显微CT观测下的煤吸附甲烷过程中的孔隙变化规律研究

Micro CT Experimental Study of Porosity Variation during Methane Adsorption on Coal Specimen

采用μCT225kVFCB型高精度显微CT试验系统和自主研制的细观吸附实验装置,进行显微CT观测下的沁水煤田3#煤层煤样的吸附甲烷实验,通过平面图像和三维重建模型分析试样孔隙随吸附压力的变化规律,得到的结论主要有:试样吸附甲烷后,孔隙率平均下降约3%,但随吸附压力的增加,孔隙率下降不明显;经由平面图像观测,吸附后试样孔隙被充填。根据三维重建实验结果,得到试样吸附甲烷后,最大连通团形成的骨架区域明显缩小,并且模型孔隙率相应降低。

High-precision micro CT experimental system μCT225kVFCB has been adopted for the study. The meso two phase fluid permeation testing machine of coal-gas-water is successfully manufactured by our research group, and it has also been adopted for the study. The minimum scale of μCT225kVFCB is 0.5 μm and magnification times are 400 once diameter up to 1 mm for cylinder specimen. In the study, it is about100 times of initial specimen. The specimen is from Qinshui Coalfield coal seam 3#, and a series of methane adsorption experiments under CT observation have been conducted. Above these, porosity variation followed by adsorption pressure increased is analyzed through 2D figures and 3-D reconstructive model. And the viewings of coal adsorbed methane and high pressure water injection experiments under micro CT are observed. It is presented for the coal specimen of 2 mm × 2.5 mm × 10 mm and the results showed that： （ 1 ） the average declined value of porosity is 3% once the coal adsorbs methane, and it is not obvious of declined law with adsorption pressure increased. From observation of 2D figures, the pores of specimen are filled filler adsorption. （ 2 ） Based on 3-D reconstructive model, the maximum connective pores group is shrunk obviously, and porosity of model is declined.