【摘要】 页岩储层微观孔隙结构特征的研究对页岩气的资源评价和成藏机理研究均具有重要的意义。前人在研究页岩的孔隙特征时常采用针对不同孔径范围孔隙特征的表征方法和模型的简单拼接,但上述不同方法拼接使用对页岩在整体孔径范围内的孔径分布特征的刻画不够准确。本文选取10个渝东石柱地区五峰组页岩作为研究对象,测定了其总有机碳(TOC)及矿物组成,并对比了二氧化碳-氮气吸附的非限定域(NLDFT)模型及限定域(DFT)模型的比表面积、孔体积等参数,探讨了页岩的孔隙结构及其对页岩气储存方面的意义。结果表明,页岩脆性矿物含量很高,脆性指数介于0.52~0.88之间,平均为0.71,页岩具有良好的可压裂性。微孔提供了用于吸附页岩气的最主要的比表面积,其比表面积为18.27 m2/g,占总比表面积的81.61%,是页岩气的最重要的吸附场所;介孔及宏孔的平均孔体积为22.51×10–3 cm3/g,占了总孔体积的81.48%,是游离态页岩气的重要储存空间。渝东石柱地区页岩吸附气含量要比先前评价中的含量有着很大比例的升高,游离气的含量比先前评价中的含量要略高一些。更多还原

【Abstract】 The study on the microscopic pore structure of shale is of great significance to performing resource assessments and understanding the accumulation mechanism of shale gas. Various test methods and models have been used to represent pore structures within different pore ranges of shale. However, it is not sufficiently accurate to represent the pore size distribution in the whole pore diameter range by simply splicing the results of different test methods and models. Therefore, ten samples of Wufeng Formation shale from the Shizhu area of the East Sichuan Basin, China, were selected to perform a series of measurements, including the determination of total organic carbon(TOC) and mineral composition. The specific surface area and pore volume obtained from the non-local density functional theory(NLDFT) with CO2-N2 adsorption data were compared with those from the density functional theory(DFT). Finally, the pore structures and significance of the pore structures on the storage of shale gas were discussed. The results showed that Wufeng Formation shale has a very high brittle mineral content. The brittleness index is in the range of 0.52~0.88(average: 0.71), indicating that the shale is very easy fractured. Micropores are the most important spaces for adsorbed shale gas, because they provide the majority of the specific surface area for adsorbing shale gas, with an average specific surface area of 18.27 m2/g, accounting for 81.61% of the total specific surface area. Mesopores and macropores are the most important storage space for free shale gas, because they provide the majority of the pore volume used for storing free shale gas, with an average pore volume of 22.51 × 10–3 cm3/g, accounting for 81.48% of the total pore volume. In the Shizhu area of eastern Chongqing, the contents of the adsorbed shale gas identified using the NLDFT model are significantly higher than those from previous assessments based on other models. The contents of free shale gas identified by the NLDFT model are also higher than those from previous assessments based on other models.更多还原