Hydrogeological characteristics and mechanism of a water-rich coal seam in the Jurassic coalfield, northern Shaanxi Province, China

Abstract

The Yuheng mining area of the Jurassic coalfield in northern Shaanxi Province is one of the most important coal-producing regions in China. The present study examines the mechanism of a water-rich coal seam in this area, namely, the No. 2 water-rich coal seam of the Balasu coal mine, by using the groundwater aquifers. From pumping and water chemistry tests, a macroscopic study of the aquifers, and a microcosmic analysis of the coal and rock, the hydrogeological conditions of the coal mine, the hydraulic relations between the various aquifers and the water-rich characteristics and the mechanism of the water-rich coal seam were analysed and summarised. According to the spatial distribution order, from shallow to deep, the salinity of the aquifers increases with an increase in the buried depth and the dissolved organic matter content decreases with aquifer depth. The direct water recharge source is the fractured sandstone aquifers of two Jurassic formations. Both aquifers are distributed in fluvial banded facies and their overall water content is relatively weak. The main mechanism for the formation of the water-rich coal seam in this area is that the No. 2 coal seam contains the original fissure and local special water-rich strata assemblage condition. This study is aimed at providing the basis for the hydrogeological characteristics of the Balasu coal mine, as well as a reference for similar mine conditions in the area.