基于氮吸附法的页岩有机孔隙结构表征

页岩的微观孔隙结构对页岩气的赋存至关重要，气体吸附法可以较好对页岩的微观孔隙结构进行表征。通过测量丁页1井不同深度样品的矿物含量、RO值和TOC含量，结果表明丁页1井龙马溪组页岩样品的矿物含量比较稳定，有机质成熟度变化不大，均为过成熟。通过低温氮吸附法计算样品的比表面积和微、介孔容积和孔径分布，结果表明：（1）样品的平均孔径为2.8 ~ 4.9 nm，10 nm以下的孔隙提供了大部分的微、介孔容积。微、介孔容积为0.00136 ~ 0.0108 cm3/g，平均0.004 cm3/g，比表面积为2.54 ~ 13.69 m2/g，平均6.68 m2/g；（2）微、介孔容积、比表面积和TOC三者之间有很强的正相关性。通过计算TOC含量为0时的微、介孔容积和比表面积推算无机孔和有机孔之间的比例和其对比表面积的影响，发现有机孔提供了大部分的微、介孔容积，有机孔还是比表面积的主要贡献因素；（3）样品的吸附曲线符合IPUAC分类中的第IV型吸附曲线，样品的脱附曲线反映样品孔隙形态随TOC含量的增加，由楔形孔（不定型孔）变为连通的墨水瓶型孔（狭缝型孔）或墨水瓶型孔。

Characterization of shale organic-pore structure using the nitrogen adsorption method

The microscopic pore structure of shale is very important for the occurrence of shale gas, and the gas adsorption method can characterize well such a feature. This work measured the mineral content, RO value and TOC content of the samples from well Dingye 1 at different depths. Results show that the mineral content of the Longmaxi Formation shale samples from well Dingye 1 is relatively stable, and the organic matter maturity does not change much, all being over-mature. The specific surface area, micro and mesopore volume and pore size distributions of the samples were calculated by the low-temperature nitrogen adsorption method. Results indicate that (1) the average pore diameter of the sample is 2.8 ~ 4.9 nm, and the pores below 10nm dominate the micro and mesopores. The micro and mesopore volume are 0.00136 ~ 0.0108 cm3/g, 0.004 cm3/g on average, and the specific surface area is 2.54 ~ 13.69 m2/g, 6.68 m2/g on average. (2) There is a strong positive correlation between the specific surface area and TOC. Calculating the volume of micro and mesopores and specific surface area with the TOC content 0 permits to estimate the ratio between inorganic pores and organic pores and the influence of their contrast surface area. It is found that organic pores provide most part of the micro and mesopore volume, while organic pores remains the main contributor to the specific surface area. (3) The adsorption curve of the sample conforms to the type IV adsorption curve in the IPUAC classification. The desorption curve of the samples indicates that with the increase of TOC content, the pore morphology changes from wedge-shaped pores (unshaped pores) into connected ink bottle type holes (slit type holes) or ink bottle type holes.