Fractal characteristics of pore of low-rank coal in Huhehu Sag in Hailar Basin

In order to investigate the pore structure characteristics of coal reservoir which is in favor of the coalbed methane exploration and development, we explored the relationship between fractal dimension and pore diameter distribution, vitriolic reflectance, Langmuir volume and Langmuir pressure in low rank coal in Huhehu area of Hailar Basin. The results showed that the pores of low rank coal in Huhehu area of Hailar Basin have obvious fractal characteristics in different pore sizes. Compared with BET model, the fractal of FHH model is more consistent with the pore characteristics of low rank coal in Huhehu area. In FHH model, the adsorption characteristics of different macroscopic coal rock types are different at the relative pressure of 0 to 0.5 and 0.5 to 1.0, and the fractal dimensions D₁ and D₂ are obtained, where D1 represents the surface roughness of coal adsorption pore and D₂ represents the irregularity of adsorption pore structure. The higher D₂ is, the bigger the BET specific surface area product is, the higher the micropore content is, and the smaller the average pore diameter is. Both the fractal dimension D₁ and D₂ can reflect the adsorption performance of low rank coal in Huhehu area, and D₁ phase plays a greater role in controlling the adsorption performance than D₂.