东营凹陷页岩油储层孔隙演化

东营凹陷古近系沙河街组三段下亚段-沙河街组四段上亚段为一套较低成熟度陆相页岩层系，通过岩石薄片、氩离子抛光扫描电镜观察分析、核磁共振、高压压汞和低温氮气吸附实验，获取了页岩储层孔隙结构及孔隙度等信息，分析了矿物成分和有机质含量对孔隙度及孔径的影响，进一步结合成岩热模拟实验，探讨了主要孔隙类型的演化特征。结果表明：①页岩储层孔隙结构复杂，微米-纳米级储集空间具有保存液态烃类的储集能力，游离相原油主要分布在孔径较大的方解石晶间溶蚀孔隙、重结晶晶间孔、黏土矿物晶间收缩缝等孔隙中。②页岩储层孔隙度及孔径主要受控于架构矿物和有机质的含量；孔隙度与长英质矿物含量、有机质含量均呈线性正相关关系，与碳酸盐矿物含量呈负相关。③埋深2 500~3 500 m是孔隙演化的关键深度段，在此深度区间，有机质生烃排出的有机酸浓度以及压力系数增大区间与孔隙度高值段有良好的对应关系；页岩油储层储集空间的形成几乎都与黏土矿物的成岩演化有关；抗压实能力强的方解石等碳酸盐晶粒形成的架构空间，以及伴随生、排烃过程的溶蚀作用形成碳酸盐晶间和晶内溶蚀孔隙，均增加了储层孔隙度；生烃超压和溶蚀的匹配作用造成3 500~3 800 m出现孔隙度局部增大的现象，孔隙大小、分布及连通性明显变好。

Pore evolution of shale oil reservoirs in Dongying sag

The Paleogene Lower sub-member 3 and Upper sub-member 4 of Shahejie Formation in Dongying sag are a set of low-maturity continental shale reservoirs. By means of rock thin sections, argon ion polishing and scanning electron microscopy (SEM)analysis, magnetic resonance technology, high-pressure Hg injection and cold nitrogen gas adsorption experiment, the pore structure, porosity and other information of shale reservoirs are acquired to further analyze the influences of mineral content and organic matter content on porosity and pore size. On this basis, the evolutional characteristics of main pore types is explored using diagenetic thermal simulation experiment. The results show that (1)Shale reservoirs have complex pore structure, the micron-nanometer reserving space has the reserving capability of liquid hydrocarbons, and the free-phase oil is mainly distributed in the intergranular dissolution pores of calcite with large pore size, the recrystallized intergranular pores, the intergranular contracted fractures of clay mineral and other pores. (2)Shale reservoir porosity and pore size are directly controlled by framework mineral and organic matter content; the porosity is linearly and positively correlated to felsic mineral content and organic matter content, while negatively correlated to carbonate mineral content. (3)The buried depth of 2 500-3 500 m is the key depth interval of pore evolution. In this interval, the concentration of organic acid and the increase range of pressure coefficient for organic-matter hydrocarbon generation and expulsion are well corresponding to the high-value zone of porosities; the formation of reserving spaces in shale oil reservoirs are almost all related to the diagenetic evolution of clay minerals; the reservoir porosity is increased by the framework space consisting of calcite and other carbonate crystals with high compaction resistance as well as the carbonate intergranular and intergranular dissolution pores formed by dissolution associated with hydrocarbon generation and expulsion; the matching effect of hydrocarbon overpressure and dissolution results in a partial increase of porosity in 3 500-3 800 m, where the size, distribution and connectivity of pore system are significantly improved.