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为深入研究皖东南地区二叠系页岩储层微观特征及其储气能力,选取2口钻井岩心样品进行负离子抛光—场发射扫描电子显微镜、氮吸附/脱附实验、甲烷吸附能力测定以及相关地球化学分析。结果表明,二叠系富Ⅱ—Ⅲ型有机质泥页岩石英等脆性矿物含量较高,存在晶间孔、粒间孔以及粒内孔、次生溶孔、有机质孔及微裂缝、构造缝等多种储集空间类型。采用He气法所测孔隙度为2.15%~6.10%、渗透率平均值为0.002 57×10-3μm2。该套页岩以中孔为主,含少量大孔和微孔,大多数的孔径分布在2~50nm之间。BJH孔容为3.30~11.23mm3/g,其中,中孔和大孔孔容约占总孔容的80%;BET比表面积介于3.91~20.84m2/g之间。T-图法计算微孔比表面积介于1.015~4.053m2/g之间,中孔和微孔是页岩比表面积的主要贡献者。大量纳米级孔隙的发育及具有较大的比表面积,为页岩储层提供了良好的吸附聚气能力,实验模拟地层温压测定页岩甲烷最大吸附量达2.3~3.2m3/t。说明研究区二叠系页岩具有良好的储集性能及甲烷吸附能力。
In order to further study the microscopic characteristics and gas storage capacity of Permian shale reservoirs in southeastern Anhui Province, two core samples were selected for negative ion polishing - field emission scanning electron microscopy, nitrogen adsorption / desorption experiments, methane adsorption capacity and correlation Geochemical analysis. The results show that the content of brittle minerals, such as quartz, rich in organic matter in the Permian Ⅱ-Ⅲ organic mud, is high, including intergranular pores, intergranular pores, intragranular pores, secondary dissolved pores, organic pores and microfractures, structural seams A variety of storage space types. The porosity measured by He method is 2.15% ~ 6.10%, and the average permeability is 0.002 57 × 10-3μm2. The shale is mainly mesoporous, with a small number of macropores and micropores, most of the pore size distribution between 2 ~ 50nm. The pore volume of BJH is 3.30 ~ 11.23mm3 / g, in which the mesopores and macropores occupy about 80% of the total pore volume and the BET specific surface area is between 3.91 ~ 20.84m2 / g. The specific surface area of micropores calculated by T-diagram is between 1.015 and 4.053 m2 / g. The mesopores and micropores are the major contributors to the specific surface area of shale. The development of a large number of nano-scale pores and the large specific surface area provide good adsorption capacity for gas accumulation in shale reservoirs. Simultaneously, the maximum adsorption capacity of methane in shale is 2.3 ~ 3.2m3 / t measured by temperature and pressure in laboratory. This shows that the Permian shale has good reservoir performance and methane adsorption capacity.