HYDRUS-2D simulations of water movement along the vertical direction of a coal briquette in the process of upward imbibition

Abstract

ABSTRACT Coal is the main fossil resources and energy source in China and some other countries in the world. Coal seam water injection is an effective and widely used technique to promote the drainage quantity of coalbed methane (CBM) and prevent coal and gas outburst in the process of coal mining, but it is difficult to evaluate the impact range of water injection in coal seams. The minimum effective influence radium of coal seam water injection can be obtained by measuring the water content distribution in the vertical direction because of the effect of gravity. The objective of this study was to use HYDRUS-2D for simulations of water movement along the vertical direction of a coal briquette in the process of upward imbibition and to compare simulated and measured data at the same time and at the same position through statistical parameters. The results showed that HYDRUS-2D is generally able to reproduce the distribution of water content of a coal briquette in the process of upward imbibition. The Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) values of simulated results and measured data were between 0.0053 and 0.0217 and between 0.0076 and 0.0307, respectively. The transport velocity of water migration in the vertical direction gradually slowed down with time, and the imbibition height tended to be stable. After slowly decreasing from about 0.3 cm3/cm3 to about 0.25 cm3/cm3, the water content of a coal briquette in the vertical direction decreased suddenly from about 0.25 cm3/cm3 to 0 cm3/cm3 with the rose of height in the process of upward imbibition.