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.