基于低温氮实验的页岩吸附孔分形特征

以低温氮吸附实验数据为基础,分析了重庆綦江观音桥剖面下志留统龙马溪组页岩样品吸附孔的吸附特征,采用FHH分形模型,计算了吸附孔分维值D,定量研究了分维值对页岩孔隙参数的变化规律。结果表明:脱附支得到的孔径分布曲线呈双优势峰,其中3.2~3.8 nm为假峰,页岩储层孔隙富含0.4~0.8 nm的微孔且分布集中,2~25 nm的中孔分布相对均匀。页岩吸附孔分形特征明显,分维值介于2.760~2.879,分维值与平均孔直径、孔隙体积呈较好的负相关,与埋深呈弱的正相关,而与比表面积无直接关系。

Fractal characteristics of adsorption pore of shale based on low temperature nitrogen experiment

Based on the results from the experiment of low temperature nitrogen adsorption，the adsorption characteristics of adsorption pores of Lower Silurian Longmaxi formation shale samples derived from the section of Guanyin Bridge in Qijiang of Chongqing were analyzed.With the FHH fractal model，the absorption pore fractal dimension values D were calculated and the change rule between fractal dimension values and pore parameters were quantitatively studied.Results show that the distribution curve of pore size obtained by the desorption branch presents dual advantage peaks with a ghost peak of 3.2-3.8 nm，and the micropore of 0.4-0.8 nm in the shale reservoir pores is rich and concentrated distribution，with relatively uniform distribution of mesopore of 2-25 nm.The fractal characteristics of shale adsorption pore are obvious that fractal dimension value varies in 2.760-2.879，and the relationships between fractal dimension values and the average pore radius，pore volume are negatively correlated.The relationship between fractal dimension values and buried depth is positively correlated，while indirectly correlated with surface.