟度较高，处于中成岩A期晚期到B期早期。成岩演化差异性主要体现在刚性颗粒与塑性颗粒含量的不同对压实作用的影响。压实程度相对强的砂岩，溶蚀作用是控制储层质量的主要因素；经历了一定压实作用的砂岩，残余粒间孔仍发育，绿泥石薄膜及钙质胶结物的充填程度是影响储层质量的关键因素。孔隙演化定量计算表明，压实作用孔隙减少率平均在49.51%，胶结作用孔隙减少率平均在30.6%，溶蚀作用孔隙增加率平均在7.0%，压实作用是导致本地区储层致密化的主要因素。不同成岩改造类型对储层孔隙结构发育特征的影响具有差异性。绿泥石薄膜发育的储层质量最好，长石溶蚀为主的储层，储集能力较好，但渗流能力相对较差；压实压溶作用强烈和钙质胶结充填为主的储层，其储层质量相对较差。压实程度、绿泥石胶结、溶蚀程度和钙质充填程度是影响储层孔径大小、储集性和渗流能力的主要因素。

Influence of diagenetic evolution on tight sandstone reservoir flow capacity: Chang 8 reservoir of Yanchang Formation in southern Maling,Ordos Basin

The difference in diagenetic evolution is the main reason for the difference in microscopic pore-throat structure affecting storage and flow capacity of reservoirs. The diagenesis and porosity evolution of the Chang 8 reservoirs in the southern Maling area of the Ordos Basin were studied quantitatively via many types of experiments, including thin sections, scanning electron microscopy, cathodoluminescence, X-ray diffraction, high pressure mercury intrusion and nuclear magnetic resonance. The Chang 8 sandstones have similar rock types, with lower compositional and higher structural maturities. The stage of diagenetic evolution is from the late stage A to the early stage B. The difference in diagenetic evolution is mainly reflected in the difference between the contents of rigid and plastic particles on compaction. For sandstones with relatively high compaction, dissolution is the main factor controlling reservoir quality. For sandstones that have undergone a certain compaction, in which residual intergranular pores are still developing, the filling degree of chlorite films and calcareous cement is the key factor affecting reservoir quality. Quantitative calculation of pore evolution reveals that the pore reduction rates due to compaction and cementation are 49.51% and 30.6%, respectively. The amount of dissolution is 7.0%. Compaction is the main factor that causes reservoir densification in this area. Different diagenetic transformation types have different effects on the development characteristics of reservoir pore structure. Reservoirs with chlorite film shows the best quality. The feldspar dissolution-based reservoir has better reservoir capacity, but poorer permeability. Reservoirs with strong compaction and calcium cementation are relatively poorer quality. The degree of compaction, chlorite cementation, dissolution and calcium filling are the main factors affecting the pore size, reservoir capacity and permeability.