Nano/Micro Pore Structure And Fractal Characteristics Of Baliancheng Coalfield In Hunchun Basin

The pore structure characteristic is an important index to measure and evaluate the storage capacity and fracturing coal reservoir. The coal of Baliancheng coalfield in Hunchun Basin was selected for experiments including low temperature nitrogen adsorption method, Argon Ion milling Scanning Electron Microscopy (Ar-SEM), Nuclear Magnetic Resonance (NMR), X-ray diffraction method, quantitative mineral clay analysis method. The pore structure of coal was quantitatively characterized by means of fractal theory. Meanwhile, the influences of pores fractal dimension were discussed with experiment data. The results show that the organic pores in Baliancheng coalfield are mainly plant tissue pores, interparticle pores and gas pores, and the mineral pores are corrosion pores and clay mineral pores. There are mainly slit pore and wedge-shaped pore in curve I of Low temperature nitrogen adsorption. There are ink pores in curve II with characteristics of a large specific surface area and average pore diameter. The two peaks of NMR T-2 spectrum indicate that the adsorption pores are relatively developed and their connectivity is poor. The three peaks show the seepage pores and cracks well developed, which are beneficial to improve the porosity and permeability of coal reservoir. When the pore diameter is 2-100 nm, the fractal dimensions D-1 and D-2 obtained by nitrogen adsorption experiment. there are positive correlations between water content and specific surface area and surface fractal dimension D-1, The fractal dimension D-2 was positively and negatively correlated with ash content and average pore diameters respectively. The fractal dimensions D-N1 and D-N2 were obtained by using the NMR in the range of 0.1 mu m similar to 10 mu m D-N1 are positively correlated with specific surface area of adsorption pores. D-N2 are positively correlated volume of seepage pores. The fractal dimension D-M and dissolution hole fractal dimension Dc were calculated by SEM image method, respectively controlled by clay mineral and feldspar content. There is a remarkable positive correlation between D-1 and D-N1 and Langmuir volume of coal, so fractal dimension can effectively quantify the adsorption capacity of coal.