Abstract:

The quantitative prediction of water content in coal seams is of significant importance for solving the problems of water disasters in mines, improving the technological level of water prevention and control in coal mines, reducing the economic costs of water prevention and control, and enhancing the safety and economic benefits of coal mines. In order to realize the quantitative prediction of coal seam water content, this paper selects the rock of the Carboniferous Taiyuan Formation aquiferous area above the No. 5 coal seam roof in Ningwu Yushupo, Shanxi, and measures its physical properties and resistivity parameters. Based on the measurement results, the parameters in the Archies formula are analyzed and determined, and the rock physics model is established to quantify the relationship between electrical parameters and water saturation, reservoir pressure, lithology and pores. The study shows that: 1) The rock of the coal seam roof has the characteristics of low porosity and low permeability. 2) The effective pressure of the reservoir affects the resistivity of the coal seam roof rock.The increase of effective pressure leads to the  decrease of the  resistivity at low frequencies, but has almost no effect on the resistivity at high frequencies. 3) Water saturation significantly influences the resistivity of the coal seam roof rock. An increase in water saturation causes a decrease in resistivity at low frequencies, but has a weak effect on high-frequency resistivity. Low water saturation has a more significant impact on resistivity dispersion，  high water saturation has a relatively weak effect on resistivity dispersion,  and full saturation has no effect on resistivity dispersion. 4) The lithology of the coal seam roof is mainly sandstone, with the presence of mudstone, limestone, etc. Lithological differences have a significant impact on both dry and water-saturated samples, and the resistivity difference between different lithologies can reach two orders of magnitude. 5) Cementation index, saturation index, and lithology coefficient all change with depth, but at a relatively steady rate, and the water saturation can be effectively predicted by the rock physics model constructed by its average value.

Key words: water inrush disaster, resistivity, rock physics model, quantitative prediction