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Pore structure and connectivity of coal are critical factors in coal gas migration and production, which can be characterized by studying the kinetics of capillary imbibition behaviour within the pore spaces. In order to investigate them, six typical coal samples from different collieries in China (Yangcun, Changcun, Gengcun, Yanbei, Dongxia, and Yuwu coal) are selected to carry out N2 sorption isotherm and spontaneous imbibition tests. Results from N2 sorption isotherm tests show that there is a great difference between the total specific surface area and total pore volume among the six coal samples. Their total specific surface area varies from 0.302 to 3.275 m2/g, and the total pore volume varies from 1.782 to 10.94 mm3/g. The pore volume relationship of coal sample among them is in order from the large to small: Dongxia>Yangcun>Gengcun>Yuwu>Changcun>Yanbei coal, and the specific surface area is in order from the large to small: Yangcun>Dongxia>Changcun>Yuwu>Gengcun>Yanbei coal. The imbibition characters of six coal samples were matched using explicit the short-time limit t ⟶ 0 and long-time limit t ⟶ ∞ models by Zhmud et al., respectively. The results show that the long-time limit t ⟶ ∞ model is better. Combined with pore structure analysis, it can be qualitatively analyzed that the imbibition capacity of six coal samples is positively correlated with the connectivity of coal pores, which is ranked as Changcun>Yanbei>Gengcun>Yangcun>Dongxia>Yuwu coal. This work will help understand the mechanism controlling fluid loss and ultimate gas/oil recovery in unconventional hydrocarbon exploration. [ABSTRACT FROM AUTHOR]

Due to the huge reserves and great commercial potential of No. A group coal seam, the study on its thermal properties and combustion kinetics have attracted much attention. Via thermogravimetric (TG) analysis, the combustion characteristics and kinetics of No. A 3 coal were studied with three types of coal samples, with the grain diameter less than 200 meshes, 200~100 meshes, 100~60meshes, seperately. Under three characteristic temperatures such as T t , T p and T b , the whole combustion process could be roughly divided into 4 stages. Combined with the T max and T i , these five characteristic temperatures increase with elevating heating rates. The Kissinger-Akahira-Sunose (KAS) method and Flynn-Wall-Ozawa (FWO) method as reliable methods were used to verify the results of activation energy ( E a ) determined by of model-fitting methods. As complementary, the Coats-Redfern method was used to calculate the pre-exponential factor ( A ) and the correlation coefficient ( R 2 ). According to the evaluation criteria of E a and R 2 , D1 mechanism was the most probable model to depict the combustion kinetics. [ABSTRACT FROM AUTHOR]